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Subject[PATCH 5.0 109/115] mt76x02: avoid status_list.lock and sta->rate_ctrl_lock dependency
Date
From: Stanislaw Gruszka <sgruszka@redhat.com>

commit bafdf85dfa59374f927ff597bc8c259193afda30 upstream.

Move ieee80211_tx_status_ext() outside of status_list lock section
in order to avoid locking dependency and possible deadlock reposed by
LOCKDEP in below warning.

Also do mt76_tx_status_lock() just before it's needed.

[ 440.224832] WARNING: possible circular locking dependency detected
[ 440.224833] 5.1.0-rc2+ #22 Not tainted
[ 440.224834] ------------------------------------------------------
[ 440.224835] kworker/u16:28/2362 is trying to acquire lock:
[ 440.224836] 0000000089b8cacf (&(&q->lock)->rlock#2){+.-.}, at: mt76_wake_tx_queue+0x4c/0xb0 [mt76]
[ 440.224842]
but task is already holding lock:
[ 440.224842] 000000002cfedc59 (&(&sta->lock)->rlock){+.-.}, at: ieee80211_stop_tx_ba_cb+0x32/0x1f0 [mac80211]
[ 440.224863]
which lock already depends on the new lock.

[ 440.224863]
the existing dependency chain (in reverse order) is:
[ 440.224864]
-> #3 (&(&sta->lock)->rlock){+.-.}:
[ 440.224869] _raw_spin_lock_bh+0x34/0x40
[ 440.224880] ieee80211_start_tx_ba_session+0xe4/0x3d0 [mac80211]
[ 440.224894] minstrel_ht_get_rate+0x45c/0x510 [mac80211]
[ 440.224906] rate_control_get_rate+0xc1/0x140 [mac80211]
[ 440.224918] ieee80211_tx_h_rate_ctrl+0x195/0x3c0 [mac80211]
[ 440.224930] ieee80211_xmit_fast+0x26d/0xa50 [mac80211]
[ 440.224942] __ieee80211_subif_start_xmit+0xfc/0x310 [mac80211]
[ 440.224954] ieee80211_subif_start_xmit+0x38/0x390 [mac80211]
[ 440.224956] dev_hard_start_xmit+0xb8/0x300
[ 440.224957] __dev_queue_xmit+0x7d4/0xbb0
[ 440.224968] ip6_finish_output2+0x246/0x860 [ipv6]
[ 440.224978] mld_sendpack+0x1bd/0x360 [ipv6]
[ 440.224987] mld_ifc_timer_expire+0x1a4/0x2f0 [ipv6]
[ 440.224989] call_timer_fn+0x89/0x2a0
[ 440.224990] run_timer_softirq+0x1bd/0x4d0
[ 440.224992] __do_softirq+0xdb/0x47c
[ 440.224994] irq_exit+0xfa/0x100
[ 440.224996] smp_apic_timer_interrupt+0x9a/0x220
[ 440.224997] apic_timer_interrupt+0xf/0x20
[ 440.224999] cpuidle_enter_state+0xc1/0x470
[ 440.225000] do_idle+0x21a/0x260
[ 440.225001] cpu_startup_entry+0x19/0x20
[ 440.225004] start_secondary+0x135/0x170
[ 440.225006] secondary_startup_64+0xa4/0xb0
[ 440.225007]
-> #2 (&(&sta->rate_ctrl_lock)->rlock){+.-.}:
[ 440.225009] _raw_spin_lock_bh+0x34/0x40
[ 440.225022] rate_control_tx_status+0x4f/0xb0 [mac80211]
[ 440.225031] ieee80211_tx_status_ext+0x142/0x1a0 [mac80211]
[ 440.225035] mt76x02_send_tx_status+0x2e4/0x340 [mt76x02_lib]
[ 440.225037] mt76x02_tx_status_data+0x31/0x40 [mt76x02_lib]
[ 440.225040] mt76u_tx_status_data+0x51/0xa0 [mt76_usb]
[ 440.225042] process_one_work+0x237/0x5d0
[ 440.225043] worker_thread+0x3c/0x390
[ 440.225045] kthread+0x11d/0x140
[ 440.225046] ret_from_fork+0x3a/0x50
[ 440.225047]
-> #1 (&(&list->lock)->rlock#8){+.-.}:
[ 440.225049] _raw_spin_lock_bh+0x34/0x40
[ 440.225052] mt76_tx_status_skb_add+0x51/0x100 [mt76]
[ 440.225054] mt76x02u_tx_prepare_skb+0xbd/0x116 [mt76x02_usb]
[ 440.225056] mt76u_tx_queue_skb+0x5f/0x180 [mt76_usb]
[ 440.225058] mt76_tx+0x93/0x190 [mt76]
[ 440.225070] ieee80211_tx_frags+0x148/0x210 [mac80211]
[ 440.225081] __ieee80211_tx+0x75/0x1b0 [mac80211]
[ 440.225092] ieee80211_tx+0xde/0x110 [mac80211]
[ 440.225105] __ieee80211_tx_skb_tid_band+0x72/0x90 [mac80211]
[ 440.225122] ieee80211_send_auth+0x1f3/0x360 [mac80211]
[ 440.225141] ieee80211_auth.cold.40+0x6c/0x100 [mac80211]
[ 440.225156] ieee80211_mgd_auth.cold.50+0x132/0x15f [mac80211]
[ 440.225171] cfg80211_mlme_auth+0x149/0x360 [cfg80211]
[ 440.225181] nl80211_authenticate+0x273/0x2e0 [cfg80211]
[ 440.225183] genl_family_rcv_msg+0x196/0x3a0
[ 440.225184] genl_rcv_msg+0x47/0x8e
[ 440.225185] netlink_rcv_skb+0x3a/0xf0
[ 440.225187] genl_rcv+0x24/0x40
[ 440.225188] netlink_unicast+0x16d/0x210
[ 440.225189] netlink_sendmsg+0x204/0x3b0
[ 440.225191] sock_sendmsg+0x36/0x40
[ 440.225193] ___sys_sendmsg+0x259/0x2b0
[ 440.225194] __sys_sendmsg+0x47/0x80
[ 440.225196] do_syscall_64+0x60/0x1f0
[ 440.225197] entry_SYSCALL_64_after_hwframe+0x49/0xbe
[ 440.225198]
-> #0 (&(&q->lock)->rlock#2){+.-.}:
[ 440.225200] lock_acquire+0xb9/0x1a0
[ 440.225202] _raw_spin_lock_bh+0x34/0x40
[ 440.225204] mt76_wake_tx_queue+0x4c/0xb0 [mt76]
[ 440.225215] ieee80211_agg_start_txq+0xe8/0x2b0 [mac80211]
[ 440.225225] ieee80211_stop_tx_ba_cb+0xb8/0x1f0 [mac80211]
[ 440.225235] ieee80211_ba_session_work+0x1c1/0x2f0 [mac80211]
[ 440.225236] process_one_work+0x237/0x5d0
[ 440.225237] worker_thread+0x3c/0x390
[ 440.225239] kthread+0x11d/0x140
[ 440.225240] ret_from_fork+0x3a/0x50
[ 440.225240]
other info that might help us debug this:

[ 440.225241] Chain exists of:
&(&q->lock)->rlock#2 --> &(&sta->rate_ctrl_lock)->rlock --> &(&sta->lock)->rlock

[ 440.225243] Possible unsafe locking scenario:

[ 440.225244] CPU0 CPU1
[ 440.225244] ---- ----
[ 440.225245] lock(&(&sta->lock)->rlock);
[ 440.225245] lock(&(&sta->rate_ctrl_lock)->rlock);
[ 440.225246] lock(&(&sta->lock)->rlock);
[ 440.225247] lock(&(&q->lock)->rlock#2);
[ 440.225248]
*** DEADLOCK ***

[ 440.225249] 5 locks held by kworker/u16:28/2362:
[ 440.225250] #0: 0000000048fcd291 ((wq_completion)phy0){+.+.}, at: process_one_work+0x1b5/0x5d0
[ 440.225252] #1: 00000000f1c6828f ((work_completion)(&sta->ampdu_mlme.work)){+.+.}, at: process_one_work+0x1b5/0x5d0
[ 440.225254] #2: 00000000433d2b2c (&sta->ampdu_mlme.mtx){+.+.}, at: ieee80211_ba_session_work+0x5c/0x2f0 [mac80211]
[ 440.225265] #3: 000000002cfedc59 (&(&sta->lock)->rlock){+.-.}, at: ieee80211_stop_tx_ba_cb+0x32/0x1f0 [mac80211]
[ 440.225276] #4: 000000009d7b9a44 (rcu_read_lock){....}, at: ieee80211_agg_start_txq+0x33/0x2b0 [mac80211]
[ 440.225286]
stack backtrace:
[ 440.225288] CPU: 2 PID: 2362 Comm: kworker/u16:28 Not tainted 5.1.0-rc2+ #22
[ 440.225289] Hardware name: LENOVO 20KGS23S0P/20KGS23S0P, BIOS N23ET55W (1.30 ) 08/31/2018
[ 440.225300] Workqueue: phy0 ieee80211_ba_session_work [mac80211]
[ 440.225301] Call Trace:
[ 440.225304] dump_stack+0x85/0xc0
[ 440.225306] print_circular_bug.isra.38.cold.58+0x15c/0x195
[ 440.225307] check_prev_add.constprop.48+0x5f0/0xc00
[ 440.225309] ? check_prev_add.constprop.48+0x39d/0xc00
[ 440.225311] ? __lock_acquire+0x41d/0x1100
[ 440.225312] __lock_acquire+0xd98/0x1100
[ 440.225313] ? __lock_acquire+0x41d/0x1100
[ 440.225315] lock_acquire+0xb9/0x1a0
[ 440.225317] ? mt76_wake_tx_queue+0x4c/0xb0 [mt76]
[ 440.225319] _raw_spin_lock_bh+0x34/0x40
[ 440.225321] ? mt76_wake_tx_queue+0x4c/0xb0 [mt76]
[ 440.225323] mt76_wake_tx_queue+0x4c/0xb0 [mt76]
[ 440.225334] ieee80211_agg_start_txq+0xe8/0x2b0 [mac80211]
[ 440.225344] ieee80211_stop_tx_ba_cb+0xb8/0x1f0 [mac80211]
[ 440.225354] ieee80211_ba_session_work+0x1c1/0x2f0 [mac80211]
[ 440.225356] process_one_work+0x237/0x5d0
[ 440.225358] worker_thread+0x3c/0x390
[ 440.225359] ? wq_calc_node_cpumask+0x70/0x70
[ 440.225360] kthread+0x11d/0x140
[ 440.225362] ? kthread_create_on_node+0x40/0x40
[ 440.225363] ret_from_fork+0x3a/0x50

Cc: stable@vger.kernel.org
Fixes: 88046b2c9f6d ("mt76: add support for reporting tx status with skb")
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/net/wireless/mediatek/mt76/mt76x02_mac.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)

--- a/drivers/net/wireless/mediatek/mt76/mt76x02_mac.c
+++ b/drivers/net/wireless/mediatek/mt76/mt76x02_mac.c
@@ -421,7 +421,6 @@ void mt76x02_send_tx_status(struct mt76x
return;

rcu_read_lock();
- mt76_tx_status_lock(mdev, &list);

if (stat->wcid < ARRAY_SIZE(dev->mt76.wcid))
wcid = rcu_dereference(dev->mt76.wcid[stat->wcid]);
@@ -434,6 +433,8 @@ void mt76x02_send_tx_status(struct mt76x
drv_priv);
}

+ mt76_tx_status_lock(mdev, &list);
+
if (wcid) {
if (stat->pktid)
status.skb = mt76_tx_status_skb_get(mdev, wcid,
@@ -453,7 +454,9 @@ void mt76x02_send_tx_status(struct mt76x
if (*update == 0 && stat_val == stat_cache &&
stat->wcid == msta->status.wcid && msta->n_frames < 32) {
msta->n_frames++;
- goto out;
+ mt76_tx_status_unlock(mdev, &list);
+ rcu_read_unlock();
+ return;
}

mt76x02_mac_fill_tx_status(dev, status.info, &msta->status,
@@ -469,11 +472,10 @@ void mt76x02_send_tx_status(struct mt76x

if (status.skb)
mt76_tx_status_skb_done(mdev, status.skb, &list);
- else
- ieee80211_tx_status_ext(mt76_hw(dev), &status);
-
-out:
mt76_tx_status_unlock(mdev, &list);
+
+ if (!status.skb)
+ ieee80211_tx_status_ext(mt76_hw(dev), &status);
rcu_read_unlock();
}


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