From: Jens Axboe <axboe@kernel.dk>
To: Pavel Begunkov <asml.silence@gmail.com>,
io-uring@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/5] io_uring: fix reassigning work.task_pid from io-wq
Date: Tue, 11 Feb 2020 13:59:23 -0700 [thread overview]
Message-ID: <82bef6dc-608e-6fde-44fb-58ee517d234d@kernel.dk> (raw)
In-Reply-To: <e60026f7-8e8f-7133-57e3-762a1d84269b@gmail.com>
On 2/11/20 1:57 PM, Pavel Begunkov wrote:
> On 11/02/2020 23:21, Jens Axboe wrote:
>> On 2/11/20 1:01 PM, Pavel Begunkov wrote:
>>> If a request got into io-wq context, io_prep_async_work() has already
>>> been called. Most of the stuff there is idempotent with an exception
>>> that it'll set work.task_pid to task_pid_vnr() of an io_wq worker thread
>>>
>>> Do only what's needed, that's io_prep_linked_timeout() and setting
>>> IO_WQ_WORK_UNBOUND.
>>
>> Rest of the series aside, I'm going to fix-up the pid addition to
>> only set if it's zero like the others.
>
> IMO, io_req_work_grab_env() should never be called from io-wq. It'd do nothing
> good but open space for subtle bugs. And if that's enforced (as done in this
> patch), it's safe to set @pid multiple times.
I agree, it'd be an issue if we ever did the first iteration through the
worker. And it'd be nice to make the flow self explanatory in that
regard.
> Probably, it worth to add the check just to not go through task_pid_vnr()
> several times.
Good point, that is worth it on its own.
--
Jens Axboe
next prev parent reply other threads:[~2020-02-11 20:59 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-11 20:01 [PATCH 0/5] async punting improvements for io_uring Pavel Begunkov
2020-02-11 20:01 ` [PATCH 1/5] io_uring: remove REQ_F_MUST_PUNT Pavel Begunkov
2020-02-11 20:01 ` [PATCH 2/5] io_uring: don't call work.func from sync ctx Pavel Begunkov
2020-02-11 20:01 ` [PATCH 3/5] io_uring: fix reassigning work.task_pid from io-wq Pavel Begunkov
2020-02-11 20:21 ` Jens Axboe
2020-02-11 20:57 ` Pavel Begunkov
2020-02-11 20:59 ` Jens Axboe [this message]
2020-02-11 20:01 ` [PATCH 4/5] io_uring: add missing io_req_cancelled() Pavel Begunkov
2020-02-11 20:01 ` [PATCH 5/5] io_uring: purge req->in_async Pavel Begunkov
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