From: Duoming Zhou <duoming@zju.edu.cn>
Date: Mon, 18 Apr 2022 15:33:22 +0000 (+0800)
Subject: RDMA/irdma: Fix deadlock in irdma_cleanup_cm_core()
X-Git-Tag: v5.15.73~4312
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=2f6b75c03c7f6b62ee6bad79304eac0ce1fd735a;p=platform%2Fkernel%2Flinux-rpi.git

RDMA/irdma: Fix deadlock in irdma_cleanup_cm_core()

[ Upstream commit 679ab61bf5f5f519377d812afb4fb93634782c74 ]

There is a deadlock in irdma_cleanup_cm_core(), which is shown below:

   (Thread 1)              |      (Thread 2)
                           | irdma_schedule_cm_timer()
irdma_cleanup_cm_core()    |  add_timer()
 spin_lock_irqsave() //(1) |  (wait a time)
 ...                       | irdma_cm_timer_tick()
 del_timer_sync()          |  spin_lock_irqsave() //(2)
 (wait timer to stop)      |  ...

We hold cm_core->ht_lock in position (1) of thread 1 and use
del_timer_sync() to wait timer to stop, but timer handler also need
cm_core->ht_lock in position (2) of thread 2.  As a result,
irdma_cleanup_cm_core() will block forever.

This patch removes the check of timer_pending() in
irdma_cleanup_cm_core(), because the del_timer_sync() function will just
return directly if there isn't a pending timer. As a result, the lock is
redundant, because there is no resource it could protect.

Link: https://lore.kernel.org/r/20220418153322.42524-1-duoming@zju.edu.cn
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Reviewed-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/drivers/infiniband/hw/irdma/cm.c b/drivers/infiniband/hw/irdma/cm.c
index 082a3dd..632f65e 100644
--- a/drivers/infiniband/hw/irdma/cm.c
+++ b/drivers/infiniband/hw/irdma/cm.c
@@ -3242,15 +3242,10 @@ enum irdma_status_code irdma_setup_cm_core(struct irdma_device *iwdev,
  */
 void irdma_cleanup_cm_core(struct irdma_cm_core *cm_core)
 {
-	unsigned long flags;
-
 	if (!cm_core)
 		return;
 
-	spin_lock_irqsave(&cm_core->ht_lock, flags);
-	if (timer_pending(&cm_core->tcp_timer))
-		del_timer_sync(&cm_core->tcp_timer);
-	spin_unlock_irqrestore(&cm_core->ht_lock, flags);
+	del_timer_sync(&cm_core->tcp_timer);
 
 	destroy_workqueue(cm_core->event_wq);
 	cm_core->dev->ws_reset(&cm_core->iwdev->vsi);