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Message-ID: <7de1e986-b6bc-8cf4-d5d6-259037fe7340@cornelisnetworks.com>
Date:   Thu, 20 Oct 2022 12:15:35 -0400
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Subject: Re: [BUG] infiniband: sw: rdmavt: possible ABBA deadlocks in
 rvt_ruc_loopback()
Content-Language: en-US
To:     Jia-Ju Bai <baijiaju1990@gmail.com>, jgg@ziepe.ca,
        Leon Romanovsky <leon@kernel.org>
Cc:     linux-rdma@vger.kernel.org,
        linux-kernel <linux-kernel@vger.kernel.org>
References: <afe67a8e-82b8-9a47-0832-527c652cc66e@gmail.com>
From:   Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
In-Reply-To: <afe67a8e-82b8-9a47-0832-527c652cc66e@gmail.com>
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On 10/20/22 9:37 AM, Jia-Ju Bai wrote:
> Hello,
> 
> My static analysis tool reports several possible ABBA deadlock in the 
> rdmavt driver in Linux 5.18:
> 
> rvt_ruc_loopback()
>    spin_lock_irqsave(&sqp->s_lock, flags); --> Line 3190 (Lock A)
>    spin_lock(&sqp->r_lock); --> Line 3195 (Lock B)
> 
> rvt_qp_mr_clean()
>    spin_lock_irq(&qp->r_lock); --> Line 698 (Lock B)
>    spin_lock(&qp->s_lock); --> Line 700 (Lock A)
> 
> rvt_rc_timeout()
>    spin_lock_irqsave(&qp->r_lock, flags); --> Line 2595 (Lock B)
>    spin_lock(&qp->s_lock); --> Line 2596 (Lock A)
> 
> rvt_modify_qp()
>    spin_lock_irq(&qp->r_lock); --> Line 1419 (Lock B)
>    spin_lock(&qp->s_lock); --> Line 1421(Lock A)
> 
> _rvt_reset_qp()
>    spin_lock_irq(&qp->r_lock); --> Line 907 (Lock B)
>    spin_lock(&qp->s_lock); --> Line 909 (Lock A)
> 
> rvt_reset_qp()
>    spin_lock_irq(&qp->r_lock); --> Line 936 (Lock B)
>    spin_lock(&qp->s_lock); --> Line 938 (Lock A)
> 
> When rvt_ruc_loopback() is concurrently executed with rvt_qp_mr_clean(), 
> rvt_rc_timeout(), rvt_modify_qp(), _rvt_reset_qp() or rvt_reset_qp(), 
> the deadlocks can occur.
> 
> I am not quite sure whether these possible deadlocks are real and how to 
> fix them if real.
> Any feedback would be appreciated, thanks :)
> 
> Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>

Thanks, we'll look into them.

-Denny