ath10k: drain tx before restarting hw

This makes sure no further tx requests are
submitted to HTT before driver teardown.

This should prevent invalid pointer/NULL
dereference on htt tx pool in ath10k_htt_tx() in
some cases of heavy traffic.

kvalo: remove the WARN_ON() if conf_mutex is held

Reported-By: Ben Greear <greearb@candelatech.com>
Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>

1 files changed, 22 insertions, 9 deletions

diff --git a/drivers/net/wireless/ath/ath10k/mac.c b/drivers/net/wireless/ath/ath10k/mac.c
index d73f146611b9..8ad03d530820 100644
--- a/drivers/net/wireless/ath/ath10k/mac.c
+++ b/drivers/net/wireless/ath/ath10k/mac.c
@@ -2289,9 +2289,19 @@ static void ath10k_tx(struct ieee80211_hw *hw,
         ath10k_tx_htt(ar, skb);
 }
 
-/*
- * Initialize various parameters with default vaules.
- */
+/* Must not be called with conf_mutex held as workers can use that also. */
+static void ath10k_drain_tx(struct ath10k *ar)
+{
+        /* make sure rcu-protected mac80211 tx path itself is drained */
+        synchronize_net();
+
+        ath10k_offchan_tx_purge(ar);
+        ath10k_mgmt_over_wmi_tx_purge(ar);
+
+        cancel_work_sync(&ar->offchan_tx_work);
+        cancel_work_sync(&ar->wmi_mgmt_tx_work);
+}
+
 void ath10k_halt(struct ath10k *ar)
 {
         struct ath10k_vif *arvif;
@@ -2307,8 +2317,6 @@ void ath10k_halt(struct ath10k *ar)
 
         del_timer_sync(&ar->scan.timeout);
         ath10k_reset_scan((unsigned long)ar);
-        ath10k_offchan_tx_purge(ar);
-        ath10k_mgmt_over_wmi_tx_purge(ar);
         ath10k_peer_cleanup_all(ar);
         ath10k_core_stop(ar);
         ath10k_hif_power_down(ar);
@@ -2394,6 +2402,13 @@ static int ath10k_start(struct ieee80211_hw *hw)
         struct ath10k *ar = hw->priv;
         int ret = 0;
 
+        /*
+         * This makes sense only when restarting hw. It is harmless to call
+         * uncoditionally. This is necessary to make sure no HTT/WMI tx
+         * commands will be submitted while restarting.
+         */
+        ath10k_drain_tx(ar);
+
         mutex_lock(&ar->conf_mutex);
 
         switch (ar->state) {
@@ -2481,6 +2496,8 @@ static void ath10k_stop(struct ieee80211_hw *hw)
 {
         struct ath10k *ar = hw->priv;
 
+        ath10k_drain_tx(ar);
+
         mutex_lock(&ar->conf_mutex);
         if (ar->state != ATH10K_STATE_OFF) {
                 ath10k_halt(ar);
@@ -2488,10 +2505,6 @@ static void ath10k_stop(struct ieee80211_hw *hw)
         }
         mutex_unlock(&ar->conf_mutex);
 
-        ath10k_mgmt_over_wmi_tx_purge(ar);
-
-        cancel_work_sync(&ar->offchan_tx_work);
-        cancel_work_sync(&ar->wmi_mgmt_tx_work);
         cancel_work_sync(&ar->restart_work);
 }