From: Mike Christie <michael.christie@oracle.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: oleg@redhat.com, linux@leemhuis.info, nicolas.dichtel@6wind.com,
axboe@kernel.dk, torvalds@linux-foundation.org,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org, mst@redhat.com,
sgarzare@redhat.com, jasowang@redhat.com, stefanha@redhat.com,
brauner@kernel.org
Subject: Re: [RFC PATCH 1/8] signal: Dequeue SIGKILL even if SIGNAL_GROUP_EXIT/group_exec_task is set
Date: Thu, 18 May 2023 10:21:39 -0500 [thread overview]
Message-ID: <ab7d07ba-5dc3-95c0-aa7c-c2575d03f429@oracle.com> (raw)
In-Reply-To: <87ednei9is.fsf@email.froward.int.ebiederm.org>
On 5/17/23 10:49 PM, Eric W. Biederman wrote:
>
> Long story short.
>
> In the patch below the first hunk is a noop.
>
> The code you are bypassing was added to ensure that process termination
> (aka SIGKILL) is processed before any other signals. Other than signal
> processing order there are not any substantive differences in the two
> code paths. With all signals except SIGSTOP == 19 and SIGKILL == 9
> blocked SIGKILL should always be processed before SIGSTOP.
>
> Can you try patch with just the last hunk that does
> s/PF_IO_WORKER/PF_USER_WORKER/ and see if that is enough?
>
If I just have the last hunk and then we get SIGKILL what happens is
in code like:
vhost_worker()
schedule()
if (has IO)
handle_IO()
The schedule() calls will hit the signal_pending_state check for
signal_pending or __fatal_signal_pending and so instead of waiting
for whatever wake_up call we normally waited for we tend to just
return immediately. If you just run Qemu (the parent of the vhost_task)
and send SIGKILL then sometimes the vhost_task just spins and it
would look like the task has taken over the CPU (this is what I hit
when I tested Linus's patch).
With the first hunk of the patch, we will end up dequeuing the SIGKILL
and clearing TIF_SIGPENDING, so the vhost_task can still do some work
before it exits.
In the other patches we do:
if (get_signal(ksig))
start_exit_cleanup_by_stopping_newIO()
flush running IO()
exit()
But to do the flush running IO() part of this I need to wait for it so
that's why I wanted to be able to dequeue the SIGKILL and clear the
TIF_SIGPENDING bit.
Or I don't need this specifically. In patch 0/8 I said I knew you guys
would not like it :) If I just have a:
if (fatal_signal())
clear_fatal_signal()
then it would work for me.
next prev parent reply other threads:[~2023-05-18 15:22 UTC|newest]
Thread overview: 98+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-18 0:09 [RFC PATCH 0/8] vhost_tasks: Use CLONE_THREAD/SIGHAND Mike Christie
2023-05-18 0:09 ` [RFC PATCH 1/8] signal: Dequeue SIGKILL even if SIGNAL_GROUP_EXIT/group_exec_task is set Mike Christie
2023-05-18 2:34 ` Eric W. Biederman
2023-05-18 3:49 ` Eric W. Biederman
2023-05-18 15:21 ` Mike Christie [this message]
2023-05-18 16:25 ` Oleg Nesterov
2023-05-18 16:42 ` Mike Christie
2023-05-18 17:04 ` Oleg Nesterov
2023-05-18 18:28 ` Eric W. Biederman
2023-05-18 22:57 ` Mike Christie
2023-05-19 4:16 ` Eric W. Biederman
2023-05-19 23:24 ` Mike Christie
2023-05-22 13:30 ` Oleg Nesterov
2023-05-18 8:08 ` Christian Brauner
2023-05-18 15:27 ` Mike Christie
2023-05-18 17:07 ` Christian Brauner
2023-05-18 18:08 ` Oleg Nesterov
2023-05-18 18:12 ` Christian Brauner
2023-05-18 18:23 ` Oleg Nesterov
2023-05-18 0:09 ` [RFC PATCH 2/8] vhost/vhost_task: Hook vhost layer into signal handler Mike Christie
2023-05-18 0:16 ` Linus Torvalds
2023-05-18 1:01 ` Mike Christie
2023-05-18 8:16 ` Christian Brauner
2023-05-18 0:09 ` [RFC PATCH 3/8] fork/vhost_task: Switch to CLONE_THREAD and CLONE_SIGHAND Mike Christie
2023-05-18 8:18 ` Christian Brauner
2023-05-18 0:09 ` [RFC PATCH 4/8] vhost-net: Move vhost_net_open Mike Christie
2023-05-18 0:09 ` [RFC PATCH 5/8] vhost: Add callback that stops new work and waits on running ones Mike Christie
2023-05-18 14:18 ` Christian Brauner
2023-05-18 15:03 ` Mike Christie
2023-05-18 15:09 ` Christian Brauner
2023-05-18 18:38 ` Eric W. Biederman
2023-05-18 0:09 ` [RFC PATCH 6/8] vhost-scsi: Add callback to stop and wait on works Mike Christie
2023-05-18 0:09 ` [RFC PATCH 7/8] vhost-net: " Mike Christie
2023-05-18 0:09 ` [RFC PATCH 8/8] fork/vhost_task: remove no_files Mike Christie
2023-05-18 1:04 ` Mike Christie
2023-05-18 8:25 ` [RFC PATCH 0/8] vhost_tasks: Use CLONE_THREAD/SIGHAND Christian Brauner
2023-05-18 8:40 ` Christian Brauner
2023-05-18 14:30 ` Christian Brauner
-- strict thread matches above, loose matches on Subject: below --
2023-02-02 23:25 [PATCH v11 0/8] Use copy_process in vhost layer Mike Christie
2023-02-02 23:25 ` [PATCH v11 1/8] fork: Make IO worker options flag based Mike Christie
2023-02-03 0:14 ` Linus Torvalds
2023-02-02 23:25 ` [PATCH v11 2/8] fork/vm: Move common PF_IO_WORKER behavior to new flag Mike Christie
2023-02-02 23:25 ` [PATCH v11 3/8] fork: add USER_WORKER flag to not dup/clone files Mike Christie
2023-02-03 0:16 ` Linus Torvalds
2023-02-02 23:25 ` [PATCH v11 4/8] fork: Add USER_WORKER flag to ignore signals Mike Christie
2023-02-03 0:19 ` Linus Torvalds
2023-02-05 16:06 ` Mike Christie
2023-02-02 23:25 ` [PATCH v11 5/8] fork: allow kernel code to call copy_process Mike Christie
2023-02-02 23:25 ` [PATCH v11 6/8] vhost_task: Allow vhost layer to use copy_process Mike Christie
2023-02-03 0:43 ` Linus Torvalds
2023-02-02 23:25 ` [PATCH v11 7/8] vhost: move worker thread fields to new struct Mike Christie
2023-02-02 23:25 ` [PATCH v11 8/8] vhost: use vhost_tasks for worker threads Mike Christie
2023-05-05 13:40 ` Nicolas Dichtel
2023-05-05 18:22 ` Linus Torvalds
2023-05-05 22:37 ` Mike Christie
2023-05-06 1:53 ` Linus Torvalds
2023-05-08 17:13 ` Christian Brauner
2023-05-09 8:09 ` Nicolas Dichtel
2023-05-09 8:17 ` Nicolas Dichtel
2023-05-13 12:39 ` Thorsten Leemhuis
2023-05-13 15:08 ` Linus Torvalds
2023-05-15 14:23 ` Christian Brauner
2023-05-15 15:44 ` Linus Torvalds
2023-05-15 15:52 ` Jens Axboe
2023-05-15 15:54 ` Linus Torvalds
2023-05-15 17:23 ` Linus Torvalds
2023-05-15 15:56 ` Linus Torvalds
2023-05-15 22:23 ` Mike Christie
2023-05-15 22:54 ` Linus Torvalds
2023-05-16 3:53 ` Mike Christie
2023-05-16 13:18 ` Oleg Nesterov
2023-05-16 13:40 ` Oleg Nesterov
2023-05-16 15:56 ` Eric W. Biederman
2023-05-16 18:37 ` Oleg Nesterov
2023-05-16 20:12 ` Eric W. Biederman
2023-05-17 17:09 ` Oleg Nesterov
2023-05-17 18:22 ` Mike Christie
2023-05-16 8:39 ` Christian Brauner
2023-05-16 16:24 ` Mike Christie
2023-05-16 16:44 ` Christian Brauner
2023-05-19 12:15 ` [RFC PATCH 0/8] vhost_tasks: Use CLONE_THREAD/SIGHAND Christian Brauner
2023-06-01 7:58 ` Thorsten Leemhuis
2023-06-01 10:18 ` Nicolas Dichtel
2023-06-01 10:47 ` Christian Brauner
2023-06-01 11:29 ` Thorsten Leemhuis
2023-06-01 12:26 ` Linus Torvalds
2023-06-01 16:10 ` Mike Christie
2023-05-16 14:06 ` [PATCH v11 8/8] vhost: use vhost_tasks for worker threads Linux regression tracking #adding (Thorsten Leemhuis)
2023-05-26 9:03 ` Linux regression tracking #update (Thorsten Leemhuis)
2023-06-02 11:38 ` Thorsten Leemhuis
2023-07-20 13:06 ` Michael S. Tsirkin
2023-07-23 4:03 ` michael.christie
2023-07-23 9:31 ` Michael S. Tsirkin
2023-08-10 18:57 ` Michael S. Tsirkin
2023-08-11 18:51 ` Mike Christie
2023-08-13 19:01 ` Michael S. Tsirkin
2023-08-14 3:13 ` michael.christie
2023-02-07 8:19 ` [PATCH v11 0/8] Use copy_process in vhost layer Christian Brauner
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