[GIT pull] timers/nohz for v5.7
From: Thomas Gleixner
Date: Mon Mar 30 2020 - 10:50:04 EST
Linus,
please pull the latest timers/nohz branch from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers-nohz-2020-03-30
up to: e4970c9c54d7: Merge branch 'arch/nohz' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks into timers/nohz
NOHZ full updates:
- Remove TIF_NOHZ from 3 architectures
These architectures use a static key to decide whether context tracking
needs to be invoked and the TIF_NOHZ flag just causes a pointless
slowpath execution for nothing.
Thanks,
tglx
------------------>
Frederic Weisbecker (4):
context-tracking: Introduce CONFIG_HAVE_TIF_NOHZ
x86: Remove TIF_NOHZ
arm: Remove TIF_NOHZ
arm64: Remove TIF_NOHZ
Thomas Gleixner (1):
x86/entry: Remove _TIF_NOHZ from _TIF_WORK_SYSCALL_ENTRY
arch/Kconfig | 16 +++++++++++-----
arch/arm/include/asm/thread_info.h | 1 -
arch/arm64/include/asm/thread_info.h | 4 +---
arch/mips/Kconfig | 1 +
arch/powerpc/Kconfig | 1 +
arch/sparc/Kconfig | 1 +
arch/x86/include/asm/thread_info.h | 10 ++--------
kernel/context_tracking.c | 2 ++
8 files changed, 19 insertions(+), 17 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index 98de654b79b3..dbf420a9f87b 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -540,11 +540,17 @@ config HAVE_CONTEXT_TRACKING
help
Provide kernel/user boundaries probes necessary for subsystems
that need it, such as userspace RCU extended quiescent state.
- Syscalls need to be wrapped inside user_exit()-user_enter() through
- the slow path using TIF_NOHZ flag. Exceptions handlers must be
- wrapped as well. Irqs are already protected inside
- rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
- irq exit still need to be protected.
+ Syscalls need to be wrapped inside user_exit()-user_enter(), either
+ optimized behind static key or through the slow path using TIF_NOHZ
+ flag. Exceptions handlers must be wrapped as well. Irqs are already
+ protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal
+ handling on irq exit still need to be protected.
+
+config HAVE_TIF_NOHZ
+ bool
+ help
+ Arch relies on TIF_NOHZ and syscall slow path to implement context
+ tracking calls to user_enter()/user_exit().
config HAVE_VIRT_CPU_ACCOUNTING
bool
diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index 0d0d5178e2c3..3609a6980c34 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -141,7 +141,6 @@ extern int vfp_restore_user_hwstate(struct user_vfp *,
#define TIF_SYSCALL_TRACEPOINT 6 /* syscall tracepoint instrumentation */
#define TIF_SECCOMP 7 /* seccomp syscall filtering active */
-#define TIF_NOHZ 12 /* in adaptive nohz mode */
#define TIF_USING_IWMMXT 17
#define TIF_MEMDIE 18 /* is terminating due to OOM killer */
#define TIF_RESTORE_SIGMASK 20
diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index f0cec4160136..512174a8e789 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -63,7 +63,6 @@ void arch_release_task_struct(struct task_struct *tsk);
#define TIF_FOREIGN_FPSTATE 3 /* CPU's FP state is not current's */
#define TIF_UPROBE 4 /* uprobe breakpoint or singlestep */
#define TIF_FSCHECK 5 /* Check FS is USER_DS on return */
-#define TIF_NOHZ 7
#define TIF_SYSCALL_TRACE 8 /* syscall trace active */
#define TIF_SYSCALL_AUDIT 9 /* syscall auditing */
#define TIF_SYSCALL_TRACEPOINT 10 /* syscall tracepoint for ftrace */
@@ -83,7 +82,6 @@ void arch_release_task_struct(struct task_struct *tsk);
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
#define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
#define _TIF_FOREIGN_FPSTATE (1 << TIF_FOREIGN_FPSTATE)
-#define _TIF_NOHZ (1 << TIF_NOHZ)
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
#define _TIF_SYSCALL_TRACEPOINT (1 << TIF_SYSCALL_TRACEPOINT)
@@ -100,7 +98,7 @@ void arch_release_task_struct(struct task_struct *tsk);
#define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
_TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \
- _TIF_NOHZ | _TIF_SYSCALL_EMU)
+ _TIF_SYSCALL_EMU)
#define INIT_THREAD_INFO(tsk) \
{ \
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 797d7f1ad5fe..2589d4760e45 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -51,6 +51,7 @@ config MIPS
select HAVE_ASM_MODVERSIONS
select HAVE_CBPF_JIT if !64BIT && !CPU_MICROMIPS
select HAVE_CONTEXT_TRACKING
+ select HAVE_TIF_NOHZ
select HAVE_COPY_THREAD_TLS
select HAVE_C_RECORDMCOUNT
select HAVE_DEBUG_KMEMLEAK
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 497b7d0b2d7e..6f40af294685 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -182,6 +182,7 @@ config PPC
select HAVE_STACKPROTECTOR if PPC64 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r13)
select HAVE_STACKPROTECTOR if PPC32 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r2)
select HAVE_CONTEXT_TRACKING if PPC64
+ select HAVE_TIF_NOHZ if PPC64
select HAVE_COPY_THREAD_TLS
select HAVE_DEBUG_KMEMLEAK
select HAVE_DEBUG_STACKOVERFLOW
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index c1dd6dd642f4..9cc9ab04bd99 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -71,6 +71,7 @@ config SPARC64
select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_SYSCALL_TRACEPOINTS
select HAVE_CONTEXT_TRACKING
+ select HAVE_TIF_NOHZ
select HAVE_DEBUG_KMEMLEAK
select IOMMU_HELPER
select SPARSE_IRQ
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index cf4327986e98..384cdde10680 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -92,7 +92,6 @@ struct thread_info {
#define TIF_NOCPUID 15 /* CPUID is not accessible in userland */
#define TIF_NOTSC 16 /* TSC is not accessible in userland */
#define TIF_IA32 17 /* IA32 compatibility process */
-#define TIF_NOHZ 19 /* in adaptive nohz mode */
#define TIF_MEMDIE 20 /* is terminating due to OOM killer */
#define TIF_POLLING_NRFLAG 21 /* idle is polling for TIF_NEED_RESCHED */
#define TIF_IO_BITMAP 22 /* uses I/O bitmap */
@@ -122,7 +121,6 @@ struct thread_info {
#define _TIF_NOCPUID (1 << TIF_NOCPUID)
#define _TIF_NOTSC (1 << TIF_NOTSC)
#define _TIF_IA32 (1 << TIF_IA32)
-#define _TIF_NOHZ (1 << TIF_NOHZ)
#define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG)
#define _TIF_IO_BITMAP (1 << TIF_IO_BITMAP)
#define _TIF_FORCED_TF (1 << TIF_FORCED_TF)
@@ -133,14 +131,10 @@ struct thread_info {
#define _TIF_X32 (1 << TIF_X32)
#define _TIF_FSCHECK (1 << TIF_FSCHECK)
-/*
- * work to do in syscall_trace_enter(). Also includes TIF_NOHZ for
- * enter_from_user_mode()
- */
+/* Work to do before invoking the actual syscall. */
#define _TIF_WORK_SYSCALL_ENTRY \
(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU | _TIF_SYSCALL_AUDIT | \
- _TIF_SECCOMP | _TIF_SYSCALL_TRACEPOINT | \
- _TIF_NOHZ)
+ _TIF_SECCOMP | _TIF_SYSCALL_TRACEPOINT)
/* flags to check in __switch_to() */
#define _TIF_WORK_CTXSW_BASE \
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 0296b4bda8f1..ce430885c26c 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -198,11 +198,13 @@ void __init context_tracking_cpu_set(int cpu)
if (initialized)
return;
+#ifdef CONFIG_HAVE_TIF_NOHZ
/*
* Set TIF_NOHZ to init/0 and let it propagate to all tasks through fork
* This assumes that init is the only task at this early boot stage.
*/
set_tsk_thread_flag(&init_task, TIF_NOHZ);
+#endif
WARN_ON_ONCE(!tasklist_empty());
initialized = true;