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To: Andrew Morton <akpm@digeo.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [BUG] 2.5.65-mm3 kernel BUG at fs/ext3/super.c:1795!
References: <20030320235821.1e4ff308.akpm@digeo.com>
	<8765qchhgo.fsf@lapper.ihatent.com>
	<20030321123919.0b8b1b86.akpm@digeo.com>
From: Alexander Hoogerhuis <alexh@ihatent.com>
Date: 22 Mar 2003 03:55:30 +0100
In-Reply-To: <20030321123919.0b8b1b86.akpm@digeo.com>
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Andrew Morton <akpm@digeo.com> writes:

> Alexander Hoogerhuis <alexh@ihatent.com> wrote:
> >
> > Andrew Morton <akpm@digeo.com> writes:
> > >
> > > [SNIP]
> > >
> > 
> > Disk I/O on my machine froze up during very light work after a few
> > hours, luckily I had a window open on another machine so I could do a
> > simple capture and save the info:
> > 
> > kernel BUG at fs/ext3/super.c:1795!
> > invalid operand: 0000 [#1]
> > CPU:    0
> > EIP:    0060:[<c018b522>]    Not tainted VLI
> > EFLAGS: 00010246
> > EIP is at ext3_write_super+0x36/0x94
> > eax: 00000000   ebx: c8834000   ecx: efb5904c   edx: efb59000
> > esi: efb59000   edi: c8834000   ebp: c8835ecc   esp: c8835ec0
> > ds: 007b   es: 007b   ss: 0068
> > Process pdflush (pid: 7853, threadinfo=c8834000 task=ed0a5880)
> > Stack: c8835ee4 00000287 efb5904c c8835ee4 c0153148 efb59000 00000077 51eb851f
> >        c8835fcc c8835fa4 c0137fd0 c03892fc 007b9f47 007b168f 00000000 00000000
> >        c8835ef4 00000000 00000001 00000000 00000001 00000000 00000053 00000000
> > Call Trace:
> >  [<c0153148>] sync_supers+0xde/0xea
> >  [<c0137fd0>] wb_kupdate+0x68/0x161
> >  [<c0118985>] schedule+0x1a4/0x3ac
> >  [<c01386e8>] __pdflush+0xdc/0x1d8
> >  [<c01387e4>] pdflush+0x0/0x15
> >  [<c01387f5>] pdflush+0x11/0x15
> >  [<c0137f68>] wb_kupdate+0x0/0x161
> >  [<c0108e69>] kernel_thread_helper+0x5/0xb
> 
> How on earth did you do that?
> 
> sync_supers() does lock_super, then calls ext3_write_super.
> 
> ext3_write_super() does a down_trylock() on sb->s_lock and goes BUG
> if it acquired the lock.
> 
> So you've effectively done this:
> 
> 	down(&sem);
> 	if (down_trylock(&sem))
> 		BUG();
> 
> This can only be a random memory scribble, a hardware bug or a
> preempt-related bug in down_trylock().

Heh. My "portable murphy field" if powerful. Honestly, all I did was
to have a few gnome-terminals, an emacs or two, a few mozillas and a
bit more up, same as always, and jut "just happened" (that's what all
kids claim when they break stuff) :)

mvh,
A
-- 
Alexander Hoogerhuis                               | alexh@ihatent.com
CCNP - CCDP - MCNE - CCSE                          | +47 908 21 485
"You have zero privacy anyway. Get over it."  --Scott McNealy
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