> Subject: [PATCH] rtw88: avoid circular locking between local->iflist_mtx and
> rtwdev->mutex
>
> Remove circular lock dependency by using atomic version of interfaces
> iterate in watch_dog_work(), hence avoid taking local->iflist_mtx
> (rtw_vif_watch_dog_iter() only update some data, it can be called from
> atomic context). Fixes below LOCKDEP warning:
>
> [ 1157.219415]
> ======================================================
> [ 1157.225772] [ INFO: possible circular locking dependency detected ]
> [ 1157.232150] 3.10.0-1043.el7.sgruszka1.x86_64.debug #1 Not tainted
> [ 1157.238346] -------------------------------------------------------
> [ 1157.244635] kworker/u4:2/14490 is trying to acquire lock:
> [ 1157.250194] (&rtwdev->mutex){+.+.+.}, at: [<ffffffffc098322b>]
> rtw_ops_config+0x2b/0x90 [rtw88]
> [ 1157.259151]
> but task is already holding lock:
> [ 1157.265085] (&local->iflist_mtx){+.+...}, at: [<ffffffffc0b8ab7a>]
> ieee80211_mgd_probe_ap.part.28+0xca/0x160 [mac80211]
> [ 1157.276169]
> which lock already depends on the new lock.
>
> [ 1157.284488]
> the existing dependency chain (in reverse order) is:
> [ 1157.292101]
> -> #2 (&local->iflist_mtx){+.+...}:
> [ 1157.296919] [<ffffffffbc741a29>] lock_acquire+0x99/0x1e0
> [ 1157.302955] [<ffffffffbce72793>] mutex_lock_nested+0x93/0x410
> [ 1157.309416] [<ffffffffc0b6038f>]
> ieee80211_iterate_interfaces+0x2f/0x60 [mac80211]
> [ 1157.317730] [<ffffffffc09811ab>]
> rtw_watch_dog_work+0xcb/0x130 [rtw88]
> [ 1157.325003] [<ffffffffbc6d77bc>] process_one_work+0x22c/0x720
> [ 1157.331481] [<ffffffffbc6d7dd6>] worker_thread+0x126/0x3b0
> [ 1157.337589] [<ffffffffbc6e107f>] kthread+0xef/0x100
> [ 1157.343260] [<ffffffffbce848b7>]
> ret_from_fork_nospec_end+0x0/0x39
> [ 1157.350091]
> -> #1 ((&(&rtwdev->watch_dog_work)->work)){+.+...}:
> [ 1157.356314] [<ffffffffbc741a29>] lock_acquire+0x99/0x1e0
> [ 1157.362427] [<ffffffffbc6d570b>] flush_work+0x5b/0x310
> [ 1157.368287] [<ffffffffbc6d740e>]
> __cancel_work_timer+0xae/0x170
> [ 1157.374940] [<ffffffffbc6d7583>]
> cancel_delayed_work_sync+0x13/0x20
> [ 1157.381930] [<ffffffffc0982b49>] rtw_core_stop+0x29/0x50
> [rtw88]
> [ 1157.388679] [<ffffffffc098bee6>] rtw_enter_ips+0x16/0x20
> [rtw88]
> [ 1157.395428] [<ffffffffc0983242>] rtw_ops_config+0x42/0x90
> [rtw88]
> [ 1157.402173] [<ffffffffc0b13343>]
> ieee80211_hw_config+0xc3/0x680 [mac80211]
> [ 1157.409854] [<ffffffffc0b3925b>]
> ieee80211_do_open+0x69b/0x9c0 [mac80211]
> [ 1157.417418] [<ffffffffc0b395e9>] ieee80211_open+0x69/0x70
> [mac80211]
> [ 1157.424496] [<ffffffffbcd03442>] __dev_open+0xe2/0x160
> [ 1157.430356] [<ffffffffbcd03773>]
> __dev_change_flags+0xa3/0x180
> [ 1157.436922] [<ffffffffbcd03879>] dev_change_flags+0x29/0x60
> [ 1157.443224] [<ffffffffbcda14c4>] devinet_ioctl+0x794/0x890
> [ 1157.449331] [<ffffffffbcda27b5>] inet_ioctl+0x75/0xa0
> [ 1157.455087] [<ffffffffbccd54eb>] sock_do_ioctl+0x2b/0x60
> [ 1157.461178] [<ffffffffbccd5753>] sock_ioctl+0x233/0x310
> [ 1157.467109] [<ffffffffbc8bd820>] do_vfs_ioctl+0x410/0x6c0
> [ 1157.473233] [<ffffffffbc8bdb71>] SyS_ioctl+0xa1/0xc0
> [ 1157.478914] [<ffffffffbce84a5e>] system_call_fastpath+0x25/0x2a
> [ 1157.485569]
> -> #0 (&rtwdev->mutex){+.+.+.}:
> [ 1157.490022] [<ffffffffbc7409d1>] __lock_acquire+0xec1/0x1630
> [ 1157.496305] [<ffffffffbc741a29>] lock_acquire+0x99/0x1e0
> [ 1157.502413] [<ffffffffbce72793>] mutex_lock_nested+0x93/0x410
> [ 1157.508890] [<ffffffffc098322b>] rtw_ops_config+0x2b/0x90
> [rtw88]
> [ 1157.515724] [<ffffffffc0b13343>]
> ieee80211_hw_config+0xc3/0x680 [mac80211]
> [ 1157.523370] [<ffffffffc0b8a4ca>]
> ieee80211_recalc_ps.part.27+0x9a/0x180 [mac80211]
> [ 1157.531685] [<ffffffffc0b8abc5>]
> ieee80211_mgd_probe_ap.part.28+0x115/0x160 [mac80211]
> [ 1157.540353] [<ffffffffc0b8b40d>]
> ieee80211_beacon_connection_loss_work+0x4d/0x80 [mac80211]
> [ 1157.549513] [<ffffffffbc6d77bc>] process_one_work+0x22c/0x720
> [ 1157.555886] [<ffffffffbc6d7dd6>] worker_thread+0x126/0x3b0
> [ 1157.562170] [<ffffffffbc6e107f>] kthread+0xef/0x100
> [ 1157.567765] [<ffffffffbce848b7>]
> ret_from_fork_nospec_end+0x0/0x39
> [ 1157.574579]
> other info that might help us debug this:
>
> [ 1157.582788] Chain exists of:
> &rtwdev->mutex --> (&(&rtwdev->watch_dog_work)->work) -->
> &local->iflist_mtx
>
> [ 1157.593024] Possible unsafe locking scenario:
>
> [ 1157.599046] CPU0 CPU1
> [ 1157.603653] ---- ----
> [ 1157.608258] lock(&local->iflist_mtx);
> [ 1157.612180]
> lock((&(&rtwdev->watch_dog_work)->work));
> [ 1157.620074] lock(&local->iflist_mtx);
> [ 1157.626555] lock(&rtwdev->mutex);
> [ 1157.630124]
> *** DEADLOCK ***
>
> [ 1157.636148] 4 locks held by kworker/u4:2/14490:
> [ 1157.640755] #0: (%s#6){.+.+.+}, at: [<ffffffffbc6d774a>]
> process_one_work+0x1ba/0x720
> [ 1157.648965] #1: ((&ifmgd->beacon_connection_loss_work)){+.+.+.}, at:
> [<ffffffffbc6d774a>] process_one_work+0x1ba/0x720
> [ 1157.659950] #2: (&wdev->mtx){+.+.+.}, at: [<ffffffffc0b8aad5>]
> ieee80211_mgd_probe_ap.part.28+0x25/0x160 [mac80211]
> [ 1157.670901] #3: (&local->iflist_mtx){+.+...}, at: [<ffffffffc0b8ab7a>]
> ieee80211_mgd_probe_ap.part.28+0xca/0x160 [mac80211]
> [ 1157.682466]
>
> Fixes: e3037485c68e ("rtw88: new Realtek 802.11ac driver")
> Signed-off-by: Stanislaw Gruszka <sgruszka@xxxxxxxxxx>
> ---
> drivers/net/wireless/realtek/rtw88/main.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/wireless/realtek/rtw88/main.c
> b/drivers/net/wireless/realtek/rtw88/main.c
> index 9893e5e297e3..f63c34a2e356 100644
> --- a/drivers/net/wireless/realtek/rtw88/main.c
> +++ b/drivers/net/wireless/realtek/rtw88/main.c
> @@ -162,7 +162,8 @@ static void rtw_watch_dog_work(struct work_struct
> *work)
> rtwdev->stats.tx_cnt = 0;
> rtwdev->stats.rx_cnt = 0;
>
> - rtw_iterate_vifs(rtwdev, rtw_vif_watch_dog_iter, &data);
> + /* use atomic version to avoid taking local->iflist_mtx mutex */
> + rtw_iterate_vifs_atomic(rtwdev, rtw_vif_watch_dog_iter, &data);
>
> /* fw supports only one station associated to enter lps, if there are
> * more than two stations associated to the AP, then we can not enter
> --
Looks good to me.
Thanks.
Acked-by: Yan-Hsuan Chuang <yhchuang@xxxxxxxxxxx>
Yan-Hsuan
