On Mon, Mar 25, 2019 at 12:58:47PM -0600, Jens Axboe wrote:
> 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.
Yup, I see. Assuming it fixes the issue,
Reviewed-by: Omar Sandoval <osandov@xxxxxx>
