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.
What`s more, we change the check of timer_pending()
in order to guarantee the add_timer() in
irdma_schedule_cm_timer() and irdma_cm_timer_tick()
could be executed.
Signed-off-by: Duoming Zhou <duoming@xxxxxxxxxx>
---
Changes in V3:
- Change the check of timer_pending().
drivers/infiniband/hw/irdma/cm.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/drivers/infiniband/hw/irdma/cm.c b/drivers/infiniband/hw/irdma/cm.c
index dedb3b7edd8..1901792fd73 100644
--- a/drivers/infiniband/hw/irdma/cm.c
+++ b/drivers/infiniband/hw/irdma/cm.c
@@ -1181,7 +1181,7 @@ int irdma_schedule_cm_timer(struct irdma_cm_node *cm_node,
spin_lock_irqsave(&cm_core->ht_lock, flags);
was_timer_set = timer_pending(&cm_core->tcp_timer);
- if (!was_timer_set) {
+ if (was_timer_set) {
cm_core->tcp_timer.expires = new_send->timetosend;
add_timer(&cm_core->tcp_timer);
}
@@ -1364,7 +1364,7 @@ static void irdma_cm_timer_tick(struct timer_list *t)
if (settimer) {
spin_lock_irqsave(&cm_core->ht_lock, flags);
- if (!timer_pending(&cm_core->tcp_timer)) {
+ if (timer_pending(&cm_core->tcp_timer)) {
cm_core->tcp_timer.expires = nexttimeout;
add_timer(&cm_core->tcp_timer);
}
@@ -3251,10 +3251,7 @@ void irdma_cleanup_cm_core(struct irdma_cm_core *cm_core)
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);
--
2.17.1
