[PATCH 075/379][SRU][OEM-5.6] ath11k: Avoid mgmt tx count underflow

[You-Sheng Yang]

From: Sriram R <srirrama at codeaurora.org>

BugLink: https://bugs.launchpad.net/bugs/1879633

The mgmt tx count reference is incremented/decremented on every mgmt tx and on
tx completion event from firmware.
In case of an unexpected mgmt tx completion event from firmware,
the counter would underflow. Avoid this by decrementing
only when the tx count is greater than 0.

Signed-off-by: Sriram R <srirrama at codeaurora.org>
Signed-off-by: Kalle Valo <kvalo at codeaurora.org>
Link: https://lore.kernel.org/r/1585567028-9242-1-git-send-email-srirrama@codeaurora.org
(cherry picked from commit 800113ff4b1d277c2b66ffc04d4d38f202a0d187)
Signed-off-by: You-Sheng Yang <vicamo.yang at canonical.com>
---
 drivers/net/wireless/ath/ath11k/wmi.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ath/ath11k/wmi.c b/drivers/net/wireless/ath/ath11k/wmi.c
index 8832b8c8e63f..973b72a0ca69 100644
--- a/drivers/net/wireless/ath/ath11k/wmi.c
+++ b/drivers/net/wireless/ath/ath11k/wmi.c
@@ -3880,8 +3880,9 @@ static int wmi_process_mgmt_tx_comp(struct ath11k *ar, u32 desc_id,
 
 	ieee80211_tx_status_irqsafe(ar->hw, msdu);
 
-	WARN_ON_ONCE(atomic_read(&ar->num_pending_mgmt_tx) == 0);
-	atomic_dec(&ar->num_pending_mgmt_tx);
+	/* WARN when we received this event without doing any mgmt tx */
+	if (atomic_dec_if_positive(&ar->num_pending_mgmt_tx) < 0)
+		WARN_ON_ONCE(1);
 
 	return 0;
 }
-- 
2.29.2