From: Steven Rostedt <rostedt@goodmis.org>
To: Corey Minyard <cminyard@mvista.com>
Cc: Corey Minyard <minyard@acm.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
tglx@linutronix.de
Subject: Re: [PATCH RT v2] Fix a lockup in wait_for_completion() and friends
Date: Mon, 1 Jul 2019 17:13:33 -0400 [thread overview]
Message-ID: <20190701171333.37cc0567@gandalf.local.home> (raw)
In-Reply-To: <20190701170602.2fdb35c2@gandalf.local.home>
On Mon, 1 Jul 2019 17:06:02 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:
> On Mon, 1 Jul 2019 15:43:25 -0500
> Corey Minyard <cminyard@mvista.com> wrote:
>
>
> > I show that patch is already applied at
> >
> > 1921ea799b7dc561c97185538100271d88ee47db
> > sched/completion: Fix a lockup in wait_for_completion()
> >
> > git describe --contains 1921ea799b7dc561c97185538100271d88ee47db
> > v4.19.37-rt20~1
> >
> > So I'm not sure what is going on.
>
> Bah, I'm replying to the wrong commit that I'm having issues with.
>
> I searched your name to find the patch that is of trouble, and picked
> this one.
>
> I'll go find the problem patch, sorry for the noise on this one.
>
No, I did reply to the right email, but it wasn't the top patch I was
having issues with. It was the patch I replied to:
This change below that Sebastian marked as stable-rt is what is causing
me an issue. Not the patch that started the thread.
-- Steve
> Now.. that will fix it, but I think it is also wrong.
>
> The problem being that it violates FIFO, something that might be more
> important on -RT than elsewhere.
>
> The regular wait API seems confused/inconsistent when it uses
> autoremove_wake_function and default_wake_function, which doesn't help,
> but we can easily support this with swait -- the problematic thing is
> the custom wake functions, we musn't do that.
>
> (also, mingo went and renamed a whole bunch of wait_* crap and didn't do
> the same to swait_ so now its named all different :/)
>
> Something like the below perhaps.
>
> ---
> diff --git a/include/linux/swait.h b/include/linux/swait.h
> index 73e06e9986d4..f194437ae7d2 100644
> --- a/include/linux/swait.h
> +++ b/include/linux/swait.h
> @@ -61,11 +61,13 @@ struct swait_queue_head {
> struct swait_queue {
> struct task_struct *task;
> struct list_head task_list;
> + unsigned int remove;
> };
>
> #define __SWAITQUEUE_INITIALIZER(name) { \
> .task = current, \
> .task_list = LIST_HEAD_INIT((name).task_list), \
> + .remove = 1, \
> }
>
> #define DECLARE_SWAITQUEUE(name) \
> diff --git a/kernel/sched/swait.c b/kernel/sched/swait.c
> index e83a3f8449f6..86974ecbabfc 100644
> --- a/kernel/sched/swait.c
> +++ b/kernel/sched/swait.c
> @@ -28,7 +28,8 @@ void swake_up_locked(struct swait_queue_head *q)
>
> curr = list_first_entry(&q->task_list, typeof(*curr), task_list);
> wake_up_process(curr->task);
> - list_del_init(&curr->task_list);
> + if (curr->remove)
> + list_del_init(&curr->task_list);
> }
> EXPORT_SYMBOL(swake_up_locked);
>
> @@ -57,7 +58,8 @@ void swake_up_all(struct swait_queue_head *q)
> curr = list_first_entry(&tmp, typeof(*curr), task_list);
>
> wake_up_state(curr->task, TASK_NORMAL);
> - list_del_init(&curr->task_list);
> + if (curr->remove)
> + list_del_init(&curr->task_list);
>
> if (list_empty(&tmp))
> break;
next prev parent reply other threads:[~2019-07-01 21:13 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-09 19:33 [PATCH RT v2] Fix a lockup in wait_for_completion() and friends minyard
2019-05-09 19:51 ` Steven Rostedt
2019-05-10 10:33 ` Sebastian Andrzej Siewior
2019-05-10 12:08 ` Corey Minyard
2019-05-10 12:26 ` Sebastian Andrzej Siewior
2019-06-29 1:49 ` Steven Rostedt
2019-07-01 19:09 ` Corey Minyard
[not found] ` <20190701161840.1a53c9e4@gandalf.local.home>
2019-07-01 20:43 ` Corey Minyard
2019-07-01 21:06 ` Steven Rostedt
2019-07-01 21:13 ` Steven Rostedt [this message]
2019-07-01 21:28 ` Steven Rostedt
2019-07-01 21:34 ` Corey Minyard
2019-07-02 7:04 ` Kurt Kanzenbach
2019-07-02 8:35 ` Sebastian Andrzej Siewior
2019-07-02 11:40 ` Corey Minyard
2019-07-02 11:53 ` Sebastian Andrzej Siewior
-- strict thread matches above, loose matches on Subject: below --
2019-05-08 20:57 [PATCH " minyard
2019-05-09 16:19 ` [PATCH RT " Sebastian Andrzej Siewior
2019-05-09 17:46 ` Corey Minyard
2019-05-14 8:43 ` Peter Zijlstra
2019-05-14 9:12 ` Sebastian Andrzej Siewior
2019-05-14 11:35 ` Peter Zijlstra
2019-05-14 15:25 ` Sebastian Andrzej Siewior
2019-05-14 12:13 ` Corey Minyard
2019-05-14 15:36 ` Sebastian Andrzej Siewior
2019-05-15 16:22 ` Corey Minyard
2019-06-26 10:35 ` Peter Zijlstra
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=20190701171333.37cc0567@gandalf.local.home \
--to=rostedt@goodmis.org \
--cc=bigeasy@linutronix.de \
--cc=cminyard@mvista.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-rt-users@vger.kernel.org \
--cc=minyard@acm.org \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
/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).