[GIT pull] core/rcu for v5.11-rc1

From: Thomas Gleixner
Date: Mon Dec 14 2020 - 15:26:44 EST

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Linus,

please pull the latest core/rcu branch from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git core-rcu-2020-12-14

up to: 50df51d12c31: Merge branch 'lkmm.2020.11.06a' into HEAD

RCU, LKMM and KCSAN updates collected by Paul McKenney:

RCU:

- Avoid cpuinfo-induced IPI pileups and idle-CPU IPIs.

- Lockdep-RCU updates reducing the need for __maybe_unused.

- Tasks-RCU updates.

- Miscellaneous fixes.

- Documentation updates.

- Torture-test updates.

KCSAN:

- updates for selftests, avoiding setting watchpoints on NULL pointers

- fix to watchpoint encoding

LKMM:

- updates for documentation along with some updates to example-code
litmus tests

Thanks,

tglx

------------------>
Alan Stern (1):
tools: memory-model: Document that the LKMM can easily miss control dependencies

Anna-Maria Behnsen (1):
tools/rcutorture: Fix BUG parsing of console.log

Asif Rasheed (1):
list.h: Update comment to explicitly note circular lists

Bhaskar Chowdhury (1):
tools/nolibc: Fix a spelling error in a comment

Fox Chen (1):
docs/memory-barriers.txt: Fix a typo in CPU MEMORY BARRIERS section

Frederic Weisbecker (1):
rcu: Implement rcu_segcblist_is_offloaded() config dependent

Hou Tao (2):
locktorture: Ignore nreaders_stress if no readlock support
locktorture: Invoke percpu_free_rwsem() to do percpu-rwsem cleanup

Hui Su (1):
docs/rcu: Update the call_rcu() API

Jakub Kicinski (7):
sched: Un-hide lockdep_tasklist_lock_is_held() for !LOCKDEP
rcu: Un-hide lockdep maps for !LOCKDEP
net: Un-hide lockdep_sock_is_held() for !LOCKDEP
net: sched: Remove broken definitions and un-hide for !LOCKDEP
srcu: Use a more appropriate lockdep helper
lockdep: Provide dummy forward declaration of *_is_held() helpers
rcu: Prevent RCU_LOCKDEP_WARN() from swallowing the condition

Joe Perches (1):
rcu/tree: Make struct kernel_param_ops definitions const

Joel Fernandes (Google) (3):
docs: Update RCU's hotplug requirements with a bit about design
rcu/tree: Add a warning if CPU being onlined did not report QS already
rcu/tree: nocb: Avoid raising softirq for offloaded ready-to-execute CBs

Marco Elver (3):
kcsan: selftest: Ensure that address is at least PAGE_SIZE
kcsan: Never set up watchpoints on NULL pointers
kcsan: Fix encoding masks and regain address bit

Mauro Carvalho Chehab (1):
docs: RCU: Requirements.rst: Fix a list block

Neeraj Upadhyay (2):
rcu: Fix single-CPU check in rcu_blocking_is_gp()
rcu: Clarify nocb kthreads naming in RCU_NOCB_CPU config

Paul E. McKenney (40):
tools/memory-model: Move Documentation description to Documentation/README
doc: Present the role of READ_ONCE()
rcutorture: Make preemptible TRACE02 enable lockdep
rcu-tasks: Convert rcu_tasks_wait_gp() for-loop to while-loop
rcutorture: Make grace-period kthread report match RCU flavor being tested
refscale: Bounds-check module parameters
torture: Don't kill gdb sessions
x86/cpu: Avoid cpuinfo-induced IPI pileups
x86/cpu: Avoid cpuinfo-induced IPIing of idle CPUs
locktorture: Track time of last ->writeunlock()
torture: Periodically pause in stutter_wait()
torture: Make torture_stutter() use hrtimer
scftorture: Add an alternative IPI vector
rcuscale: Add RCU Tasks Trace
rcuscale: Avoid divide by zero
torture: Exclude "NOHZ tick-stop error" from fatal errors
rcuscale: Prevent hangs for invalid arguments
refscale: Prevent hangs for invalid arguments
rcutorture: Adjust scenarios SRCU-t and SRCU-u to make kconfig happy
locktorture: Prevent hangs for invalid arguments
torture: Prevent jitter processes from delaying failed run
rcutorture: Prevent hangs for invalid arguments
torture: Force weak-hashed pointers on console log
rcutorture: Make stutter_wait() caller restore priority
torture: Accept time units on kvm.sh --duration argument
rcutorture: Small code cleanups
torture: Allow alternative forms of kvm.sh command-line arguments
scftorture: Add full-test stutter capability
rcutorture: Don't do need_resched() testing if ->sync is NULL
torture: Make kvm-check-branches.sh use --allcpus
rcu-tasks: Make the units of ->init_fract be jiffies
tools/memory-model: Document categories of ordering primitives
tools/memory-model: Add a glossary of LKMM terms
tools/memory-model: Add types to litmus tests
tools/memory-model: Use "buf" and "flag" for message-passing tests
tools/memory-model: Label MP tests' producers and consumers
x86/smpboot: Move rcu_cpu_starting() earlier
rcu: Prevent lockdep-RCU splats on lock acquisition/release
rcu: Do not report strict GPs for outgoing CPUs
srcu: Take early exit on memory-allocation failure

Peter Zijlstra (2):
rcu: Allow rcu_irq_enter_check_tick() from NMI
rcu,ftrace: Fix ftrace recursion

Samuel Hernandez (1):
rcutorture/nolibc: Fix a typo in header file

Uladzislau Rezki (Sony) (1):
rcu/tree: Defer kvfree_rcu() allocation to a clean context

Zhouyi Zhou (1):
rcu: Fix a typo in rcu_blocking_is_gp() header comment

chao (1):
rcu: Panic after fixed number of stalls

.../RCU/Design/Requirements/Requirements.rst | 50 +-
Documentation/RCU/checklist.rst | 7 +
Documentation/RCU/rcu_dereference.rst | 6 +
Documentation/RCU/whatisRCU.rst | 3 +-
Documentation/memory-barriers.txt | 2 +-
arch/x86/kernel/cpu/aperfmperf.c | 16 +-
arch/x86/kernel/cpu/mtrr/mtrr.c | 2 -
arch/x86/kernel/smpboot.c | 1 +
include/linux/kernel.h | 1 +
include/linux/list.h | 2 +-
include/linux/lockdep.h | 6 +
include/linux/rcupdate.h | 11 +-
include/linux/rcupdate_trace.h | 4 +-
include/linux/rcutiny.h | 2 +
include/linux/rcutree.h | 1 +
include/linux/sched/task.h | 2 -
include/net/sch_generic.h | 12 -
include/net/sock.h | 2 -
kernel/kcsan/encoding.h | 20 +-
kernel/kcsan/selftest.c | 3 +
kernel/locking/locktorture.c | 36 +-
kernel/rcu/Kconfig | 20 +-
kernel/rcu/rcu.h | 16 +
kernel/rcu/rcu_segcblist.h | 2 +-
kernel/rcu/rcuscale.c | 37 +-
kernel/rcu/rcutorture.c | 52 +-
kernel/rcu/refscale.c | 11 +-
kernel/rcu/srcutree.c | 6 +-
kernel/rcu/tasks.h | 49 +-
kernel/rcu/tree.c | 200 +++++---
kernel/rcu/tree.h | 2 +
kernel/rcu/tree_plugin.h | 2 +-
kernel/rcu/tree_stall.h | 6 +
kernel/scftorture.c | 49 +-
kernel/sysctl.c | 11 +
kernel/torture.c | 34 +-
tools/include/nolibc/nolibc.h | 4 +-
tools/memory-model/Documentation/README | 76 +++
.../Documentation/control-dependencies.txt | 258 ++++++++++
tools/memory-model/Documentation/glossary.txt | 172 +++++++
tools/memory-model/Documentation/litmus-tests.txt | 17 +
tools/memory-model/Documentation/ordering.txt | 556 +++++++++++++++++++++
tools/memory-model/README | 22 +-
.../litmus-tests/CoRR+poonceonce+Once.litmus | 4 +-
.../litmus-tests/CoRW+poonceonce+Once.litmus | 4 +-
.../litmus-tests/CoWR+poonceonce+Once.litmus | 4 +-
.../litmus-tests/CoWW+poonceonce.litmus | 4 +-
.../IRIW+fencembonceonces+OnceOnce.litmus | 5 +-
.../litmus-tests/IRIW+poonceonces+OnceOnce.litmus | 5 +-
.../ISA2+pooncelock+pooncelock+pombonce.litmus | 7 +-
.../litmus-tests/ISA2+poonceonces.litmus | 6 +-
...cerelease+poacquirerelease+poacquireonce.litmus | 6 +-
.../LB+fencembonceonce+ctrlonceonce.litmus | 5 +-
.../LB+poacquireonce+pooncerelease.litmus | 5 +-
.../litmus-tests/LB+poonceonces.litmus | 5 +-
.../MP+fencewmbonceonce+fencermbonceonce.litmus | 19 +-
.../litmus-tests/MP+onceassign+derefonce.litmus | 15 +-
.../MP+polockmbonce+poacquiresilsil.litmus | 8 +-
.../MP+polockonce+poacquiresilsil.litmus | 8 +-
tools/memory-model/litmus-tests/MP+polocks.litmus | 20 +-
.../litmus-tests/MP+poonceonces.litmus | 19 +-
.../MP+pooncerelease+poacquireonce.litmus | 19 +-
.../memory-model/litmus-tests/MP+porevlocks.litmus | 20 +-
.../litmus-tests/R+fencembonceonces.litmus | 5 +-
.../memory-model/litmus-tests/R+poonceonces.litmus | 5 +-
.../S+fencewmbonceonce+poacquireonce.litmus | 5 +-
.../memory-model/litmus-tests/S+poonceonces.litmus | 5 +-
.../litmus-tests/SB+fencembonceonces.litmus | 5 +-
.../litmus-tests/SB+poonceonces.litmus | 5 +-
.../litmus-tests/SB+rfionceonce-poonceonces.litmus | 5 +-
.../litmus-tests/WRC+poonceonces+Once.litmus | 5 +-
.../WRC+pooncerelease+fencermbonceonce+Once.litmus | 5 +-
.../Z6.0+pooncelock+poonceLock+pombonce.litmus | 7 +-
.../Z6.0+pooncelock+pooncelock+pombonce.litmus | 7 +-
...release+poacquirerelease+fencembonceonce.litmus | 6 +-
.../selftests/rcutorture/bin/console-badness.sh | 3 +-
.../testing/selftests/rcutorture/bin/functions.sh | 1 +
.../selftests/rcutorture/bin/kvm-check-branches.sh | 5 +-
.../rcutorture/bin/kvm-recheck-rcuscale.sh | 2 +-
.../selftests/rcutorture/bin/kvm-test-1-run.sh | 19 +-
tools/testing/selftests/rcutorture/bin/kvm.sh | 29 +-
.../selftests/rcutorture/bin/parse-console.sh | 2 +-
.../selftests/rcutorture/configs/rcu/SRCU-t | 3 +-
.../selftests/rcutorture/configs/rcu/SRCU-u | 3 +-
.../selftests/rcutorture/configs/rcu/TRACE01 | 6 +-
.../selftests/rcutorture/configs/rcu/TRACE02 | 6 +-
.../selftests/rcutorture/configs/rcuscale/CFcommon | 3 +
.../selftests/rcutorture/configs/rcuscale/TRACE01 | 15 +
.../rcutorture/configs/rcuscale/TRACE01.boot | 1 +
89 files changed, 1822 insertions(+), 320 deletions(-)
create mode 100644 tools/memory-model/Documentation/README
create mode 100644 tools/memory-model/Documentation/control-dependencies.txt
create mode 100644 tools/memory-model/Documentation/glossary.txt
create mode 100644 tools/memory-model/Documentation/ordering.txt
create mode 100644 tools/testing/selftests/rcutorture/configs/rcuscale/TRACE01
create mode 100644 tools/testing/selftests/rcutorture/configs/rcuscale/TRACE01.boot

diff --git a/Documentation/RCU/Design/Requirements/Requirements.rst b/Documentation/RCU/Design/Requirements/Requirements.rst
index 1ae79a10a8de..e8c84fcc0507 100644
--- a/Documentation/RCU/Design/Requirements/Requirements.rst
+++ b/Documentation/RCU/Design/Requirements/Requirements.rst
@@ -1929,16 +1929,46 @@ The Linux-kernel CPU-hotplug implementation has notifiers that are used
to allow the various kernel subsystems (including RCU) to respond
appropriately to a given CPU-hotplug operation. Most RCU operations may
be invoked from CPU-hotplug notifiers, including even synchronous
-grace-period operations such as ``synchronize_rcu()`` and
-``synchronize_rcu_expedited()``.
-
-However, all-callback-wait operations such as ``rcu_barrier()`` are also
-not supported, due to the fact that there are phases of CPU-hotplug
-operations where the outgoing CPU's callbacks will not be invoked until
-after the CPU-hotplug operation ends, which could also result in
-deadlock. Furthermore, ``rcu_barrier()`` blocks CPU-hotplug operations
-during its execution, which results in another type of deadlock when
-invoked from a CPU-hotplug notifier.
+grace-period operations such as (``synchronize_rcu()`` and
+``synchronize_rcu_expedited()``). However, these synchronous operations
+do block and therefore cannot be invoked from notifiers that execute via
+``stop_machine()``, specifically those between the ``CPUHP_AP_OFFLINE``
+and ``CPUHP_AP_ONLINE`` states.
+
+In addition, all-callback-wait operations such as ``rcu_barrier()`` may
+not be invoked from any CPU-hotplug notifier. This restriction is due
+to the fact that there are phases of CPU-hotplug operations where the
+outgoing CPU's callbacks will not be invoked until after the CPU-hotplug
+operation ends, which could also result in deadlock. Furthermore,
+``rcu_barrier()`` blocks CPU-hotplug operations during its execution,
+which results in another type of deadlock when invoked from a CPU-hotplug
+notifier.
+
+Finally, RCU must avoid deadlocks due to interaction between hotplug,
+timers and grace period processing. It does so by maintaining its own set
+of books that duplicate the centrally maintained ``cpu_online_mask``,
+and also by reporting quiescent states explicitly when a CPU goes
+offline. This explicit reporting of quiescent states avoids any need
+for the force-quiescent-state loop (FQS) to report quiescent states for
+offline CPUs. However, as a debugging measure, the FQS loop does splat
+if offline CPUs block an RCU grace period for too long.
+
+An offline CPU's quiescent state will be reported either:
+
+1. As the CPU goes offline using RCU's hotplug notifier (``rcu_report_dead()``).
+2. When grace period initialization (``rcu_gp_init()``) detects a
+ race either with CPU offlining or with a task unblocking on a leaf
+ ``rcu_node`` structure whose CPUs are all offline.
+
+The CPU-online path (``rcu_cpu_starting()``) should never need to report
+a quiescent state for an offline CPU. However, as a debugging measure,
+it does emit a warning if a quiescent state was not already reported
+for that CPU.
+
+During the checking/modification of RCU's hotplug bookkeeping, the
+corresponding CPU's leaf node lock is held. This avoids race conditions
+between RCU's hotplug notifier hooks, the grace period initialization
+code, and the FQS loop, all of which refer to or modify this bookkeeping.

Scheduler and RCU
~~~~~~~~~~~~~~~~~
diff --git a/Documentation/RCU/checklist.rst b/Documentation/RCU/checklist.rst
index 2efed9926c3f..bb7128eb322e 100644
--- a/Documentation/RCU/checklist.rst
+++ b/Documentation/RCU/checklist.rst
@@ -314,6 +314,13 @@ over a rather long period of time, but improvements are always welcome!
shared between readers and updaters. Additional primitives
are provided for this case, as discussed in lockdep.txt.

+ One exception to this rule is when data is only ever added to
+ the linked data structure, and is never removed during any
+ time that readers might be accessing that structure. In such
+ cases, READ_ONCE() may be used in place of rcu_dereference()
+ and the read-side markers (rcu_read_lock() and rcu_read_unlock(),
+ for example) may be omitted.
+
10. Conversely, if you are in an RCU read-side critical section,
and you don't hold the appropriate update-side lock, you -must-
use the "_rcu()" variants of the list macros. Failing to do so
diff --git a/Documentation/RCU/rcu_dereference.rst b/Documentation/RCU/rcu_dereference.rst
index c9667eb0d444..f3e587acb4de 100644
--- a/Documentation/RCU/rcu_dereference.rst
+++ b/Documentation/RCU/rcu_dereference.rst
@@ -28,6 +28,12 @@ Follow these rules to keep your RCU code working properly:
for an example where the compiler can in fact deduce the exact
value of the pointer, and thus cause misordering.

+- In the special case where data is added but is never removed
+ while readers are accessing the structure, READ_ONCE() may be used
+ instead of rcu_dereference(). In this case, use of READ_ONCE()
+ takes on the role of the lockless_dereference() primitive that
+ was removed in v4.15.
+
- You are only permitted to use rcu_dereference on pointer values.
The compiler simply knows too much about integral values to
trust it to carry dependencies through integer operations.
diff --git a/Documentation/RCU/whatisRCU.rst b/Documentation/RCU/whatisRCU.rst
index fb3ff76c3e73..1a4723f48bd9 100644
--- a/Documentation/RCU/whatisRCU.rst
+++ b/Documentation/RCU/whatisRCU.rst
@@ -497,8 +497,7 @@ long -- there might be other high-priority work to be done.
In such cases, one uses call_rcu() rather than synchronize_rcu().
The call_rcu() API is as follows::

- void call_rcu(struct rcu_head * head,
- void (*func)(struct rcu_head *head));
+ void call_rcu(struct rcu_head *head, rcu_callback_t func);

This function invokes func(head) after a grace period has elapsed.
This invocation might happen from either softirq or process context,
diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index 17c8e0c2deb4..7367ada13208 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -1870,7 +1870,7 @@ There are some more advanced barrier functions:

These are for use with atomic RMW functions that do not imply memory
barriers, but where the code needs a memory barrier. Examples for atomic
- RMW functions that do not imply are memory barrier are e.g. add,
+ RMW functions that do not imply a memory barrier are e.g. add,
subtract, (failed) conditional operations, _relaxed functions,
but not atomic_read or atomic_set. A common example where a memory
barrier may be required is when atomic ops are used for reference
diff --git a/arch/x86/kernel/cpu/aperfmperf.c b/arch/x86/kernel/cpu/aperfmperf.c
index e2f319dc992d..22911deacb6e 100644
--- a/arch/x86/kernel/cpu/aperfmperf.c
+++ b/arch/x86/kernel/cpu/aperfmperf.c
@@ -14,11 +14,13 @@
#include <linux/cpufreq.h>
#include <linux/smp.h>
#include <linux/sched/isolation.h>
+#include <linux/rcupdate.h>

#include "cpu.h"

struct aperfmperf_sample {
unsigned int khz;
+ atomic_t scfpending;
ktime_t time;
u64 aperf;
u64 mperf;
@@ -62,17 +64,20 @@ static void aperfmperf_snapshot_khz(void *dummy)
s->aperf = aperf;
s->mperf = mperf;
s->khz = div64_u64((cpu_khz * aperf_delta), mperf_delta);
+ atomic_set_release(&s->scfpending, 0);
}

static bool aperfmperf_snapshot_cpu(int cpu, ktime_t now, bool wait)
{
s64 time_delta = ktime_ms_delta(now, per_cpu(samples.time, cpu));
+ struct aperfmperf_sample *s = per_cpu_ptr(&samples, cpu);

/* Don't bother re-computing within the cache threshold time. */
if (time_delta < APERFMPERF_CACHE_THRESHOLD_MS)
return true;

- smp_call_function_single(cpu, aperfmperf_snapshot_khz, NULL, wait);
+ if (!atomic_xchg(&s->scfpending, 1) || wait)
+ smp_call_function_single(cpu, aperfmperf_snapshot_khz, NULL, wait);

/* Return false if the previous iteration was too long ago. */
return time_delta <= APERFMPERF_STALE_THRESHOLD_MS;
@@ -89,6 +94,9 @@ unsigned int aperfmperf_get_khz(int cpu)
if (!housekeeping_cpu(cpu, HK_FLAG_MISC))
return 0;

+ if (rcu_is_idle_cpu(cpu))
+ return 0; /* Idle CPUs are completely uninteresting. */
+
aperfmperf_snapshot_cpu(cpu, ktime_get(), true);
return per_cpu(samples.khz, cpu);
}
@@ -108,6 +116,8 @@ void arch_freq_prepare_all(void)
for_each_online_cpu(cpu) {
if (!housekeeping_cpu(cpu, HK_FLAG_MISC))
continue;
+ if (rcu_is_idle_cpu(cpu))
+ continue; /* Idle CPUs are completely uninteresting. */
if (!aperfmperf_snapshot_cpu(cpu, now, false))
wait = true;
}
@@ -118,6 +128,8 @@ void arch_freq_prepare_all(void)

unsigned int arch_freq_get_on_cpu(int cpu)
{
+ struct aperfmperf_sample *s = per_cpu_ptr(&samples, cpu);
+
if (!cpu_khz)
return 0;

@@ -131,6 +143,8 @@ unsigned int arch_freq_get_on_cpu(int cpu)
return per_cpu(samples.khz, cpu);

msleep(APERFMPERF_REFRESH_DELAY_MS);
+ atomic_set(&s->scfpending, 1);
+ smp_mb(); /* ->scfpending before smp_call_function_single(). */
smp_call_function_single(cpu, aperfmperf_snapshot_khz, NULL, 1);

return per_cpu(samples.khz, cpu);
diff --git a/arch/x86/kernel/cpu/mtrr/mtrr.c b/arch/x86/kernel/cpu/mtrr/mtrr.c
index 6a80f36b5d59..5f436cb4f7c4 100644
--- a/arch/x86/kernel/cpu/mtrr/mtrr.c
+++ b/arch/x86/kernel/cpu/mtrr/mtrr.c
@@ -794,8 +794,6 @@ void mtrr_ap_init(void)
if (!use_intel() || mtrr_aps_delayed_init)
return;

- rcu_cpu_starting(smp_processor_id());
-
/*
* Ideally we should hold mtrr_mutex here to avoid mtrr entries
* changed, but this routine will be called in cpu boot time,
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index de776b2e6046..99bdcebaedfc 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -229,6 +229,7 @@ static void notrace start_secondary(void *unused)
#endif
cpu_init_exception_handling();
cpu_init();
+ rcu_cpu_starting(raw_smp_processor_id());
x86_cpuinit.early_percpu_clock_init();
preempt_disable();
smp_callin();
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 2f05e9128201..4b5fd3da5fe8 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -536,6 +536,7 @@ extern int panic_on_warn;
extern unsigned long panic_on_taint;
extern bool panic_on_taint_nousertaint;
extern int sysctl_panic_on_rcu_stall;
+extern int sysctl_max_rcu_stall_to_panic;
extern int sysctl_panic_on_stackoverflow;

extern bool crash_kexec_post_notifiers;
diff --git a/include/linux/list.h b/include/linux/list.h
index a18c87b63376..89bdc92e75c3 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -9,7 +9,7 @@
#include <linux/kernel.h>

/*
- * Simple doubly linked list implementation.
+ * Circular doubly linked list implementation.
*
* Some of the internal functions ("__xxx") are useful when
* manipulating whole lists rather than single entries, as
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index f5594879175a..ccc3ce66c7e0 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -375,6 +375,12 @@ static inline void lockdep_unregister_key(struct lock_class_key *key)

#define lockdep_depth(tsk) (0)

+/*
+ * Dummy forward declarations, allow users to write less ifdef-y code
+ * and depend on dead code elimination.
+ */
+extern int lock_is_held(const void *);
+extern int lockdep_is_held(const void *);
#define lockdep_is_held_type(l, r) (1)

#define lockdep_assert_held(l) do { (void)(l); } while (0)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 6cdd0152c253..de0826411311 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -241,6 +241,11 @@ bool rcu_lockdep_current_cpu_online(void);
static inline bool rcu_lockdep_current_cpu_online(void) { return true; }
#endif /* #else #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */

+extern struct lockdep_map rcu_lock_map;
+extern struct lockdep_map rcu_bh_lock_map;
+extern struct lockdep_map rcu_sched_lock_map;
+extern struct lockdep_map rcu_callback_map;
+
#ifdef CONFIG_DEBUG_LOCK_ALLOC

static inline void rcu_lock_acquire(struct lockdep_map *map)
@@ -253,10 +258,6 @@ static inline void rcu_lock_release(struct lockdep_map *map)
lock_release(map, _THIS_IP_);
}

-extern struct lockdep_map rcu_lock_map;
-extern struct lockdep_map rcu_bh_lock_map;
-extern struct lockdep_map rcu_sched_lock_map;
-extern struct lockdep_map rcu_callback_map;
int debug_lockdep_rcu_enabled(void);
int rcu_read_lock_held(void);
int rcu_read_lock_bh_held(void);
@@ -327,7 +328,7 @@ static inline void rcu_preempt_sleep_check(void) { }

#else /* #ifdef CONFIG_PROVE_RCU */

-#define RCU_LOCKDEP_WARN(c, s) do { } while (0)
+#define RCU_LOCKDEP_WARN(c, s) do { } while (0 && (c))
#define rcu_sleep_check() do { } while (0)

#endif /* #else #ifdef CONFIG_PROVE_RCU */
diff --git a/include/linux/rcupdate_trace.h b/include/linux/rcupdate_trace.h
index 3e7919fc5f34..86c8f6c98412 100644
--- a/include/linux/rcupdate_trace.h
+++ b/include/linux/rcupdate_trace.h
@@ -11,10 +11,10 @@
#include <linux/sched.h>
#include <linux/rcupdate.h>

-#ifdef CONFIG_DEBUG_LOCK_ALLOC
-
extern struct lockdep_map rcu_trace_lock_map;

+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+
static inline int rcu_read_lock_trace_held(void)
{
return lock_is_held(&rcu_trace_lock_map);
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index 7c1ecdb356d8..2a97334eb786 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -89,6 +89,8 @@ static inline void rcu_irq_enter_irqson(void) { }
static inline void rcu_irq_exit(void) { }
static inline void rcu_irq_exit_preempt(void) { }
static inline void rcu_irq_exit_check_preempt(void) { }
+#define rcu_is_idle_cpu(cpu) \
+ (is_idle_task(current) && !in_nmi() && !in_irq() && !in_serving_softirq())
static inline void exit_rcu(void) { }
static inline bool rcu_preempt_need_deferred_qs(struct task_struct *t)
{
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 59eb5cd567d7..df578b73960f 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -50,6 +50,7 @@ void rcu_irq_exit(void);
void rcu_irq_exit_preempt(void);
void rcu_irq_enter_irqson(void);
void rcu_irq_exit_irqson(void);
+bool rcu_is_idle_cpu(int cpu);

#ifdef CONFIG_PROVE_RCU
void rcu_irq_exit_check_preempt(void);
diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index 85fb2f34c59b..c0f71f2e7160 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -47,9 +47,7 @@ extern spinlock_t mmlist_lock;
extern union thread_union init_thread_union;
extern struct task_struct init_task;

-#ifdef CONFIG_PROVE_RCU
extern int lockdep_tasklist_lock_is_held(void);
-#endif /* #ifdef CONFIG_PROVE_RCU */

extern asmlinkage void schedule_tail(struct task_struct *prev);
extern void init_idle(struct task_struct *idle, int cpu);
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index d8fd8676fc72..749db62f6215 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -435,7 +435,6 @@ struct tcf_block {
struct mutex proto_destroy_lock; /* Lock for proto_destroy hashtable. */
};

-#ifdef CONFIG_PROVE_LOCKING
static inline bool lockdep_tcf_chain_is_locked(struct tcf_chain *chain)
{
return lockdep_is_held(&chain->filter_chain_lock);
@@ -445,17 +444,6 @@ static inline bool lockdep_tcf_proto_is_locked(struct tcf_proto *tp)
{
return lockdep_is_held(&tp->lock);
}
-#else
-static inline bool lockdep_tcf_chain_is_locked(struct tcf_block *chain)
-{
- return true;
-}
-
-static inline bool lockdep_tcf_proto_is_locked(struct tcf_proto *tp)
-{
- return true;
-}
-#endif /* #ifdef CONFIG_PROVE_LOCKING */

#define tcf_chain_dereference(p, chain) \
rcu_dereference_protected(p, lockdep_tcf_chain_is_locked(chain))
diff --git a/include/net/sock.h b/include/net/sock.h
index a5c6ae78df77..198d5486fb09 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1566,13 +1566,11 @@ do { \
lockdep_init_map(&(sk)->sk_lock.dep_map, (name), (key), 0); \
} while (0)

-#ifdef CONFIG_LOCKDEP
static inline bool lockdep_sock_is_held(const struct sock *sk)
{
return lockdep_is_held(&sk->sk_lock) ||
lockdep_is_held(&sk->sk_lock.slock);
}
-#endif

void lock_sock_nested(struct sock *sk, int subclass);

diff --git a/kernel/kcsan/encoding.h b/kernel/kcsan/encoding.h
index 1a6db2f797ac..7ee405524904 100644
--- a/kernel/kcsan/encoding.h
+++ b/kernel/kcsan/encoding.h
@@ -37,18 +37,20 @@
*/
#define WATCHPOINT_ADDR_BITS (BITS_PER_LONG-1 - WATCHPOINT_SIZE_BITS)

-/*
- * Masks to set/retrieve the encoded data.
- */
-#define WATCHPOINT_WRITE_MASK BIT(BITS_PER_LONG-1)
-#define WATCHPOINT_SIZE_MASK \
- GENMASK(BITS_PER_LONG-2, BITS_PER_LONG-2 - WATCHPOINT_SIZE_BITS)
-#define WATCHPOINT_ADDR_MASK \
- GENMASK(BITS_PER_LONG-3 - WATCHPOINT_SIZE_BITS, 0)
+/* Bitmasks for the encoded watchpoint access information. */
+#define WATCHPOINT_WRITE_MASK BIT(BITS_PER_LONG-1)
+#define WATCHPOINT_SIZE_MASK GENMASK(BITS_PER_LONG-2, WATCHPOINT_ADDR_BITS)
+#define WATCHPOINT_ADDR_MASK GENMASK(WATCHPOINT_ADDR_BITS-1, 0)
+static_assert(WATCHPOINT_ADDR_MASK == (1UL << WATCHPOINT_ADDR_BITS) - 1);
+static_assert((WATCHPOINT_WRITE_MASK ^ WATCHPOINT_SIZE_MASK ^ WATCHPOINT_ADDR_MASK) == ~0UL);

static inline bool check_encodable(unsigned long addr, size_t size)
{
- return size <= MAX_ENCODABLE_SIZE;
+ /*
+ * While we can encode addrs<PAGE_SIZE, avoid crashing with a NULL
+ * pointer deref inside KCSAN.
+ */
+ return addr >= PAGE_SIZE && size <= MAX_ENCODABLE_SIZE;
}

static inline long
diff --git a/kernel/kcsan/selftest.c b/kernel/kcsan/selftest.c
index d98bc208d06d..9014a3a82cf9 100644
--- a/kernel/kcsan/selftest.c
+++ b/kernel/kcsan/selftest.c
@@ -33,6 +33,9 @@ static bool test_encode_decode(void)
unsigned long addr;

prandom_bytes(&addr, sizeof(addr));
+ if (addr < PAGE_SIZE)
+ addr = PAGE_SIZE;
+
if (WARN_ON(!check_encodable(addr, size)))
return false;

diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index 62d215b2e39f..fd838cea3934 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -29,6 +29,7 @@
#include <linux/slab.h>
#include <linux/percpu-rwsem.h>
#include <linux/torture.h>
+#include <linux/reboot.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Paul E. McKenney <paulmck@xxxxxxxxxxxxx>");
@@ -60,6 +61,7 @@ static struct task_struct **reader_tasks;

static bool lock_is_write_held;
static bool lock_is_read_held;
+static unsigned long last_lock_release;

struct lock_stress_stats {
long n_lock_fail;
@@ -74,6 +76,7 @@ static void lock_torture_cleanup(void);
*/
struct lock_torture_ops {
void (*init)(void);
+ void (*exit)(void);
int (*writelock)(void);
void (*write_delay)(struct torture_random_state *trsp);
void (*task_boost)(struct torture_random_state *trsp);
@@ -90,12 +93,13 @@ struct lock_torture_cxt {
int nrealwriters_stress;
int nrealreaders_stress;
bool debug_lock;
+ bool init_called;
atomic_t n_lock_torture_errors;
struct lock_torture_ops *cur_ops;
struct lock_stress_stats *lwsa; /* writer statistics */
struct lock_stress_stats *lrsa; /* reader statistics */
};
-static struct lock_torture_cxt cxt = { 0, 0, false,
+static struct lock_torture_cxt cxt = { 0, 0, false, false,
ATOMIC_INIT(0),
NULL, NULL};
/*
@@ -571,6 +575,11 @@ static void torture_percpu_rwsem_init(void)
BUG_ON(percpu_init_rwsem(&pcpu_rwsem));
}

+static void torture_percpu_rwsem_exit(void)
+{
+ percpu_free_rwsem(&pcpu_rwsem);
+}
+
static int torture_percpu_rwsem_down_write(void) __acquires(pcpu_rwsem)
{
percpu_down_write(&pcpu_rwsem);
@@ -595,6 +604,7 @@ static void torture_percpu_rwsem_up_read(void) __releases(pcpu_rwsem)

static struct lock_torture_ops percpu_rwsem_lock_ops = {
.init = torture_percpu_rwsem_init,
+ .exit = torture_percpu_rwsem_exit,
.writelock = torture_percpu_rwsem_down_write,
.write_delay = torture_rwsem_write_delay,
.task_boost = torture_boost_dummy,
@@ -632,6 +642,7 @@ static int lock_torture_writer(void *arg)
lwsp->n_lock_acquired++;
cxt.cur_ops->write_delay(&rand);
lock_is_write_held = false;
+ WRITE_ONCE(last_lock_release, jiffies);
cxt.cur_ops->writeunlock();

stutter_wait("lock_torture_writer");
@@ -786,9 +797,10 @@ static void lock_torture_cleanup(void)

/*
* Indicates early cleanup, meaning that the test has not run,
- * such as when passing bogus args when loading the module. As
- * such, only perform the underlying torture-specific cleanups,
- * and avoid anything related to locktorture.
+ * such as when passing bogus args when loading the module.
+ * However cxt->cur_ops.init() may have been invoked, so beside
+ * perform the underlying torture-specific cleanups, cur_ops.exit()
+ * will be invoked if needed.
*/
if (!cxt.lwsa && !cxt.lrsa)
goto end;
@@ -828,6 +840,11 @@ static void lock_torture_cleanup(void)
cxt.lrsa = NULL;

end:
+ if (cxt.init_called) {
+ if (cxt.cur_ops->exit)
+ cxt.cur_ops->exit();
+ cxt.init_called = false;
+ }
torture_cleanup_end();
}

@@ -868,14 +885,17 @@ static int __init lock_torture_init(void)
goto unwind;
}

- if (nwriters_stress == 0 && nreaders_stress == 0) {
+ if (nwriters_stress == 0 &&
+ (!cxt.cur_ops->readlock || nreaders_stress == 0)) {
pr_alert("lock-torture: must run at least one locking thread\n");
firsterr = -EINVAL;
goto unwind;
}

- if (cxt.cur_ops->init)
+ if (cxt.cur_ops->init) {
cxt.cur_ops->init();
+ cxt.init_called = true;
+ }

if (nwriters_stress >= 0)
cxt.nrealwriters_stress = nwriters_stress;
@@ -1038,6 +1058,10 @@ static int __init lock_torture_init(void)
unwind:
torture_init_end();
lock_torture_cleanup();
+ if (shutdown_secs) {
+ WARN_ON(!IS_MODULE(CONFIG_LOCK_TORTURE_TEST));
+ kernel_power_off();
+ }
return firsterr;
}

diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig
index b71e21f73c40..cdc57b4f6d48 100644
--- a/kernel/rcu/Kconfig
+++ b/kernel/rcu/Kconfig
@@ -221,19 +221,23 @@ config RCU_NOCB_CPU
Use this option to reduce OS jitter for aggressive HPC or
real-time workloads. It can also be used to offload RCU
callback invocation to energy-efficient CPUs in battery-powered
- asymmetric multiprocessors.
+ asymmetric multiprocessors. The price of this reduced jitter
+ is that the overhead of call_rcu() increases and that some
+ workloads will incur significant increases in context-switch
+ rates.

This option offloads callback invocation from the set of CPUs
specified at boot time by the rcu_nocbs parameter. For each
such CPU, a kthread ("rcuox/N") will be created to invoke
callbacks, where the "N" is the CPU being offloaded, and where
- the "p" for RCU-preempt (PREEMPTION kernels) and "s" for RCU-sched
- (!PREEMPTION kernels). Nothing prevents this kthread from running
- on the specified CPUs, but (1) the kthreads may be preempted
- between each callback, and (2) affinity or cgroups can be used
- to force the kthreads to run on whatever set of CPUs is desired.
-
- Say Y here if you want to help to debug reduced OS jitter.
+ the "x" is "p" for RCU-preempt (PREEMPTION kernels) and "s" for
+ RCU-sched (!PREEMPTION kernels). Nothing prevents this kthread
+ from running on the specified CPUs, but (1) the kthreads may be
+ preempted between each callback, and (2) affinity or cgroups can
+ be used to force the kthreads to run on whatever set of CPUs is
+ desired.
+
+ Say Y here if you need reduced OS jitter, despite added overhead.
Say N here if you are unsure.

config TASKS_TRACE_RCU_READ_MB
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index e01cba5e4b52..59ef1ae6dc37 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -533,4 +533,20 @@ static inline bool rcu_is_nocb_cpu(int cpu) { return false; }
static inline void rcu_bind_current_to_nocb(void) { }
#endif

+#if !defined(CONFIG_TINY_RCU) && defined(CONFIG_TASKS_RCU)
+void show_rcu_tasks_classic_gp_kthread(void);
+#else
+static inline void show_rcu_tasks_classic_gp_kthread(void) {}
+#endif
+#if !defined(CONFIG_TINY_RCU) && defined(CONFIG_TASKS_RUDE_RCU)
+void show_rcu_tasks_rude_gp_kthread(void);
+#else
+static inline void show_rcu_tasks_rude_gp_kthread(void) {}
+#endif
+#if !defined(CONFIG_TINY_RCU) && defined(CONFIG_TASKS_TRACE_RCU)
+void show_rcu_tasks_trace_gp_kthread(void);
+#else
+static inline void show_rcu_tasks_trace_gp_kthread(void) {}
+#endif
+
#endif /* __LINUX_RCU_H */
diff --git a/kernel/rcu/rcu_segcblist.h b/kernel/rcu/rcu_segcblist.h
index 5c293afc07b8..492262bcb591 100644
--- a/kernel/rcu/rcu_segcblist.h
+++ b/kernel/rcu/rcu_segcblist.h
@@ -62,7 +62,7 @@ static inline bool rcu_segcblist_is_enabled(struct rcu_segcblist *rsclp)
/* Is the specified rcu_segcblist offloaded? */
static inline bool rcu_segcblist_is_offloaded(struct rcu_segcblist *rsclp)
{
- return rsclp->offloaded;
+ return IS_ENABLED(CONFIG_RCU_NOCB_CPU) && rsclp->offloaded;
}

/*
diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
index 2819b95479af..06491d5530db 100644
--- a/kernel/rcu/rcuscale.c
+++ b/kernel/rcu/rcuscale.c
@@ -38,6 +38,7 @@
#include <asm/byteorder.h>
#include <linux/torture.h>
#include <linux/vmalloc.h>
+#include <linux/rcupdate_trace.h>

#include "rcu.h"

@@ -294,6 +295,35 @@ static struct rcu_scale_ops tasks_ops = {
.name = "tasks"
};

+/*
+ * Definitions for RCU-tasks-trace scalability testing.
+ */
+
+static int tasks_trace_scale_read_lock(void)
+{
+ rcu_read_lock_trace();
+ return 0;
+}
+
+static void tasks_trace_scale_read_unlock(int idx)
+{
+ rcu_read_unlock_trace();
+}
+
+static struct rcu_scale_ops tasks_tracing_ops = {
+ .ptype = RCU_TASKS_FLAVOR,
+ .init = rcu_sync_scale_init,
+ .readlock = tasks_trace_scale_read_lock,
+ .readunlock = tasks_trace_scale_read_unlock,
+ .get_gp_seq = rcu_no_completed,
+ .gp_diff = rcu_seq_diff,
+ .async = call_rcu_tasks_trace,
+ .gp_barrier = rcu_barrier_tasks_trace,
+ .sync = synchronize_rcu_tasks_trace,
+ .exp_sync = synchronize_rcu_tasks_trace,
+ .name = "tasks-tracing"
+};
+
static unsigned long rcuscale_seq_diff(unsigned long new, unsigned long old)
{
if (!cur_ops->gp_diff)
@@ -754,7 +784,7 @@ rcu_scale_init(void)
long i;
int firsterr = 0;
static struct rcu_scale_ops *scale_ops[] = {
- &rcu_ops, &srcu_ops, &srcud_ops, &tasks_ops,
+ &rcu_ops, &srcu_ops, &srcud_ops, &tasks_ops, &tasks_tracing_ops
};

if (!torture_init_begin(scale_type, verbose))
@@ -772,7 +802,6 @@ rcu_scale_init(void)
for (i = 0; i < ARRAY_SIZE(scale_ops); i++)
pr_cont(" %s", scale_ops[i]->name);
pr_cont("\n");
- WARN_ON(!IS_MODULE(CONFIG_RCU_SCALE_TEST));
firsterr = -EINVAL;
cur_ops = NULL;
goto unwind;
@@ -846,6 +875,10 @@ rcu_scale_init(void)
unwind:
torture_init_end();
rcu_scale_cleanup();
+ if (shutdown) {
+ WARN_ON(!IS_MODULE(CONFIG_RCU_SCALE_TEST));
+ kernel_power_off();
+ }
return firsterr;
}

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 916ea4f66e4b..528ed10b78fd 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -317,6 +317,7 @@ struct rcu_torture_ops {
void (*cb_barrier)(void);
void (*fqs)(void);
void (*stats)(void);
+ void (*gp_kthread_dbg)(void);
int (*stall_dur)(void);
int irq_capable;
int can_boost;
@@ -466,6 +467,7 @@ static struct rcu_torture_ops rcu_ops = {
.cb_barrier = rcu_barrier,
.fqs = rcu_force_quiescent_state,
.stats = NULL,
+ .gp_kthread_dbg = show_rcu_gp_kthreads,
.stall_dur = rcu_jiffies_till_stall_check,
.irq_capable = 1,
.can_boost = rcu_can_boost(),
@@ -693,6 +695,7 @@ static struct rcu_torture_ops tasks_ops = {
.exp_sync = synchronize_rcu_mult_test,
.call = call_rcu_tasks,
.cb_barrier = rcu_barrier_tasks,
+ .gp_kthread_dbg = show_rcu_tasks_classic_gp_kthread,
.fqs = NULL,
.stats = NULL,
.irq_capable = 1,
@@ -762,6 +765,7 @@ static struct rcu_torture_ops tasks_rude_ops = {
.exp_sync = synchronize_rcu_tasks_rude,
.call = call_rcu_tasks_rude,
.cb_barrier = rcu_barrier_tasks_rude,
+ .gp_kthread_dbg = show_rcu_tasks_rude_gp_kthread,
.fqs = NULL,
.stats = NULL,
.irq_capable = 1,
@@ -800,6 +804,7 @@ static struct rcu_torture_ops tasks_tracing_ops = {
.exp_sync = synchronize_rcu_tasks_trace,
.call = call_rcu_tasks_trace,
.cb_barrier = rcu_barrier_tasks_trace,
+ .gp_kthread_dbg = show_rcu_tasks_trace_gp_kthread,
.fqs = NULL,
.stats = NULL,
.irq_capable = 1,
@@ -912,7 +917,8 @@ static int rcu_torture_boost(void *arg)
oldstarttime = boost_starttime;
while (time_before(jiffies, oldstarttime)) {
schedule_timeout_interruptible(oldstarttime - jiffies);
- stutter_wait("rcu_torture_boost");
+ if (stutter_wait("rcu_torture_boost"))
+ sched_set_fifo_low(current);
if (torture_must_stop())
goto checkwait;
}
@@ -932,7 +938,8 @@ static int rcu_torture_boost(void *arg)
jiffies);
call_rcu_time = jiffies;
}
- stutter_wait("rcu_torture_boost");
+ if (stutter_wait("rcu_torture_boost"))
+ sched_set_fifo_low(current);
if (torture_must_stop())
goto checkwait;
}
@@ -964,7 +971,8 @@ static int rcu_torture_boost(void *arg)
}

/* Go do the stutter. */
-checkwait: stutter_wait("rcu_torture_boost");
+checkwait: if (stutter_wait("rcu_torture_boost"))
+ sched_set_fifo_low(current);
} while (!torture_must_stop());

/* Clean up and exit. */
@@ -987,6 +995,7 @@ rcu_torture_fqs(void *arg)
{
unsigned long fqs_resume_time;
int fqs_burst_remaining;
+ int oldnice = task_nice(current);

VERBOSE_TOROUT_STRING("rcu_torture_fqs task started");
do {
@@ -1002,7 +1011,8 @@ rcu_torture_fqs(void *arg)
udelay(fqs_holdoff);
fqs_burst_remaining -= fqs_holdoff;
}
- stutter_wait("rcu_torture_fqs");
+ if (stutter_wait("rcu_torture_fqs"))
+ sched_set_normal(current, oldnice);
} while (!torture_must_stop());
torture_kthread_stopping("rcu_torture_fqs");
return 0;
@@ -1022,9 +1032,11 @@ rcu_torture_writer(void *arg)
bool gp_cond1 = gp_cond, gp_exp1 = gp_exp, gp_normal1 = gp_normal;
bool gp_sync1 = gp_sync;
int i;
+ int oldnice = task_nice(current);
struct rcu_torture *rp;
struct rcu_torture *old_rp;
static DEFINE_TORTURE_RANDOM(rand);
+ bool stutter_waited;
int synctype[] = { RTWS_DEF_FREE, RTWS_EXP_SYNC,
RTWS_COND_GET, RTWS_SYNC };
int nsynctypes = 0;
@@ -1143,7 +1155,8 @@ rcu_torture_writer(void *arg)
!rcu_gp_is_normal();
}
rcu_torture_writer_state = RTWS_STUTTER;
- if (stutter_wait("rcu_torture_writer") &&
+ stutter_waited = stutter_wait("rcu_torture_writer");
+ if (stutter_waited &&
!READ_ONCE(rcu_fwd_cb_nodelay) &&
!cur_ops->slow_gps &&
!torture_must_stop() &&
@@ -1155,6 +1168,8 @@ rcu_torture_writer(void *arg)
rcu_ftrace_dump(DUMP_ALL);
WARN(1, "%s: rtort_pipe_count: %d\n", __func__, rcu_tortures[i].rtort_pipe_count);
}
+ if (stutter_waited)
+ sched_set_normal(current, oldnice);
} while (!torture_must_stop());
rcu_torture_current = NULL; // Let stats task know that we are done.
/* Reset expediting back to unexpedited. */
@@ -1594,7 +1609,8 @@ rcu_torture_stats_print(void)
sched_show_task(wtp);
splatted = true;
}
- show_rcu_gp_kthreads();
+ if (cur_ops->gp_kthread_dbg)
+ cur_ops->gp_kthread_dbg();
rcu_ftrace_dump(DUMP_ALL);
}
rtcv_snap = rcu_torture_current_version;
@@ -1913,7 +1929,9 @@ static void rcu_torture_fwd_prog_nr(struct rcu_fwd *rfp,
unsigned long stopat;
static DEFINE_TORTURE_RANDOM(trs);

- if (cur_ops->call && cur_ops->sync && cur_ops->cb_barrier) {
+ if (!cur_ops->sync)
+ return; // Cannot do need_resched() forward progress testing without ->sync.
+ if (cur_ops->call && cur_ops->cb_barrier) {
init_rcu_head_on_stack(&fcs.rh);
selfpropcb = true;
}
@@ -2103,6 +2121,7 @@ static struct notifier_block rcutorture_oom_nb = {
/* Carry out grace-period forward-progress testing. */
static int rcu_torture_fwd_prog(void *args)
{
+ int oldnice = task_nice(current);
struct rcu_fwd *rfp = args;
int tested = 0;
int tested_tries = 0;
@@ -2121,7 +2140,8 @@ static int rcu_torture_fwd_prog(void *args)
rcu_torture_fwd_prog_cr(rfp);

/* Avoid slow periods, better to test when busy. */
- stutter_wait("rcu_torture_fwd_prog");
+ if (stutter_wait("rcu_torture_fwd_prog"))
+ sched_set_normal(current, oldnice);
} while (!torture_must_stop());
/* Short runs might not contain a valid forward-progress attempt. */
WARN_ON(!tested && tested_tries >= 5);
@@ -2137,8 +2157,8 @@ static int __init rcu_torture_fwd_prog_init(void)

if (!fwd_progress)
return 0; /* Not requested, so don't do it. */
- if (!cur_ops->stall_dur || cur_ops->stall_dur() <= 0 ||
- cur_ops == &rcu_busted_ops) {
+ if ((!cur_ops->sync && !cur_ops->call) ||
+ !cur_ops->stall_dur || cur_ops->stall_dur() <= 0 || cur_ops == &rcu_busted_ops) {
VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, unsupported by RCU flavor under test");
return 0;
}
@@ -2472,7 +2492,8 @@ rcu_torture_cleanup(void)
return;
}

- show_rcu_gp_kthreads();
+ if (cur_ops->gp_kthread_dbg)
+ cur_ops->gp_kthread_dbg();
rcu_torture_read_exit_cleanup();
rcu_torture_barrier_cleanup();
rcu_torture_fwd_prog_cleanup();
@@ -2484,13 +2505,13 @@ rcu_torture_cleanup(void)
torture_stop_kthread(rcu_torture_reader,
reader_tasks[i]);
kfree(reader_tasks);
+ reader_tasks = NULL;
}

if (fakewriter_tasks) {
- for (i = 0; i < nfakewriters; i++) {
+ for (i = 0; i < nfakewriters; i++)
torture_stop_kthread(rcu_torture_fakewriter,
fakewriter_tasks[i]);
- }
kfree(fakewriter_tasks);
fakewriter_tasks = NULL;
}
@@ -2647,7 +2668,6 @@ rcu_torture_init(void)
for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
pr_cont(" %s", torture_ops[i]->name);
pr_cont("\n");
- WARN_ON(!IS_MODULE(CONFIG_RCU_TORTURE_TEST));
firsterr = -EINVAL;
cur_ops = NULL;
goto unwind;
@@ -2815,6 +2835,10 @@ rcu_torture_init(void)
unwind:
torture_init_end();
rcu_torture_cleanup();
+ if (shutdown_secs) {
+ WARN_ON(!IS_MODULE(CONFIG_RCU_TORTURE_TEST));
+ kernel_power_off();
+ }
return firsterr;
}

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index 952595c678b3..23ff36a66f97 100644
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -658,7 +658,6 @@ ref_scale_init(void)
for (i = 0; i < ARRAY_SIZE(scale_ops); i++)
pr_cont(" %s", scale_ops[i]->name);
pr_cont("\n");
- WARN_ON(!IS_MODULE(CONFIG_RCU_REF_SCALE_TEST));
firsterr = -EINVAL;
cur_ops = NULL;
goto unwind;
@@ -681,6 +680,12 @@ ref_scale_init(void)
// Reader tasks (default to ~75% of online CPUs).
if (nreaders < 0)
nreaders = (num_online_cpus() >> 1) + (num_online_cpus() >> 2);
+ if (WARN_ONCE(loops <= 0, "%s: loops = %ld, adjusted to 1\n", __func__, loops))
+ loops = 1;
+ if (WARN_ONCE(nreaders <= 0, "%s: nreaders = %d, adjusted to 1\n", __func__, nreaders))
+ nreaders = 1;
+ if (WARN_ONCE(nruns <= 0, "%s: nruns = %d, adjusted to 1\n", __func__, nruns))
+ nruns = 1;
reader_tasks = kcalloc(nreaders, sizeof(reader_tasks[0]),
GFP_KERNEL);
if (!reader_tasks) {
@@ -712,6 +717,10 @@ ref_scale_init(void)
unwind:
torture_init_end();
ref_scale_cleanup();
+ if (shutdown) {
+ WARN_ON(!IS_MODULE(CONFIG_RCU_REF_SCALE_TEST));
+ kernel_power_off();
+ }
return firsterr;
}

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index c13348ee80a5..0f23d20d485a 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -177,11 +177,13 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static)
INIT_DELAYED_WORK(&ssp->work, process_srcu);
if (!is_static)
ssp->sda = alloc_percpu(struct srcu_data);
+ if (!ssp->sda)
+ return -ENOMEM;
init_srcu_struct_nodes(ssp, is_static);
ssp->srcu_gp_seq_needed_exp = 0;
ssp->srcu_last_gp_end = ktime_get_mono_fast_ns();
smp_store_release(&ssp->srcu_gp_seq_needed, 0); /* Init done. */
- return ssp->sda ? 0 : -ENOMEM;
+ return 0;
}

#ifdef CONFIG_DEBUG_LOCK_ALLOC
@@ -906,7 +908,7 @@ static void __synchronize_srcu(struct srcu_struct *ssp, bool do_norm)
{
struct rcu_synchronize rcu;

- RCU_LOCKDEP_WARN(lock_is_held(&ssp->dep_map) ||
+ RCU_LOCKDEP_WARN(lockdep_is_held(ssp) ||
lock_is_held(&rcu_bh_lock_map) ||
lock_is_held(&rcu_lock_map) ||
lock_is_held(&rcu_sched_lock_map),
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index d5d9f2d03e8a..35bdcfd84d42 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -290,7 +290,7 @@ static void show_rcu_tasks_generic_gp_kthread(struct rcu_tasks *rtp, char *s)
".C"[!!data_race(rtp->cbs_head)],
s);
}
-#endif /* #ifndef CONFIG_TINY_RCU */
+#endif // #ifndef CONFIG_TINY_RCU

static void exit_tasks_rcu_finish_trace(struct task_struct *t);

@@ -335,23 +335,18 @@ static void rcu_tasks_wait_gp(struct rcu_tasks *rtp)

// Start off with initial wait and slowly back off to 1 HZ wait.
fract = rtp->init_fract;
- if (fract > HZ)
- fract = HZ;

- for (;;) {
+ while (!list_empty(&holdouts)) {
bool firstreport;
bool needreport;
int rtst;

- if (list_empty(&holdouts))
- break;
-
/* Slowly back off waiting for holdouts */
set_tasks_gp_state(rtp, RTGS_WAIT_SCAN_HOLDOUTS);
- schedule_timeout_idle(HZ/fract);
+ schedule_timeout_idle(fract);

- if (fract > 1)
- fract--;
+ if (fract < HZ)
+ fract++;

rtst = READ_ONCE(rcu_task_stall_timeout);
needreport = rtst > 0 && time_after(jiffies, lastreport + rtst);
@@ -560,7 +555,7 @@ EXPORT_SYMBOL_GPL(rcu_barrier_tasks);
static int __init rcu_spawn_tasks_kthread(void)
{
rcu_tasks.gp_sleep = HZ / 10;
- rcu_tasks.init_fract = 10;
+ rcu_tasks.init_fract = HZ / 10;
rcu_tasks.pregp_func = rcu_tasks_pregp_step;
rcu_tasks.pertask_func = rcu_tasks_pertask;
rcu_tasks.postscan_func = rcu_tasks_postscan;
@@ -571,12 +566,13 @@ static int __init rcu_spawn_tasks_kthread(void)
}
core_initcall(rcu_spawn_tasks_kthread);

-#ifndef CONFIG_TINY_RCU
-static void show_rcu_tasks_classic_gp_kthread(void)
+#if !defined(CONFIG_TINY_RCU)
+void show_rcu_tasks_classic_gp_kthread(void)
{
show_rcu_tasks_generic_gp_kthread(&rcu_tasks, "");
}
-#endif /* #ifndef CONFIG_TINY_RCU */
+EXPORT_SYMBOL_GPL(show_rcu_tasks_classic_gp_kthread);
+#endif // !defined(CONFIG_TINY_RCU)

/* Do the srcu_read_lock() for the above synchronize_srcu(). */
void exit_tasks_rcu_start(void) __acquires(&tasks_rcu_exit_srcu)
@@ -598,7 +594,6 @@ void exit_tasks_rcu_finish(void) __releases(&tasks_rcu_exit_srcu)
}

#else /* #ifdef CONFIG_TASKS_RCU */
-static inline void show_rcu_tasks_classic_gp_kthread(void) { }
void exit_tasks_rcu_start(void) { }
void exit_tasks_rcu_finish(void) { exit_tasks_rcu_finish_trace(current); }
#endif /* #else #ifdef CONFIG_TASKS_RCU */
@@ -699,16 +694,14 @@ static int __init rcu_spawn_tasks_rude_kthread(void)
}
core_initcall(rcu_spawn_tasks_rude_kthread);

-#ifndef CONFIG_TINY_RCU
-static void show_rcu_tasks_rude_gp_kthread(void)
+#if !defined(CONFIG_TINY_RCU)
+void show_rcu_tasks_rude_gp_kthread(void)
{
show_rcu_tasks_generic_gp_kthread(&rcu_tasks_rude, "");
}
-#endif /* #ifndef CONFIG_TINY_RCU */
-
-#else /* #ifdef CONFIG_TASKS_RUDE_RCU */
-static void show_rcu_tasks_rude_gp_kthread(void) {}
-#endif /* #else #ifdef CONFIG_TASKS_RUDE_RCU */
+EXPORT_SYMBOL_GPL(show_rcu_tasks_rude_gp_kthread);
+#endif // !defined(CONFIG_TINY_RCU)
+#endif /* #ifdef CONFIG_TASKS_RUDE_RCU */

////////////////////////////////////////////////////////////////////////
//
@@ -1183,12 +1176,12 @@ static int __init rcu_spawn_tasks_trace_kthread(void)
{
if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB)) {
rcu_tasks_trace.gp_sleep = HZ / 10;
- rcu_tasks_trace.init_fract = 10;
+ rcu_tasks_trace.init_fract = HZ / 10;
} else {
rcu_tasks_trace.gp_sleep = HZ / 200;
if (rcu_tasks_trace.gp_sleep <= 0)
rcu_tasks_trace.gp_sleep = 1;
- rcu_tasks_trace.init_fract = HZ / 5;
+ rcu_tasks_trace.init_fract = HZ / 200;
if (rcu_tasks_trace.init_fract <= 0)
rcu_tasks_trace.init_fract = 1;
}
@@ -1202,8 +1195,8 @@ static int __init rcu_spawn_tasks_trace_kthread(void)
}
core_initcall(rcu_spawn_tasks_trace_kthread);

-#ifndef CONFIG_TINY_RCU
-static void show_rcu_tasks_trace_gp_kthread(void)
+#if !defined(CONFIG_TINY_RCU)
+void show_rcu_tasks_trace_gp_kthread(void)
{
char buf[64];

@@ -1213,11 +1206,11 @@ static void show_rcu_tasks_trace_gp_kthread(void)
data_race(n_heavy_reader_attempts));
show_rcu_tasks_generic_gp_kthread(&rcu_tasks_trace, buf);
}
-#endif /* #ifndef CONFIG_TINY_RCU */
+EXPORT_SYMBOL_GPL(show_rcu_tasks_trace_gp_kthread);
+#endif // !defined(CONFIG_TINY_RCU)

#else /* #ifdef CONFIG_TASKS_TRACE_RCU */
static void exit_tasks_rcu_finish_trace(struct task_struct *t) { }
-static inline void show_rcu_tasks_trace_gp_kthread(void) {}
#endif /* #else #ifdef CONFIG_TASKS_TRACE_RCU */

#ifndef CONFIG_TINY_RCU
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 06895ef85d69..516c6893e359 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -177,7 +177,7 @@ module_param(rcu_unlock_delay, int, 0444);
* per-CPU. Object size is equal to one page. This value
* can be changed at boot time.
*/
-static int rcu_min_cached_objs = 2;
+static int rcu_min_cached_objs = 5;
module_param(rcu_min_cached_objs, int, 0444);

/* Retrieve RCU kthreads priority for rcutorture */
@@ -341,6 +341,14 @@ static bool rcu_dynticks_in_eqs(int snap)
return !(snap & RCU_DYNTICK_CTRL_CTR);
}

+/* Return true if the specified CPU is currently idle from an RCU viewpoint. */
+bool rcu_is_idle_cpu(int cpu)
+{
+ struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
+
+ return rcu_dynticks_in_eqs(rcu_dynticks_snap(rdp));
+}
+
/*
* Return true if the CPU corresponding to the specified rcu_data
* structure has spent some time in an extended quiescent state since
@@ -546,12 +554,12 @@ static int param_set_next_fqs_jiffies(const char *val, const struct kernel_param
return ret;
}

-static struct kernel_param_ops first_fqs_jiffies_ops = {
+static const struct kernel_param_ops first_fqs_jiffies_ops = {
.set = param_set_first_fqs_jiffies,
.get = param_get_ulong,
};

-static struct kernel_param_ops next_fqs_jiffies_ops = {
+static const struct kernel_param_ops next_fqs_jiffies_ops = {
.set = param_set_next_fqs_jiffies,
.get = param_get_ulong,
};
@@ -928,8 +936,8 @@ void __rcu_irq_enter_check_tick(void)
{
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);

- // Enabling the tick is unsafe in NMI handlers.
- if (WARN_ON_ONCE(in_nmi()))
+ // If we're here from NMI there's nothing to do.
+ if (in_nmi())
return;

RCU_LOCKDEP_WARN(rcu_dynticks_curr_cpu_in_eqs(),
@@ -1093,8 +1101,11 @@ static void rcu_disable_urgency_upon_qs(struct rcu_data *rdp)
* CPU can safely enter RCU read-side critical sections. In other words,
* if the current CPU is not in its idle loop or is in an interrupt or
* NMI handler, return true.
+ *
+ * Make notrace because it can be called by the internal functions of
+ * ftrace, and making this notrace removes unnecessary recursion calls.
*/
-bool rcu_is_watching(void)
+notrace bool rcu_is_watching(void)
{
bool ret;

@@ -1149,7 +1160,7 @@ bool rcu_lockdep_current_cpu_online(void)
preempt_disable_notrace();
rdp = this_cpu_ptr(&rcu_data);
rnp = rdp->mynode;
- if (rdp->grpmask & rcu_rnp_online_cpus(rnp))
+ if (rdp->grpmask & rcu_rnp_online_cpus(rnp) || READ_ONCE(rnp->ofl_seq) & 0x1)
ret = true;
preempt_enable_notrace();
return ret;
@@ -1603,8 +1614,7 @@ static bool __note_gp_changes(struct rcu_node *rnp, struct rcu_data *rdp)
{
bool ret = false;
bool need_qs;
- const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
- rcu_segcblist_is_offloaded(&rdp->cblist);
+ const bool offloaded = rcu_segcblist_is_offloaded(&rdp->cblist);

raw_lockdep_assert_held_rcu_node(rnp);

@@ -1715,6 +1725,7 @@ static void rcu_strict_gp_boundary(void *unused)
*/
static bool rcu_gp_init(void)
{
+ unsigned long firstseq;
unsigned long flags;
unsigned long oldmask;
unsigned long mask;
@@ -1758,6 +1769,12 @@ static bool rcu_gp_init(void)
*/
rcu_state.gp_state = RCU_GP_ONOFF;
rcu_for_each_leaf_node(rnp) {
+ smp_mb(); // Pair with barriers used when updating ->ofl_seq to odd values.
+ firstseq = READ_ONCE(rnp->ofl_seq);
+ if (firstseq & 0x1)
+ while (firstseq == READ_ONCE(rnp->ofl_seq))
+ schedule_timeout_idle(1); // Can't wake unless RCU is watching.
+ smp_mb(); // Pair with barriers used when updating ->ofl_seq to even values.
raw_spin_lock(&rcu_state.ofl_lock);
raw_spin_lock_irq_rcu_node(rnp);
if (rnp->qsmaskinit == rnp->qsmaskinitnext &&
@@ -2048,8 +2065,7 @@ static void rcu_gp_cleanup(void)
needgp = true;
}
/* Advance CBs to reduce false positives below. */
- offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
- rcu_segcblist_is_offloaded(&rdp->cblist);
+ offloaded = rcu_segcblist_is_offloaded(&rdp->cblist);
if ((offloaded || !rcu_accelerate_cbs(rnp, rdp)) && needgp) {
WRITE_ONCE(rcu_state.gp_flags, RCU_GP_FLAG_INIT);
WRITE_ONCE(rcu_state.gp_req_activity, jiffies);
@@ -2248,8 +2264,7 @@ rcu_report_qs_rdp(struct rcu_data *rdp)
unsigned long flags;
unsigned long mask;
bool needwake = false;
- const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
- rcu_segcblist_is_offloaded(&rdp->cblist);
+ const bool offloaded = rcu_segcblist_is_offloaded(&rdp->cblist);
struct rcu_node *rnp;

WARN_ON_ONCE(rdp->cpu != smp_processor_id());
@@ -2399,6 +2414,7 @@ int rcutree_dead_cpu(unsigned int cpu)
if (!IS_ENABLED(CONFIG_HOTPLUG_CPU))
return 0;

+ WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus - 1);
/* Adjust any no-longer-needed kthreads. */
rcu_boost_kthread_setaffinity(rnp, -1);
/* Do any needed no-CB deferred wakeups from this CPU. */
@@ -2417,8 +2433,7 @@ static void rcu_do_batch(struct rcu_data *rdp)
{
int div;
unsigned long flags;
- const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
- rcu_segcblist_is_offloaded(&rdp->cblist);
+ const bool offloaded = rcu_segcblist_is_offloaded(&rdp->cblist);
struct rcu_head *rhp;
struct rcu_cblist rcl = RCU_CBLIST_INITIALIZER(rcl);
long bl, count;
@@ -2675,8 +2690,7 @@ static __latent_entropy void rcu_core(void)
unsigned long flags;
struct rcu_data *rdp = raw_cpu_ptr(&rcu_data);
struct rcu_node *rnp = rdp->mynode;
- const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
- rcu_segcblist_is_offloaded(&rdp->cblist);
+ const bool offloaded = rcu_segcblist_is_offloaded(&rdp->cblist);

if (cpu_is_offline(smp_processor_id()))
return;
@@ -2978,8 +2992,7 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func)
rcu_segcblist_n_cbs(&rdp->cblist));

/* Go handle any RCU core processing required. */
- if (IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
- unlikely(rcu_segcblist_is_offloaded(&rdp->cblist))) {
+ if (unlikely(rcu_segcblist_is_offloaded(&rdp->cblist))) {
__call_rcu_nocb_wake(rdp, was_alldone, flags); /* unlocks */
} else {
__call_rcu_core(rdp, head, flags);
@@ -3084,6 +3097,9 @@ struct kfree_rcu_cpu_work {
* In order to save some per-cpu space the list is singular.
* Even though it is lockless an access has to be protected by the
* per-cpu lock.
+ * @page_cache_work: A work to refill the cache when it is empty
+ * @work_in_progress: Indicates that page_cache_work is running
+ * @hrtimer: A hrtimer for scheduling a page_cache_work
* @nr_bkv_objs: number of allocated objects at @bkvcache.
*
* This is a per-CPU structure. The reason that it is not included in
@@ -3100,6 +3116,11 @@ struct kfree_rcu_cpu {
bool monitor_todo;
bool initialized;
int count;
+
+ struct work_struct page_cache_work;
+ atomic_t work_in_progress;
+ struct hrtimer hrtimer;
+
struct llist_head bkvcache;
int nr_bkv_objs;
};
@@ -3217,10 +3238,10 @@ static void kfree_rcu_work(struct work_struct *work)
}
rcu_lock_release(&rcu_callback_map);

- krcp = krc_this_cpu_lock(&flags);
+ raw_spin_lock_irqsave(&krcp->lock, flags);
if (put_cached_bnode(krcp, bkvhead[i]))
bkvhead[i] = NULL;
- krc_this_cpu_unlock(krcp, flags);
+ raw_spin_unlock_irqrestore(&krcp->lock, flags);

if (bkvhead[i])
free_page((unsigned long) bkvhead[i]);
@@ -3347,6 +3368,57 @@ static void kfree_rcu_monitor(struct work_struct *work)
raw_spin_unlock_irqrestore(&krcp->lock, flags);
}

+static enum hrtimer_restart
+schedule_page_work_fn(struct hrtimer *t)
+{
+ struct kfree_rcu_cpu *krcp =
+ container_of(t, struct kfree_rcu_cpu, hrtimer);
+
+ queue_work(system_highpri_wq, &krcp->page_cache_work);
+ return HRTIMER_NORESTART;
+}
+
+static void fill_page_cache_func(struct work_struct *work)
+{
+ struct kvfree_rcu_bulk_data *bnode;
+ struct kfree_rcu_cpu *krcp =
+ container_of(work, struct kfree_rcu_cpu,
+ page_cache_work);
+ unsigned long flags;
+ bool pushed;
+ int i;
+
+ for (i = 0; i < rcu_min_cached_objs; i++) {
+ bnode = (struct kvfree_rcu_bulk_data *)
+ __get_free_page(GFP_KERNEL | __GFP_NOWARN);
+
+ if (bnode) {
+ raw_spin_lock_irqsave(&krcp->lock, flags);
+ pushed = put_cached_bnode(krcp, bnode);
+ raw_spin_unlock_irqrestore(&krcp->lock, flags);
+
+ if (!pushed) {
+ free_page((unsigned long) bnode);
+ break;
+ }
+ }
+ }
+
+ atomic_set(&krcp->work_in_progress, 0);
+}
+
+static void
+run_page_cache_worker(struct kfree_rcu_cpu *krcp)
+{
+ if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING &&
+ !atomic_xchg(&krcp->work_in_progress, 1)) {
+ hrtimer_init(&krcp->hrtimer, CLOCK_MONOTONIC,
+ HRTIMER_MODE_REL);
+ krcp->hrtimer.function = schedule_page_work_fn;
+ hrtimer_start(&krcp->hrtimer, 0, HRTIMER_MODE_REL);
+ }
+}
+
static inline bool
kvfree_call_rcu_add_ptr_to_bulk(struct kfree_rcu_cpu *krcp, void *ptr)
{
@@ -3363,32 +3435,8 @@ kvfree_call_rcu_add_ptr_to_bulk(struct kfree_rcu_cpu *krcp, void *ptr)
if (!krcp->bkvhead[idx] ||
krcp->bkvhead[idx]->nr_records == KVFREE_BULK_MAX_ENTR) {
bnode = get_cached_bnode(krcp);
- if (!bnode) {
- /*
- * To keep this path working on raw non-preemptible
- * sections, prevent the optional entry into the
- * allocator as it uses sleeping locks. In fact, even
- * if the caller of kfree_rcu() is preemptible, this
- * path still is not, as krcp->lock is a raw spinlock.
- * With additional page pre-allocation in the works,
- * hitting this return is going to be much less likely.
- */
- if (IS_ENABLED(CONFIG_PREEMPT_RT))
- return false;
-
- /*
- * NOTE: For one argument of kvfree_rcu() we can
- * drop the lock and get the page in sleepable
- * context. That would allow to maintain an array
- * for the CONFIG_PREEMPT_RT as well if no cached
- * pages are available.
- */
- bnode = (struct kvfree_rcu_bulk_data *)
- __get_free_page(GFP_NOWAIT | __GFP_NOWARN);
- }
-
/* Switch to emergency path. */
- if (unlikely(!bnode))
+ if (!bnode)
return false;

/* Initialize the new block. */
@@ -3452,12 +3500,10 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
goto unlock_return;
}

- /*
- * Under high memory pressure GFP_NOWAIT can fail,
- * in that case the emergency path is maintained.
- */
success = kvfree_call_rcu_add_ptr_to_bulk(krcp, ptr);
if (!success) {
+ run_page_cache_worker(krcp);
+
if (head == NULL)
// Inline if kvfree_rcu(one_arg) call.
goto unlock_return;
@@ -3567,7 +3613,7 @@ void __init kfree_rcu_scheduler_running(void)
* During early boot, any blocking grace-period wait automatically
* implies a grace period. Later on, this is never the case for PREEMPTION.
*
- * Howevr, because a context switch is a grace period for !PREEMPTION, any
+ * However, because a context switch is a grace period for !PREEMPTION, any
* blocking grace-period wait automatically implies a grace period if
* there is only one CPU online at any point time during execution of
* either synchronize_rcu() or synchronize_rcu_expedited(). It is OK to
@@ -3583,7 +3629,20 @@ static int rcu_blocking_is_gp(void)
return rcu_scheduler_active == RCU_SCHEDULER_INACTIVE;
might_sleep(); /* Check for RCU read-side critical section. */
preempt_disable();
- ret = num_online_cpus() <= 1;
+ /*
+ * If the rcu_state.n_online_cpus counter is equal to one,
+ * there is only one CPU, and that CPU sees all prior accesses
+ * made by any CPU that was online at the time of its access.
+ * Furthermore, if this counter is equal to one, its value cannot
+ * change until after the preempt_enable() below.
+ *
+ * Furthermore, if rcu_state.n_online_cpus is equal to one here,
+ * all later CPUs (both this one and any that come online later
+ * on) are guaranteed to see all accesses prior to this point
+ * in the code, without the need for additional memory barriers.
+ * Those memory barriers are provided by CPU-hotplug code.
+ */
+ ret = READ_ONCE(rcu_state.n_online_cpus) <= 1;
preempt_enable();
return ret;
}
@@ -3628,7 +3687,7 @@ void synchronize_rcu(void)
lock_is_held(&rcu_sched_lock_map),
"Illegal synchronize_rcu() in RCU read-side critical section");
if (rcu_blocking_is_gp())
- return;
+ return; // Context allows vacuous grace periods.
if (rcu_gp_is_expedited())
synchronize_rcu_expedited();
else
@@ -3707,13 +3766,13 @@ static int rcu_pending(int user)
return 1;

/* Does this CPU have callbacks ready to invoke? */
- if (rcu_segcblist_ready_cbs(&rdp->cblist))
+ if (!rcu_segcblist_is_offloaded(&rdp->cblist) &&
+ rcu_segcblist_ready_cbs(&rdp->cblist))
return 1;

/* Has RCU gone idle with this CPU needing another grace period? */
if (!gp_in_progress && rcu_segcblist_is_enabled(&rdp->cblist) &&
- (!IS_ENABLED(CONFIG_RCU_NOCB_CPU) ||
- !rcu_segcblist_is_offloaded(&rdp->cblist)) &&
+ !rcu_segcblist_is_offloaded(&rdp->cblist) &&
!rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL))
return 1;

@@ -3969,6 +4028,7 @@ int rcutree_prepare_cpu(unsigned int cpu)
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
rcu_prepare_kthreads(cpu);
rcu_spawn_cpu_nocb_kthread(cpu);
+ WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus + 1);

return 0;
}
@@ -4057,6 +4117,9 @@ void rcu_cpu_starting(unsigned int cpu)

rnp = rdp->mynode;
mask = rdp->grpmask;
+ WRITE_ONCE(rnp->ofl_seq, rnp->ofl_seq + 1);
+ WARN_ON_ONCE(!(rnp->ofl_seq & 0x1));
+ smp_mb(); // Pair with rcu_gp_cleanup()'s ->ofl_seq barrier().
raw_spin_lock_irqsave_rcu_node(rnp, flags);
WRITE_ONCE(rnp->qsmaskinitnext, rnp->qsmaskinitnext | mask);
newcpu = !(rnp->expmaskinitnext & mask);
@@ -4067,13 +4130,18 @@ void rcu_cpu_starting(unsigned int cpu)
rcu_gpnum_ovf(rnp, rdp); /* Offline-induced counter wrap? */
rdp->rcu_onl_gp_seq = READ_ONCE(rcu_state.gp_seq);
rdp->rcu_onl_gp_flags = READ_ONCE(rcu_state.gp_flags);
- if (rnp->qsmask & mask) { /* RCU waiting on incoming CPU? */
+
+ /* An incoming CPU should never be blocking a grace period. */
+ if (WARN_ON_ONCE(rnp->qsmask & mask)) { /* RCU waiting on incoming CPU? */
rcu_disable_urgency_upon_qs(rdp);
/* Report QS -after- changing ->qsmaskinitnext! */
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags);
} else {
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
}
+ smp_mb(); // Pair with rcu_gp_cleanup()'s ->ofl_seq barrier().
+ WRITE_ONCE(rnp->ofl_seq, rnp->ofl_seq + 1);
+ WARN_ON_ONCE(rnp->ofl_seq & 0x1);
smp_mb(); /* Ensure RCU read-side usage follows above initialization. */
}

@@ -4101,6 +4169,9 @@ void rcu_report_dead(unsigned int cpu)

/* Remove outgoing CPU from mask in the leaf rcu_node structure. */
mask = rdp->grpmask;
+ WRITE_ONCE(rnp->ofl_seq, rnp->ofl_seq + 1);
+ WARN_ON_ONCE(!(rnp->ofl_seq & 0x1));
+ smp_mb(); // Pair with rcu_gp_cleanup()'s ->ofl_seq barrier().
raw_spin_lock(&rcu_state.ofl_lock);
raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order guarantee. */
rdp->rcu_ofl_gp_seq = READ_ONCE(rcu_state.gp_seq);
@@ -4113,6 +4184,9 @@ void rcu_report_dead(unsigned int cpu)
WRITE_ONCE(rnp->qsmaskinitnext, rnp->qsmaskinitnext & ~mask);
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
raw_spin_unlock(&rcu_state.ofl_lock);
+ smp_mb(); // Pair with rcu_gp_cleanup()'s ->ofl_seq barrier().
+ WRITE_ONCE(rnp->ofl_seq, rnp->ofl_seq + 1);
+ WARN_ON_ONCE(rnp->ofl_seq & 0x1);

rdp->cpu_started = false;
}
@@ -4449,24 +4523,14 @@ static void __init kfree_rcu_batch_init(void)

for_each_possible_cpu(cpu) {
struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
- struct kvfree_rcu_bulk_data *bnode;

for (i = 0; i < KFREE_N_BATCHES; i++) {
INIT_RCU_WORK(&krcp->krw_arr[i].rcu_work, kfree_rcu_work);
krcp->krw_arr[i].krcp = krcp;
}

- for (i = 0; i < rcu_min_cached_objs; i++) {
- bnode = (struct kvfree_rcu_bulk_data *)
- __get_free_page(GFP_NOWAIT | __GFP_NOWARN);
-
- if (bnode)
- put_cached_bnode(krcp, bnode);
- else
- pr_err("Failed to preallocate for %d CPU!\n", cpu);
- }
-
INIT_DELAYED_WORK(&krcp->monitor_work, kfree_rcu_monitor);
+ INIT_WORK(&krcp->page_cache_work, fill_page_cache_func);
krcp->initialized = true;
}
if (register_shrinker(&kfree_rcu_shrinker))
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index e4f66b8f7c47..7708ed161f4a 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -56,6 +56,7 @@ struct rcu_node {
/* Initialized from ->qsmaskinitnext at the */
/* beginning of each grace period. */
unsigned long qsmaskinitnext;
+ unsigned long ofl_seq; /* CPU-hotplug operation sequence count. */
/* Online CPUs for next grace period. */
unsigned long expmask; /* CPUs or groups that need to check in */
/* to allow the current expedited GP */
@@ -298,6 +299,7 @@ struct rcu_state {
/* Hierarchy levels (+1 to */
/* shut bogus gcc warning) */
int ncpus; /* # CPUs seen so far. */
+ int n_online_cpus; /* # CPUs online for RCU. */

/* The following fields are guarded by the root rcu_node's lock. */

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index fd8a52e9a887..7e291ce0a1d6 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -628,7 +628,7 @@ static void rcu_read_unlock_special(struct task_struct *t)
set_tsk_need_resched(current);
set_preempt_need_resched();
if (IS_ENABLED(CONFIG_IRQ_WORK) && irqs_were_disabled &&
- !rdp->defer_qs_iw_pending && exp) {
+ !rdp->defer_qs_iw_pending && exp && cpu_online(rdp->cpu)) {
// Get scheduler to re-evaluate and call hooks.
// If !IRQ_WORK, FQS scan will eventually IPI.
init_irq_work(&rdp->defer_qs_iw,
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index ca21d28a0f98..70d48c52fabc 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -13,6 +13,7 @@

/* panic() on RCU Stall sysctl. */
int sysctl_panic_on_rcu_stall __read_mostly;
+int sysctl_max_rcu_stall_to_panic __read_mostly;

#ifdef CONFIG_PROVE_RCU
#define RCU_STALL_DELAY_DELTA (5 * HZ)
@@ -106,6 +107,11 @@ early_initcall(check_cpu_stall_init);
/* If so specified via sysctl, panic, yielding cleaner stall-warning output. */
static void panic_on_rcu_stall(void)
{
+ static int cpu_stall;
+
+ if (++cpu_stall < sysctl_max_rcu_stall_to_panic)
+ return;
+
if (sysctl_panic_on_rcu_stall)
panic("RCU Stall\n");
}
diff --git a/kernel/scftorture.c b/kernel/scftorture.c
index 554a521ee235..d55a9f8cda3d 100644
--- a/kernel/scftorture.c
+++ b/kernel/scftorture.c
@@ -59,9 +59,10 @@ torture_param(int, onoff_holdoff, 0, "Time after boot before CPU hotplugs (s)");
torture_param(int, onoff_interval, 0, "Time between CPU hotplugs (s), 0=disable");
torture_param(int, shutdown_secs, 0, "Shutdown time (ms), <= zero to disable.");
torture_param(int, stat_interval, 60, "Number of seconds between stats printk()s.");
-torture_param(int, stutter_cpus, 5, "Number of jiffies to change CPUs under test, 0=disable");
+torture_param(int, stutter, 5, "Number of jiffies to run/halt test, 0=disable");
torture_param(bool, use_cpus_read_lock, 0, "Use cpus_read_lock() to exclude CPU hotplug.");
torture_param(int, verbose, 0, "Enable verbose debugging printk()s");
+torture_param(int, weight_resched, -1, "Testing weight for resched_cpu() operations.");
torture_param(int, weight_single, -1, "Testing weight for single-CPU no-wait operations.");
torture_param(int, weight_single_wait, -1, "Testing weight for single-CPU operations.");
torture_param(int, weight_many, -1, "Testing weight for multi-CPU no-wait operations.");
@@ -82,6 +83,7 @@ torture_param(bool, shutdown, SCFTORT_SHUTDOWN, "Shutdown at end of torture test
struct scf_statistics {
struct task_struct *task;
int cpu;
+ long long n_resched;
long long n_single;
long long n_single_ofl;
long long n_single_wait;
@@ -97,12 +99,15 @@ static struct task_struct *scf_torture_stats_task;
static DEFINE_PER_CPU(long long, scf_invoked_count);

// Data for random primitive selection
-#define SCF_PRIM_SINGLE 0
-#define SCF_PRIM_MANY 1
-#define SCF_PRIM_ALL 2
-#define SCF_NPRIMS (2 * 3) // Need wait and no-wait versions of each.
+#define SCF_PRIM_RESCHED 0
+#define SCF_PRIM_SINGLE 1
+#define SCF_PRIM_MANY 2
+#define SCF_PRIM_ALL 3
+#define SCF_NPRIMS 7 // Need wait and no-wait versions of each,
+ // except for SCF_PRIM_RESCHED.

static char *scf_prim_name[] = {
+ "resched_cpu",
"smp_call_function_single",
"smp_call_function_many",
"smp_call_function",
@@ -136,6 +141,8 @@ static char *bangstr = "";

static DEFINE_TORTURE_RANDOM_PERCPU(scf_torture_rand);

+extern void resched_cpu(int cpu); // An alternative IPI vector.
+
// Print torture statistics. Caller must ensure serialization.
static void scf_torture_stats_print(void)
{
@@ -148,6 +155,7 @@ static void scf_torture_stats_print(void)
for_each_possible_cpu(cpu)
invoked_count += data_race(per_cpu(scf_invoked_count, cpu));
for (i = 0; i < nthreads; i++) {
+ scfs.n_resched += scf_stats_p[i].n_resched;
scfs.n_single += scf_stats_p[i].n_single;
scfs.n_single_ofl += scf_stats_p[i].n_single_ofl;
scfs.n_single_wait += scf_stats_p[i].n_single_wait;
@@ -160,8 +168,8 @@ static void scf_torture_stats_print(void)
if (atomic_read(&n_errs) || atomic_read(&n_mb_in_errs) ||
atomic_read(&n_mb_out_errs) || atomic_read(&n_alloc_errs))
bangstr = "!!! ";
- pr_alert("%s %sscf_invoked_count %s: %lld single: %lld/%lld single_ofl: %lld/%lld many: %lld/%lld all: %lld/%lld ",
- SCFTORT_FLAG, bangstr, isdone ? "VER" : "ver", invoked_count,
+ pr_alert("%s %sscf_invoked_count %s: %lld resched: %lld single: %lld/%lld single_ofl: %lld/%lld many: %lld/%lld all: %lld/%lld ",
+ SCFTORT_FLAG, bangstr, isdone ? "VER" : "ver", invoked_count, scfs.n_resched,
scfs.n_single, scfs.n_single_wait, scfs.n_single_ofl, scfs.n_single_wait_ofl,
scfs.n_many, scfs.n_many_wait, scfs.n_all, scfs.n_all_wait);
torture_onoff_stats();
@@ -314,6 +322,13 @@ static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_ra
}
}
switch (scfsp->scfs_prim) {
+ case SCF_PRIM_RESCHED:
+ if (IS_BUILTIN(CONFIG_SCF_TORTURE_TEST)) {
+ cpu = torture_random(trsp) % nr_cpu_ids;
+ scfp->n_resched++;
+ resched_cpu(cpu);
+ }
+ break;
case SCF_PRIM_SINGLE:
cpu = torture_random(trsp) % nr_cpu_ids;
if (scfsp->scfs_wait)
@@ -421,6 +436,7 @@ static int scftorture_invoker(void *arg)
was_offline = false;
}
cond_resched();
+ stutter_wait("scftorture_invoker");
} while (!torture_must_stop());

VERBOSE_SCFTORTOUT("scftorture_invoker %d ended", scfp->cpu);
@@ -433,8 +449,8 @@ static void
scftorture_print_module_parms(const char *tag)
{
pr_alert(SCFTORT_FLAG
- "--- %s: verbose=%d holdoff=%d longwait=%d nthreads=%d onoff_holdoff=%d onoff_interval=%d shutdown_secs=%d stat_interval=%d stutter_cpus=%d use_cpus_read_lock=%d, weight_single=%d, weight_single_wait=%d, weight_many=%d, weight_many_wait=%d, weight_all=%d, weight_all_wait=%d\n", tag,
- verbose, holdoff, longwait, nthreads, onoff_holdoff, onoff_interval, shutdown, stat_interval, stutter_cpus, use_cpus_read_lock, weight_single, weight_single_wait, weight_many, weight_many_wait, weight_all, weight_all_wait);
+ "--- %s: verbose=%d holdoff=%d longwait=%d nthreads=%d onoff_holdoff=%d onoff_interval=%d shutdown_secs=%d stat_interval=%d stutter=%d use_cpus_read_lock=%d, weight_resched=%d, weight_single=%d, weight_single_wait=%d, weight_many=%d, weight_many_wait=%d, weight_all=%d, weight_all_wait=%d\n", tag,
+ verbose, holdoff, longwait, nthreads, onoff_holdoff, onoff_interval, shutdown, stat_interval, stutter, use_cpus_read_lock, weight_resched, weight_single, weight_single_wait, weight_many, weight_many_wait, weight_all, weight_all_wait);
}

static void scf_cleanup_handler(void *unused)
@@ -475,6 +491,7 @@ static int __init scf_torture_init(void)
{
long i;
int firsterr = 0;
+ unsigned long weight_resched1 = weight_resched;
unsigned long weight_single1 = weight_single;
unsigned long weight_single_wait1 = weight_single_wait;
unsigned long weight_many1 = weight_many;
@@ -487,9 +504,10 @@ static int __init scf_torture_init(void)

scftorture_print_module_parms("Start of test");

- if (weight_single == -1 && weight_single_wait == -1 &&
+ if (weight_resched == -1 && weight_single == -1 && weight_single_wait == -1 &&
weight_many == -1 && weight_many_wait == -1 &&
weight_all == -1 && weight_all_wait == -1) {
+ weight_resched1 = 2 * nr_cpu_ids;
weight_single1 = 2 * nr_cpu_ids;
weight_single_wait1 = 2 * nr_cpu_ids;
weight_many1 = 2;
@@ -497,6 +515,8 @@ static int __init scf_torture_init(void)
weight_all1 = 1;
weight_all_wait1 = 1;
} else {
+ if (weight_resched == -1)
+ weight_resched1 = 0;
if (weight_single == -1)
weight_single1 = 0;
if (weight_single_wait == -1)
@@ -517,6 +537,10 @@ static int __init scf_torture_init(void)
firsterr = -EINVAL;
goto unwind;
}
+ if (IS_BUILTIN(CONFIG_SCF_TORTURE_TEST))
+ scf_sel_add(weight_resched1, SCF_PRIM_RESCHED, false);
+ else if (weight_resched1)
+ VERBOSE_SCFTORTOUT_ERRSTRING("built as module, weight_resched ignored");
scf_sel_add(weight_single1, SCF_PRIM_SINGLE, false);
scf_sel_add(weight_single_wait1, SCF_PRIM_SINGLE, true);
scf_sel_add(weight_many1, SCF_PRIM_MANY, false);
@@ -535,6 +559,11 @@ static int __init scf_torture_init(void)
if (firsterr)
goto unwind;
}
+ if (stutter > 0) {
+ firsterr = torture_stutter_init(stutter, stutter);
+ if (firsterr)
+ goto unwind;
+ }

// Worker tasks invoking smp_call_function().
if (nthreads < 0)
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index afad085960b8..c9fbdd848138 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2650,6 +2650,17 @@ static struct ctl_table kern_table[] = {
.extra2 = SYSCTL_ONE,
},
#endif
+#if defined(CONFIG_TREE_RCU)
+ {
+ .procname = "max_rcu_stall_to_panic",
+ .data = &sysctl_max_rcu_stall_to_panic,
+ .maxlen = sizeof(sysctl_max_rcu_stall_to_panic),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = SYSCTL_ONE,
+ .extra2 = SYSCTL_INT_MAX,
+ },
+#endif
#ifdef CONFIG_STACKLEAK_RUNTIME_DISABLE
{
.procname = "stack_erasing",
diff --git a/kernel/torture.c b/kernel/torture.c
index 1061492f14bd..8562ac18d2eb 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -602,18 +602,29 @@ static int stutter_gap;
*/
bool stutter_wait(const char *title)
{
- int spt;
+ ktime_t delay;
+ unsigned int i = 0;
bool ret = false;
+ int spt;

cond_resched_tasks_rcu_qs();
spt = READ_ONCE(stutter_pause_test);
for (; spt; spt = READ_ONCE(stutter_pause_test)) {
- ret = true;
+ if (!ret) {
+ sched_set_normal(current, MAX_NICE);
+ ret = true;
+ }
if (spt == 1) {
schedule_timeout_interruptible(1);
} else if (spt == 2) {
- while (READ_ONCE(stutter_pause_test))
+ while (READ_ONCE(stutter_pause_test)) {
+ if (!(i++ & 0xffff)) {
+ set_current_state(TASK_INTERRUPTIBLE);
+ delay = 10 * NSEC_PER_USEC;
+ schedule_hrtimeout(&delay, HRTIMER_MODE_REL);
+ }
cond_resched();
+ }
} else {
schedule_timeout_interruptible(round_jiffies_relative(HZ));
}
@@ -629,20 +640,27 @@ EXPORT_SYMBOL_GPL(stutter_wait);
*/
static int torture_stutter(void *arg)
{
+ ktime_t delay;
+ DEFINE_TORTURE_RANDOM(rand);
int wtime;

VERBOSE_TOROUT_STRING("torture_stutter task started");
do {
if (!torture_must_stop() && stutter > 1) {
wtime = stutter;
- if (stutter > HZ + 1) {
+ if (stutter > 2) {
WRITE_ONCE(stutter_pause_test, 1);
- wtime = stutter - HZ - 1;
- schedule_timeout_interruptible(wtime);
- wtime = HZ + 1;
+ wtime = stutter - 3;
+ delay = ktime_divns(NSEC_PER_SEC * wtime, HZ);
+ delay += (torture_random(&rand) >> 3) % NSEC_PER_MSEC;
+ set_current_state(TASK_INTERRUPTIBLE);
+ schedule_hrtimeout(&delay, HRTIMER_MODE_REL);
+ wtime = 2;
}
WRITE_ONCE(stutter_pause_test, 2);
- schedule_timeout_interruptible(wtime);
+ delay = ktime_divns(NSEC_PER_SEC * wtime, HZ);
+ set_current_state(TASK_INTERRUPTIBLE);
+ schedule_hrtimeout(&delay, HRTIMER_MODE_REL);
}
WRITE_ONCE(stutter_pause_test, 0);
if (!torture_must_stop())
diff --git a/tools/include/nolibc/nolibc.h b/tools/include/nolibc/nolibc.h
index 2551e9b71167..e61d36cd4e50 100644
--- a/tools/include/nolibc/nolibc.h
+++ b/tools/include/nolibc/nolibc.h
@@ -107,7 +107,7 @@ static int errno;
#endif

/* errno codes all ensure that they will not conflict with a valid pointer
- * because they all correspond to the highest addressable memry page.
+ * because they all correspond to the highest addressable memory page.
*/
#define MAX_ERRNO 4095

@@ -231,7 +231,7 @@ struct rusage {
#define DT_SOCK 12

/* all the *at functions */
-#ifndef AT_FDWCD
+#ifndef AT_FDCWD
#define AT_FDCWD -100
#endif

diff --git a/tools/memory-model/Documentation/README b/tools/memory-model/Documentation/README
new file mode 100644
index 000000000000..db90a26dbdf4
--- /dev/null
+++ b/tools/memory-model/Documentation/README
@@ -0,0 +1,76 @@
+It has been said that successful communication requires first identifying
+what your audience knows and then building a bridge from their current
+knowledge to what they need to know. Unfortunately, the expected
+Linux-kernel memory model (LKMM) audience might be anywhere from novice
+to expert both in kernel hacking and in understanding LKMM.
+
+This document therefore points out a number of places to start reading,
+depending on what you know and what you would like to learn. Please note
+that the documents later in this list assume that the reader understands
+the material provided by documents earlier in this list.
+
+o You are new to Linux-kernel concurrency: simple.txt
+
+o You have some background in Linux-kernel concurrency, and would
+ like an overview of the types of low-level concurrency primitives
+ that the Linux kernel provides: ordering.txt
+
+ Here, "low level" means atomic operations to single variables.
+
+o You are familiar with the Linux-kernel concurrency primitives
+ that you need, and just want to get started with LKMM litmus
+ tests: litmus-tests.txt
+
+o You are familiar with Linux-kernel concurrency, and would
+ like a detailed intuitive understanding of LKMM, including
+ situations involving more than two threads: recipes.txt
+
+o You would like a detailed understanding of what your compiler can
+ and cannot do to control dependencies: control-dependencies.txt
+
+o You are familiar with Linux-kernel concurrency and the use of
+ LKMM, and would like a quick reference: cheatsheet.txt
+
+o You are familiar with Linux-kernel concurrency and the use
+ of LKMM, and would like to learn about LKMM's requirements,
+ rationale, and implementation: explanation.txt
+
+o You are interested in the publications related to LKMM, including
+ hardware manuals, academic literature, standards-committee
+ working papers, and LWN articles: references.txt
+
+
+====================
+DESCRIPTION OF FILES
+====================
+
+README
+ This file.
+
+cheatsheet.txt
+ Quick-reference guide to the Linux-kernel memory model.
+
+control-dependencies.txt
+ Guide to preventing compiler optimizations from destroying
+ your control dependencies.
+
+explanation.txt
+ Detailed description of the memory model.
+
+litmus-tests.txt
+ The format, features, capabilities, and limitations of the litmus
+ tests that LKMM can evaluate.
+
+ordering.txt
+ Overview of the Linux kernel's low-level memory-ordering
+ primitives by category.
+
+recipes.txt
+ Common memory-ordering patterns.
+
+references.txt
+ Background information.
+
+simple.txt
+ Starting point for someone new to Linux-kernel concurrency.
+ And also a reminder of the simpler approaches to concurrency!
diff --git a/tools/memory-model/Documentation/control-dependencies.txt b/tools/memory-model/Documentation/control-dependencies.txt
new file mode 100644
index 000000000000..8b743d20fe27
--- /dev/null
+++ b/tools/memory-model/Documentation/control-dependencies.txt
@@ -0,0 +1,258 @@
+CONTROL DEPENDENCIES
+====================
+
+A major difficulty with control dependencies is that current compilers
+do not support them. One purpose of this document is therefore to
+help you prevent your compiler from breaking your code. However,
+control dependencies also pose other challenges, which leads to the
+second purpose of this document, namely to help you to avoid breaking
+your own code, even in the absence of help from your compiler.
+
+One such challenge is that control dependencies order only later stores.
+Therefore, a load-load control dependency will not preserve ordering
+unless a read memory barrier is provided. Consider the following code:
+
+ q = READ_ONCE(a);
+ if (q)
+ p = READ_ONCE(b);
+
+This is not guaranteed to provide any ordering because some types of CPUs
+are permitted to predict the result of the load from "b". This prediction
+can cause other CPUs to see this load as having happened before the load
+from "a". This means that an explicit read barrier is required, for example
+as follows:
+
+ q = READ_ONCE(a);
+ if (q) {
+ smp_rmb();
+ p = READ_ONCE(b);
+ }
+
+However, stores are not speculated. This means that ordering is
+(usually) guaranteed for load-store control dependencies, as in the
+following example:
+
+ q = READ_ONCE(a);
+ if (q)
+ WRITE_ONCE(b, 1);
+
+Control dependencies can pair with each other and with other types
+of ordering. But please note that neither the READ_ONCE() nor the
+WRITE_ONCE() are optional. Without the READ_ONCE(), the compiler might
+fuse the load from "a" with other loads. Without the WRITE_ONCE(),
+the compiler might fuse the store to "b" with other stores. Worse yet,
+the compiler might convert the store into a load and a check followed
+by a store, and this compiler-generated load would not be ordered by
+the control dependency.
+
+Furthermore, if the compiler is able to prove that the value of variable
+"a" is always non-zero, it would be well within its rights to optimize
+the original example by eliminating the "if" statement as follows:
+
+ q = a;
+ b = 1; /* BUG: Compiler and CPU can both reorder!!! */
+
+So don't leave out either the READ_ONCE() or the WRITE_ONCE().
+In particular, although READ_ONCE() does force the compiler to emit a
+load, it does *not* force the compiler to actually use the loaded value.
+
+It is tempting to try use control dependencies to enforce ordering on
+identical stores on both branches of the "if" statement as follows:
+
+ q = READ_ONCE(a);
+ if (q) {
+ barrier();
+ WRITE_ONCE(b, 1);
+ do_something();
+ } else {
+ barrier();
+ WRITE_ONCE(b, 1);
+ do_something_else();
+ }
+
+Unfortunately, current compilers will transform this as follows at high
+optimization levels:
+
+ q = READ_ONCE(a);
+ barrier();
+ WRITE_ONCE(b, 1); /* BUG: No ordering vs. load from a!!! */
+ if (q) {
+ /* WRITE_ONCE(b, 1); -- moved up, BUG!!! */
+ do_something();
+ } else {
+ /* WRITE_ONCE(b, 1); -- moved up, BUG!!! */
+ do_something_else();
+ }
+
+Now there is no conditional between the load from "a" and the store to
+"b", which means that the CPU is within its rights to reorder them: The
+conditional is absolutely required, and must be present in the final
+assembly code, after all of the compiler and link-time optimizations
+have been applied. Therefore, if you need ordering in this example,
+you must use explicit memory ordering, for example, smp_store_release():
+
+ q = READ_ONCE(a);
+ if (q) {
+ smp_store_release(&b, 1);
+ do_something();
+ } else {
+ smp_store_release(&b, 1);
+ do_something_else();
+ }
+
+Without explicit memory ordering, control-dependency-based ordering is
+guaranteed only when the stores differ, for example:
+
+ q = READ_ONCE(a);
+ if (q) {
+ WRITE_ONCE(b, 1);
+ do_something();
+ } else {
+ WRITE_ONCE(b, 2);
+ do_something_else();
+ }
+
+The initial READ_ONCE() is still required to prevent the compiler from
+knowing too much about the value of "a".
+
+But please note that you need to be careful what you do with the local
+variable "q", otherwise the compiler might be able to guess the value
+and again remove the conditional branch that is absolutely required to
+preserve ordering. For example:
+
+ q = READ_ONCE(a);
+ if (q % MAX) {
+ WRITE_ONCE(b, 1);
+ do_something();
+ } else {
+ WRITE_ONCE(b, 2);
+ do_something_else();
+ }
+
+If MAX is compile-time defined to be 1, then the compiler knows that
+(q % MAX) must be equal to zero, regardless of the value of "q".
+The compiler is therefore within its rights to transform the above code
+into the following:
+
+ q = READ_ONCE(a);
+ WRITE_ONCE(b, 2);
+ do_something_else();
+
+Given this transformation, the CPU is not required to respect the ordering
+between the load from variable "a" and the store to variable "b". It is
+tempting to add a barrier(), but this does not help. The conditional
+is gone, and the barrier won't bring it back. Therefore, if you need
+to relying on control dependencies to produce this ordering, you should
+make sure that MAX is greater than one, perhaps as follows:
+
+ q = READ_ONCE(a);
+ BUILD_BUG_ON(MAX <= 1); /* Order load from a with store to b. */
+ if (q % MAX) {
+ WRITE_ONCE(b, 1);
+ do_something();
+ } else {
+ WRITE_ONCE(b, 2);
+ do_something_else();
+ }
+
+Please note once again that each leg of the "if" statement absolutely
+must store different values to "b". As in previous examples, if the two
+values were identical, the compiler could pull this store outside of the
+"if" statement, destroying the control dependency's ordering properties.
+
+You must also be careful avoid relying too much on boolean short-circuit
+evaluation. Consider this example:
+
+ q = READ_ONCE(a);
+ if (q || 1 > 0)
+ WRITE_ONCE(b, 1);
+
+Because the first condition cannot fault and the second condition is
+always true, the compiler can transform this example as follows, again
+destroying the control dependency's ordering:
+
+ q = READ_ONCE(a);
+ WRITE_ONCE(b, 1);
+
+This is yet another example showing the importance of preventing the
+compiler from out-guessing your code. Again, although READ_ONCE() really
+does force the compiler to emit code for a given load, the compiler is
+within its rights to discard the loaded value.
+
+In addition, control dependencies apply only to the then-clause and
+else-clause of the "if" statement in question. In particular, they do
+not necessarily order the code following the entire "if" statement:
+
+ q = READ_ONCE(a);
+ if (q) {
+ WRITE_ONCE(b, 1);
+ } else {
+ WRITE_ONCE(b, 2);
+ }
+ WRITE_ONCE(c, 1); /* BUG: No ordering against the read from "a". */
+
+It is tempting to argue that there in fact is ordering because the
+compiler cannot reorder volatile accesses and also cannot reorder
+the writes to "b" with the condition. Unfortunately for this line
+of reasoning, the compiler might compile the two writes to "b" as
+conditional-move instructions, as in this fanciful pseudo-assembly
+language:
+
+ ld r1,a
+ cmp r1,$0
+ cmov,ne r4,$1
+ cmov,eq r4,$2
+ st r4,b
+ st $1,c
+
+The control dependencies would then extend only to the pair of cmov
+instructions and the store depending on them. This means that a weakly
+ordered CPU would have no dependency of any sort between the load from
+"a" and the store to "c". In short, control dependencies provide ordering
+only to the stores in the then-clause and else-clause of the "if" statement
+in question (including functions invoked by those two clauses), and not
+to code following that "if" statement.
+
+
+In summary:
+
+ (*) Control dependencies can order prior loads against later stores.
+ However, they do *not* guarantee any other sort of ordering:
+ Not prior loads against later loads, nor prior stores against
+ later anything. If you need these other forms of ordering, use
+ smp_load_acquire(), smp_store_release(), or, in the case of prior
+ stores and later loads, smp_mb().
+
+ (*) If both legs of the "if" statement contain identical stores to
+ the same variable, then you must explicitly order those stores,
+ either by preceding both of them with smp_mb() or by using
+ smp_store_release(). Please note that it is *not* sufficient to use
+ barrier() at beginning and end of each leg of the "if" statement
+ because, as shown by the example above, optimizing compilers can
+ destroy the control dependency while respecting the letter of the
+ barrier() law.
+
+ (*) Control dependencies require at least one run-time conditional
+ between the prior load and the subsequent store, and this
+ conditional must involve the prior load. If the compiler is able
+ to optimize the conditional away, it will have also optimized
+ away the ordering. Careful use of READ_ONCE() and WRITE_ONCE()
+ can help to preserve the needed conditional.
+
+ (*) Control dependencies require that the compiler avoid reordering the
+ dependency into nonexistence. Careful use of READ_ONCE() or
+ atomic{,64}_read() can help to preserve your control dependency.
+
+ (*) Control dependencies apply only to the then-clause and else-clause
+ of the "if" statement containing the control dependency, including
+ any functions that these two clauses call. Control dependencies
+ do *not* apply to code beyond the end of that "if" statement.
+
+ (*) Control dependencies pair normally with other types of barriers.
+
+ (*) Control dependencies do *not* provide multicopy atomicity. If you
+ need all the CPUs to agree on the ordering of a given store against
+ all other accesses, use smp_mb().
+
+ (*) Compilers do not understand control dependencies. It is therefore
+ your job to ensure that they do not break your code.
diff --git a/tools/memory-model/Documentation/glossary.txt b/tools/memory-model/Documentation/glossary.txt
new file mode 100644
index 000000000000..79acb75d56ea
--- /dev/null
+++ b/tools/memory-model/Documentation/glossary.txt
@@ -0,0 +1,172 @@
+This document contains brief definitions of LKMM-related terms. Like most
+glossaries, it is not intended to be read front to back (except perhaps
+as a way of confirming a diagnosis of OCD), but rather to be searched
+for specific terms.
+
+
+Address Dependency: When the address of a later memory access is computed
+ based on the value returned by an earlier load, an "address
+ dependency" extends from that load extending to the later access.
+ Address dependencies are quite common in RCU read-side critical
+ sections:
+
+ 1 rcu_read_lock();
+ 2 p = rcu_dereference(gp);
+ 3 do_something(p->a);
+ 4 rcu_read_unlock();
+
+ In this case, because the address of "p->a" on line 3 is computed
+ from the value returned by the rcu_dereference() on line 2, the
+ address dependency extends from that rcu_dereference() to that
+ "p->a". In rare cases, optimizing compilers can destroy address
+ dependencies. Please see Documentation/RCU/rcu_dereference.txt
+ for more information.
+
+ See also "Control Dependency" and "Data Dependency".
+
+Acquire: With respect to a lock, acquiring that lock, for example,
+ using spin_lock(). With respect to a non-lock shared variable,
+ a special operation that includes a load and which orders that
+ load before later memory references running on that same CPU.
+ An example special acquire operation is smp_load_acquire(),
+ but atomic_read_acquire() and atomic_xchg_acquire() also include
+ acquire loads.
+
+ When an acquire load returns the value stored by a release store
+ to that same variable, then all operations preceding that store
+ happen before any operations following that load acquire.
+
+ See also "Relaxed" and "Release".
+
+Coherence (co): When one CPU's store to a given variable overwrites
+ either the value from another CPU's store or some later value,
+ there is said to be a coherence link from the second CPU to
+ the first.
+
+ It is also possible to have a coherence link within a CPU, which
+ is a "coherence internal" (coi) link. The term "coherence
+ external" (coe) link is used when it is necessary to exclude
+ the coi case.
+
+ See also "From-reads" and "Reads-from".
+
+Control Dependency: When a later store's execution depends on a test
+ of a value computed from a value returned by an earlier load,
+ a "control dependency" extends from that load to that store.
+ For example:
+
+ 1 if (READ_ONCE(x))
+ 2 WRITE_ONCE(y, 1);
+
+ Here, the control dependency extends from the READ_ONCE() on
+ line 1 to the WRITE_ONCE() on line 2. Control dependencies are
+ fragile, and can be easily destroyed by optimizing compilers.
+ Please see control-dependencies.txt for more information.
+
+ See also "Address Dependency" and "Data Dependency".
+
+Cycle: Memory-barrier pairing is restricted to a pair of CPUs, as the
+ name suggests. And in a great many cases, a pair of CPUs is all
+ that is required. In other cases, the notion of pairing must be
+ extended to additional CPUs, and the result is called a "cycle".
+ In a cycle, each CPU's ordering interacts with that of the next:
+
+ CPU 0 CPU 1 CPU 2
+ WRITE_ONCE(x, 1); WRITE_ONCE(y, 1); WRITE_ONCE(z, 1);
+ smp_mb(); smp_mb(); smp_mb();
+ r0 = READ_ONCE(y); r1 = READ_ONCE(z); r2 = READ_ONCE(x);
+
+ CPU 0's smp_mb() interacts with that of CPU 1, which interacts
+ with that of CPU 2, which in turn interacts with that of CPU 0
+ to complete the cycle. Because of the smp_mb() calls between
+ each pair of memory accesses, the outcome where r0, r1, and r2
+ are all equal to zero is forbidden by LKMM.
+
+ See also "Pairing".
+
+Data Dependency: When the data written by a later store is computed based
+ on the value returned by an earlier load, a "data dependency"
+ extends from that load to that later store. For example:
+
+ 1 r1 = READ_ONCE(x);
+ 2 WRITE_ONCE(y, r1 + 1);
+
+ In this case, the data dependency extends from the READ_ONCE()
+ on line 1 to the WRITE_ONCE() on line 2. Data dependencies are
+ fragile and can be easily destroyed by optimizing compilers.
+ Because optimizing compilers put a great deal of effort into
+ working out what values integer variables might have, this is
+ especially true in cases where the dependency is carried through
+ an integer.
+
+ See also "Address Dependency" and "Control Dependency".
+
+From-Reads (fr): When one CPU's store to a given variable happened
+ too late to affect the value returned by another CPU's
+ load from that same variable, there is said to be a from-reads
+ link from the load to the store.
+
+ It is also possible to have a from-reads link within a CPU, which
+ is a "from-reads internal" (fri) link. The term "from-reads
+ external" (fre) link is used when it is necessary to exclude
+ the fri case.
+
+ See also "Coherence" and "Reads-from".
+
+Fully Ordered: An operation such as smp_mb() that orders all of
+ its CPU's prior accesses with all of that CPU's subsequent
+ accesses, or a marked access such as atomic_add_return()
+ that orders all of its CPU's prior accesses, itself, and
+ all of its CPU's subsequent accesses.
+
+Marked Access: An access to a variable that uses an special function or
+ macro such as "r1 = READ_ONCE(x)" or "smp_store_release(&a, 1)".
+
+ See also "Unmarked Access".
+
+Pairing: "Memory-barrier pairing" reflects the fact that synchronizing
+ data between two CPUs requires that both CPUs their accesses.
+ Memory barriers thus tend to come in pairs, one executed by
+ one of the CPUs and the other by the other CPU. Of course,
+ pairing also occurs with other types of operations, so that a
+ smp_store_release() pairs with an smp_load_acquire() that reads
+ the value stored.
+
+ See also "Cycle".
+
+Reads-From (rf): When one CPU's load returns the value stored by some other
+ CPU, there is said to be a reads-from link from the second
+ CPU's store to the first CPU's load. Reads-from links have the
+ nice property that time must advance from the store to the load,
+ which means that algorithms using reads-from links can use lighter
+ weight ordering and synchronization compared to algorithms using
+ coherence and from-reads links.
+
+ It is also possible to have a reads-from link within a CPU, which
+ is a "reads-from internal" (rfi) link. The term "reads-from
+ external" (rfe) link is used when it is necessary to exclude
+ the rfi case.
+
+ See also Coherence" and "From-reads".
+
+Relaxed: A marked access that does not imply ordering, for example, a
+ READ_ONCE(), WRITE_ONCE(), a non-value-returning read-modify-write
+ operation, or a value-returning read-modify-write operation whose
+ name ends in "_relaxed".
+
+ See also "Acquire" and "Release".
+
+Release: With respect to a lock, releasing that lock, for example,
+ using spin_unlock(). With respect to a non-lock shared variable,
+ a special operation that includes a store and which orders that
+ store after earlier memory references that ran on that same CPU.
+ An example special release store is smp_store_release(), but
+ atomic_set_release() and atomic_cmpxchg_release() also include
+ release stores.
+
+ See also "Acquire" and "Relaxed".
+
+Unmarked Access: An access to a variable that uses normal C-language
+ syntax, for example, "a = b[2]";
+
+ See also "Marked Access".
diff --git a/tools/memory-model/Documentation/litmus-tests.txt b/tools/memory-model/Documentation/litmus-tests.txt
index 2f840dcd15cf..8a9d5d2787f9 100644
--- a/tools/memory-model/Documentation/litmus-tests.txt
+++ b/tools/memory-model/Documentation/litmus-tests.txt
@@ -946,6 +946,23 @@ Limitations of the Linux-kernel memory model (LKMM) include:
carrying a dependency, then the compiler can break that dependency
by substituting a constant of that value.

+ Conversely, LKMM sometimes doesn't recognize that a particular
+ optimization is not allowed, and as a result, thinks that a
+ dependency is not present (because the optimization would break it).
+ The memory model misses some pretty obvious control dependencies
+ because of this limitation. A simple example is:
+
+ r1 = READ_ONCE(x);
+ if (r1 == 0)
+ smp_mb();
+ WRITE_ONCE(y, 1);
+
+ There is a control dependency from the READ_ONCE to the WRITE_ONCE,
+ even when r1 is nonzero, but LKMM doesn't realize this and thinks
+ that the write may execute before the read if r1 != 0. (Yes, that
+ doesn't make sense if you think about it, but the memory model's
+ intelligence is limited.)
+
2. Multiple access sizes for a single variable are not supported,
and neither are misaligned or partially overlapping accesses.

diff --git a/tools/memory-model/Documentation/ordering.txt b/tools/memory-model/Documentation/ordering.txt
new file mode 100644
index 000000000000..9b0949d3f5ec
--- /dev/null
+++ b/tools/memory-model/Documentation/ordering.txt
@@ -0,0 +1,556 @@
+This document gives an overview of the categories of memory-ordering
+operations provided by the Linux-kernel memory model (LKMM).
+
+
+Categories of Ordering
+======================
+
+This section lists LKMM's three top-level categories of memory-ordering
+operations in decreasing order of strength:
+
+1. Barriers (also known as "fences"). A barrier orders some or
+ all of the CPU's prior operations against some or all of its
+ subsequent operations.
+
+2. Ordered memory accesses. These operations order themselves
+ against some or all of the CPU's prior accesses or some or all
+ of the CPU's subsequent accesses, depending on the subcategory
+ of the operation.
+
+3. Unordered accesses, as the name indicates, have no ordering
+ properties except to the extent that they interact with an
+ operation in the previous categories. This being the real world,
+ some of these "unordered" operations provide limited ordering
+ in some special situations.
+
+Each of the above categories is described in more detail by one of the
+following sections.
+
+
+Barriers
+========
+
+Each of the following categories of barriers is described in its own
+subsection below:
+
+a. Full memory barriers.
+
+b. Read-modify-write (RMW) ordering augmentation barriers.
+
+c. Write memory barrier.
+
+d. Read memory barrier.
+
+e. Compiler barrier.
+
+Note well that many of these primitives generate absolutely no code
+in kernels built with CONFIG_SMP=n. Therefore, if you are writing
+a device driver, which must correctly order accesses to a physical
+device even in kernels built with CONFIG_SMP=n, please use the
+ordering primitives provided for that purpose. For example, instead of
+smp_mb(), use mb(). See the "Linux Kernel Device Drivers" book or the
+https://lwn.net/Articles/698014/ article for more information.
+
+
+Full Memory Barriers
+--------------------
+
+The Linux-kernel primitives that provide full ordering include:
+
+o The smp_mb() full memory barrier.
+
+o Value-returning RMW atomic operations whose names do not end in
+ _acquire, _release, or _relaxed.
+
+o RCU's grace-period primitives.
+
+First, the smp_mb() full memory barrier orders all of the CPU's prior
+accesses against all subsequent accesses from the viewpoint of all CPUs.
+In other words, all CPUs will agree that any earlier action taken
+by that CPU happened before any later action taken by that same CPU.
+For example, consider the following:
+
+ WRITE_ONCE(x, 1);
+ smp_mb(); // Order store to x before load from y.
+ r1 = READ_ONCE(y);
+
+All CPUs will agree that the store to "x" happened before the load
+from "y", as indicated by the comment. And yes, please comment your
+memory-ordering primitives. It is surprisingly hard to remember their
+purpose after even a few months.
+
+Second, some RMW atomic operations provide full ordering. These
+operations include value-returning RMW atomic operations (that is, those
+with non-void return types) whose names do not end in _acquire, _release,
+or _relaxed. Examples include atomic_add_return(), atomic_dec_and_test(),
+cmpxchg(), and xchg(). Note that conditional RMW atomic operations such
+as cmpxchg() are only guaranteed to provide ordering when they succeed.
+When RMW atomic operations provide full ordering, they partition the
+CPU's accesses into three groups:
+
+1. All code that executed prior to the RMW atomic operation.
+
+2. The RMW atomic operation itself.
+
+3. All code that executed after the RMW atomic operation.
+
+All CPUs will agree that any operation in a given partition happened
+before any operation in a higher-numbered partition.
+
+In contrast, non-value-returning RMW atomic operations (that is, those
+with void return types) do not guarantee any ordering whatsoever. Nor do
+value-returning RMW atomic operations whose names end in _relaxed.
+Examples of the former include atomic_inc() and atomic_dec(),
+while examples of the latter include atomic_cmpxchg_relaxed() and
+atomic_xchg_relaxed(). Similarly, value-returning non-RMW atomic
+operations such as atomic_read() do not guarantee full ordering, and
+are covered in the later section on unordered operations.
+
+Value-returning RMW atomic operations whose names end in _acquire or
+_release provide limited ordering, and will be described later in this
+document.
+
+Finally, RCU's grace-period primitives provide full ordering. These
+primitives include synchronize_rcu(), synchronize_rcu_expedited(),
+synchronize_srcu() and so on. However, these primitives have orders
+of magnitude greater overhead than smp_mb(), atomic_xchg(), and so on.
+Furthermore, RCU's grace-period primitives can only be invoked in
+sleepable contexts. Therefore, RCU's grace-period primitives are
+typically instead used to provide ordering against RCU read-side critical
+sections, as documented in their comment headers. But of course if you
+need a synchronize_rcu() to interact with readers, it costs you nothing
+to also rely on its additional full-memory-barrier semantics. Just please
+carefully comment this, otherwise your future self will hate you.
+
+
+RMW Ordering Augmentation Barriers
+----------------------------------
+
+As noted in the previous section, non-value-returning RMW operations
+such as atomic_inc() and atomic_dec() guarantee no ordering whatsoever.
+Nevertheless, a number of popular CPU families, including x86, provide
+full ordering for these primitives. One way to obtain full ordering on
+all architectures is to add a call to smp_mb():
+
+ WRITE_ONCE(x, 1);
+ atomic_inc(&my_counter);
+ smp_mb(); // Inefficient on x86!!!
+ r1 = READ_ONCE(y);
+
+This works, but the added smp_mb() adds needless overhead for
+x86, on which atomic_inc() provides full ordering all by itself.
+The smp_mb__after_atomic() primitive can be used instead:
+
+ WRITE_ONCE(x, 1);
+ atomic_inc(&my_counter);
+ smp_mb__after_atomic(); // Order store to x before load from y.
+ r1 = READ_ONCE(y);
+
+The smp_mb__after_atomic() primitive emits code only on CPUs whose
+atomic_inc() implementations do not guarantee full ordering, thus
+incurring no unnecessary overhead on x86. There are a number of
+variations on the smp_mb__*() theme:
+
+o smp_mb__before_atomic(), which provides full ordering prior
+ to an unordered RMW atomic operation.
+
+o smp_mb__after_atomic(), which, as shown above, provides full
+ ordering subsequent to an unordered RMW atomic operation.
+
+o smp_mb__after_spinlock(), which provides full ordering subsequent
+ to a successful spinlock acquisition. Note that spin_lock() is
+ always successful but spin_trylock() might not be.
+
+o smp_mb__after_srcu_read_unlock(), which provides full ordering
+ subsequent to an srcu_read_unlock().
+
+It is bad practice to place code between the smp__*() primitive and the
+operation whose ordering that it is augmenting. The reason is that the
+ordering of this intervening code will differ from one CPU architecture
+to another.
+
+
+Write Memory Barrier
+--------------------
+
+The Linux kernel's write memory barrier is smp_wmb(). If a CPU executes
+the following code:
+
+ WRITE_ONCE(x, 1);
+ smp_wmb();
+ WRITE_ONCE(y, 1);
+
+Then any given CPU will see the write to "x" has having happened before
+the write to "y". However, you are usually better off using a release
+store, as described in the "Release Operations" section below.
+
+Note that smp_wmb() might fail to provide ordering for unmarked C-language
+stores because profile-driven optimization could determine that the
+value being overwritten is almost always equal to the new value. Such a
+compiler might then reasonably decide to transform "x = 1" and "y = 1"
+as follows:
+
+ if (x != 1)
+ x = 1;
+ smp_wmb(); // BUG: does not order the reads!!!
+ if (y != 1)
+ y = 1;
+
+Therefore, if you need to use smp_wmb() with unmarked C-language writes,
+you will need to make sure that none of the compilers used to build
+the Linux kernel carry out this sort of transformation, both now and in
+the future.
+
+
+Read Memory Barrier
+-------------------
+
+The Linux kernel's read memory barrier is smp_rmb(). If a CPU executes
+the following code:
+
+ r0 = READ_ONCE(y);
+ smp_rmb();
+ r1 = READ_ONCE(x);
+
+Then any given CPU will see the read from "y" as having preceded the read from
+"x". However, you are usually better off using an acquire load, as described
+in the "Acquire Operations" section below.
+
+Compiler Barrier
+----------------
+
+The Linux kernel's compiler barrier is barrier(). This primitive
+prohibits compiler code-motion optimizations that might move memory
+references across the point in the code containing the barrier(), but
+does not constrain hardware memory ordering. For example, this can be
+used to prevent to compiler from moving code across an infinite loop:
+
+ WRITE_ONCE(x, 1);
+ while (dontstop)
+ barrier();
+ r1 = READ_ONCE(y);
+
+Without the barrier(), the compiler would be within its rights to move the
+WRITE_ONCE() to follow the loop. This code motion could be problematic
+in the case where an interrupt handler terminates the loop. Another way
+to handle this is to use READ_ONCE() for the load of "dontstop".
+
+Note that the barriers discussed previously use barrier() or its low-level
+equivalent in their implementations.
+
+
+Ordered Memory Accesses
+=======================
+
+The Linux kernel provides a wide variety of ordered memory accesses:
+
+a. Release operations.
+
+b. Acquire operations.
+
+c. RCU read-side ordering.
+
+d. Control dependencies.
+
+Each of the above categories has its own section below.
+
+
+Release Operations
+------------------
+
+Release operations include smp_store_release(), atomic_set_release(),
+rcu_assign_pointer(), and value-returning RMW operations whose names
+end in _release. These operations order their own store against all
+of the CPU's prior memory accesses. Release operations often provide
+improved readability and performance compared to explicit barriers.
+For example, use of smp_store_release() saves a line compared to the
+smp_wmb() example above:
+
+ WRITE_ONCE(x, 1);
+ smp_store_release(&y, 1);
+
+More important, smp_store_release() makes it easier to connect up the
+different pieces of the concurrent algorithm. The variable stored to
+by the smp_store_release(), in this case "y", will normally be used in
+an acquire operation in other parts of the concurrent algorithm.
+
+To see the performance advantages, suppose that the above example read
+from "x" instead of writing to it. Then an smp_wmb() could not guarantee
+ordering, and an smp_mb() would be needed instead:
+
+ r1 = READ_ONCE(x);
+ smp_mb();
+ WRITE_ONCE(y, 1);
+
+But smp_mb() often incurs much higher overhead than does
+smp_store_release(), which still provides the needed ordering of "x"
+against "y". On x86, the version using smp_store_release() might compile
+to a simple load instruction followed by a simple store instruction.
+In contrast, the smp_mb() compiles to an expensive instruction that
+provides the needed ordering.
+
+There is a wide variety of release operations:
+
+o Store operations, including not only the aforementioned
+ smp_store_release(), but also atomic_set_release(), and
+ atomic_long_set_release().
+
+o RCU's rcu_assign_pointer() operation. This is the same as
+ smp_store_release() except that: (1) It takes the pointer to
+ be assigned to instead of a pointer to that pointer, (2) It
+ is intended to be used in conjunction with rcu_dereference()
+ and similar rather than smp_load_acquire(), and (3) It checks
+ for an RCU-protected pointer in "sparse" runs.
+
+o Value-returning RMW operations whose names end in _release,
+ such as atomic_fetch_add_release() and cmpxchg_release().
+ Note that release ordering is guaranteed only against the
+ memory-store portion of the RMW operation, and not against the
+ memory-load portion. Note also that conditional operations such
+ as cmpxchg_release() are only guaranteed to provide ordering
+ when they succeed.
+
+As mentioned earlier, release operations are often paired with acquire
+operations, which are the subject of the next section.
+
+
+Acquire Operations
+------------------
+
+Acquire operations include smp_load_acquire(), atomic_read_acquire(),
+and value-returning RMW operations whose names end in _acquire. These
+operations order their own load against all of the CPU's subsequent
+memory accesses. Acquire operations often provide improved performance
+and readability compared to explicit barriers. For example, use of
+smp_load_acquire() saves a line compared to the smp_rmb() example above:
+
+ r0 = smp_load_acquire(&y);
+ r1 = READ_ONCE(x);
+
+As with smp_store_release(), this also makes it easier to connect
+the different pieces of the concurrent algorithm by looking for the
+smp_store_release() that stores to "y". In addition, smp_load_acquire()
+improves upon smp_rmb() by ordering against subsequent stores as well
+as against subsequent loads.
+
+There are a couple of categories of acquire operations:
+
+o Load operations, including not only the aforementioned
+ smp_load_acquire(), but also atomic_read_acquire(), and
+ atomic64_read_acquire().
+
+o Value-returning RMW operations whose names end in _acquire,
+ such as atomic_xchg_acquire() and atomic_cmpxchg_acquire().
+ Note that acquire ordering is guaranteed only against the
+ memory-load portion of the RMW operation, and not against the
+ memory-store portion. Note also that conditional operations
+ such as atomic_cmpxchg_acquire() are only guaranteed to provide
+ ordering when they succeed.
+
+Symmetry being what it is, acquire operations are often paired with the
+release operations covered earlier. For example, consider the following
+example, where task0() and task1() execute concurrently:
+
+ void task0(void)
+ {
+ WRITE_ONCE(x, 1);
+ smp_store_release(&y, 1);
+ }
+
+ void task1(void)
+ {
+ r0 = smp_load_acquire(&y);
+ r1 = READ_ONCE(x);
+ }
+
+If "x" and "y" are both initially zero, then either r0's final value
+will be zero or r1's final value will be one, thus providing the required
+ordering.
+
+
+RCU Read-Side Ordering
+----------------------
+
+This category includes read-side markers such as rcu_read_lock()
+and rcu_read_unlock() as well as pointer-traversal primitives such as
+rcu_dereference() and srcu_dereference().
+
+Compared to locking primitives and RMW atomic operations, markers
+for RCU read-side critical sections incur very low overhead because
+they interact only with the corresponding grace-period primitives.
+For example, the rcu_read_lock() and rcu_read_unlock() markers interact
+with synchronize_rcu(), synchronize_rcu_expedited(), and call_rcu().
+The way this works is that if a given call to synchronize_rcu() cannot
+prove that it started before a given call to rcu_read_lock(), then
+that synchronize_rcu() must block until the matching rcu_read_unlock()
+is reached. For more information, please see the synchronize_rcu()
+docbook header comment and the material in Documentation/RCU.
+
+RCU's pointer-traversal primitives, including rcu_dereference() and
+srcu_dereference(), order their load (which must be a pointer) against any
+of the CPU's subsequent memory accesses whose address has been calculated
+from the value loaded. There is said to be an *address dependency*
+from the value returned by the rcu_dereference() or srcu_dereference()
+to that subsequent memory access.
+
+A call to rcu_dereference() for a given RCU-protected pointer is
+usually paired with a call to a call to rcu_assign_pointer() for that
+same pointer in much the same way that a call to smp_load_acquire() is
+paired with a call to smp_store_release(). Calls to rcu_dereference()
+and rcu_assign_pointer are often buried in other APIs, for example,
+the RCU list API members defined in include/linux/rculist.h. For more
+information, please see the docbook headers in that file, the most
+recent LWN article on the RCU API (https://lwn.net/Articles/777036/),
+and of course the material in Documentation/RCU.
+
+If the pointer value is manipulated between the rcu_dereference()
+that returned it and a later dereference(), please read
+Documentation/RCU/rcu_dereference.rst. It can also be quite helpful to
+review uses in the Linux kernel.
+
+
+Control Dependencies
+--------------------
+
+A control dependency extends from a marked load (READ_ONCE() or stronger)
+through an "if" condition to a marked store (WRITE_ONCE() or stronger)
+that is executed only by one of the legs of that "if" statement.
+Control dependencies are so named because they are mediated by
+control-flow instructions such as comparisons and conditional branches.
+
+In short, you can use a control dependency to enforce ordering between
+an READ_ONCE() and a WRITE_ONCE() when there is an "if" condition
+between them. The canonical example is as follows:
+
+ q = READ_ONCE(a);
+ if (q)
+ WRITE_ONCE(b, 1);
+
+In this case, all CPUs would see the read from "a" as happening before
+the write to "b".
+
+However, control dependencies are easily destroyed by compiler
+optimizations, so any use of control dependencies must take into account
+all of the compilers used to build the Linux kernel. Please see the
+"control-dependencies.txt" file for more information.
+
+
+Unordered Accesses
+==================
+
+Each of these two categories of unordered accesses has a section below:
+
+a. Unordered marked operations.
+
+b. Unmarked C-language accesses.
+
+
+Unordered Marked Operations
+---------------------------
+
+Unordered operations to different variables are just that, unordered.
+However, if a group of CPUs apply these operations to a single variable,
+all the CPUs will agree on the operation order. Of course, the ordering
+of unordered marked accesses can also be constrained using the mechanisms
+described earlier in this document.
+
+These operations come in three categories:
+
+o Marked writes, such as WRITE_ONCE() and atomic_set(). These
+ primitives required the compiler to emit the corresponding store
+ instructions in the expected execution order, thus suppressing
+ a number of destructive optimizations. However, they provide no
+ hardware ordering guarantees, and in fact many CPUs will happily
+ reorder marked writes with each other or with other unordered
+ operations, unless these operations are to the same variable.
+
+o Marked reads, such as READ_ONCE() and atomic_read(). These
+ primitives required the compiler to emit the corresponding load
+ instructions in the expected execution order, thus suppressing
+ a number of destructive optimizations. However, they provide no
+ hardware ordering guarantees, and in fact many CPUs will happily
+ reorder marked reads with each other or with other unordered
+ operations, unless these operations are to the same variable.
+
+o Unordered RMW atomic operations. These are non-value-returning
+ RMW atomic operations whose names do not end in _acquire or
+ _release, and also value-returning RMW operations whose names
+ end in _relaxed. Examples include atomic_add(), atomic_or(),
+ and atomic64_fetch_xor_relaxed(). These operations do carry
+ out the specified RMW operation atomically, for example, five
+ concurrent atomic_inc() operations applied to a given variable
+ will reliably increase the value of that variable by five.
+ However, many CPUs will happily reorder these operations with
+ each other or with other unordered operations.
+
+ This category of operations can be efficiently ordered using
+ smp_mb__before_atomic() and smp_mb__after_atomic(), as was
+ discussed in the "RMW Ordering Augmentation Barriers" section.
+
+In short, these operations can be freely reordered unless they are all
+operating on a single variable or unless they are constrained by one of
+the operations called out earlier in this document.
+
+
+Unmarked C-Language Accesses
+----------------------------
+
+Unmarked C-language accesses are normal variable accesses to normal
+variables, that is, to variables that are not "volatile" and are not
+C11 atomic variables. These operations provide no ordering guarantees,
+and further do not guarantee "atomic" access. For example, the compiler
+might (and sometimes does) split a plain C-language store into multiple
+smaller stores. A load from that same variable running on some other
+CPU while such a store is executing might see a value that is a mashup
+of the old value and the new value.
+
+Unmarked C-language accesses are unordered, and are also subject to
+any number of compiler optimizations, many of which can break your
+concurrent code. It is possible to used unmarked C-language accesses for
+shared variables that are subject to concurrent access, but great care
+is required on an ongoing basis. The compiler-constraining barrier()
+primitive can be helpful, as can the various ordering primitives discussed
+in this document. It nevertheless bears repeating that use of unmarked
+C-language accesses requires careful attention to not just your code,
+but to all the compilers that might be used to build it. Such compilers
+might replace a series of loads with a single load, and might replace
+a series of stores with a single store. Some compilers will even split
+a single store into multiple smaller stores.
+
+But there are some ways of using unmarked C-language accesses for shared
+variables without such worries:
+
+o Guard all accesses to a given variable by a particular lock,
+ so that there are never concurrent conflicting accesses to
+ that variable. (There are "conflicting accesses" when
+ (1) at least one of the concurrent accesses to a variable is an
+ unmarked C-language access and (2) when at least one of those
+ accesses is a write, whether marked or not.)
+
+o As above, but using other synchronization primitives such
+ as reader-writer locks or sequence locks.
+
+o Use locking or other means to ensure that all concurrent accesses
+ to a given variable are reads.
+
+o Restrict use of a given variable to statistics or heuristics
+ where the occasional bogus value can be tolerated.
+
+o Declare the accessed variables as C11 atomics.
+ https://lwn.net/Articles/691128/
+
+o Declare the accessed variables as "volatile".
+
+If you need to live more dangerously, please do take the time to
+understand the compilers. One place to start is these two LWN
+articles:
+
+Who's afraid of a big bad optimizing compiler?
+ https://lwn.net/Articles/793253
+Calibrating your fear of big bad optimizing compilers
+ https://lwn.net/Articles/799218
+
+Used properly, unmarked C-language accesses can reduce overhead on
+fastpaths. However, the price is great care and continual attention
+to your compiler as new versions come out and as new optimizations
+are enabled.
diff --git a/tools/memory-model/README b/tools/memory-model/README
index c8144d4aafa0..39d08d1f0443 100644
--- a/tools/memory-model/README
+++ b/tools/memory-model/README
@@ -161,26 +161,8 @@ running LKMM litmus tests.
DESCRIPTION OF FILES
====================

-Documentation/cheatsheet.txt
- Quick-reference guide to the Linux-kernel memory model.
-
-Documentation/explanation.txt
- Describes the memory model in detail.
-
-Documentation/litmus-tests.txt
- Describes the format, features, capabilities, and limitations
- of the litmus tests that LKMM can evaluate.
-
-Documentation/recipes.txt
- Lists common memory-ordering patterns.
-
-Documentation/references.txt
- Provides background reading.
-
-Documentation/simple.txt
- Starting point for someone new to Linux-kernel concurrency.
- And also for those needing a reminder of the simpler approaches
- to concurrency!
+Documentation/README
+ Guide to the other documents in the Documentation/ directory.

linux-kernel.bell
Categorizes the relevant instructions, including memory
diff --git a/tools/memory-model/litmus-tests/CoRR+poonceonce+Once.litmus b/tools/memory-model/litmus-tests/CoRR+poonceonce+Once.litmus
index 967f9f2a6226..772544f03fb5 100644
--- a/tools/memory-model/litmus-tests/CoRR+poonceonce+Once.litmus
+++ b/tools/memory-model/litmus-tests/CoRR+poonceonce+Once.litmus
@@ -7,7 +7,9 @@ C CoRR+poonceonce+Once
* reads from the same variable are ordered.
*)

-{}
+{
+ int x;
+}

P0(int *x)
{
diff --git a/tools/memory-model/litmus-tests/CoRW+poonceonce+Once.litmus b/tools/memory-model/litmus-tests/CoRW+poonceonce+Once.litmus
index 4635739f3974..5faae98f7ffb 100644
--- a/tools/memory-model/litmus-tests/CoRW+poonceonce+Once.litmus
+++ b/tools/memory-model/litmus-tests/CoRW+poonceonce+Once.litmus
@@ -7,7 +7,9 @@ C CoRW+poonceonce+Once
* a given variable and a later write to that same variable are ordered.
*)

-{}
+{
+ int x;
+}

P0(int *x)
{
diff --git a/tools/memory-model/litmus-tests/CoWR+poonceonce+Once.litmus b/tools/memory-model/litmus-tests/CoWR+poonceonce+Once.litmus
index bb068c92d8da..77c9cc9f8dc6 100644
--- a/tools/memory-model/litmus-tests/CoWR+poonceonce+Once.litmus
+++ b/tools/memory-model/litmus-tests/CoWR+poonceonce+Once.litmus
@@ -7,7 +7,9 @@ C CoWR+poonceonce+Once
* given variable and a later read from that same variable are ordered.
*)

-{}
+{
+ int x;
+}

P0(int *x)
{
diff --git a/tools/memory-model/litmus-tests/CoWW+poonceonce.litmus b/tools/memory-model/litmus-tests/CoWW+poonceonce.litmus
index 0d9f0a958799..85ef746f511a 100644
--- a/tools/memory-model/litmus-tests/CoWW+poonceonce.litmus
+++ b/tools/memory-model/litmus-tests/CoWW+poonceonce.litmus
@@ -7,7 +7,9 @@ C CoWW+poonceonce
* writes to the same variable are ordered.
*)

-{}
+{
+ int x;
+}

P0(int *x)
{
diff --git a/tools/memory-model/litmus-tests/IRIW+fencembonceonces+OnceOnce.litmus b/tools/memory-model/litmus-tests/IRIW+fencembonceonces+OnceOnce.litmus
index e729d2776e89..87aa900125ab 100644
--- a/tools/memory-model/litmus-tests/IRIW+fencembonceonces+OnceOnce.litmus
+++ b/tools/memory-model/litmus-tests/IRIW+fencembonceonces+OnceOnce.litmus
@@ -10,7 +10,10 @@ C IRIW+fencembonceonces+OnceOnce
* process? This litmus test exercises LKMM's "propagation" rule.
*)

-{}
+{
+ int x;
+ int y;
+}

P0(int *x)
{
diff --git a/tools/memory-model/litmus-tests/IRIW+poonceonces+OnceOnce.litmus b/tools/memory-model/litmus-tests/IRIW+poonceonces+OnceOnce.litmus
index 4b54dd6a6cd9..f84022dca555 100644
--- a/tools/memory-model/litmus-tests/IRIW+poonceonces+OnceOnce.litmus
+++ b/tools/memory-model/litmus-tests/IRIW+poonceonces+OnceOnce.litmus
@@ -10,7 +10,10 @@ C IRIW+poonceonces+OnceOnce
* different process?
*)

-{}
+{
+ int x;
+ int y;
+}

P0(int *x)
{
diff --git a/tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus b/tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus
index 094d58df7789..398f624daa77 100644
--- a/tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus
+++ b/tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus
@@ -7,7 +7,12 @@ C ISA2+pooncelock+pooncelock+pombonce
* (in P0() and P1()) is visible to external process P2().
*)

-{}
+{
+ spinlock_t mylock;
+ int x;
+ int y;
+ int z;
+}

P0(int *x, int *y, spinlock_t *mylock)
{
diff --git a/tools/memory-model/litmus-tests/ISA2+poonceonces.litmus b/tools/memory-model/litmus-tests/ISA2+poonceonces.litmus
index b321aa6f4ea5..212a432ba16b 100644
--- a/tools/memory-model/litmus-tests/ISA2+poonceonces.litmus
+++ b/tools/memory-model/litmus-tests/ISA2+poonceonces.litmus
@@ -9,7 +9,11 @@ C ISA2+poonceonces
* of the smp_load_acquire() invocations are replaced by READ_ONCE()?
*)

-{}
+{
+ int x;
+ int y;
+ int z;
+}

P0(int *x, int *y)
{
diff --git a/tools/memory-model/litmus-tests/ISA2+pooncerelease+poacquirerelease+poacquireonce.litmus b/tools/memory-model/litmus-tests/ISA2+pooncerelease+poacquirerelease+poacquireonce.litmus
index 025b0462ec9b..7afd85672ccd 100644
--- a/tools/memory-model/litmus-tests/ISA2+pooncerelease+poacquirerelease+poacquireonce.litmus
+++ b/tools/memory-model/litmus-tests/ISA2+pooncerelease+poacquirerelease+poacquireonce.litmus
@@ -11,7 +11,11 @@ C ISA2+pooncerelease+poacquirerelease+poacquireonce
* (AKA non-rf) link, so release-acquire is all that is needed.
*)

-{}
+{
+ int x;
+ int y;
+ int z;
+}

P0(int *x, int *y)
{
diff --git a/tools/memory-model/litmus-tests/LB+fencembonceonce+ctrlonceonce.litmus b/tools/memory-model/litmus-tests/LB+fencembonceonce+ctrlonceonce.litmus
index 4727f5aaf03b..c8a93c7ee556 100644
--- a/tools/memory-model/litmus-tests/LB+fencembonceonce+ctrlonceonce.litmus
+++ b/tools/memory-model/litmus-tests/LB+fencembonceonce+ctrlonceonce.litmus
@@ -11,7 +11,10 @@ C LB+fencembonceonce+ctrlonceonce
* another control dependency and order would still be maintained.)
*)

-{}
+{
+ int x;
+ int y;
+}

P0(int *x, int *y)
{
diff --git a/tools/memory-model/litmus-tests/LB+poacquireonce+pooncerelease.litmus b/tools/memory-model/litmus-tests/LB+poacquireonce+pooncerelease.litmus
index 07b9904b0e49..2fa029568fa1 100644
--- a/tools/memory-model/litmus-tests/LB+poacquireonce+pooncerelease.litmus
+++ b/tools/memory-model/litmus-tests/LB+poacquireonce+pooncerelease.litmus
@@ -8,7 +8,10 @@ C LB+poacquireonce+pooncerelease
* to the other?
*)

-{}
+{
+ int x;
+ int y;
+}

P0(int *x, int *y)
{
diff --git a/tools/memory-model/litmus-tests/LB+poonceonces.litmus b/tools/memory-model/litmus-tests/LB+poonceonces.litmus
index 74c49cb3c37b..2107306e8625 100644
--- a/tools/memory-model/litmus-tests/LB+poonceonces.litmus
+++ b/tools/memory-model/litmus-tests/LB+poonceonces.litmus
@@ -7,7 +7,10 @@ C LB+poonceonces
* be prevented even with no explicit ordering?
*)

-{}
+{
+ int x;
+ int y;
+}

P0(int *x, int *y)
{
diff --git a/tools/memory-model/litmus-tests/MP+fencewmbonceonce+fencermbonceonce.litmus b/tools/memory-model/litmus-tests/MP+fencewmbonceonce+fencermbonceonce.litmus
index a273da9faa6d..c5c168d92973 100644
--- a/tools/memory-model/litmus-tests/MP+fencewmbonceonce+fencermbonceonce.litmus
+++ b/tools/memory-model/litmus-tests/MP+fencewmbonceonce+fencermbonceonce.litmus
@@ -8,23 +8,26 @@ C MP+fencewmbonceonce+fencermbonceonce
* is usually better to use smp_store_release() and smp_load_acquire().
*)

-{}
+{
+ int buf;
+ int flag;
+}

-P0(int *x, int *y)
+P0(int *buf, int *flag) // Producer
{
- WRITE_ONCE(*x, 1);
+ WRITE_ONCE(*buf, 1);
smp_wmb();
- WRITE_ONCE(*y, 1);
+ WRITE_ONCE(*flag, 1);
}

-P1(int *x, int *y)
+P1(int *buf, int *flag) // Consumer
{
int r0;
int r1;

- r0 = READ_ONCE(*y);
+ r0 = READ_ONCE(*flag);
smp_rmb();
- r1 = READ_ONCE(*x);
+ r1 = READ_ONCE(*buf);
}

-exists (1:r0=1 /\ 1:r1=0)
+exists (1:r0=1 /\ 1:r1=0) (* Bad outcome. *)
diff --git a/tools/memory-model/litmus-tests/MP+onceassign+derefonce.litmus b/tools/memory-model/litmus-tests/MP+onceassign+derefonce.litmus
index 97731b4bbdd8..20ff62649f1e 100644
--- a/tools/memory-model/litmus-tests/MP+onceassign+derefonce.litmus
+++ b/tools/memory-model/litmus-tests/MP+onceassign+derefonce.litmus
@@ -10,25 +10,26 @@ C MP+onceassign+derefonce
*)

{
-y=z;
-z=0;
+ int *p=y;
+ int x;
+ int y=0;
}

-P0(int *x, int **y)
+P0(int *x, int **p) // Producer
{
WRITE_ONCE(*x, 1);
- rcu_assign_pointer(*y, x);
+ rcu_assign_pointer(*p, x);
}

-P1(int *x, int **y)
+P1(int *x, int **p) // Consumer
{
int *r0;
int r1;

rcu_read_lock();
- r0 = rcu_dereference(*y);
+ r0 = rcu_dereference(*p);
r1 = READ_ONCE(*r0);
rcu_read_unlock();
}

-exists (1:r0=x /\ 1:r1=0)
+exists (1:r0=x /\ 1:r1=0) (* Bad outcome. *)
diff --git a/tools/memory-model/litmus-tests/MP+polockmbonce+poacquiresilsil.litmus b/tools/memory-model/litmus-tests/MP+polockmbonce+poacquiresilsil.litmus
index 50f4d62bbf0e..153917ad5dc9 100644
--- a/tools/memory-model/litmus-tests/MP+polockmbonce+poacquiresilsil.litmus
+++ b/tools/memory-model/litmus-tests/MP+polockmbonce+poacquiresilsil.litmus
@@ -11,9 +11,11 @@ C MP+polockmbonce+poacquiresilsil
*)

{
+ spinlock_t lo;
+ int x;
}

-P0(spinlock_t *lo, int *x)
+P0(spinlock_t *lo, int *x) // Producer
{
spin_lock(lo);
smp_mb__after_spinlock();
@@ -21,7 +23,7 @@ P0(spinlock_t *lo, int *x)
spin_unlock(lo);
}

-P1(spinlock_t *lo, int *x)
+P1(spinlock_t *lo, int *x) // Consumer
{
int r1;
int r2;
@@ -32,4 +34,4 @@ P1(spinlock_t *lo, int *x)
r3 = spin_is_locked(lo);
}

-exists (1:r1=1 /\ 1:r2=0 /\ 1:r3=1)
+exists (1:r1=1 /\ 1:r2=0 /\ 1:r3=1) (* Bad outcome. *)
diff --git a/tools/memory-model/litmus-tests/MP+polockonce+poacquiresilsil.litmus b/tools/memory-model/litmus-tests/MP+polockonce+poacquiresilsil.litmus
index abf81e7a0895..aad64397bb8c 100644
--- a/tools/memory-model/litmus-tests/MP+polockonce+poacquiresilsil.litmus
+++ b/tools/memory-model/litmus-tests/MP+polockonce+poacquiresilsil.litmus
@@ -11,16 +11,18 @@ C MP+polockonce+poacquiresilsil
*)

{
+ spinlock_t lo;
+ int x;
}

-P0(spinlock_t *lo, int *x)
+P0(spinlock_t *lo, int *x) // Producer
{
spin_lock(lo);
WRITE_ONCE(*x, 1);
spin_unlock(lo);
}

-P1(spinlock_t *lo, int *x)
+P1(spinlock_t *lo, int *x) // Consumer
{
int r1;
int r2;
@@ -31,4 +33,4 @@ P1(spinlock_t *lo, int *x)
r3 = spin_is_locked(lo);
}

-exists (1:r1=1 /\ 1:r2=0 /\ 1:r3=1)
+exists (1:r1=1 /\ 1:r2=0 /\ 1:r3=1) (* Bad outcome. *)
diff --git a/tools/memory-model/litmus-tests/MP+polocks.litmus b/tools/memory-model/litmus-tests/MP+polocks.litmus
index 712a4fcdf6ce..21cbca6f3be4 100644
--- a/tools/memory-model/litmus-tests/MP+polocks.litmus
+++ b/tools/memory-model/litmus-tests/MP+polocks.litmus
@@ -11,25 +11,29 @@ C MP+polocks
* to see all prior accesses by those other CPUs.
*)

-{}
+{
+ spinlock_t mylock;
+ int buf;
+ int flag;
+}

-P0(int *x, int *y, spinlock_t *mylock)
+P0(int *buf, int *flag, spinlock_t *mylock) // Producer
{
- WRITE_ONCE(*x, 1);
+ WRITE_ONCE(*buf, 1);
spin_lock(mylock);
- WRITE_ONCE(*y, 1);
+ WRITE_ONCE(*flag, 1);
spin_unlock(mylock);
}

-P1(int *x, int *y, spinlock_t *mylock)
+P1(int *buf, int *flag, spinlock_t *mylock) // Consumer
{
int r0;
int r1;

spin_lock(mylock);
- r0 = READ_ONCE(*y);
+ r0 = READ_ONCE(*flag);
spin_unlock(mylock);
- r1 = READ_ONCE(*x);
+ r1 = READ_ONCE(*buf);
}

-exists (1:r0=1 /\ 1:r1=0)
+exists (1:r0=1 /\ 1:r1=0) (* Bad outcome. *)
diff --git a/tools/memory-model/litmus-tests/MP+poonceonces.litmus b/tools/memory-model/litmus-tests/MP+poonceonces.litmus
index 172f0145301c..9f9769d647c7 100644
--- a/tools/memory-model/litmus-tests/MP+poonceonces.litmus
+++ b/tools/memory-model/litmus-tests/MP+poonceonces.litmus
@@ -7,21 +7,24 @@ C MP+poonceonces
* no ordering at all?
*)

-{}
+{
+ int buf;
+ int flag;
+}

-P0(int *x, int *y)
+P0(int *buf, int *flag) // Producer
{
- WRITE_ONCE(*x, 1);
- WRITE_ONCE(*y, 1);
+ WRITE_ONCE(*buf, 1);
+ WRITE_ONCE(*flag, 1);
}

-P1(int *x, int *y)
+P1(int *buf, int *flag) // Consumer
{
int r0;
int r1;

- r0 = READ_ONCE(*y);
- r1 = READ_ONCE(*x);
+ r0 = READ_ONCE(*flag);
+ r1 = READ_ONCE(*buf);
}

-exists (1:r0=1 /\ 1:r1=0)
+exists (1:r0=1 /\ 1:r1=0) (* Bad outcome. *)
diff --git a/tools/memory-model/litmus-tests/MP+pooncerelease+poacquireonce.litmus b/tools/memory-model/litmus-tests/MP+pooncerelease+poacquireonce.litmus
index d52c68429722..cbe28e733443 100644
--- a/tools/memory-model/litmus-tests/MP+pooncerelease+poacquireonce.litmus
+++ b/tools/memory-model/litmus-tests/MP+pooncerelease+poacquireonce.litmus
@@ -8,21 +8,24 @@ C MP+pooncerelease+poacquireonce
* pattern.
*)

-{}
+{
+ int buf;
+ int flag;
+}

-P0(int *x, int *y)
+P0(int *buf, int *flag) // Producer
{
- WRITE_ONCE(*x, 1);
- smp_store_release(y, 1);
+ WRITE_ONCE(*buf, 1);
+ smp_store_release(flag, 1);
}

-P1(int *x, int *y)
+P1(int *buf, int *flag) // Consumer
{
int r0;
int r1;

- r0 = smp_load_acquire(y);
- r1 = READ_ONCE(*x);
+ r0 = smp_load_acquire(flag);
+ r1 = READ_ONCE(*buf);
}

-exists (1:r0=1 /\ 1:r1=0)
+exists (1:r0=1 /\ 1:r1=0) (* Bad outcome. *)
diff --git a/tools/memory-model/litmus-tests/MP+porevlocks.litmus b/tools/memory-model/litmus-tests/MP+porevlocks.litmus
index 72c9276b363e..012041bd4feb 100644
--- a/tools/memory-model/litmus-tests/MP+porevlocks.litmus
+++ b/tools/memory-model/litmus-tests/MP+porevlocks.litmus
@@ -11,25 +11,29 @@ C MP+porevlocks
* see all prior accesses by those other CPUs.
*)

-{}
+{
+ spinlock_t mylock;
+ int buf;
+ int flag;
+}

-P0(int *x, int *y, spinlock_t *mylock)
+P0(int *buf, int *flag, spinlock_t *mylock) // Consumer
{
int r0;
int r1;

- r0 = READ_ONCE(*y);
+ r0 = READ_ONCE(*flag);
spin_lock(mylock);
- r1 = READ_ONCE(*x);
+ r1 = READ_ONCE(*buf);
spin_unlock(mylock);
}

-P1(int *x, int *y, spinlock_t *mylock)
+P1(int *buf, int *flag, spinlock_t *mylock) // Producer
{
spin_lock(mylock);
- WRITE_ONCE(*x, 1);
+ WRITE_ONCE(*buf, 1);
spin_unlock(mylock);
- WRITE_ONCE(*y, 1);
+ WRITE_ONCE(*flag, 1);
}

-exists (0:r0=1 /\ 0:r1=0)
+exists (0:r0=1 /\ 0:r1=0) (* Bad outcome. *)
diff --git a/tools/memory-model/litmus-tests/R+fencembonceonces.litmus b/tools/memory-model/litmus-tests/R+fencembonceonces.litmus
index 222a0b850b4a..af9463b39b4a 100644
--- a/tools/memory-model/litmus-tests/R+fencembonceonces.litmus
+++ b/tools/memory-model/litmus-tests/R+fencembonceonces.litmus
@@ -9,7 +9,10 @@ C R+fencembonceonces
* cause the resulting test to be allowed.
*)

-{}
+{
+ int x;
+ int y;
+}

P0(int *x, int *y)
{
diff --git a/tools/memory-model/litmus-tests/R+poonceonces.litmus b/tools/memory-model/litmus-tests/R+poonceonces.litmus
index 5386f128a131..bcd5574e304a 100644
--- a/tools/memory-model/litmus-tests/R+poonceonces.litmus
+++ b/tools/memory-model/litmus-tests/R+poonceonces.litmus
@@ -8,7 +8,10 @@ C R+poonceonces
* store propagation delays.
*)

-{}
+{
+ int x;
+ int y;
+}

P0(int *x, int *y)
{
diff --git a/tools/memory-model/litmus-tests/S+fencewmbonceonce+poacquireonce.litmus b/tools/memory-model/litmus-tests/S+fencewmbonceonce+poacquireonce.litmus
index 18479823cd6c..c36341d1aed6 100644
--- a/tools/memory-model/litmus-tests/S+fencewmbonceonce+poacquireonce.litmus
+++ b/tools/memory-model/litmus-tests/S+fencewmbonceonce+poacquireonce.litmus
@@ -7,7 +7,10 @@ C S+fencewmbonceonce+poacquireonce
* store against a subsequent store?
*)

-{}
+{
+ int x;
+ int y;
+}

P0(int *x, int *y)
{
diff --git a/tools/memory-model/litmus-tests/S+poonceonces.litmus b/tools/memory-model/litmus-tests/S+poonceonces.litmus
index 8c9c2f81a580..7775c23143a0 100644
--- a/tools/memory-model/litmus-tests/S+poonceonces.litmus
+++ b/tools/memory-model/litmus-tests/S+poonceonces.litmus
@@ -9,7 +9,10 @@ C S+poonceonces
* READ_ONCE(), is ordering preserved?
*)

-{}
+{
+ int x;
+ int y;
+}

P0(int *x, int *y)
{
diff --git a/tools/memory-model/litmus-tests/SB+fencembonceonces.litmus b/tools/memory-model/litmus-tests/SB+fencembonceonces.litmus
index ed5fff18d223..833cdfeb7c09 100644
--- a/tools/memory-model/litmus-tests/SB+fencembonceonces.litmus
+++ b/tools/memory-model/litmus-tests/SB+fencembonceonces.litmus
@@ -9,7 +9,10 @@ C SB+fencembonceonces
* suffice, but not much else.)
*)

-{}
+{
+ int x;
+ int y;
+}

P0(int *x, int *y)
{
diff --git a/tools/memory-model/litmus-tests/SB+poonceonces.litmus b/tools/memory-model/litmus-tests/SB+poonceonces.litmus
index 10d550730b25..c92211ecbfdf 100644
--- a/tools/memory-model/litmus-tests/SB+poonceonces.litmus
+++ b/tools/memory-model/litmus-tests/SB+poonceonces.litmus
@@ -8,7 +8,10 @@ C SB+poonceonces
* variable that the preceding process reads.
*)

-{}
+{
+ int x;
+ int y;
+}

P0(int *x, int *y)
{
diff --git a/tools/memory-model/litmus-tests/SB+rfionceonce-poonceonces.litmus b/tools/memory-model/litmus-tests/SB+rfionceonce-poonceonces.litmus
index 04a16603660b..84344b455eb7 100644
--- a/tools/memory-model/litmus-tests/SB+rfionceonce-poonceonces.litmus
+++ b/tools/memory-model/litmus-tests/SB+rfionceonce-poonceonces.litmus
@@ -6,7 +6,10 @@ C SB+rfionceonce-poonceonces
* This litmus test demonstrates that LKMM is not fully multicopy atomic.
*)

-{}
+{
+ int x;
+ int y;
+}

P0(int *x, int *y)
{
diff --git a/tools/memory-model/litmus-tests/WRC+poonceonces+Once.litmus b/tools/memory-model/litmus-tests/WRC+poonceonces+Once.litmus
index 6a2bc12a1af1..431494708611 100644
--- a/tools/memory-model/litmus-tests/WRC+poonceonces+Once.litmus
+++ b/tools/memory-model/litmus-tests/WRC+poonceonces+Once.litmus
@@ -8,7 +8,10 @@ C WRC+poonceonces+Once
* test has no ordering at all.
*)

-{}
+{
+ int x;
+ int y;
+}

P0(int *x)
{
diff --git a/tools/memory-model/litmus-tests/WRC+pooncerelease+fencermbonceonce+Once.litmus b/tools/memory-model/litmus-tests/WRC+pooncerelease+fencermbonceonce+Once.litmus
index e9947250d7de..554999c64db5 100644
--- a/tools/memory-model/litmus-tests/WRC+pooncerelease+fencermbonceonce+Once.litmus
+++ b/tools/memory-model/litmus-tests/WRC+pooncerelease+fencermbonceonce+Once.litmus
@@ -10,7 +10,10 @@ C WRC+pooncerelease+fencermbonceonce+Once
* is A-cumulative in LKMM.
*)

-{}
+{
+ int x;
+ int y;
+}

P0(int *x)
{
diff --git a/tools/memory-model/litmus-tests/Z6.0+pooncelock+poonceLock+pombonce.litmus b/tools/memory-model/litmus-tests/Z6.0+pooncelock+poonceLock+pombonce.litmus
index 415248fb6699..265a95ffef13 100644
--- a/tools/memory-model/litmus-tests/Z6.0+pooncelock+poonceLock+pombonce.litmus
+++ b/tools/memory-model/litmus-tests/Z6.0+pooncelock+poonceLock+pombonce.litmus
@@ -9,7 +9,12 @@ C Z6.0+pooncelock+poonceLock+pombonce
* by CPUs not holding that lock.
*)

-{}
+{
+ spinlock_t mylock;
+ int x;
+ int y;
+ int z;
+}

P0(int *x, int *y, spinlock_t *mylock)
{
diff --git a/tools/memory-model/litmus-tests/Z6.0+pooncelock+pooncelock+pombonce.litmus b/tools/memory-model/litmus-tests/Z6.0+pooncelock+pooncelock+pombonce.litmus
index 10a2aa04cd07..0c9aea8e80df 100644
--- a/tools/memory-model/litmus-tests/Z6.0+pooncelock+pooncelock+pombonce.litmus
+++ b/tools/memory-model/litmus-tests/Z6.0+pooncelock+pooncelock+pombonce.litmus
@@ -8,7 +8,12 @@ C Z6.0+pooncelock+pooncelock+pombonce
* seen as ordered by a third process not holding that lock.
*)

-{}
+{
+ spinlock_t mylock;
+ int x;
+ int y;
+ int z;
+}

P0(int *x, int *y, spinlock_t *mylock)
{
diff --git a/tools/memory-model/litmus-tests/Z6.0+pooncerelease+poacquirerelease+fencembonceonce.litmus b/tools/memory-model/litmus-tests/Z6.0+pooncerelease+poacquirerelease+fencembonceonce.litmus
index 88e70b87a683..661f9aaa5791 100644
--- a/tools/memory-model/litmus-tests/Z6.0+pooncerelease+poacquirerelease+fencembonceonce.litmus
+++ b/tools/memory-model/litmus-tests/Z6.0+pooncerelease+poacquirerelease+fencembonceonce.litmus
@@ -14,7 +14,11 @@ C Z6.0+pooncerelease+poacquirerelease+fencembonceonce
* involving locking.)
*)

-{}
+{
+ int x;
+ int y;
+ int z;
+}

P0(int *x, int *y)
{
diff --git a/tools/testing/selftests/rcutorture/bin/console-badness.sh b/tools/testing/selftests/rcutorture/bin/console-badness.sh
index 0e4c0b2eb7f0..80ae7f08b363 100755
--- a/tools/testing/selftests/rcutorture/bin/console-badness.sh
+++ b/tools/testing/selftests/rcutorture/bin/console-badness.sh
@@ -13,4 +13,5 @@
egrep 'Badness|WARNING:|Warn|BUG|===========|Call Trace:|Oops:|detected stalls on CPUs/tasks:|self-detected stall on CPU|Stall ended before state dump start|\?\?\? Writer stall state|rcu_.*kthread starved for|!!!' |
grep -v 'ODEBUG: ' |
grep -v 'This means that this is a DEBUG kernel and it is' |
-grep -v 'Warning: unable to open an initial console'
+grep -v 'Warning: unable to open an initial console' |
+grep -v 'NOHZ tick-stop error: Non-RCU local softirq work is pending, handler'
diff --git a/tools/testing/selftests/rcutorture/bin/functions.sh b/tools/testing/selftests/rcutorture/bin/functions.sh
index 51f3464b96d3..82663495fb38 100644
--- a/tools/testing/selftests/rcutorture/bin/functions.sh
+++ b/tools/testing/selftests/rcutorture/bin/functions.sh
@@ -169,6 +169,7 @@ identify_qemu () {
# Output arguments for the qemu "-append" string based on CPU type
# and the TORTURE_QEMU_INTERACTIVE environment variable.
identify_qemu_append () {
+ echo debug_boot_weak_hash
local console=ttyS0
case "$1" in
qemu-system-x86_64|qemu-system-i386)
diff --git a/tools/testing/selftests/rcutorture/bin/kvm-check-branches.sh b/tools/testing/selftests/rcutorture/bin/kvm-check-branches.sh
index 6e65c134e5f1..370406bbfeed 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-check-branches.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-check-branches.sh
@@ -52,8 +52,7 @@ echo Results directory: $resdir/$ds
KVM="`pwd`/tools/testing/selftests/rcutorture"; export KVM
PATH=${KVM}/bin:$PATH; export PATH
. functions.sh
-cpus="`identify_qemu_vcpus`"
-echo Using up to $cpus CPUs.
+echo Using all `identify_qemu_vcpus` CPUs.

# Each pass through this loop does one command-line argument.
for gitbr in $@
@@ -74,7 +73,7 @@ do
# Test the specified commit.
git checkout $i > $resdir/$ds/$idir/git-checkout.out 2>&1
echo git checkout return code: $? "(Commit $ntry: $i)"
- kvm.sh --cpus $cpus --duration 3 --trust-make > $resdir/$ds/$idir/kvm.sh.out 2>&1
+ kvm.sh --allcpus --duration 3 --trust-make > $resdir/$ds/$idir/kvm.sh.out 2>&1
ret=$?
echo kvm.sh return code $ret for commit $i from branch $gitbr

diff --git a/tools/testing/selftests/rcutorture/bin/kvm-recheck-rcuscale.sh b/tools/testing/selftests/rcutorture/bin/kvm-recheck-rcuscale.sh
index aa745152a525..b582113178ac 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-recheck-rcuscale.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-recheck-rcuscale.sh
@@ -32,7 +32,7 @@ sed -e 's/^\[[^]]*]//' < $i/console.log |
awk '
/-scale: .* gps: .* batches:/ {
ngps = $9;
- nbatches = $11;
+ nbatches = 1;
}

/-scale: .*writer-duration/ {
diff --git a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
index 6dc2b49b85ea..3cd03d01857c 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
@@ -206,7 +206,10 @@ do
kruntime=`gawk 'BEGIN { print systime() - '"$kstarttime"' }' < /dev/null`
if test -z "$qemu_pid" || kill -0 "$qemu_pid" > /dev/null 2>&1
then
- if test $kruntime -ge $seconds -o -f "$TORTURE_STOPFILE"
+ if test -n "$TORTURE_KCONFIG_GDB_ARG"
+ then
+ :
+ elif test $kruntime -ge $seconds || test -f "$TORTURE_STOPFILE"
then
break;
fi
@@ -223,6 +226,20 @@ do
echo "ps -fp $killpid" >> $resdir/Warnings 2>&1
ps -fp $killpid >> $resdir/Warnings 2>&1
fi
+ # Reduce probability of PID reuse by allowing a one-minute buffer
+ if test $((kruntime + 60)) -lt $seconds && test -s "$resdir/../jitter_pids"
+ then
+ awk < "$resdir/../jitter_pids" '
+ NF > 0 {
+ pidlist = pidlist " " $1;
+ n++;
+ }
+ END {
+ if (n > 0) {
+ print "kill " pidlist;
+ }
+ }' | sh
+ fi
else
echo ' ---' `date`: "Kernel done"
fi
diff --git a/tools/testing/selftests/rcutorture/bin/kvm.sh b/tools/testing/selftests/rcutorture/bin/kvm.sh
index 6eb1d3f6524d..45d07b7b69f5 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm.sh
@@ -58,7 +58,7 @@ usage () {
echo " --datestamp string"
echo " --defconfig string"
echo " --dryrun sched|script"
- echo " --duration minutes"
+ echo " --duration minutes | <seconds>s | <hours>h | <days>d"
echo " --gdb"
echo " --help"
echo " --interactive"
@@ -93,7 +93,7 @@ do
TORTURE_BOOT_IMAGE="$2"
shift
;;
- --buildonly)
+ --buildonly|--build-only)
TORTURE_BUILDONLY=1
;;
--configs|--config)
@@ -128,8 +128,20 @@ do
shift
;;
--duration)
- checkarg --duration "(minutes)" $# "$2" '^[0-9]*$' '^error'
- dur=$(($2*60))
+ checkarg --duration "(minutes)" $# "$2" '^[0-9][0-9]*$s\|m\|h\|d\|$$' '^error'
+ mult=60
+ if echo "$2" | grep -q 's$'
+ then
+ mult=1
+ elif echo "$2" | grep -q 'h$'
+ then
+ mult=3600
+ elif echo "$2" | grep -q 'd$'
+ then
+ mult=86400
+ fi
+ ts=`echo $2 | sed -e 's/[smhd]$//'`
+ dur=$(($ts*mult))
shift
;;
--gdb)
@@ -148,7 +160,7 @@ do
jitter="$2"
shift
;;
- --kconfig)
+ --kconfig|--kconfigs)
checkarg --kconfig "(Kconfig options)" $# "$2" '^CONFIG_[A-Z0-9_]\+=$[ynm]\|[0-9]\+$$ CONFIG_[A-Z0-9_]\+=\([ynm]\|[0-9]\+$\)*$' '^error$'
TORTURE_KCONFIG_ARG="$2"
shift
@@ -159,7 +171,7 @@ do
--kcsan)
TORTURE_KCONFIG_KCSAN_ARG="CONFIG_DEBUG_INFO=y CONFIG_KCSAN=y CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC=n CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY=n CONFIG_KCSAN_REPORT_ONCE_IN_MS=100000 CONFIG_KCSAN_VERBOSE=y CONFIG_KCSAN_INTERRUPT_WATCHER=y"; export TORTURE_KCONFIG_KCSAN_ARG
;;
- --kmake-arg)
+ --kmake-arg|--kmake-args)
checkarg --kmake-arg "(kernel make arguments)" $# "$2" '.*' '^error$'
TORTURE_KMAKE_ARG="$2"
shift
@@ -459,8 +471,11 @@ function dump(first, pastlast, batchnum)
print "if test -n \"$needqemurun\""
print "then"
print "\techo ---- Starting kernels. `date` | tee -a " rd "log";
- for (j = 0; j < njitter; j++)
+ print "\techo > " rd "jitter_pids"
+ for (j = 0; j < njitter; j++) {
print "\tjitter.sh " j " " dur " " ja[2] " " ja[3] "&"
+ print "\techo $! >> " rd "jitter_pids"
+ }
print "\twait"
print "\techo ---- All kernel runs complete. `date` | tee -a " rd "log";
print "else"
diff --git a/tools/testing/selftests/rcutorture/bin/parse-console.sh b/tools/testing/selftests/rcutorture/bin/parse-console.sh
index e03338091a06..263b1be50008 100755
--- a/tools/testing/selftests/rcutorture/bin/parse-console.sh
+++ b/tools/testing/selftests/rcutorture/bin/parse-console.sh
@@ -133,7 +133,7 @@ then
then
summary="$summary Warnings: $n_warn"
fi
- n_bugs=`egrep -c 'BUG|Oops:' $file`
+ n_bugs=`egrep -c '\bBUG|Oops:' $file`
if test "$n_bugs" -ne 0
then
summary="$summary Bugs: $n_bugs"
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/SRCU-t b/tools/testing/selftests/rcutorture/configs/rcu/SRCU-t
index 6c78022c8cd8..d6557c38dfe4 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/SRCU-t
+++ b/tools/testing/selftests/rcutorture/configs/rcu/SRCU-t
@@ -4,7 +4,8 @@ CONFIG_PREEMPT_VOLUNTARY=n
CONFIG_PREEMPT=n
#CHECK#CONFIG_TINY_SRCU=y
CONFIG_RCU_TRACE=n
-CONFIG_DEBUG_LOCK_ALLOC=n
+CONFIG_DEBUG_LOCK_ALLOC=y
+CONFIG_PROVE_LOCKING=y
CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
CONFIG_DEBUG_ATOMIC_SLEEP=y
#CHECK#CONFIG_PREEMPT_COUNT=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/SRCU-u b/tools/testing/selftests/rcutorture/configs/rcu/SRCU-u
index c15ada821e45..6bc24e99862f 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/SRCU-u
+++ b/tools/testing/selftests/rcutorture/configs/rcu/SRCU-u
@@ -4,7 +4,6 @@ CONFIG_PREEMPT_VOLUNTARY=n
CONFIG_PREEMPT=n
#CHECK#CONFIG_TINY_SRCU=y
CONFIG_RCU_TRACE=n
-CONFIG_DEBUG_LOCK_ALLOC=y
-CONFIG_PROVE_LOCKING=y
+CONFIG_DEBUG_LOCK_ALLOC=n
CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
CONFIG_PREEMPT_COUNT=n
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TRACE01 b/tools/testing/selftests/rcutorture/configs/rcu/TRACE01
index 12e7661b86f5..34c8ff5a12f2 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TRACE01
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TRACE01
@@ -4,8 +4,8 @@ CONFIG_HOTPLUG_CPU=y
CONFIG_PREEMPT_NONE=y
CONFIG_PREEMPT_VOLUNTARY=n
CONFIG_PREEMPT=n
-CONFIG_DEBUG_LOCK_ALLOC=y
-CONFIG_PROVE_LOCKING=y
-#CHECK#CONFIG_PROVE_RCU=y
+CONFIG_DEBUG_LOCK_ALLOC=n
+CONFIG_PROVE_LOCKING=n
+#CHECK#CONFIG_PROVE_RCU=n
CONFIG_TASKS_TRACE_RCU_READ_MB=y
CONFIG_RCU_EXPERT=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TRACE02 b/tools/testing/selftests/rcutorture/configs/rcu/TRACE02
index b69ed6673c41..77541eeb4e9f 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TRACE02
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TRACE02
@@ -4,8 +4,8 @@ CONFIG_HOTPLUG_CPU=y
CONFIG_PREEMPT_NONE=n
CONFIG_PREEMPT_VOLUNTARY=n
CONFIG_PREEMPT=y
-CONFIG_DEBUG_LOCK_ALLOC=n
-CONFIG_PROVE_LOCKING=n
-#CHECK#CONFIG_PROVE_RCU=n
+CONFIG_DEBUG_LOCK_ALLOC=y
+CONFIG_PROVE_LOCKING=y
+#CHECK#CONFIG_PROVE_RCU=y
CONFIG_TASKS_TRACE_RCU_READ_MB=n
CONFIG_RCU_EXPERT=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcuscale/CFcommon b/tools/testing/selftests/rcutorture/configs/rcuscale/CFcommon
index 87caa0e932c7..90942bb5bebc 100644
--- a/tools/testing/selftests/rcutorture/configs/rcuscale/CFcommon
+++ b/tools/testing/selftests/rcutorture/configs/rcuscale/CFcommon
@@ -1,2 +1,5 @@
CONFIG_RCU_SCALE_TEST=y
CONFIG_PRINTK_TIME=y
+CONFIG_TASKS_RCU_GENERIC=y
+CONFIG_TASKS_RCU=y
+CONFIG_TASKS_TRACE_RCU=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcuscale/TRACE01 b/tools/testing/selftests/rcutorture/configs/rcuscale/TRACE01
new file mode 100644
index 000000000000..e6baa2fbaeb3
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/configs/rcuscale/TRACE01
@@ -0,0 +1,15 @@
+CONFIG_SMP=y
+CONFIG_PREEMPT_NONE=y
+CONFIG_PREEMPT_VOLUNTARY=n
+CONFIG_PREEMPT=n
+CONFIG_HZ_PERIODIC=n
+CONFIG_NO_HZ_IDLE=y
+CONFIG_NO_HZ_FULL=n
+CONFIG_RCU_FAST_NO_HZ=n
+CONFIG_RCU_NOCB_CPU=n
+CONFIG_DEBUG_LOCK_ALLOC=n
+CONFIG_PROVE_LOCKING=n
+CONFIG_RCU_BOOST=n
+CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
+CONFIG_RCU_EXPERT=y
+CONFIG_RCU_TRACE=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcuscale/TRACE01.boot b/tools/testing/selftests/rcutorture/configs/rcuscale/TRACE01.boot
new file mode 100644
index 000000000000..af0aff1457a4
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/configs/rcuscale/TRACE01.boot
@@ -0,0 +1 @@
+rcuscale.scale_type=tasks-tracing

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