linux-kernel - Re: [PATCH] rcu/torture replace wait_event with wait_event

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Message-ID: <0e334497-fbc1-49f7-87ef-8dbf6d25d6a7@paulmck-laptop>
Date:   Tue, 11 Apr 2023 21:54:34 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     zhouzhouyi@...il.com
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org, lance@...osl.org
Subject: Re: [PATCH] rcu/torture replace wait_event with
 wait_event_interruptible

On Wed, Apr 12, 2023 at 09:54:43AM +0800, zhouzhouyi@...il.com wrote:
> From: Zhouyi Zhou <zhouzhouyi@...il.com>
> 
> In kfree_rcu_test, kfree_scale_shutdown will be detected as hung task
> if kfree_loops is too big. Replace wait_event with wait_event_interruptible
> to avoid false positive.
> 
> Tested in the PPC VM of Open Source Lab of Oregon State University.
> 
> Signed-off-by: Zhouyi Zhou <zhouzhouyi@...il.com>                
> ---
>  kernel/rcu/rcuscale.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
> index 91fb5905a008..b37eec94957c 100644
> --- a/kernel/rcu/rcuscale.c
> +++ b/kernel/rcu/rcuscale.c
> @@ -771,7 +771,7 @@ kfree_scale_cleanup(void)
>  static int
>  kfree_scale_shutdown(void *arg)
>  {
> -	wait_event(shutdown_wq,
> +	wait_event_interruptible(shutdown_wq,

Good catch!!!

Would wait_event_idle() work in this case?  The _interruptible()
variant indicates that wakeups due to things like POSIX signals is
permitted.

							Thanx, Paul

>  		   atomic_read(&n_kfree_scale_thread_ended) >= kfree_nrealthreads);
>  
>  	smp_mb(); /* Wake before output. */
> -- 
> 2.34.1
>