From: Waiman Long <waiman.long@hp.com>
To: Josef Bacik <jbacik@fb.com>
Cc: Marc Dionne <marc.c.dionne@gmail.com>,
linux-btrfs@vger.kernel.org, clm@fb.com, t-itoh@jp.fujitsu.com
Subject: Re: Lockups with btrfs on 3.16-rc1 - bisected
Date: Wed, 18 Jun 2014 18:47:30 -0400 [thread overview]
Message-ID: <53A21702.8090109@hp.com> (raw)
In-Reply-To: <53A2125B.3050701@fb.com>
On 06/18/2014 06:27 PM, Josef Bacik wrote:
>
>
> On 06/18/2014 03:17 PM, Waiman Long wrote:
>> On 06/18/2014 04:57 PM, Marc Dionne wrote:
>>> Hi,
>>>
>>> I've been seeing very reproducible soft lockups with 3.16-rc1 similar
>>> to what is reported here:
>>> https://urldefense.proofpoint.com/v1/url?u=http://marc.info/?l%3Dlinux-btrfs%26m%3D140290088532203%26w%3D2&k=ZVNjlDMF0FElm4dQtryO4A%3D%3D%0A&r=cKCbChRKsMpTX8ybrSkonQ%3D%3D%0A&m=aoagvtZMwVb16gh1HApZZL00I7eP50GurBpuEo3l%2B5g%3D%0A&s=c62558feb60a480bbb52802093de8c97b5e1f23d4100265b6120c8065bd99565
>>>
>>> , along with the
>>> occasional hard lockup, making it impossible to complete a parallel
>>> build on a btrfs filesystem for the package I work on. This was
>>> working fine just a few days before rc1.
>>>
>>> Bisecting brought me to the following commit:
>>>
>>> commit bd01ec1a13f9a327950c8e3080096446c7804753
>>> Author: Waiman Long<Waiman.Long@hp.com>
>>> Date: Mon Feb 3 13:18:57 2014 +0100
>>>
>>> x86, locking/rwlocks: Enable qrwlocks on x86
>>>
>>> And sure enough if I revert that commit on top of current mainline,
>>> I'm unable to reproduce the soft lockups and hangs.
>>>
>>> Marc
>>
>> The queue rwlock is fair. As a result, recursive read_lock is not
>> allowed unless the task is in an interrupt context. Doing recursive
>> read_lock will hang the process when a write_lock happens somewhere in
>> between. Are recursive read_lock being done in the btrfs code?
>>
>
> We walk down a tree and read lock each node as we walk down, is that
> what you mean? Or do you mean read_lock multiple times on the same
> lock in the same process, cause we definitely don't do that. Thanks,
>
> Josef
I meant recursively read_lock the same lock in a process.
-Longman
next prev parent reply other threads:[~2014-06-18 22:47 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-18 20:57 Lockups with btrfs on 3.16-rc1 - bisected Marc Dionne
2014-06-18 22:17 ` Waiman Long
2014-06-18 22:27 ` Josef Bacik
2014-06-18 22:47 ` Waiman Long [this message]
2014-06-18 23:10 ` Josef Bacik
2014-06-18 23:19 ` Waiman Long
2014-06-18 23:27 ` Chris Mason
2014-06-18 23:30 ` Waiman Long
2014-06-18 23:53 ` Chris Mason
2014-06-19 0:03 ` Marc Dionne
2014-06-19 0:08 ` Waiman Long
2014-06-19 0:41 ` Marc Dionne
2014-06-19 2:03 ` Marc Dionne
2014-06-19 2:11 ` Chris Mason
2014-06-19 3:21 ` Waiman Long
2014-06-19 16:51 ` Chris Mason
2014-06-19 17:52 ` Waiman Long
2014-06-19 20:10 ` Chris Mason
2014-06-19 21:50 ` Chris Mason
2014-06-19 23:21 ` Waiman Long
2014-06-20 3:20 ` Tsutomu Itoh
2014-06-21 1:09 ` Long, Wai Man
2014-06-19 9:49 ` btrfs-transacti:516 blocked 120 seconds on 3.16-rc1 Konstantinos Skarlatos
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