[PATCH v2] wifi: mt76: mt792x: Fix a potential deadlock in high-load situations

[Leon Yen]

A deadlock may occur between two works, ps_work and mac_work, if their work
functions run simultaneously as they attempt to cancel each other by
calling cancel_delayed_work_sync().

mt792x_mac_work() ->   ...  -> cancel_delayed_work_sync(&pm->ps_work);
mt792x_pm_power_save_work() -> cancel_delayed_work_sync(&mphy->mac_work);

In high-load situations, they are queued but may not have chance to be
executed until the CPUs are released. Once the CPUs are available, there
is a high possibility that the ps_work function and mac_work function will
be executed simultaneously, resulting in a possible deadlock.

This patch replaces cancel_delayed_work_sync() with cancel_delayed_work()
in ps_work to eliminate the deadlock and make the code easier to maintain.

Signed-off-by: Leon Yen <leon.yen at mediatek.com>
---
v2: Modify the solution to make it simpler and easier to maintain
---
 drivers/net/wireless/mediatek/mt76/mt792x_mac.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt792x_mac.c b/drivers/net/wireless/mediatek/mt76/mt792x_mac.c
index 71dec93094eb..888e5a505673 100644
--- a/drivers/net/wireless/mediatek/mt76/mt792x_mac.c
+++ b/drivers/net/wireless/mediatek/mt76/mt792x_mac.c
@@ -375,7 +375,7 @@ void mt792x_pm_power_save_work(struct work_struct *work)
 	}
 
 	if (!mt792x_mcu_fw_pmctrl(dev)) {
-		cancel_delayed_work_sync(&mphy->mac_work);
+		cancel_delayed_work(&mphy->mac_work);
 		return;
 	}
 out:
-- 
2.45.2