linux-kernel - Re: [ANNOUNCE] 3.12.6-rt9

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Message-ID: <52E24C58.2000205@linutronix.de>
Date:	Fri, 24 Jan 2014 12:19:52 +0100
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	Mike Galbraith <bitbucket@...ine.de>,
	linux-rt-users <linux-rt-users@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	John Kacur <jkacur@...hat.com>
Subject: Re: [ANNOUNCE] 3.12.6-rt9

On 01/21/2014 03:17 AM, Steven Rostedt wrote:
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
> 
> diff --git a/kernel/timer.c b/kernel/timer.c
> index 46467be..8212c10 100644
> --- a/kernel/timer.c
> +++ b/kernel/timer.c
> @@ -1464,13 +1464,11 @@ void run_local_timers(void)
>  		raise_softirq(TIMER_SOFTIRQ);
>  		return;
>  	}
> -	if (!base->active_timers)
> -		goto out;
>  
>  	/* Check whether the next pending timer has expired */
>  	if (time_before_eq(base->next_timer, jiffies))
>  		raise_softirq(TIMER_SOFTIRQ);

Hmmm. If active_timers is 0 and "time_before_eq(base->next_timer,
jiffies))" is true than that timer should have been initialized with
init_timer_deferrable() or we have a serious bug here where
active_timers isn't properly synchronized anymore.

Now. If there is really just a deferrable timer that expired and nothing
else then this would explain it.

> -out:
> +
>  	rt_spin_unlock_after_trylock_in_irq(&base->lock);
>  
>  }

Sebastian
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