Messages in this thread | | | Date | Wed, 31 May 2006 14:38:49 +1000 | From | Nathan Scott <> | Subject | XFS related hang (was Re: How to send a break? - dump from frozen 64bit linux) |
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On Tue, May 30, 2006 at 09:20:31PM -0400, Steven Rostedt wrote: > Added all those listed in the MAINTAINERS file for XFS.
Thanks Steve.
> On Tue, 2006-05-30 at 15:03 -0400, Valdis.Kletnieks@vt.edu wrote: > > On Tue, 30 May 2006 12:22:01 +0200, Janos Haar said: > > Half the processes on the box seem wedged at that same mutex_lock. I can't > > seem to find an xfs_qm_shake in my source tree though.
Its in fs/xfs/quota/xfs_qm.c.
> kswapd0 D ffff81011fe03c38 0 297 1 1287 19 (L-TLB) > ffff81011fe03c38 0000000000000004 000000000000000a ffff81011f92ba68 > ffff81011f92b850 ffffffff805a23a0 0000149f99fa7d7c 000000000003bcde > 000000002f2c46e0 ffff81008bc37180 > Call Trace: <ffffffff804e5522>{schedule_timeout+34} > <ffffffff80269f87>{xfs_qm_dqunpin_wait+220} <ffffffff80140e74>{debug_mutex_free_waiter+141}
So, we're waiting here on a synchronisation variable that'll be released once the dquot metadata buffer write completes.
> So it is now waiting to be woken up by something that calls: > > xfs_qm_dquot_logitem_unpin which seems to be the function to wake it > up.
Mhmm, that'd be called by the I/O completion handler on the buffer containing that dquot.
> And decyphering all the macro crap it seems that the function that wakes > it up is xfs_trans_chunk_committed, or xfs_trans_uncommit.
Right (the former, at this point in the code).
> The above xfs_qm_dqunpin_wait still looks awfully racy, and the > xfs_log_force, which I'm assuming wakes up whoever is suppose to wake up > kswapd0, doesn't have a return code check. So if it failed to do
The logforce isn't race-critical here - its ensuring writeout of previously logged buffers is started before we go to sleep waiting for the driver to wake us up when its done.
An earlier I/O error on the journal is the only thing the log force can return as an error there, which isnt useful at that point anyway (we're in a kernel thread trying to free mem).
> whatever the hell it's doing (that code gives me a headache), it looks
Heh, likewise. I have voodoo dolls of one or two of the early XFS folks that I like to poke with needles occasionally.. :)
> like this guy might sleep forever holding a lock that will prevent > others from freeing kernel memory.
It will sleep until the previously initiated buffer write is done. AFAICT, we aren't seeing the I/O completion here for some reason... which points more to a possible device driver or h/ware issue (that is the usual root cause of this sort of hang, anyway).
cheers.
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