linux-kernel - Re: Writing watchdog_thresh triggers BUG: sleeping function called from invalid context

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Date:	Mon, 16 Jun 2014 22:58:44 +0200
From:	Peter Wu <peter@...ensteyn.nl>
To:	Don Zickus <dzickus@...hat.com>
Cc:	mhocko@...e.cz, linux-kernel@...r.kernel.org,
	linux-watchdog@...r.kernel.org
Subject: Re: Writing watchdog_thresh triggers BUG: sleeping function called from invalid context

On Monday 16 June 2014 16:52:45 Don Zickus wrote:
> On Mon, Jun 16, 2014 at 04:12:44PM +0200, Peter Wu wrote:
> > Hi,
> > 
> > Writing to /proc/sys/kernel/watchdog_thresh causes the following BUG in
> > at least v3.13-rc2-625-g06151db, v3.15 and v3.16-rc1. Kernel config is
> > attached.
> > 
> > It was originally found on bare metal, since then reproduced in QEMU in
> > init, and when directly executing it.
> > 
> > Regards,
> > Peter
> 
> Hi Peter,
> 
> I assume the following patch will work?

Yes, the patch works (no more BUG). No idea whether it is
(in)correct though.

Regards,
Peter

> Michal, do you remember why we needed preempt here?  I wouldn't think it
> mattered as we are not doing anything per-cpu specific.
> 
> Cheers,
> Don
> 
> diff --git a/kernel/watchdog.c b/kernel/watchdog.c
> index 516203e..30e4822 100644
> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -527,10 +527,8 @@ static void update_timers_all_cpus(void)
>  	int cpu;
>  
>  	get_online_cpus();
> -	preempt_disable();
>  	for_each_online_cpu(cpu)
>  		update_timers(cpu);
> -	preempt_enable();
>  	put_online_cpus();
>  }
>  

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