linux-kernel - Re: [rfc] disable scheduler warnings during oopses.

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Date:	Fri, 23 Dec 2011 11:19:17 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Mike Galbraith <efault@....de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Dave Airlie <airlied@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [rfc] disable scheduler warnings during oopses.


* Dave Jones <davej@...hat.com> wrote:

> The panic-on-framebuffer code seems to cause a schedule
> to occur during an oops. This causes a bunch of extra
> spew as can be seen in https://bugzilla.redhat.com/attachment.cgi?id=549230
> 
> Would this (untested) patch be sufficient here, or does the drm
> code need rearchitecting to not perform allocations during panic ?
> 
> Signed-off-by: Dave Jones <davej@...hat.com>
> 
> diff --git a/kernel/sched.c b/kernel/sched.c
> index d6b149c..627f788 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -4321,6 +4321,9 @@ static noinline void __schedule_bug(struct task_struct *prev)
>  {
>  	struct pt_regs *regs = get_irq_regs();
>  
> +	if (oops_in_progress)
> +		return;
> +
>  	printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n",
>  		prev->comm, prev->pid, preempt_count());
>  

Doing that makes sense - if an oops in going on we don't want to 
produce recursive messages. Note that scheduler code has been 
moved to kernel/sched/, so i've changed the patch accordingly.

Note that despite that, the DRM code *definitely* needs to be 
fixed to not allocate and schedule while printing on the 
framebuffer in KMS mode ...

Thanks,

	Ingo
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