linux-kernel - Re: [PATCH 3/5] io_uring: fix reassigning work.task

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Message-ID: <e60026f7-8e8f-7133-57e3-762a1d84269b@gmail.com>
Date:   Tue, 11 Feb 2020 23:57:13 +0300
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Jens Axboe <axboe@...nel.dk>, io-uring@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] io_uring: fix reassigning work.task_pid from io-wq

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.

Probably, it worth to add the check just to not go through task_pid_vnr()
several times.

-- 
Pavel Begunkov



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