linux-kernel - Re: [BUG] fs: dlm: possible ABBA deadlock

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Date:   Fri, 20 Aug 2021 16:16:02 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     David Teigland <teigland@...hat.com>
Cc:     cluster-devel@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [BUG] fs: dlm: possible ABBA deadlock



On 2021/8/19 23:55, David Teigland wrote:
> On Thu, Aug 19, 2021 at 04:54:57PM +0800, Jia-Ju Bai wrote:
>> Hello,
>>
>> My static analysis tool reports a possible ABBA deadlock in the dlm
>> filesystem in Linux 5.10:
>>
>> dlm_recover_waiters_pre()
>>    mutex_lock(&ls->ls_waiters_mutex); --> line 5130
>>    recover_convert_waiter()
>>      _receive_convert_reply()
>>        lock_rsb()
>>          mutex_lock(&r->res_mutex); --> line 69
>>
>> dlm_recover_waiters_post()
>>    lock_rsb()
>>      mutex_lock(&r->res_mutex); --> line 69
>>    mutex_lock(&ls->ls_waiters_mutex); --> line 5307
>>
>> When dlm_recover_waiters_pre() and dlm_recover_waiters_post() are
>> concurrently executed, the deadlock can occur.
>>
>> I am not quite sure whether this possible deadlock is real and how to fix it
>> if it is real.
>> Any feedback would be appreciated, thanks :)
> They won't be concurrent, "pre" runs before recovery, and "post" is after.

Okay, thanks for your reply :)


Best wishes,
Jia-Ju Bai