linux-kernel - Re: [patch V2 6/9] rcu: Prevent false positive softirq warning on RT

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Date:   Fri, 4 Dec 2020 09:59:24 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: [patch V2 6/9] rcu: Prevent false positive softirq warning on RT

On Fri, Dec 04, 2020 at 06:01:57PM +0100, Thomas Gleixner wrote:
> From: Thomas Gleixner <tglx@...utronix.de>
> 
> 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>

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
> @@ -319,7 +319,8 @@ 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"); \
>