From: Jens Axboe <axboe@kernel.dk>
To: Pavel Begunkov <asml.silence@gmail.com>, io-uring@vger.kernel.org
Subject: Re: [PATCH 7/8] io_uring: fix sequencing issues with linked timeouts
Date: Tue, 19 Nov 2019 15:13:07 -0700 [thread overview]
Message-ID: <b98a91cd-54c1-49ef-d75d-8007dcc470c1@kernel.dk> (raw)
In-Reply-To: <ccf48def-1a4a-9cb1-aa9a-467294487856@gmail.com>
On 11/19/19 1:51 PM, Pavel Begunkov wrote:
> On 16/11/2019 04:53, Jens Axboe wrote:
>> We have an issue with timeout links that are deeper in the submit chain,
>> because we only handle it upfront, not from later submissions. Move the
>> prep + issue of the timeout link to the async work prep handler, and do
>> it normally for non-async queue. If we validate and prepare the timeout
>> links upfront when we first see them, there's nothing stopping us from
>> supporting any sort of nesting.
>>
>> Fixes: 2665abfd757f ("io_uring: add support for linked SQE timeouts")
>> Reported-by: Pavel Begunkov <asml.silence@gmail.com>
>> Signed-off-by: Jens Axboe <axboe@kernel.dk>
>> ---
>
>> @@ -923,6 +942,7 @@ static void io_fail_links(struct io_kiocb *req)
>> io_cqring_fill_event(link, -ECANCELED);
>> __io_double_put_req(link);
>> }
>> + kfree(sqe_to_free);
>> }
>>
>> io_commit_cqring(ctx);
>> @@ -2668,8 +2688,12 @@ static void io_wq_submit_work(struct io_wq_work **workptr)
>>
>> /* if a dependent link is ready, pass it back */
>> if (!ret && nxt) {
>> - io_prep_async_work(nxt);
>> + struct io_kiocb *link;
>> +
>> + io_prep_async_work(nxt, &link);
>> *workptr = &nxt->work;
> Are we safe here without synchronisation?
> Probably io_link_timeout_fn() may miss the new value
> (doing io-wq cancel).
Miss what new value? Don't follow that part.
This should be safe, by the time the request is findable, we have
made the necessary setup in io_prep_async_work().
--
Jens Axboe
next prev parent reply other threads:[~2019-11-19 22:13 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-16 1:53 [PATCHSET] Pending io_uring items not yet queued up for 5.5 Jens Axboe
2019-11-16 1:53 ` [PATCH 1/8] io-wq: remove now redundant struct io_wq_nulls_list Jens Axboe
2019-11-16 1:53 ` [PATCH 2/8] io_uring: make POLL_ADD/POLL_REMOVE scale better Jens Axboe
2019-11-16 1:53 ` [PATCH 3/8] io_uring: io_async_cancel() should pass in 'nxt' request pointer Jens Axboe
2019-11-16 1:53 ` [PATCH 4/8] io_uring: cleanup return values from the queueing functions Jens Axboe
2019-11-16 1:53 ` [PATCH 5/8] io_uring: make io_double_put_req() use normal completion path Jens Axboe
2019-11-16 1:53 ` [PATCH 6/8] io_uring: make req->timeout be dynamically allocated Jens Axboe
2019-11-16 1:53 ` [PATCH 7/8] io_uring: fix sequencing issues with linked timeouts Jens Axboe
2019-11-19 20:51 ` Pavel Begunkov
2019-11-19 22:13 ` Jens Axboe [this message]
2019-11-20 12:42 ` Pavel Begunkov
2019-11-20 17:19 ` Jens Axboe
2019-11-20 18:15 ` Jens Axboe
2019-11-16 1:53 ` [PATCH 8/8] io_uring: remove dead REQ_F_SEQ_PREV flag Jens Axboe
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