There is a deadlock in rtw_surveydone_event_callback(),
which is shown below:
(Thread 1) | (Thread 2)
| _set_timer()
rtw_surveydone_event_callback()| mod_timer()
spin_lock_bh() //(1) | (wait a time)
... | rtw_scan_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_surveydone_event_callback() 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.
Signed-off-by: Duoming Zhou <duoming@xxxxxxxxxx>
---
drivers/staging/rtl8723bs/core/rtw_mlme.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/staging/rtl8723bs/core/rtw_mlme.c b/drivers/staging/rtl8723bs/core/rtw_mlme.c
index ed2d3b7d44d..d559eefe633 100644
--- a/drivers/staging/rtl8723bs/core/rtw_mlme.c
+++ b/drivers/staging/rtl8723bs/core/rtw_mlme.c
@@ -751,7 +751,9 @@ void rtw_surveydone_event_callback(struct adapter *adapter, u8 *pbuf)
}
if (check_fwstate(pmlmepriv, _FW_UNDER_SURVEY)) {
+ spin_unlock_bh(&pmlmepriv->lock);
del_timer_sync(&pmlmepriv->scan_to_timer);
+ spin_lock_bh(&pmlmepriv->lock);
_clr_fwstate_(pmlmepriv, _FW_UNDER_SURVEY);
}
--
2.17.1
