[PATCH 5.15 046/102] RDMA/irdma: Fix deadlock in irdma_cleanup_cm_core()

Greg Kroah-Hartman
2022-05-16T20:27:45Z

From: Duoming Zhou <duoming@zju.edu.cn>

[ 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>
---
drivers/infiniband/hw/irdma/cm.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/infiniband/hw/irdma/cm.c b/drivers/infiniband/hw/irdma/cm.c
index 082a3ddb0fa3..632f65e53b63 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);
--
2.35.1