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From: Hao Xu <haoxu@linux.alibaba.com>
To: Pavel Begunkov <asml.silence@gmail.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: Tue, 7 Sep 2021 14:48:53 +0800	[thread overview]
Message-ID: <8c052e2a-0ee6-7dac-1169-9d395d2ecad8@linux.alibaba.com> (raw)
In-Reply-To: <9a8efd19-a320-29a4-7132-7b5ae5b994ff@gmail.com>

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.
> 
>> +	}
>> +
>>   	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))
>>
> 


  reply	other threads:[~2021-09-07  6:49 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 [this message]
2021-09-08 11:21       ` Hao Xu
2021-09-08 12:03         ` Pavel Begunkov
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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