From: Miroslav Benes <mbenes@suse.cz>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Petr Mladek <pmladek@suse.com>,
jpoimboe@redhat.com, jeyu@kernel.org, jikos@kernel.org,
lpechacek@suse.cz, pavel@ucw.cz, live-patching@vger.kernel.org,
linux-kernel@vger.kernel.org,
Michael Ellerman <mpe@ellerman.id.au>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Andy Lutomirski <luto@kernel.org>,
linuxppc-dev@lists.ozlabs.org, x86@kernel.org
Subject: Re: [PATCH v3 1/2] livepatch: send a fake signal to all blocking tasks
Date: Thu, 2 Nov 2017 11:36:17 +0100 (CET) [thread overview]
Message-ID: <alpine.LSU.2.21.1711021128220.19544@san.suse.cz> (raw)
In-Reply-To: <20171101164314.GA32760@redhat.com>
On Wed, 1 Nov 2017, Oleg Nesterov wrote:
> On 11/01, Petr Mladek wrote:
> >
> > On Tue 2017-10-31 12:48:52, Miroslav Benes wrote:
> > > + if (task->flags & PF_KTHREAD) {
> > > + /*
> > > + * Wake up a kthread which still has not been migrated.
> > > + */
> > > + wake_up_process(task);
> >
> > I have just noticed that freezer used wake_up_state(p, TASK_INTERRUPTIBLE);
> > IMHO, we should do so as well.
>
> I won't argue, but...
>
> > wake_up_process() wakes also tasks in TASK_UNINTERRUPTIBLE state.
> > These might not be ready for an unexpected wakeup. For example,
> > see concat_dev_erase() in drivers/mtd/mtdcontact.c.
>
> I'd say that concat_dev_erase() should be fixed, any code should be ready
> for spurious wakeup.
I agree.
> Note also that wake_up_state(TASK_INTERRUPTIBLE) won't wakeup the TASK_IDLE
> kthreads, and most of the kthreads which use TASK_INTERRUPTIBLE should use
> TASK_IDLE today, because in most cases TASK_INTERRUPTIBLE was used to not
> contribute to loadavg.
Yes. Unfortunately, we have TASK_IDLE for more than two years now and
nothing much has happened yet. TASK_IDLE is still used sporadically. I'd
like to be on the safe side with livepatch and given that
TASK_INTERRUPTIBLE loops should be prepared for spurious wakeups by
definition, I think it is better to have wake_up_state(TASK_INTERRUPTIBLE)
there. At least till all "concat_dev_erase" beauties are fixed (sigh).
Miroslav
next prev parent reply other threads:[~2017-11-02 10:36 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-31 11:48 [PATCH v3 0/2] livepatch: Introduce signal and force sysfs attributes Miroslav Benes
2017-10-31 11:48 ` [PATCH v3 1/2] livepatch: send a fake signal to all blocking tasks Miroslav Benes
2017-11-01 15:06 ` Miroslav Benes
2017-11-01 15:13 ` Petr Mladek
2017-11-01 16:43 ` Oleg Nesterov
2017-11-02 10:36 ` Miroslav Benes [this message]
2017-11-02 14:08 ` Oleg Nesterov
2017-11-02 13:09 ` Josh Poimboeuf
2017-11-03 8:02 ` Miroslav Benes
2017-11-03 12:57 ` Josh Poimboeuf
2017-11-02 13:32 ` Josh Poimboeuf
2017-11-03 8:06 ` Miroslav Benes
2017-11-06 11:08 ` Pavel Machek
2017-10-31 11:48 ` [PATCH v3 2/2] livepatch: force transition process to finish Miroslav Benes
2017-11-01 15:32 ` Petr Mladek
2017-11-02 13:13 ` Josh Poimboeuf
2017-11-03 8:07 ` Miroslav Benes
2017-11-06 11:11 ` Pavel Machek
2017-11-06 12:03 ` Jiri Kosina
2017-11-09 11:14 ` Pavel Machek
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