linux-kernel - Re: BUG: unable to handle kernel NULL pointer dereference

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Date:	Sat, 26 Mar 2011 09:09:28 -0600
From:	Thomas Fjellstrom <thomas@...llstrom.ca>
To:	linux-kernel@...r.kernel.org
Subject: Re: BUG: unable to handle kernel NULL pointer dereference

On March 26, 2011, Thomas Fjellstrom wrote:
> On March 26, 2011, Thomas Fjellstrom wrote:
> > I was unable to capture the full OOPS/panic message as it was a full
> > panic. The kernel switched to a vt first so I could at least take a
> > picture, which I've attached.
> > 
> > This is with 2.6.37.2. A brief snippet from the image is as follows:
> > 
> > IP: [<ffffffff8110f3a7>] __mark_inode_dirty+0xca/0x1ac
> > PGD 9fe96067 PUD 30e34067 PMD 0
> > Oops: 0000 [#1] SMP
> > ...
> > 
> > Call Trace:
> >  ? touch_atime+0x111/0x13a
> >  ? filldir+0x0/0xc3
> >  ? vfs_readdir+0x84/0xaa
> >  ? sys_getdents+0x7d/0xcd
> >  ? page_fault+0x25/0x30
> >  ? system_call_fastpath+0x16/0x1b
> > 
> > This has only happened once so far, and a little while before this OOPS
> > happened, X crashed and was restarted.
> 
> And here's another possible related problem:
> 
> [13082.904110] INFO: task updatedb.mlocat:6215 blocked for more than 120
> seconds.
> [13082.904113] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables
> this message.
> [13082.904116] updatedb.mloc D ffff88002adf3600     0  6215   6208
> 0x00000000 [13082.904120]  ffff88002adf3600 0000000000000082
> ffff880100000000 ffffffff8160b020 [13082.904124]  00000000000136c0
> ffff88002a091fd8 00000000000136c0 00000000000136c0
> [13082.904127]  ffff88002adf38d8 ffff88002adf38e0 ffff88002adf3600
> 00000000000136c0 [13082.904130] Call Trace:
> [13082.904137]  [<ffffffff8111513b>] ? sync_buffer+0x0/0x3f
> [13082.904141]  [<ffffffff8131d6f3>] ? io_schedule+0x68/0xa7
> [13082.904144]  [<ffffffff81115176>] ? sync_buffer+0x3b/0x3f
> [13082.904146]  [<ffffffff8131db3f>] ? __wait_on_bit_lock+0x3c/0x85
> [13082.904149]  [<ffffffff8131dbf6>] ?
> out_of_line_wait_on_bit_lock+0x6e/0x77 [13082.904151] 
> [<ffffffff8111513b>] ? sync_buffer+0x0/0x3f
> [13082.904155]  [<ffffffff810605ab>] ? wake_bit_function+0x0/0x2e
> [13082.904164]  [<ffffffff81116033>] ? lock_buffer+0xe/0x2c
> [13082.904166]  [<ffffffff811168e5>] ? __bread+0x1d/0x62
> [13082.904171]  [<ffffffffa04639b2>] ? fat_get_entry+0x189/0x1ef [fat]
> [13082.904175]  [<ffffffffa0463a59>] ? fat_get_short_entry+0x41/0x53 [fat]
> [13082.904178]  [<ffffffffa0464b19>] ? fat_subdirs+0x57/0x74 [fat]
> [13082.904181]  [<ffffffffa0468e18>] ? fat_build_inode+0x1af/0x402 [fat]
> [13082.904184]  [<ffffffff81202020>] ? startup_pirq+0x3a/0x139
> [13082.904188]  [<ffffffffa02184cc>] ? vfat_lookup+0x57/0x16f [vfat]
> [13082.904191]  [<ffffffff810fbc19>] ? d_alloc_and_lookup+0x4a/0x67
> [13082.904193]  [<ffffffff810fbd26>] ? do_lookup+0xaa/0x100
> [13082.904196]  [<ffffffff81103590>] ? dput+0x2c/0x12f
> [13082.904198]  [<ffffffff810fdb69>] ? link_path_walk+0x2a1/0x3fb
> [13082.904201]  [<ffffffff810fddb2>] ? path_walk+0x63/0xd6
> [13082.904203]  [<ffffffff810fd406>] ? path_init+0x9a/0x16e
> [13082.904205]  [<ffffffff810fdf1b>] ? do_path_lookup+0x20/0x85
> [13082.904207]  [<ffffffff810fe9a9>] ? user_path_at+0x46/0x78
> [13082.904210]  [<ffffffff810f70dc>] ? cp_new_stat+0xe6/0xfa
> [13082.904213]  [<ffffffff810f7183>] ? vfs_fstatat+0x2e/0x5b
> [13082.904215]  [<ffffffff810f7208>] ? sys_newlstat+0x11/0x2d
> [13082.904218]  [<ffffffff810f2c00>] ? sys_fchdir+0x67/0x6e
> [13082.904221]  [<ffffffff81009a12>] ? system_call_fastpath+0x16/0x1b
> 
> theres 5-10 of those in dmesg, which started after I started copying some
> files to a new 16GB usb flash drive. The copies them selves have been
> going for hours now, waay too long, and both my CPU cores are pegged in
> iowait, and anything that tries to do too much with /any/ disk seems to
> hang up, including chromium and plain old 'ls'. according to iostat, io is
> going at about 8-40KB/s to the flash drive, and much less to my root
> drive.

I just noticed, that not all commands hang, but it seems that anything that 
tries to access my nfs share hangs up (like a 'ls ~/' since theres a couple 
links in ~ pointing to dirs on the nfs share). The nfs server is up though, 
and neither side lists any problems relating to nfs in dmesg.

Things have started working again just now as I'm writing this, but I killed 
the file copies about 10-20 minutes ago or so, that might have something to do 
with it. Also the light on the flash drive is still flashing, as if its still 
being written to.

-- 
Thomas Fjellstrom
thomas@...llstrom.ca
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