Re: [PATCH] blk-wbt: get back the missed wakeup from __wbt_done

[Jens Axboe]

On 8/26/18 9:52 PM, jianchao.wang wrote:
> Hi Jens
> 
> On 08/25/2018 11:41 PM, Jens Axboe wrote:
>>  	do {
>> -		set_current_state(TASK_UNINTERRUPTIBLE);
>> +		if (test_bit(0, &data.flags))
>> +			break;
>>  
>> -		if (!has_sleeper && rq_wait_inc_below(rqw, get_limit(rwb, rw)))
>> +		WARN_ON_ONCE(list_empty(&data.wq.entry));
>> +
>> +		if (!has_sleeper &&
>> +		    rq_wait_inc_below(rqw, get_limit(rwb, rw))) {
>> +			finish_wait(&rqw->wait, &data.wq);
>> +
>> +			/*
>> +			 * We raced with wbt_wake_function() getting a token,
>> +			 * which means we now have two. Put ours and wake
>> +			 * anyone else potentially waiting for one.
>> +			 */
>> +			if (test_bit(0, &data.flags))
>> +				wbt_rqw_done(rwb, rqw, wb_acct);
>>  			break;
> 
> Just use 'bool' variable should be OK 
> After finish_wait, no one could race with us here.

I was mostly concerned with the check post prep_to_wait(), but since the
spin unlock should include a barrier, the bool should actually be enough.
I'll change that back once I test.

-- 
Jens Axboe