From: Pavel Begunkov <asml.silence@gmail.com> To: Hao Xu <haoxu@linux.alibaba.com>, Jens Axboe <axboe@kernel.dk> Cc: io-uring@vger.kernel.org, Joseph Qi <joseph.qi@linux.alibaba.com> Subject: Re: [PATCH 4/6] io_uring: let fast poll support multishot Date: Wed, 8 Sep 2021 13:03:04 +0100 [thread overview] Message-ID: <a73331f7-11ce-1a67-c312-c20553338682@gmail.com> (raw) In-Reply-To: <2ba9fdb5-6d60-21f5-3e20-bc1687c9509f@linux.alibaba.com> On 9/8/21 12:21 PM, Hao Xu wrote: > 在 2021/9/7 下午2:48, Hao Xu 写道: >> 在 2021/9/7 上午3:04, Pavel Begunkov 写道: >>> On 9/3/21 12:00 PM, Hao Xu wrote: >>>> For operations like accept, multishot is a useful feature, since we can >>>> reduce a number of accept sqe. Let's integrate it to fast poll, it may >>>> be good for other operations in the future. >>>> >>>> Signed-off-by: Hao Xu <haoxu@linux.alibaba.com> >>>> --- >>>> fs/io_uring.c | 15 ++++++++++++--- >>>> 1 file changed, 12 insertions(+), 3 deletions(-) >>>> >>>> diff --git a/fs/io_uring.c b/fs/io_uring.c >>>> index d6df60c4cdb9..dae7044e0c24 100644 >>>> --- a/fs/io_uring.c >>>> +++ b/fs/io_uring.c >>>> @@ -5277,8 +5277,15 @@ static void io_async_task_func(struct io_kiocb *req, bool *locked) >>>> return; >>>> } >>>> - hash_del(&req->hash_node); >>>> - io_poll_remove_double(req); >>>> + if (READ_ONCE(apoll->poll.canceled)) >>>> + apoll->poll.events |= EPOLLONESHOT; >>>> + if (apoll->poll.events & EPOLLONESHOT) { >>>> + hash_del(&req->hash_node); >>>> + io_poll_remove_double(req); >>>> + } else { >>>> + add_wait_queue(apoll->poll.head, &apoll->poll.wait); >>> >>> It looks like it does both io_req_task_submit() and adding back >>> to the wq, so io_issue_sqe() may be called in parallel with >>> io_async_task_func(). If so, there will be tons of all kind of >>> races. >> IMHO, io_async_task_func() is called in original context one by >> one(except PF_EXITING is set, it is also called in system-wq), so >> shouldn't be parallel case there. > ping... fwiw, the case we're talking about: CPU0 | CPU1 io_async_task_func() | -> add_wait_queue(); | -> io_req_task_submit(); | /* no tw run happened in between */ | io_async_task_func() | --> io_req_task_submit() We called io_req_task_submit() twice without running tw in-between, both of the calls use the same req->io_task_work.node field in the request for accounting, and so the second call will screw tctx->task_list and not only by not considering that req->io_task_work.node is already taken/enqueued. io_req_task_work_add() { wq_list_add_tail(&req->io_task_work.node, &tctx->task_list); } >>> >>>> + } >>>> + >>>> spin_unlock(&ctx->completion_lock); >>>> if (!READ_ONCE(apoll->poll.canceled)) >>>> @@ -5366,7 +5373,7 @@ static int io_arm_poll_handler(struct io_kiocb *req) >>>> struct io_ring_ctx *ctx = req->ctx; >>>> struct async_poll *apoll; >>>> struct io_poll_table ipt; >>>> - __poll_t ret, mask = EPOLLONESHOT | POLLERR | POLLPRI; >>>> + __poll_t ret, mask = POLLERR | POLLPRI; >>>> int rw; >>>> if (!req->file || !file_can_poll(req->file)) >>>> @@ -5388,6 +5395,8 @@ static int io_arm_poll_handler(struct io_kiocb *req) >>>> rw = WRITE; >>>> mask |= POLLOUT | POLLWRNORM; >>>> } >>>> + if (!(req->flags & REQ_F_APOLL_MULTISHOT)) >>>> + mask |= EPOLLONESHOT; >>>> /* if we can't nonblock try, then no point in arming a poll handler */ >>>> if (!io_file_supports_nowait(req, rw)) >>>> >>> > -- Pavel Begunkov
next prev parent reply other threads:[~2021-09-08 12:03 UTC|newest] Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-09-03 11:00 [RFC 0/6] fast poll multishot mode Hao Xu 2021-09-03 11:00 ` [PATCH 1/6] io_uring: enhance flush completion logic Hao Xu 2021-09-03 11:42 ` Pavel Begunkov 2021-09-03 12:08 ` Hao Xu 2021-09-03 12:27 ` Pavel Begunkov 2021-09-03 13:38 ` Hao Xu 2021-09-17 18:49 ` Hao Xu 2021-09-03 11:00 ` [PATCH 2/6] io_uring: add IORING_ACCEPT_MULTISHOT for accept Hao Xu 2021-09-03 11:00 ` [PATCH 3/6] io_uring: add REQ_F_APOLL_MULTISHOT for requests Hao Xu 2021-09-03 11:00 ` [PATCH 4/6] io_uring: let fast poll support multishot Hao Xu 2021-09-06 15:56 ` Pavel Begunkov 2021-09-06 17:40 ` Hao Xu 2021-09-06 19:09 ` Pavel Begunkov 2021-09-07 6:38 ` Hao Xu 2021-09-06 19:04 ` Pavel Begunkov 2021-09-07 6:48 ` Hao Xu 2021-09-08 11:21 ` Hao Xu 2021-09-08 12:03 ` Pavel Begunkov [this message] 2021-09-08 13:13 ` Pavel Begunkov 2021-09-09 7:01 ` Hao Xu 2021-09-09 8:29 ` Hao Xu 2021-09-11 10:49 ` Pavel Begunkov 2021-09-11 20:19 ` Hao Xu 2021-09-03 11:00 ` [PATCH 5/6] io_uring: implement multishot mode for accept Hao Xu 2021-09-04 22:39 ` Pavel Begunkov 2021-09-04 22:40 ` Pavel Begunkov 2021-09-06 15:34 ` Pavel Begunkov 2021-09-03 11:00 ` [PATCH 6/6] io_uring: enable " Hao Xu 2021-09-03 16:29 ` Jens Axboe 2021-09-04 15:34 ` Hao Xu 2021-09-04 18:40 ` Jens Axboe 2021-09-04 22:46 ` Pavel Begunkov 2021-09-05 7:29 ` Hao Xu 2021-09-05 19:44 ` Jens Axboe 2021-09-06 8:26 ` Hao Xu 2021-09-06 8:28 ` Hao Xu 2021-09-06 13:24 ` Jens Axboe 2021-09-06 12:35 ` Hao Xu 2021-09-06 13:31 ` Jens Axboe 2021-09-06 15:00 ` Hao Xu 2021-09-06 15:32 ` Pavel Begunkov 2021-09-06 16:42 ` Jens Axboe 2021-09-04 22:43 ` Pavel Begunkov 2021-09-05 6:25 ` Hao Xu 2021-09-05 8:27 ` Pavel Begunkov 2021-09-03 11:02 ` [RFC 0/6] fast poll multishot mode Hao Xu
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