There is a deadlock in rtw_joinbss_event_prehandle(), which is shown below:
(Thread 1) | (Thread 2)
| _set_timer()
rtw_joinbss_event_prehandle()| mod_timer()
spin_lock_bh() //(1) | (wait a time)
... | rtw_join_timeout_handler()
| _rtw_join_timeout_handler()
del_timer_sync() | spin_lock_bh() //(2)
(wait timer to stop) | ...
We hold pmlmepriv->lock in position (1) of thread 1 and
use del_timer_sync() to wait timer to stop, but timer handler
also need pmlmepriv->lock in position (2) of thread 2.
As a result, rtw_joinbss_event_prehandle() will block forever.
This patch extracts del_timer_sync() from the protection of
spin_lock_bh(), which could let timer handler to obtain
the needed lock. What`s more, we change spin_lock_bh() to
spin_lock_irq() in _rtw_join_timeout_handler() in order to
prevent deadlock.
Signed-off-by: Duoming Zhou <duoming@xxxxxxxxxx>
---
drivers/staging/r8188eu/core/rtw_mlme.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/staging/r8188eu/core/rtw_mlme.c b/drivers/staging/r8188eu/core/rtw_mlme.c
index 6f0bff18647..76cf6a69bf0 100644
--- a/drivers/staging/r8188eu/core/rtw_mlme.c
+++ b/drivers/staging/r8188eu/core/rtw_mlme.c
@@ -1071,8 +1071,10 @@ void rtw_joinbss_event_prehandle(struct adapter *adapter, u8 *pbuf)
rtw_indicate_connect(adapter);
}
+ spin_unlock_bh(&pmlmepriv->lock);
/* s5. Cancel assoc_timer */
del_timer_sync(&pmlmepriv->assoc_timer);
+ spin_lock_bh(&pmlmepriv->lock);
} else {
spin_unlock_bh(&pmlmepriv->scanned_queue.lock);
goto ignore_joinbss_callback;
@@ -1310,7 +1312,7 @@ void _rtw_join_timeout_handler (struct adapter *adapter)
if (adapter->bDriverStopped || adapter->bSurpriseRemoved)
return;
- spin_lock_bh(&pmlmepriv->lock);
+ spin_lock_irq(&pmlmepriv->lock);
if (rtw_to_roaming(adapter) > 0) { /* join timeout caused by roaming */
while (1) {
@@ -1329,7 +1331,7 @@ void _rtw_join_timeout_handler (struct adapter *adapter)
rtw_indicate_disconnect(adapter);
free_scanqueue(pmlmepriv);/* */
}
- spin_unlock_bh(&pmlmepriv->lock);
+ spin_unlock_irq(&pmlmepriv->lock);
}
--
2.17.1
