[PATCH RFC 16/16] rcu: Mark interrupts-enabled accesses to rdp->cpu_no_qs.s

[Paul E. McKenney]

The rdp->cpu_no_qs.s field is accessed only by the current CPU,
but can be accessed both at task level and from interrupt handlers.
All accesses from interrupts-enabled code must therefore be marked.
This commit therefore converts from __this_cpu_read() to this_cpu_read(),
but only in interrupts-enabled code, that is, the rcu_qs() function.

KCSAN located this issue.

Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
 kernel/rcu/tree_plugin.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 844a9ced67cc0e..6904a4f826d1ea 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -976,7 +976,7 @@ static void __init rcu_bootup_announce(void)
 static void rcu_qs(void)
 {
 	RCU_LOCKDEP_WARN(preemptible(), "rcu_qs() invoked with preemption enabled!!!");
-	if (!__this_cpu_read(rcu_data.cpu_no_qs.s))
+	if (!this_cpu_read(rcu_data.cpu_no_qs.s))
 		return;
 	trace_rcu_grace_period(TPS("rcu_sched"),
 			       __this_cpu_read(rcu_data.gp_seq), TPS("cpuqs"));
-- 
2.40.1