[tip: irq/core] rcu: Prevent false positive softirq warning on RT

[tip-bot2 for Thomas Gleixner]

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

Commit-ID:     ba9e6cab49c1465c2c322dcb03d771d5cbecb692
Gitweb:        https://git.kernel.org/tip/ba9e6cab49c1465c2c322dcb03d771d5cbecb692
Author:        Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate:    Tue, 09 Mar 2021 09:55:58 +01:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Wed, 17 Mar 2021 16:34:12 +01:00

rcu: Prevent false positive softirq warning on RT

Soft interrupt disabled sections can legitimately be preempted or schedule
out when blocking on a lock on RT enabled kernels so the RCU preempt check
warning has to be disabled for RT kernels.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Tested-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Tested-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Reviewed-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Reviewed-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20210309085727.626304079@xxxxxxxxxxxxx

---
 include/linux/rcupdate.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index bd04f72..6d855ef 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -334,7 +334,8 @@ static inline void rcu_preempt_sleep_check(void) { }
 #define rcu_sleep_check()						\
 	do {								\
 		rcu_preempt_sleep_check();				\
-		RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map),	\
+		if (!IS_ENABLED(CONFIG_PREEMPT_RT))			\
+		    RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map),	\
 				 "Illegal context switch in RCU-bh read-side critical section"); \
 		RCU_LOCKDEP_WARN(lock_is_held(&rcu_sched_lock_map),	\
 				 "Illegal context switch in RCU-sched read-side critical section"); \