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Date:   Tue, 8 Feb 2022 11:10:56 -0600
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Subject: Re: [BUG] scsi: qedi: possible ABBA deadlock in
 qedi_process_tmf_resp() and qedi_process_cmd_cleanup_resp()
Content-Language: en-US
To:     Jia-Ju Bai <baijiaju1990@gmail.com>, njavali@marvell.com,
        mrangankar@marvell.com, GR-QLogic-Storage-Upstream@marvell.com,
        jejb@linux.ibm.com, martin.petersen@oracle.com
Cc:     linux-scsi@vger.kernel.org,
        linux-kernel <linux-kernel@vger.kernel.org>
References: <e468fdcb-f47f-e01a-da65-68da79020165@gmail.com>
From:   Mike Christie <michael.christie@oracle.com>
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On 2/8/22 5:23 AM, Jia-Ju Bai wrote:
> Hello,
> 
> My static analysis tool reports a possible ABBA deadlock in the qedi driver in Linux 5.16:
> 
> qedi_process_tmf_resp()
>   spin_lock(&session->back_lock); --> Line 201 (Lock A)
>   spin_lock(&qedi_conn->tmf_work_lock); --> Line 230 (Lock B)
> 
> qedi_process_cmd_cleanup_resp()
>   spin_lock_bh(&qedi_conn->tmf_work_lock); --> Line 752 (Lock B)
>   spin_lock_bh(&conn->session->back_lock); --> Line 784 (Lock A)
> 
> When qedi_process_tmf_resp() and qedi_process_cmd_cleanup_resp() 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 :)
> 

That looks like a valid deadlock. I'll send a patch. Thanks.

> Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
> 
> 
> Best wishes,
> Jia-Ju Bai