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Re: [RFC PATCH v3 2/2] xfs: fix xfsaild hang due to lost wake ups

To: Brian Foster <bfoster@xxxxxxxxxx>
Subject: Re: [RFC PATCH v3 2/2] xfs: fix xfsaild hang due to lost wake ups
From: Mark Tinguely <tinguely@xxxxxxx>
Date: Wed, 23 May 2012 13:19:31 -0500
Cc: Dave Chinner <david@xxxxxxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <4FBD2306.8090000@xxxxxxxxxx>
References: <1337704714-50235-1-git-send-email-bfoster@xxxxxxxxxx> <1337704714-50235-3-git-send-email-bfoster@xxxxxxxxxx> <20120523005830.GL25351@dastard> <4FBD2306.8090000@xxxxxxxxxx>
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On 05/23/12 12:48, Brian Foster wrote:
On 05/22/2012 08:58 PM, Dave Chinner wrote:

Finally, rather than calling wake_up_process() in the
xfs_ail_push*() functions, call wake_up(&ailp->xa_idle); There can
only be one thread sleeping on that (the xfsaild) so there is no
need to use the wake_up_all() variant...

FWIW, you might be able to do this without the idle wait queue and
just use wake_up_process() -

Hi Dave,

I have a working version of your suggested algorithm. It looks mostly the same 
with the exception of a spin_unlock fix. I also have the below version that 
uses a wait_queue and that I plan to test overnight tonight:


FYI. Test 273 in a loop will still cause the sync_worker to lock when it tries to allocate a dummy transaction.

PID: 29214  TASK: ffff8807e66404c0  CPU: 1   COMMAND: "kworker/1:15"
 #0 [ffff88081f551b60] __schedule at ffffffff814175d0
 #1 [ffff88081f551ca8] schedule at ffffffff81417944
 #2 [ffff88081f551cb8] xlog_grant_head_wait at ffffffffa055a6d5 [xfs]
 #3 [ffff88081f551d08] xlog_grant_head_check at ffffffffa055a856 [xfs]
 #4 [ffff88081f551d48] xfs_log_reserve at ffffffffa055a95f [xfs]
 #5 [ffff88081f551d88] xfs_trans_reserve at ffffffffa0557ee4 [xfs]
 #6 [ffff88081f551dd8] xfs_fs_log_dummy at ffffffffa050cf88 [xfs]
 #7 [ffff88081f551df8] xfs_sync_worker at ffffffffa0518454 [xfs]
 #8 [ffff88081f551e18] process_one_work at ffffffff810564ad
 #9 [ffff88081f551e68] worker_thread at ffffffff81059203
#10 [ffff88081f551ee8] kthread at ffffffff8105dd2e
#11 [ffff88081f551f48] kernel_thread_helper at ffffffff81421a64

I understand why the dummy transaction was added and I think we can anticipate the hang before it happens and avoid it.

--Mark T.

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