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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        syzbot+831661966588c802aae9@syzkaller.appspotmail.com,
        Bart Van Assche <bvanassche@acm.org>,
        Leon Romanovsky <leonro@nvidia.com>,
        Jason Gunthorpe <jgg@nvidia.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.4 31/53] RDMA/ib_srp: Fix a deadlock
Date:   Mon, 28 Feb 2022 18:24:29 +0100
Message-Id: <20220228172250.528772715@linuxfoundation.org>
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From: Bart Van Assche <bvanassche@acm.org>

[ Upstream commit 081bdc9fe05bb23248f5effb6f811da3da4b8252 ]

Remove the flush_workqueue(system_long_wq) call since flushing
system_long_wq is deadlock-prone and since that call is redundant with a
preceding cancel_work_sync()

Link: https://lore.kernel.org/r/20220215210511.28303-3-bvanassche@acm.org
Fixes: ef6c49d87c34 ("IB/srp: Eliminate state SRP_TARGET_DEAD")
Reported-by: syzbot+831661966588c802aae9@syzkaller.appspotmail.com
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/infiniband/ulp/srp/ib_srp.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index 8708ed5477e99..dac806b715afa 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -4222,9 +4222,11 @@ static void srp_remove_one(struct ib_device *device, void *client_data)
 		spin_unlock(&host->target_lock);
 
 		/*
-		 * Wait for tl_err and target port removal tasks.
+		 * srp_queue_remove_work() queues a call to
+		 * srp_remove_target(). The latter function cancels
+		 * target->tl_err_work so waiting for the remove works to
+		 * finish is sufficient.
 		 */
-		flush_workqueue(system_long_wq);
 		flush_workqueue(srp_remove_wq);
 
 		kfree(host);
-- 
2.34.1