linux-kernel - Re: [PATCH 3/3] task_work: use TIF

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Message-ID: <9c1a3233-b359-85ee-34cc-6b7bf6244a4d@kernel.dk>
Date:   Sat, 3 Oct 2020 09:35:25 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Oleg Nesterov <oleg@...hat.com>
Cc:     linux-kernel@...r.kernel.org, io-uring@...r.kernel.org,
        peterz@...radead.org
Subject: Re: [PATCH 3/3] task_work: use TIF_TASKWORK if available

On 10/2/20 7:49 PM, Thomas Gleixner wrote:
> On Fri, Oct 02 2020 at 17:38, Oleg Nesterov wrote:
>> On 10/02, Thomas Gleixner wrote:
>>>
>>> I think it's fundamentaly wrong that we have several places and several
>>> flags which handle task_work_run() instead of having exactly one place
>>> and one flag.
>>
>> Damn yes, agreed.
> 
> Actually there are TWO places, but they don't interfere:
> 
>    1) exit to user
> 
>    2) enter guest
> 
> From the kernel POV they are pretty much the same as both are leaving
> the kernel domain. But they have a few subtle different requirements
> what has to be done or not.
> 
> So any change to that logic needs to fixup both places,

Right, I actually did spot that, but didn't include it in the initial
series. I've split up the series a bit more, into functional bits.
Should be easier to reason/discuss:

https://git.kernel.dk/cgit/linux-block/log/?h=tif-task_work

-- 
Jens Axboe