linux-kernel - Re: 3.7-rc6 soft lockup in kswapd0

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Message-ID: <20121122220600.GA20326@quack.suse.cz>
Date:	Thu, 22 Nov 2012 23:06:00 +0100
From:	Jan Kara <jack@...e.cz>
To:	George Spelvin <linux@...izon.com>
Cc:	linux-kernel@...r.kernel.org, mgorman@...e.de, linux-mm@...ck.org
Subject: Re: 3.7-rc6 soft lockup in kswapd0

On Thu 22-11-12 12:58:24, George Spelvin wrote:
> I'm having an interesting issue with a uniprocessor Pentium 4 machine
> locking up overnight.  3.6.5 didn't do that, but 3.7-rc6 is not doing
> so well.
  I've added some CCs which are hopefully relevant. Specifially I remember
Mel fixing some -mm lockup recently although after googling for a while
that is likely something different.

> It's kind of a funny lockup.  Some things work:
> 
> - TCP SYN handshake
> - Alt-SysRq
> 
> And others don't:
> 
> - Caps lock
> - Shift-PgUp
> - Alt-Fn
> - Screen unblanking
> - Actually talking to a daemon
> 
> This is a "headless" machine that boots to a text console and has zero
> console activity until the lockup.
> 
> This has happened overnight, three nights in a row.  I had to turn screen
> blanking off to see anything on the screen.  Running the daily cron jobs
> manually just now didn't trigger it, so I haven't found a proximate cause.
> 
> The *first* error has scrolled off the screen, but what I can see
> an infinite stream (at about 20s intervals) of:
> 
> BUG: soft lockup - CPU#0 stuck for 22s! [kswapd0:317]
> Pid: 317, comm: kswapd0 Not tainted 3.7.0-RC6 #224 HP Pavilion 04 P6319A-ABA 750N/P4B266LA
> EIP: 0060:[<c10571f7>] EFLAGS: 00000202 CPU: 0
> EIP is at __zone_watermark_ok+0x5f/7e, 0x67/7e, 0x6e/0x7e, or 0x74/7e
> (Didn't type registers & stack)
> Call Trace:
>  [<c105774f>] ? zone_watermark_ok_safe+0x34/0x3a
>  [<c105ec7e>] ? kswapd+0x2fa/0x6f6
>  [<c105e984>] ? try_to_free_pages+0x4b8/0x4b8
>  [<c103106b>] ? kthread+0x67/0x6c
>  [<c12559b7>] ? ret_from_kernel_thread+0x1b/0x28
>  [<c1031004>] ? -_kthread_parkme+0x4c.0x4c
> Code: (didn't type in first line)
>                                 5f                        67                     6e                  74                             7e
>  c9 39 d6 7f 14 eb 1c 6b c1 2c <8b> 44 05 60 d3 e0 29 c6 <d1> fb 39 de 7e 09 41 <39> f9 7c ea b0 01 <eb> 02 31 c0 5a 5b 5e 5f 5d c3 01 14 85 7c 16
  Taking picture of the screen with a digital camera can usually save you
some typing :)

> The lack of scrollback limits me to 49 lines of SysRq output, and usually the most interesting
> part disappears off the screen.  Two things I can see:
> 
> - SysRq-W shows no blocked tasks
> - SysRq-M shows zero swap in use, and apparently adequate free memory
> 	DMA: <various segments> = 9048kB
> 	Normal: <various> = 116312kB
> 	HighMem: <various> = 41660kB
> 	416557 total pagecache pages
> 	0 pages in swap cache
> 	Swap cache stats: add 0, delete 0, find 0/0
> 	Free swap  = 4883724kB
> 	Total swap = 4883724kB
> 	524260 pages RAM
> 	296958 pages HighMem
> 	5221 pages reserved
> 	406417 pages shared
> 	351419 pages non-shared
> 
> Does anyone have any debugging suggestions?  Waiting overnight to
> make a good/bad decision makes bisecting pretty slow...

							Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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