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

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Date:	Fri, 23 Dec 2011 14:42:25 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	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.


* Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:

> On Fri, 2011-12-23 at 11:19 +0100, Ingo Molnar wrote:
> > * 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.
> 
> Urgh I would actually argue against merging this. What the KSM 
> console does is horridly wrong, and simply papering over it 
> doesn't help its cause. Its up there with USB-Serial console 
> on wrongness.

Well, i agree in principle, but not escallating an already bad 
scenario would be a basic robustness rule. We do skip certain 
things on oops_in_progress already.

Linus, Andrew, what would be your preference?

Thanks,

	Ingo
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