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

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Message-ID: <20140617085943.GA19886@dhcp22.suse.cz>
Date:	Tue, 17 Jun 2014 10:59:43 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Don Zickus <dzickus@...hat.com>
Cc:	Peter Wu <peter@...ensteyn.nl>, linux-kernel@...r.kernel.org,
	linux-watchdog@...r.kernel.org
Subject: Re: Writing watchdog_thresh triggers BUG: sleeping function called
 from invalid context

On Mon 16-06-14 16:52:45, Don Zickus wrote:
[...]
> Michal, do you remember why we needed preempt here?  I wouldn't think it
> mattered as we are not doing anything per-cpu specific.

Yes, you are right. Preempt can be enabled because we are always
accessing watchdog_ev on a specific cpu so reschedule doesn't matter.

> 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();
>  }
>  

-- 
Michal Hocko
SUSE Labs
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