linux-kernel - Re: 3.14-rc2 XFS backtrace because irqs

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Date:	Wed, 12 Feb 2014 09:25:38 -0500
From:	Dave Jones <davej@...hat.com>
To:	Dave Chinner <david@...morbit.com>
Cc:	Al Viro <viro@...IV.linux.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Eric Sandeen <sandeen@...deen.net>,
	Linux Kernel <linux-kernel@...r.kernel.org>, xfs@....sgi.com
Subject: Re: 3.14-rc2 XFS backtrace because irqs_disabled.

On Wed, Feb 12, 2014 at 05:10:38PM +1100, Dave Chinner wrote:
 > On Wed, Feb 12, 2014 at 12:50:27AM -0500, Dave Jones wrote:
 > > On Wed, Feb 12, 2014 at 04:40:43PM +1100, Dave Chinner wrote:
 > > 
 > >  > None of the XFS code disables interrupts in that path, not does is
 > >  > call outside XFS except to dispatch IO. The stack is pretty deep at
 > >  > this point and I know that the standard (non stacked) IO stack can
 > >  > consume >3kb of stack space when it gets down to having to do memory
 > >  > reclaim during GFP_NOIO allocation at the lowest level of SCSI
 > >  > drivers. Stack overruns typically show up with symptoms like we are
 > >  > seeing.
 > >  > ..
 > >  > 
 > >  > Dave, before chasing ghosts, can you (like Eric originally asked)
 > >  > turn on stack overrun detection?
 > > 
 > > CONFIG_DEBUG_STACKOVERFLOW ? Already turned on.
 > 
 > That only checks stack usage when an interrupt is taken. If no
 > interrupts are taken when stack usage is within 128 bytes of
 > overflow, then it doesn't catch it.
 > 
 > I tend to use CONFIG_DEBUG_STACK_USAGE=y as it records the maximum
 > stack usage of a process via canary overwrites and it records it in
 > do_exit().

I had that on too. The only message from it came from quite a while
before the trace that happened overnight..

[ 3415.655125] trinity-c0 (4383) used greatest stack depth: 992 bytes left
[12900.804230] BUG: sleeping function called from invalid context at mm/mempool.c:203

 > I also use the stack tracer to record the largest stack
 > usage seen so I know exactly what code paths are approaching stack
 > overruns...

I can give that a try later.

	Dave

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