On 3/25/19 12:56 PM, Omar Sandoval wrote:
> On Mon, Mar 25, 2019 at 10:22:50AM -0600, Jens Axboe wrote:
>> We now wrap sbitmap waitqueues in an active counter, so we can avoid
>> iterating wakeups unless we have waiters there. This works as long as
>> everyone that's manipulating the waitqueues use the proper helpers. For
>> the tag wait case for shared tags, however, we add ourselves to the
>> waitqueue without incrementing/decrementing the ->ws_active count. This
>> means that wakeups can take a long time to happen.
>>
>> Fix this by manually doing the inc/dec as needed for the wait queue
>> handling.
>>
>> Fixes: 5d2ee7122c73 ("sbitmap: optimize wakeup check")
>> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
>
> Can this use the helpers we added in 9f6b7ef6c3eb ("sbitmap: add helpers
> for add/del wait queue handling")?
I don't think so without adding more, which seems kind of silly for this
very specialized use case of openly manipulating the wait queues. The
blk-mq setup there is very special cased.
--
Jens Axboe
