[PATCH ath-current] wifi: ath12k: fix dead lock while flushing management frames

[Baochen Qiang]

Commit [1] converted the management transmission work item into a
wiphy work. Since a wiphy work can only run under wiphy lock
protection, a race condition happens in below scenario:

1. a management frame is queued for transmission.
2. ath12k_mac_op_flush() gets called to flush pending frames associated
   with the hardware (i.e, vif being NULL). Then in ath12k_mac_flush()
   the process waits for the transmission done.
3. Since wiphy lock has been taken by the flush process, the transmission
   work item has no chance to run, hence the dead lock.

>From user view, this dead lock results in below issue:

 wlp8s0: authenticate with xxxxxx (local address=xxxxxx)
 wlp8s0: send auth to xxxxxx (try 1/3)
 wlp8s0: authenticate with xxxxxx (local address=xxxxxx)
 wlp8s0: send auth to xxxxxx (try 1/3)
 wlp8s0: authenticated
 wlp8s0: associate with xxxxxx (try 1/3)
 wlp8s0: aborting association with xxxxxx by local choice (Reason: 3=DEAUTH_LEAVING)
 ath12k_pci 0000:08:00.0: failed to flush mgmt transmit queue, mgmt pkts pending 1

The dead lock can be avoided by invoking wiphy_work_flush() to proactively
run the queued work item. Note actually it is already present in
ath12k_mac_op_flush(), however it does not protect the case where vif
being NULL. Hence move it ahead to cover this case as well.

Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.1.c5-00302-QCAHMTSWPL_V1.0_V2.0_SILICONZ-1.115823.3

Fixes: 56dcbf0b5207 ("wifi: ath12k: convert struct ath12k::wmi_mgmt_tx_work to struct wiphy_work") # [1]
Reported-by: Stuart Hayhurst <stuart.a.hayhurst at gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220959
Signed-off-by: Baochen Qiang <baochen.qiang at oss.qualcomm.com>
---
 drivers/net/wireless/ath/ath12k/mac.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/ath/ath12k/mac.c b/drivers/net/wireless/ath/ath12k/mac.c
index 2f4daee9e2f0..7481f64f6937 100644
--- a/drivers/net/wireless/ath/ath12k/mac.c
+++ b/drivers/net/wireless/ath/ath12k/mac.c
@@ -12214,6 +12214,9 @@ void ath12k_mac_op_flush(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 	if (drop)
 		return;
 
+	for_each_ar(ah, ar, i)
+		wiphy_work_flush(hw->wiphy, &ar->wmi_mgmt_tx_work);
+
 	/* vif can be NULL when flush() is considered for hw */
 	if (!vif) {
 		for_each_ar(ah, ar, i)
@@ -12221,9 +12224,6 @@ void ath12k_mac_op_flush(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 		return;
 	}
 
-	for_each_ar(ah, ar, i)
-		wiphy_work_flush(hw->wiphy, &ar->wmi_mgmt_tx_work);
-
 	ahvif = ath12k_vif_to_ahvif(vif);
 	links = ahvif->links_map;
 	for_each_set_bit(link_id, &links, IEEE80211_MLD_MAX_NUM_LINKS) {

---
base-commit: e33fc1c6d54ee1569a57255e11c2978ba9a42ffc
change-id: 20260109-ath12k-fix-dead-lock-while-flushing-9a4d8be9cebc

Best regards,
-- 
Baochen Qiang <baochen.qiang at oss.qualcomm.com>