Re: [RFC v7] wait: prevent exclusive waiter starvation

[Oleg Nesterov <oleg@redhat.com>]

On 01/28, Johannes Weiner wrote:
>
> Add abort_exclusive_wait() which removes the process' wait descriptor
> from the waitqueue, iff still queued, or wakes up the next waiter
> otherwise.  It does so under the waitqueue lock.  Racing with a wake
> up means the aborting process is either already woken (removed from
> the queue) and will wake up the next waiter, or it will remove itself
> from the queue and the concurrent wake up will apply to the next
> waiter after it.
>
> Use abort_exclusive_wait() in __wait_event_interruptible_exclusive()
> and __wait_on_bit_lock() when they were interrupted by other means
> than a wake up through the queue.

Imho, this all is right, and this patch should replace
lock_page_killable-avoid-lost-wakeups.patch (except for stable tree).

But I guess we need maintainer's opinion, we have them in cc ;)

Oleg.

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