From: "Paul E. McKenney" <paulmck@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <frederic@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Boqun Feng <boqun.feng@gmail.com>,
Joel Fernandes <joel@joelfernandes.org>,
Josh Triplett <josh@joshtriplett.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Neeraj Upadhyay <neeraj.upadhyay@amd.com>,
Steven Rostedt <rostedt@goodmis.org>,
Uladzislau Rezki <urezki@gmail.com>, rcu <rcu@vger.kernel.org>,
Zqiang <qiang.zhang1211@gmail.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
"Liam R . Howlett" <Liam.Howlett@oracle.com>,
Sebastian Siewior <bigeasy@linutronix.de>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 4/4] Revert "kernel/sched: Modify initial boot task idle setup"
Date: Fri, 20 Oct 2023 08:05:06 -0700 [thread overview]
Message-ID: <6fdfe084-866a-4ab4-ac03-a8e0e5b5a35e@paulmck-laptop> (raw)
In-Reply-To: <20231020134836.GE33965@noisy.programming.kicks-ass.net>
On Fri, Oct 20, 2023 at 03:48:36PM +0200, Peter Zijlstra wrote:
> On Fri, Oct 20, 2023 at 02:31:13PM +0200, Frederic Weisbecker wrote:
>
> > Yeah I can't say I really like the old coverage of PF_IDLE either. The new one
> > (after Liam's patch) is only halfway better defined though: it makes the boot
> > CPU's idle behave quite well: PF_IDLE is set on idle entry. And secondary
> > CPU's idle behave quite well also except when they go offline and then online
> > again. And then the secondary boot code becomes PF_IDLE.
>
> Bah offline, yeah, we should just not do that :-)
>
> > We probably need something like this:
> >
> > diff --git a/kernel/cpu.c b/kernel/cpu.c
> > index 3b9d5c7eb4a2..b24d7937b989 100644
> > --- a/kernel/cpu.c
> > +++ b/kernel/cpu.c
> > @@ -1394,7 +1394,9 @@ void cpuhp_report_idle_dead(void)
> > {
> > struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
> >
> > + current->flags &= ~PF_IDLE;
> > BUG_ON(st->state != CPUHP_AP_OFFLINE);
> > +
> > rcutree_report_cpu_dead();
> > st->state = CPUHP_AP_IDLE_DEAD;
> > /*
> > @@ -1642,6 +1644,8 @@ void cpuhp_online_idle(enum cpuhp_state state)
> > {
> > struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
> >
> > + current->flags |= PF_IDLE;
> > +
> > /* Happens for the boot cpu */
> > if (state != CPUHP_AP_ONLINE_IDLE)
> > return;
>
> Yeah that works I suppose.
Booting up kernels being what it is, there might not be a completely
pretty solution. Not that I would say "no" to such a solution should
it appear, mind you! ;-)
Thanx, Paul
prev parent reply other threads:[~2023-10-20 15:05 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-19 23:35 [PATCH 0/4] rcu: Fix PF_IDLE related issues, part. 1 Frederic Weisbecker
2023-10-19 23:35 ` [PATCH 1/4] softirq: Rename __raise_softirq_irqoff() to raise_softirq_no_wake() Frederic Weisbecker
2023-10-19 23:35 ` [PATCH 2/4] softirq: Introduce raise_ksoftirqd_irqoff() Frederic Weisbecker
2023-10-19 23:35 ` [PATCH 3/4] rcu: Make tiny RCU use ksoftirqd to trigger a QS from idle Frederic Weisbecker
2023-10-20 0:49 ` Paul E. McKenney
2023-10-19 23:35 ` [PATCH 4/4] Revert "kernel/sched: Modify initial boot task idle setup" Frederic Weisbecker
2023-10-20 8:25 ` Peter Zijlstra
2023-10-20 12:31 ` Frederic Weisbecker
2023-10-20 13:48 ` Peter Zijlstra
2023-10-20 15:05 ` Paul E. McKenney [this message]
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=6fdfe084-866a-4ab4-ac03-a8e0e5b5a35e@paulmck-laptop \
--to=paulmck@kernel.org \
--cc=Liam.Howlett@oracle.com \
--cc=bigeasy@linutronix.de \
--cc=boqun.feng@gmail.com \
--cc=frederic@kernel.org \
--cc=jiangshanlai@gmail.com \
--cc=joel@joelfernandes.org \
--cc=josh@joshtriplett.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mathieu.desnoyers@efficios.com \
--cc=neeraj.upadhyay@amd.com \
--cc=peterz@infradead.org \
--cc=qiang.zhang1211@gmail.com \
--cc=rcu@vger.kernel.org \
--cc=rostedt@goodmis.org \
--cc=tglx@linutronix.de \
--cc=urezki@gmail.com \
/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 read-only IMAP folder(s) and NNTP newsgroup(s).