Date:	Sun, 27 Jan 2008 00:46:26 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Frederik Himpe <fhimpe@...enet.be>
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?

Possible. Though I think it is more likely to be a bug in the
new deadlock avoidance code in the generic buffered write path.
Dang... I wonder why this hasn't come up earlier. It looks like
pan's use of writev might be tickling it.

How quickly can you reproduce this?

Can you use strace to see what the hanging syscall looks like?

Thanks,
Nick


> 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]
> generic_file_buffered_write+0x17f/0x6c0 Jan 26 14:17:43 Anastacia kernel: 
> [current_fs_time+30/48] current_fs_time+0x1e/0x30 Jan 26 14:17:43 Anastacia
> kernel:  [_end+127997742/2129947720] :xfs:xfs_write+0x676/0x910 Jan 26
> 14:17:43 Anastacia kernel:  [find_lock_page+61/192]
> find_lock_page+0x3d/0xc0 Jan 26 14:17:43 Anastacia kernel: 
> [_end+127981080/2129947720] :xfs:xfs_file_aio_write+0x0/0x50 Jan 26
> 14:17:43 Anastacia kernel:  [do_sync_readv_writev+203/272]
> do_sync_readv_writev+0xcb/0x110 Jan 26 14:17:43 Anastacia kernel: 
> [__do_fault+501/1056] __do_fault+0x1f5/0x420 Jan 26 14:17:43 Anastacia
> kernel:  [autoremove_wake_function+0/48] autoremove_wake_function+0x0/0x30
> Jan 26 14:17:43 Anastacia kernel:  [handle_mm_fault+1344/2048]
> handle_mm_fault+0x540/0x800 Jan 26 14:17:43 Anastacia kernel: 
> [rw_copy_check_uvector+157/336] rw_copy_check_uvector+0x9d/0x150 Jan 26
> 14:17:43 Anastacia kernel:  [do_readv_writev+253/560]
> do_readv_writev+0xfd/0x230 Jan 26 14:17:43 Anastacia kernel: 
> [sys_writev+83/144] sys_writev+0x53/0x90 Jan 26 14:17:43 Anastacia kernel: 
> [system_call+126/131] system_call+0x7e/0x83 Jan 26 14:17:43 Anastacia
> kernel:


> SysRq : Show Regs
> CPU 0:
> Modules linked in: usb_storage af_packet nvidia(P) vboxdrv ipv6 fuse
> snd_seq_dummy snd_seq_oss snd_seq_midi_event snd_seq cpufreq_ondemand
> video output tc1100_wmi sbs sbshc container dock battery ac binfmt_misc
> loop ext3 jbd dm_mirror sr_mod dm_mod pata_amd ata_generic sata_sil
> usbmouse usbhid ff_memless floppy usblp powernow_k8 freq_table
> snd_pcm_oss snd_mixer_oss snd_mpu401 snd_mpu401_uart snd_rawmidi ns558
> gameport parport_pc snd_seq_device parport rtc_cmos pcspkr snd_intel8x0
> k8temp snd_ac97_codec ohci1394 ac97_bus ieee1394 snd_pcm snd_timer skge
> ohci_hcd ehci_hcd snd soundcore usbcore forcedeth snd_page_alloc ssb fan
> pcmcia pcmcia_core i2c_nforce2 i2c_core button thermal processor sg
> evdev genrtc xfs scsi_wait_scan sd_mod sata_nv libata scsi_mod
> Pid: 7564, comm: pan Tainted: P        2.6.24-desktop-0.rc8.2.1mdv #1
> RIP: 0010:[<ffffffff802d5a57>]  [<ffffffff802d5a57>] block_write_begin
> +0x87/0xe0
> RSP: 0018:ffff81002e9b5ac8  EFLAGS: 00000286
> RAX: ffff81003f5b3248 RBX: 00000000fffffff4 RCX: 0000000000000000
> RDX: ffff81003f5b3248 RSI: 0000000000000000 RDI: ffff81002d1eda18
> RBP: ffff81003f5b3248 R08: 0000000000000000 R09: ffff81002e9b5be0
> R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000
> R13: ffffffff880c28b0 R14: 0000000000001000 R15: 000000003f5b3248
> FS:  00002b6bb3bf7960(0000) GS:ffffffff80589000(0000)
> knlGS:00000000f78568d0
> CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> CR2: 00002b0537cf6000 CR3: 00000000391d2000 CR4: 00000000000006e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
>
> Call Trace:
>  [<ffffffff802d5a4f>] block_write_begin+0x7f/0xe0
>  [<ffffffff880c2102>] :xfs:xfs_vm_write_begin+0x22/0x30
>  [<ffffffff880c28b0>] :xfs:xfs_get_blocks+0x0/0x10
>  [<ffffffff80280ba9>] generic_file_buffered_write+0x149/0x6c0
>  [<ffffffff80240a2e>] current_fs_time+0x1e/0x30
>  [<ffffffff880caae6>] :xfs:xfs_write+0x676/0x910
>  [<ffffffff8027f98d>] find_lock_page+0x3d/0xc0
>  [<ffffffff880c69d0>] :xfs:xfs_file_aio_write+0x0/0x50
>  [<ffffffff802aee9b>] do_sync_readv_writev+0xcb/0x110
>  [<ffffffff8028eb95>] __do_fault+0x1f5/0x420
>  [<ffffffff802522b0>] autoremove_wake_function+0x0/0x30
>  [<ffffffff80290b90>] handle_mm_fault+0x540/0x800
>  [<ffffffff802aecdd>] rw_copy_check_uvector+0x9d/0x150
>  [<ffffffff802af5fd>] do_readv_writev+0xfd/0x230
>  [<ffffffff802afc33>] sys_writev+0x53/0x90
>  [<ffffffff8020c36e>] system_call+0x7e/0x83
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