From: Pavel Begunkov <asml.silence@gmail.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
linux-kernel@vger.kernel.org, Jens Axboe <axboe@kernel.dk>
Subject: Re: [RFC] exit: do exit_task_work() before shooting off mm
Date: Sun, 20 Dec 2020 14:42:10 +0000 [thread overview]
Message-ID: <de4bdebf-89ad-fd74-bac0-c3359994b488@gmail.com> (raw)
In-Reply-To: <20201220135803.GA16470@redhat.com>
On 20/12/2020 13:58, Oleg Nesterov wrote:
> On 12/20, Pavel Begunkov wrote:
>>
>> On 08/12/2020 01:37, Al Viro wrote:
>>> 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.
>
> I too do not understand this patch. task_work_add() will fail after
> exit_task_work(). This means that, for example, exit_files() will use
> schedule_delayed_work().
The first one? Between PF_EXITING and exit_task_work() do_exit() will
kill mm/etc., I wanted to not see tasks half dismantled for task_works
run in the exit_task_work(). Anyway, forget about it :)
>> One more moment, after we've set PF_EXITING any task_work_run() would be
>> equivalent to exit_task_work()
>
> Yes, currently task_work_run() can not be called after exit_signals().
> And shouldn't be called imo ;)
>
>> io_uring
>> may want (currently doesn't) to run works for cancellation purposes.t
>
> Please see https://lore.kernel.org/io-uring/20200407163816.GB9655@redhat.com/>> Shouldn't it be like below (not tested)? Also simplifies task_work_run().
>
> I'd prefer the patch from the link above, but your version looks correct too.
I missed the thread, thanks! tbh, splitting into 2 functions looks better
to me, but it's not like that matters
> However, I still think it would be better to not abuse task_work_run() too
> much...
The problem is that io_uring cancels requests in exit_files() and some
of them may be sitting in task_works, and we need to get them out of there
to complete.
Also, I need to double check, but seems new requests may be added during
and by cancellation because we did not yet set it to work_exited by the
time (in exit_files()).
--
Pavel Begunkov
next prev parent reply other threads:[~2020-12-20 14:46 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-03 2:30 [RFC] exit: do exit_task_work() before shooting off mm Pavel Begunkov
2020-12-08 1:37 ` Al Viro
2020-12-08 3:00 ` Pavel Begunkov
2020-12-20 12:50 ` Pavel Begunkov
2020-12-20 13:58 ` Oleg Nesterov
2020-12-20 14:42 ` Pavel Begunkov [this message]
2020-12-14 14:51 ` [exit] 80fae08355: stderr.mount:/fs/sda1:/dev/sda1_already_mounted_or_mount_point_busy kernel test robot
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=de4bdebf-89ad-fd74-bac0-c3359994b488@gmail.com \
--to=asml.silence@gmail.com \
--cc=axboe@kernel.dk \
--cc=linux-kernel@vger.kernel.org \
--cc=oleg@redhat.com \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).