Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Jia-Ju Bai <baijiaju1990@gmail.com>
Subject: [BUG] infiniband: sw: rdmavt: possible ABBA deadlocks in
 rvt_ruc_loopback()
To:     dennis.dalessandro@cornelisnetworks.com, jgg@ziepe.ca,
        Leon Romanovsky <leon@kernel.org>
Cc:     linux-rdma@vger.kernel.org,
        linux-kernel <linux-kernel@vger.kernel.org>
Message-ID: <afe67a8e-82b8-9a47-0832-527c652cc66e@gmail.com>
Date:   Thu, 20 Oct 2022 21:37:47 +0800
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101
 Thunderbird/68.4.1
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit
Content-Language: en-US
Precedence: bulk

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>


Best wishes,
Jia-Ju Bai