Hi Brian, Thanks for your reply and explanation! The patch looks good to me :) Best wishes, Jia-Ju Bai On 2021/11/30 8:47, Brian Norris wrote:
Quoting Jia-Ju Bai <baijiaju1990@xxxxxxxxx>: mwifiex_dequeue_tx_packet() spin_lock_bh(&priv->wmm.ra_list_spinlock); --> Line 1432 (Lock A) mwifiex_send_addba() spin_lock_bh(&priv->sta_list_spinlock); --> Line 608 (Lock B) mwifiex_process_sta_tx_pause() spin_lock_bh(&priv->sta_list_spinlock); --> Line 398 (Lock B) mwifiex_update_ralist_tx_pause() spin_lock_bh(&priv->wmm.ra_list_spinlock); --> Line 941 (Lock A) Similar report for mwifiex_process_uap_tx_pause(). While the locking expectations in this driver are a bit unclear, the Fixed commit only intended to protect the sta_ptr, so we can drop the lock as soon as we're done with it. IIUC, this deadlock cannot actually happen, because command event processing (which calls mwifiex_process_sta_tx_pause()) is sequentialized with TX packet processing (e.g., mwifiex_dequeue_tx_packet()) via the main loop (mwifiex_main_process()). But it's good not to leave this potential issue lurking. Fixes: ("f0f7c2275fb9 mwifiex: minor cleanups w/ sta_list_spinlock in cfg80211.c") Cc: Douglas Anderson <dianders@xxxxxxxxxxxx> Reported-by: TOTE Robot <oslab@xxxxxxxxxxxxxxx> Link: https://lore.kernel.org/linux-wireless/0e495b14-efbb-e0da-37bd-af6bd677ee2c@xxxxxxxxx/ Signed-off-by: Brian Norris <briannorris@xxxxxxxxxxxx> --- On Tue, Nov 23, 2021 at 11:31:34AM +0800, Jia-Ju Bai wrote:I am not quite sure whether these possible deadlocks are real and how to fix them if they are real. Any feedback would be appreciated, thanks :)I think these are at least theoretically real, and so we should take something like the $subject patch probably. But I don't believe we can actually hit this due to the main-loop structure of this driver. Anyway, see the surrounding patch. Thanks, Brian drivers/net/wireless/marvell/mwifiex/sta_event.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/net/wireless/marvell/mwifiex/sta_event.c b/drivers/net/wireless/marvell/mwifiex/sta_event.c index 80e5d44bad9d..7d42c5d2dbf6 100644 --- a/drivers/net/wireless/marvell/mwifiex/sta_event.c +++ b/drivers/net/wireless/marvell/mwifiex/sta_event.c @@ -365,10 +365,12 @@ static void mwifiex_process_uap_tx_pause(struct mwifiex_private *priv, sta_ptr = mwifiex_get_sta_entry(priv, tp->peermac); if (sta_ptr && sta_ptr->tx_pause != tp->tx_pause) { sta_ptr->tx_pause = tp->tx_pause; + spin_unlock_bh(&priv->sta_list_spinlock); mwifiex_update_ralist_tx_pause(priv, tp->peermac, tp->tx_pause); + } else { + spin_unlock_bh(&priv->sta_list_spinlock); } - spin_unlock_bh(&priv->sta_list_spinlock); } }@@ -400,11 +402,13 @@ static void mwifiex_process_sta_tx_pause(struct mwifiex_private *priv,sta_ptr = mwifiex_get_sta_entry(priv, tp->peermac); if (sta_ptr && sta_ptr->tx_pause != tp->tx_pause) { sta_ptr->tx_pause = tp->tx_pause; + spin_unlock_bh(&priv->sta_list_spinlock); mwifiex_update_ralist_tx_pause(priv, tp->peermac, tp->tx_pause); + } else { + spin_unlock_bh(&priv->sta_list_spinlock); } - spin_unlock_bh(&priv->sta_list_spinlock); } } }
