Messages in this thread | | | Date | Tue, 23 Nov 2010 16:51:11 +0100 | From | Spelic <> | Subject | Bug: sync's hangup forever in call_rwsem_down_read_failed |
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Hi there on 2.6.37-rc2 I was doing some speed tests. I had just unmounted various arrays, recreated them differently with mdadm assume-clean, and then I was formatting all of them:
# for i in /dev/md10* ; do echo $i ; time mkfs.ext4 -m0 $i ; time sync ; done /dev/md101 mke2fs 1.41.9 (22-Aug-2009) /dev/md101 is apparently in use by the system; will not make a filesystem here!
real 0m0.038s user 0m0.000s sys 0m0.000s
Here I was pretty sure the error message was wrong: md101 was not in use by the system anyhow, and was not mounted. I had just created it. Anyway the subsequent sync hanged!
# cat /proc/7686/stack [<ffffffff8129e894>] call_rwsem_down_read_failed+0x14/0x30 [<ffffffff81137ff1>] iterate_supers+0x71/0xf0 [<ffffffff8115d92b>] sync_filesystems+0x1b/0x20 [<ffffffff8115da32>] sys_sync+0x12/0x40 [<ffffffff8100af42>] system_call_fastpath+0x16/0x1b [<ffffffffffffffff>] 0xffffffffffffffff
After a while I tried to launch another sync, from another shell; that hanged identically.
/proc# grep call_rwsem */stack 7686/stack:[<ffffffff8129e894>] call_rwsem_down_read_failed+0x14/0x30 7714/stack:[<ffffffff8129e894>] call_rwsem_down_read_failed+0x14/0x30 (this shows only the two syncs)
Then I tried to shut it down with poweroff -f (which does sync) and that hanged again
/proc# grep rwsem */stack 7686/stack:[<ffffffff8129e894>] call_rwsem_down_read_failed+0x14/0x30 7714/stack:[<ffffffff8129e894>] call_rwsem_down_read_failed+0x14/0x30 7815/stack:[<ffffffff8129e894>] call_rwsem_down_read_failed+0x14/0x30
so I shut it down with poweroff -n -f ; that worked.
It seems to me some process did not reset the semaphore after having finished (= resource leak)
Sorry for not being able to help you much more than this as I have reset the computer now, but this is another guy reporting apparently the same problem on Ubuntu 10.10 kernel (I was on vanilla 2.6.37-rc2) http://www.mail-archive.com/ubuntu-bugs@lists.ubuntu.com/msg2579131.html
My dmesg never notified about the problem, in something like 5minutes, btw.
If you reply, please reply also to me as I am not subsribed to linuk-kernel . Thanks for your work
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