[PATCH 5.10 045/236] rcu: Add lockdep_assert_irqs_disabled() to rcu_sched_clock_irq() and callees

Greg Kroah-Hartman
2021-09-13T13:34:31Z

From: Paul E. McKenney <paulmck@kernel.org>

[ Upstream commit a649d25dcc671a33b9cc3176411920fdc5fbd98e ]

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@elver.google.com/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 8c3ba0185082..8c81c05c4236 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2561,6 +2561,7 @@ 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))) {
@@ -2574,6 +2575,7 @@ 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"));
}
@@ -3730,6 +3732,8 @@ 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 7d4f78bf4057..574aeaac9272 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 cdfaa44ffd70..3fc21617546d 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -262,6 +262,7 @@ 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):",
@@ -286,6 +287,7 @@ 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++;
}
@@ -474,6 +476,8 @@ 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())
@@ -495,6 +499,7 @@ 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)
@@ -540,6 +545,8 @@ 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())
@@ -594,6 +601,7 @@ 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;
--
2.30.2