Re: [BUG] scsi: qedi: possible ABBA deadlock in qedi_process_tmf_resp() and qedi_process_cmd_cleanup_resp()

[Mike Christie]

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@xxxxxxxxxxxxxxx>
> 
> 
> Best wishes,
> Jia-Ju Bai