linux-kernel - Re: 2.6.24 regression: pan hanging unkilleable and un-straceable

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Date:	Mon, 28 Jan 2008 12:46:23 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Frederik Himpe <fhimpe@...enet.be>,
	Andrew Morton <akpm@...ux-foundation.org>, stable@...nel.org
Cc:	Mike Galbraith <efault@....de>, linux-kernel@...r.kernel.org
Subject: Re: 2.6.24 regression: pan hanging unkilleable and un-straceable

On Sunday 27 January 2008 00:29, Frederik Himpe wrote:
> On di, 2008-01-22 at 16:25 +1100, Nick Piggin wrote:
> > > > On Tuesday 22 January 2008 07:58, Frederik Himpe wrote:
> > > > > With Linux 2.6.24-rc8 I often have the problem that the pan usenet
> > > > > reader starts using 100% of CPU time after some time. When this
> > > > > happens, kill -9 does not work, and strace just hangs when trying
> > > > > to attach to the process. The same with gdb. ps shows the process
> > > > > as being in the R state.
> > > > >
> > > > > I pressed Ctrl-Alt-SysRq-T, and this was shown for pan:
> > > > > Jan 21 21:45:01 Anastacia kernel: pan           R  running task
> > > > > 0
> >
> > Nasty. The attached patch is something really simple that can sometimes
> > help. sysrq+p is also an option, if you're on a UP system.
> >
> > Any luck getting traces?
>
> I just succeeded to reproduce the problem with this patch. Does this
> smell like an XFS problem?
>
> Jan 26 14:17:43 Anastacia kernel: pan           R  running task        0 
> 7564      1 Jan 26 14:17:43 Anastacia kernel:  000000003f5b3248
> 0000000000001000 ffffffff880c28b0 0000000000000000 Jan 26 14:17:43
> Anastacia kernel:  ffff81003f5b3248 ffff81002d1ed900 000000002d1ed900
> 0000000000000000 Jan 26 14:17:43 Anastacia kernel:  ffff810016050dd0
> fffff000fffff000 0000000000000000 ffff81002d1eda10 Jan 26 14:17:43
> Anastacia kernel: Call Trace:
> Jan 26 14:17:43 Anastacia kernel:  [_end+127964408/2129947720]
> :xfs:xfs_get_blocks+0x0/0x10 Jan 26 14:17:43 Anastacia kernel: 
> [unix_poll+0/176] unix_poll+0x0/0xb0 Jan 26 14:17:43 Anastacia kernel: 
> [_end+127964408/2129947720] :xfs:xfs_get_blocks+0x0/0x10 Jan 26 14:17:43
> Anastacia kernel:  [iov_iter_copy_from_user_atomic+65/160]
> iov_iter_copy_from_user_atomic+0x41/0xa0 Jan 26 14:17:43 Anastacia kernel: 
> [iov_iter_copy_from_user_atomic+46/160]
> iov_iter_copy_from_user_atomic+0x2e/0xa0 Jan 26 14:17:43 Anastacia kernel: 
> [generic_file_buffered_write+383/1728]

Well after trying a lot of writev combinations, I've reproduced a hang
*hangs head*.

Does this help?

View attachment "mm-zerolen-iov-fix.patch" of type "text/x-diff" (1682 bytes)