Re: [PATCH 2/3] ath10k: Grab rcu_read_lock before the txqs spinlock.

[Ben Greear <greearb@candelatech.com>]

On 09/09/2016 06:36 AM, Valo, Kalle wrote:
> greearb@candelatech.com writes:
>
>> From: Ben Greear <greearb@candelatech.com>
>>
>> I was seeing some spin-lock hangs in this area of the code,
>> and it seems more proper to do the rcu-read-lock outside of
>> the spin lock.  I am not sure how much this matters, however.
>>
>> Signed-off-by: Ben Greear <greearb@candelatech.com>
>> ---
>>   drivers/net/wireless/ath/ath10k/mac.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/wireless/ath/ath10k/mac.c b/drivers/net/wireless/ath/ath10k/mac.c
>> index 916119c..d96c06e 100644
>> --- a/drivers/net/wireless/ath/ath10k/mac.c
>> +++ b/drivers/net/wireless/ath/ath10k/mac.c
>> @@ -4307,8 +4307,8 @@ void ath10k_mac_tx_push_pending(struct ath10k *ar)
>>   	int max;
>>   	int loop_max = 2000;
>>
>> -	spin_lock_bh(&ar->txqs_lock);
>>   	rcu_read_lock();
>> +	spin_lock_bh(&ar->txqs_lock);
>>
>>   	last = list_last_entry(&ar->txqs, struct ath10k_txq, list);
>>   	while (!list_empty(&ar->txqs)) {
>> @@ -4342,8 +4342,8 @@ void ath10k_mac_tx_push_pending(struct ath10k *ar)
>>   			break;
>>   	}
>>
>> -	rcu_read_unlock();
>>   	spin_unlock_bh(&ar->txqs_lock);
>> +	rcu_read_unlock();
>
> I'm no RCU expert but this isn't making any sense. Maybe it changes
> timings on your kernel so that it hides the real problem?

I'm not sure this fixed anything or not, it just seemed weird so I changed it.

I was hoping someone that understood rcu locking would comment...

Thanks,
Ben

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

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