Messages in this thread | | | From | Kalle Valo <> | Subject | Re: [PATCH wireless] ar5523: Fix deadlock bugs caused by cancel_work_sync in ar5523_stop | Date | Mon, 30 May 2022 14:24:04 +0300 |
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Duoming Zhou <duoming@zju.edu.cn> writes:
> If the work item is running, the cancel_work_sync in ar5523_stop will > not return until work item is finished. If we hold mutex_lock and use > cancel_work_sync to wait the work item to finish, the work item such as > ar5523_tx_wd_work and ar5523_tx_work also require mutex_lock. As a result, > the ar5523_stop will be blocked forever. One of the race conditions is > shown below: > > (Thread 1) | (Thread 2) > ar5523_stop | > mutex_lock(&ar->mutex) | ar5523_tx_wd_work > | mutex_lock(&ar->mutex) > cancel_work_sync | ... > > This patch moves cancel_work_sync out of mutex_lock in order to mitigate > deadlock bugs. > > Fixes: b7d572e1871d ("ar5523: Add new driver") > Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
I assume you have found this with a static checker tool, it would be good document what tool you are using. And if you have not tested this with real hardware clearly mention that with "Compile tested only".
> --- > drivers/net/wireless/ath/ar5523/ar5523.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/net/wireless/ath/ar5523/ar5523.c b/drivers/net/wireless/ath/ar5523/ar5523.c > index 9cabd342d15..99d6b13ffcf 100644 > --- a/drivers/net/wireless/ath/ar5523/ar5523.c > +++ b/drivers/net/wireless/ath/ar5523/ar5523.c > @@ -1071,8 +1071,10 @@ static void ar5523_stop(struct ieee80211_hw *hw) > ar5523_cmd_write(ar, WDCMSG_TARGET_STOP, NULL, 0, 0); > > del_timer_sync(&ar->tx_wd_timer); > + mutex_unlock(&ar->mutex); > cancel_work_sync(&ar->tx_wd_work); > cancel_work_sync(&ar->rx_refill_work); > + mutex_lock(&ar->mutex); > ar5523_cancel_rx_bufs(ar); > mutex_unlock(&ar->mutex); > }
Releasing a lock and taking it again looks like a hack to me. Please test with a real device and try to find a better solution.
-- https://patchwork.kernel.org/project/linux-wireless/list/
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
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