From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jia-Ju Bai <baijiaju1990@gmail.com>
Date: Thu, 19 Aug 2021 16:54:57 +0800
Subject: [Cluster-devel] [BUG] fs: dlm: possible ABBA deadlock
Message-ID: <79f8d302-f53f-3891-965a-bcb460ab15ca@gmail.com>
List-Id: <cluster-devel.redhat.com>
To: cluster-devel.redhat.com
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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 :)

Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>


Best wishes,
Jia-Ju Bai