On 12/05/2017 10:57 PM, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@xxxxxx>
>
> Commit 8cf466602028 ("kyber: fix hang on domain token wait queue") fixed
> a hang caused by leaving wait entries on the domain token wait queue
> after the __sbitmap_queue_get() retry succeeded, making that wait entry
> a "dud" which won't in turn wake more entries up. However, we can also
> get a dud entry if kyber_get_domain_token() fails once but is then
> called again and succeeds. This can happen if the hardware queue is
> rerun for some other reason, or, more likely, kyber_dispatch_request()
> tries the same domain twice.
>
> The fix is to remove our entry from the wait queue whenever we
> successfully get a token. The only complication is that we might be on
> one of many wait queues in the struct sbitmap_queue, but that's easily
> fixed by remembering which wait queue we were put on.
>
> While we're here, only initialize the wait queue entry once instead of
> on every wait, and use spin_lock_irq() instead of spin_lock_irqsave(),
> since this is always called from process context with irqs enabled.
That latter part probably should have been a separate patch... But
applied for this series, thanks Omar.
--
Jens Axboe
