linux-kernel - Re: [1/6] 2.6.21-rc4: known regressions

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Message-ID: <6bffcb0e0703230051i5accb180r7bd0fb16de85198a@mail.gmail.com>
Date:	Fri, 23 Mar 2007 08:51:13 +0100
From:	"Michal Piotrowski" <michal.k.k.piotrowski@...il.com>
To:	"Nick Piggin" <npiggin@...e.de>
Cc:	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Nick Piggin" <nickpiggin@...oo.com.au>,
	"Mingming Cao" <cmm@...ibm.com>, "Adrian Bunk" <bunk@...sta.de>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	"Mariusz Kozlowski" <m.kozlowski@...land.pl>,
	"Oliver Pinter" <oliver.pntr@...il.com>,
	"Sid Boyce" <g3vbv@...eyonder.co.uk>,
	"Jens Axboe" <jens.axboe@...cle.com>
Subject: Re: [1/6] 2.6.21-rc4: known regressions

On 23/03/07, Nick Piggin <npiggin@...e.de> wrote:
> On Thu, Mar 22, 2007 at 06:40:41PM -0700, Linus Torvalds wrote:
> >
> > [ Ok, I think it's those timers again...
> >
> >   Ingo: let me just state how *happy* I am that I told you off when you
> >   wanted to merge the hires timers and NO_HZ before 2.6.20 because they
> >   were "stable". You were wrong, and 2.6.20 is at least in reasonable
> >   shape. Now we just need to make sure that 2.6.21 will be too.. ]
> >
> > On Thu, 22 Mar 2007, Mingming Cao wrote:
> > >
> > > I might missed something, so far I can't see a deadlock yet.
> > > If there is a deadlock, I think we should see ext3_xattr_release_block()
> > > and ext3_forget() on the stack. Is this the case?
> >
> > No. What's strange is that two (maybe more, I didn't check) processes seem
> > to be stuck in
> >
> >        [<c0318981>] schedule_timeout+0x70/0x8e
> >        [<c03189b4>] schedule_timeout_uninterruptible+0x15/0x17
> >        [<c01b964a>] journal_stop+0xe2/0x1e6
> >        [<c01ba2b0>] journal_force_commit+0x1d/0x1f
> >        [<c01b29fb>] ext3_force_commit+0x22/0x24
> >        [<c01ad607>] ext3_write_inode+0x34/0x3a
> >        [<c0189f74>] __writeback_single_inode+0x1c5/0x2cb
> >        [<c018a096>] sync_inode+0x1c/0x2e
> >        [<c01a9ff7>] ext3_sync_file+0xab/0xc0
> >        [<c018c8c5>] do_fsync+0x4b/0x98
> >        [<c018c932>] __do_fsync+0x20/0x2f
> >        [<c018c960>] sys_fsync+0xd/0xf
> >        [<c0104064>] syscall_call+0x7/0xb
> >
> > but that that thing is literally:
> >
> >               ...
> >                 do {
> >                         old_handle_count = transaction->t_handle_count;
> >                         schedule_timeout_uninterruptible(1);
> >                 } while (old_handle_count != transaction->t_handle_count);
> >               ...
> >
> > and especially if nothing is happening, I'd not expect
> > "transaction->t_handle_count" to keep changing, so it should stop very
> > quickly.
> >
> > Maybe it's CONFIG_NO_HZ again, and the problem is that timeout, and simply
> > no timer tick happening?
> >
> > Bingo. I think that's it.
> >
> >       active timers:
> >        #0: hardirq_stack, tick_sched_timer, S:01
> >        # expires at 9530893000000 nsecs [in -2567889 nsecs]
> >        #1: hardirq_stack, hrtimer_wakeup, S:01
> >        # expires at 10858649798503 nsecs [in 1327754230614 nsecs]
> >         .expires_next   : 9530893000000 nsecs
> >
> > See
> >
> >       http://lkml.org/lkml/2007/3/16/288
> >
> > and that in turn points to the kernel log:
> >
> >       http://www.stardust.webpages.pl/files/tbf/bitis-gabonica/2.6.21-rc4/git-console.log
>
> Seems convincing. Michal, can you post your .config, and if you had
> dynticks and hrtimers enabled, try reproducing without them?
>

http://www.stardust.webpages.pl/files/tbf/bitis-gabonica/2.6.21-rc4/git-config

I don't know how to reproduce this bug on 2.6.21-rc4.On 2.6.21-rc2-mm1
it was very simple, just run youtube, bash_shared_mapping etc. In fact
I didn't see this bug for a week.

Unfortunately, I wasn't able to take a crash dump because of sound
card driver bug (I've got crash dump from 2.6.21-rc2-mm1).

Regards,
Michal

-- 
Michal K. K. Piotrowski
LTG - Linux Testers Group (PL)
(http://www.stardust.webpages.pl/ltg/)
LTG - Linux Testers Group (EN)
(http://www.stardust.webpages.pl/linux_testers_group_en/)
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