[tip: core/rcu] rcu: Add lockdep_assert_irqs_disabled() to rcu_sched_clock_irq() and callees

From: tip-bot2 for Paul E. McKenney
Date: Fri Feb 12 2021 - 08:03:07 EST


The following commit has been merged into the core/rcu branch of tip:

Commit-ID: a649d25dcc671a33b9cc3176411920fdc5fbd98e
Gitweb: https://git.kernel.org/tip/a649d25dcc671a33b9cc3176411920fdc5fbd98e
Author: Paul E. McKenney <paulmck@xxxxxxxxxx>
AuthorDate: Thu, 19 Nov 2020 10:13:06 -08:00
Committer: Paul E. McKenney <paulmck@xxxxxxxxxx>
CommitterDate: Mon, 04 Jan 2021 15:54:49 -08:00

rcu: Add lockdep_assert_irqs_disabled() to rcu_sched_clock_irq() and callees

This commit adds a number of lockdep_assert_irqs_disabled() calls
to rcu_sched_clock_irq() and a number of the functions that it calls.
The point of this is to help track down a situation where lockdep appears
to be insisting that interrupts are enabled within these functions, which
should only ever be invoked from the scheduling-clock interrupt handler.

Link: https://lore.kernel.org/lkml/20201111133813.GA81547@xxxxxxxxxxxxxxxx/
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
kernel/rcu/tree.c | 4 ++++
kernel/rcu/tree_plugin.h | 1 +
kernel/rcu/tree_stall.h | 8 ++++++++
3 files changed, 13 insertions(+)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index bd04b09..f70634f 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2553,6 +2553,7 @@ static void rcu_do_batch(struct rcu_data *rdp)
void rcu_sched_clock_irq(int user)
{
trace_rcu_utilization(TPS("Start scheduler-tick"));
+ lockdep_assert_irqs_disabled();
raw_cpu_inc(rcu_data.ticks_this_gp);
/* The load-acquire pairs with the store-release setting to true. */
if (smp_load_acquire(this_cpu_ptr(&rcu_data.rcu_urgent_qs))) {
@@ -2566,6 +2567,7 @@ void rcu_sched_clock_irq(int user)
rcu_flavor_sched_clock_irq(user);
if (rcu_pending(user))
invoke_rcu_core();
+ lockdep_assert_irqs_disabled();

trace_rcu_utilization(TPS("End scheduler-tick"));
}
@@ -3690,6 +3692,8 @@ static int rcu_pending(int user)
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
struct rcu_node *rnp = rdp->mynode;

+ lockdep_assert_irqs_disabled();
+
/* Check for CPU stalls, if enabled. */
check_cpu_stall(rdp);

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index fd8a52e..cb76e70 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -682,6 +682,7 @@ static void rcu_flavor_sched_clock_irq(int user)
{
struct task_struct *t = current;

+ lockdep_assert_irqs_disabled();
if (user || rcu_is_cpu_rrupt_from_idle()) {
rcu_note_voluntary_context_switch(current);
}
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index ca21d28..4024dcc 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -260,6 +260,7 @@ static int rcu_print_task_stall(struct rcu_node *rnp, unsigned long flags)
struct task_struct *t;
struct task_struct *ts[8];

+ lockdep_assert_irqs_disabled();
if (!rcu_preempt_blocked_readers_cgp(rnp))
return 0;
pr_err("\tTasks blocked on level-%d rcu_node (CPUs %d-%d):",
@@ -284,6 +285,7 @@ static int rcu_print_task_stall(struct rcu_node *rnp, unsigned long flags)
".q"[rscr.rs.b.need_qs],
".e"[rscr.rs.b.exp_hint],
".l"[rscr.on_blkd_list]);
+ lockdep_assert_irqs_disabled();
put_task_struct(t);
ndetected++;
}
@@ -472,6 +474,8 @@ static void print_other_cpu_stall(unsigned long gp_seq, unsigned long gps)
struct rcu_node *rnp;
long totqlen = 0;

+ lockdep_assert_irqs_disabled();
+
/* Kick and suppress, if so configured. */
rcu_stall_kick_kthreads();
if (rcu_stall_is_suppressed())
@@ -493,6 +497,7 @@ static void print_other_cpu_stall(unsigned long gp_seq, unsigned long gps)
}
}
ndetected += rcu_print_task_stall(rnp, flags); // Releases rnp->lock.
+ lockdep_assert_irqs_disabled();
}

for_each_possible_cpu(cpu)
@@ -538,6 +543,8 @@ static void print_cpu_stall(unsigned long gps)
struct rcu_node *rnp = rcu_get_root();
long totqlen = 0;

+ lockdep_assert_irqs_disabled();
+
/* Kick and suppress, if so configured. */
rcu_stall_kick_kthreads();
if (rcu_stall_is_suppressed())
@@ -592,6 +599,7 @@ static void check_cpu_stall(struct rcu_data *rdp)
unsigned long js;
struct rcu_node *rnp;

+ lockdep_assert_irqs_disabled();
if ((rcu_stall_is_suppressed() && !READ_ONCE(rcu_kick_kthreads)) ||
!rcu_gp_in_progress())
return;