On 08/10/2019 20:00, Jens Axboe wrote: > On 10/8/19 10:43 AM, Pavel Begunkov wrote: >> On 08/10/2019 06:16, Jens Axboe wrote: >>> On 10/7/19 5:18 PM, Pavel Begunkov (Silence) wrote: >>>> From: Pavel Begunkov <asml.silence@xxxxxxxxx> >>>> >>>> Any changes interesting to tasks waiting in io_cqring_wait() are >>>> commited with io_cqring_ev_posted(). However, io_ring_drop_ctx_refs() >>>> also tries to do that but with no reason, that means spurious wakeups >>>> every io_free_req() and io_uring_enter(). >>>> >>>> Just use percpu_ref_put() instead. >>> >>> Looks good, this is a leftover from when the ctx teardown used >>> the waitqueue as well. >>> >> BTW, is there a reason for ref-counting in struct io_kiocb? I understand >> the idea behind submission reference, but don't see any actual part >> needing it. > > In short, it's to prevent the completion running before we're done with > the iocb on the submission side. Yep, that's what I expected. Perhaps I missed something, but what I've seen following code paths all the way down, it either 1. gets error / completes synchronously and then frees req locally 2. or passes it further (e.g. async list) and never accesses it after -- Yours sincerely, Pavel Begunkov
Attachment:
signature.asc
Description: OpenPGP digital signature
