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Subject: Re: [BUG] fs: dlm: possible ABBA deadlock
To:     David Teigland <teigland@redhat.com>
Cc:     cluster-devel@redhat.com, linux-kernel@vger.kernel.org
References: <79f8d302-f53f-3891-965a-bcb460ab15ca@gmail.com>
 <20210819155509.GB21218@redhat.com>
From:   Jia-Ju Bai <baijiaju1990@gmail.com>
Message-ID: <fbf23736-26a7-7442-2c19-ae0bea25b296@gmail.com>
Date:   Fri, 20 Aug 2021 16:16:02 +0800
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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