Messages in this thread | | | Subject | Re: [PATCH] mwifiex: Fix possible ABBA deadlock | From | Jia-Ju Bai <> | Date | Tue, 30 Nov 2021 10:18:10 +0800 |
| |
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@gmail.com>: > > 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@chromium.org> > Reported-by: TOTE Robot <oslab@tsinghua.edu.cn> > Link: https://lore.kernel.org/linux-wireless/0e495b14-efbb-e0da-37bd-af6bd677ee2c@gmail.com/ > Signed-off-by: Brian Norris <briannorris@chromium.org> > --- > > 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); > } > } > }
| |