ath10k: Fix soft lockup during firmware crash/hw-restart

[Ben Greear]

Is this something for stable?  And if so, how far back should it be applied?

I'll add this patch to my 4.9 tree and test it...

Thanks,
Ben

On 11/29/2016 06:46 AM, Mohammed Shafi Shajakhan wrote:
> From: Mohammed Shafi Shajakhan <mohammed at qti.qualcomm.com>
>
> 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'
>
> Signed-off-by: Mohammed Shafi Shajakhan <mohammed at qti.qualcomm.com>
> ---
> [thanks to Kalle and Michal for their inputs]
>
>  drivers/net/wireless/ath/ath10k/core.c | 2 +-
>  drivers/net/wireless/ath/ath10k/mac.c  | 1 -
>  2 files changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/net/wireless/ath/ath10k/core.c b/drivers/net/wireless/ath/ath10k/core.c
> index 7005e2a..5bc6847 100644
> --- a/drivers/net/wireless/ath/ath10k/core.c
> +++ b/drivers/net/wireless/ath/ath10k/core.c
> @@ -1536,7 +1536,7 @@ static void ath10k_core_restart(struct work_struct *work)
>  	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;
> diff --git a/drivers/net/wireless/ath/ath10k/mac.c b/drivers/net/wireless/ath/ath10k/mac.c
> index 717b2fa..481842b 100644
> --- 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_hw *hw)
>  		ar->state = ATH10K_STATE_ON;
>  		break;
>  	case ATH10K_STATE_RESTARTING:
> -		ath10k_halt(ar);
>  		ar->state = ATH10K_STATE_RESTARTED;
>  		break;
>  	case ATH10K_STATE_ON:
>


-- 
Ben Greear <greearb at candelatech.com>
Candela Technologies Inc  http://www.candelatech.com