[PATCH 24/48] rcu: Bring diagnostic read of rcu_state.gp_flags into alignment

Uladzislau Rezki (Sony)
2024-05-07T09:35:57Z

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

This commit adds READ_ONCE() to a lockless diagnostic read from
rcu_state.gp_flags to avoid giving the compiler any chance whatsoever
of confusing the diagnostic state printed.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
---
kernel/rcu/tree_stall.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index 5d666428546b..62b2c4858028 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -579,7 +579,7 @@ static void rcu_check_gp_kthread_expired_fqs_timer(void)
pr_err("%s kthread timer wakeup didn't happen for %ld jiffies! g%ld f%#x %s(%d) ->state=%#x\n",
rcu_state.name, (jiffies - jiffies_fqs),
(long)rcu_seq_current(&rcu_state.gp_seq),
- data_race(rcu_state.gp_flags),
+ data_race(READ_ONCE(rcu_state.gp_flags)), // Diagnostic read
gp_state_getname(RCU_GP_WAIT_FQS), RCU_GP_WAIT_FQS,
data_race(READ_ONCE(gpk->__state)));
pr_err("\tPossible timer handling issue on cpu=%d timer-softirq=%u\n",
--
2.39.2