linux-kernel - Re: [RT PATCH 2/2] timers: wakeup all timer waiters without holding the base lock

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Message-ID: <20160714120917.038b215b@gandalf.local.home>
Date:	Thu, 14 Jul 2016 12:09:17 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:	linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	tglx@...utronix.de
Subject: Re: [RT PATCH 2/2] timers: wakeup all timer waiters without holding
 the base lock

On Thu, 14 Jul 2016 18:05:04 +0200
Sebastian Andrzej Siewior <bigeasy@...utronix.de> wrote:

> There should be no need to hold the base lock during the wakeup. There
> should be no boosting involved, the wakeup list has its own lock so it
> should be safe to do this without the lock.
> 
> Cc: stable-rt@...r.kernel.org

Nothing against this patch, but as you marked it for stable, can you
add to the change log what issue you had that caused you to make this
change?

-- Steve

> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> ---
>  kernel/time/timer.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/time/timer.c b/kernel/time/timer.c
> index b3c3d3a6216f..716ef84a5d87 100644
> --- a/kernel/time/timer.c
> +++ b/kernel/time/timer.c
> @@ -1313,8 +1313,8 @@ static inline void __run_timers(struct tvec_base *base)
>  			}
>  		}
>  	}
> -	wakeup_timer_waiters(base);
>  	spin_unlock_irq(&base->lock);
> +	wakeup_timer_waiters(base);
>  }
>  
>  #ifdef CONFIG_NO_HZ_COMMON