Hi Kalle, > ---------------------------------------------------------------------- > Ganapathi Bhat <gbhat@xxxxxxxxxxx> writes: > > > Whenever sched_scan(BG_SCAN) is in progress and driver downloads any > > command, firmware will send an event BG_SCAN_STOPPED. On recieving > > this, driver calls cfg80211_sched_scan_stopped. This function in turn > > will try to acquire rtnl_lock. But if the rtnl_lock was already > > held(while sending the command above), this will result in nested rtnl > > locking. To fix this driver must call rtnl version of the API if > > rtnl_is_locked(). > > > > Signed-off-by: Cathy Luo <cluo@xxxxxxxxxxx> > > Signed-off-by: Ganapathi Bhat <gbhat@xxxxxxxxxxx> > > Which one is the author? If Cathy is the author, you should add a From > header to indicate that. Sorry for the miss. Myself was the author. Will send v2 with corrections once we address the below comment. > > > --- a/drivers/net/wireless/marvell/mwifiex/sta_event.c > > +++ b/drivers/net/wireless/marvell/mwifiex/sta_event.c > > @@ -848,7 +848,10 @@ int mwifiex_process_sta_event(struct > > mwifiex_private *priv) > > > > case EVENT_BG_SCAN_STOPPED: > > dev_dbg(adapter->dev, "event: BGS_STOPPED\n"); > > - cfg80211_sched_scan_stopped(priv->wdev.wiphy, 0); > > + if (rtnl_is_locked()) > > + cfg80211_sched_scan_stopped_rtnl(priv- > >wdev.wiphy, 0); > > + else > > + cfg80211_sched_scan_stopped(priv->wdev.wiphy, > 0); > > IMHO checking if a lock is taking is rather ugly and an indication there's a > problem with the locking. Instead making an ugly workaround like this I > would rather investigate who is holding the rtnl and solve that. There can be applications trying to access driver(via cfg80211), holding rtnl_lock. For example(in our case): 1. "iw dev" was called, when BG_SCAN was active. 2. NL80211_CMD_GET_INTERFACE requires rtnl_lock to be hold(specified in internal_flags) 3. cfg80211 will hold rtnl_lock before calling "get_tx_power"(in pre_doit). 4. mwifiex will download RF_TX_PWR command to firmware 5. firmware will send BG_SCAN_STOPPED event(since BG_SCAN was active). 6. mwifiex will call "cfg80211_sched_scan_stopped" causing nested rtnl locking. Please share your comments further. > > -- > Kalle Valo
