[PATCH 4.9 002/116] ath10k: fix soft lockup during firmware crash/hw-restart

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mohammed Shafi Shajakhan <mohammed@xxxxxxxxxxxxxxxx>

commit c2cac2f74ab4bcf0db0dcf3a612f1e5b52d145c8 upstream.

During firmware crash (or) user requested manual restart
the system gets into a soft lock up state because of the
below root cause.

During user requested hardware restart / firmware crash
the system goes into a soft lockup state as 'napi_synchronize'
is called after 'napi_disable' (which sets 'NAPI_STATE_SCHED'
bit) and it sleeps into infinite loop as it waits for
'NAPI_STATE_SCHED' to be cleared. This condition is hit because
'ath10k_hif_stop' is called twice as below (resulting in calling
'napi_synchronize' after 'napi_disable')

'ath10k_core_restart' -> 'ath10k_hif_stop' (ATH10K_STATE_ON) ->
-> 'ieee80211_restart_hw' -> 'ath10k_start' -> 'ath10k_halt' ->
'ath10k_core_stop' -> 'ath10k_hif_stop' (ATH10K_STATE_RESTARTING)

Fix this by calling 'ath10k_halt' in ath10k_core_restart itself
as it makes more sense before informing mac80211 to restart h/w
Also remove 'ath10k_halt' in ath10k_start for the state of 'restarting'

Fixes: 3c97f5de1f28 ("ath10k: implement NAPI support")
Signed-off-by: Mohammed Shafi Shajakhan <mohammed@xxxxxxxxxxxxxxxx>
Signed-off-by: Kalle Valo <kvalo@xxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/net/wireless/ath/ath10k/core.c |    2 +-
 drivers/net/wireless/ath/ath10k/mac.c  |    1 -
 2 files changed, 1 insertion(+), 2 deletions(-)

--- a/drivers/net/wireless/ath/ath10k/core.c
+++ b/drivers/net/wireless/ath/ath10k/core.c
@@ -1534,7 +1534,7 @@ static void ath10k_core_restart(struct w
 	switch (ar->state) {
 	case ATH10K_STATE_ON:
 		ar->state = ATH10K_STATE_RESTARTING;
-		ath10k_hif_stop(ar);
+		ath10k_halt(ar);
 		ath10k_scan_finish(ar);
 		ieee80211_restart_hw(ar->hw);
 		break;
--- a/drivers/net/wireless/ath/ath10k/mac.c
+++ b/drivers/net/wireless/ath/ath10k/mac.c
@@ -4449,7 +4449,6 @@ static int ath10k_start(struct ieee80211
 		ar->state = ATH10K_STATE_ON;
 		break;
 	case ATH10K_STATE_RESTARTING:
-		ath10k_halt(ar);
 		ar->state = ATH10K_STATE_RESTARTED;
 		break;
 	case ATH10K_STATE_ON: