linux-kernel - Re: [RFC] exit: do exit_task_work() before shooting off mm

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Message-ID: <20201208013722.GG3579531@ZenIV.linux.org.uk>
Date:   Tue, 8 Dec 2020 01:37:22 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Pavel Begunkov <asml.silence@...il.com>
Cc:     linux-kernel@...r.kernel.org, Jens Axboe <axboe@...nel.dk>
Subject: Re: [RFC] exit: do exit_task_work() before shooting off mm

On Thu, Dec 03, 2020 at 02:30:46AM +0000, Pavel Begunkov wrote:
> Handle task works and lock it earlier before it starts killing off
> task's resources like mm. io_uring makes use of it a lot and it'd
> nicer to have all added task_work finding tasks in a consistent state.
> 
> Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
> ---
> 
> Would it be correct? I clearly don't know all the exit invariants, but
> can't find any users relying on task_works in-between.

You've just gotten rid of exit_task_work() anywhere after exit_files().
And exit_mm() can trigger the final fput() just as easily as exit_files().

IOW, you have just made the effect of final close on exit() completely
asynchronous.

NAK.