linux-kernel - [patch V3 6/6] rcu: Prevent false positive softirq warning on RT

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Message-Id: <20210309085727.626304079@linutronix.de>
Date:   Tue, 09 Mar 2021 09:55:58 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Paul McKenney <paulmck@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Frederic Weisbecker <frederic@...nel.org>
Subject: [patch V3 6/6] 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@...utronix.de>
Tested-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Reviewed-by: Paul E. McKenney <paulmck@...nel.org>
---
 include/linux/rcupdate.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -334,7 +334,8 @@ static inline void rcu_preempt_sleep_che
 #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"); \