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

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Date:	Mon, 16 Jun 2014 16:52:45 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Peter Wu <peter@...ensteyn.nl>, mhocko@...e.cz
Cc:	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, 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?

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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