From: Peter Zijlstra <peterz@infradead.org>
To: Frederic Weisbecker <frederic@kernel.org>
Cc: Qian Cai <cai@lca.pw>, "Paul E. McKenney" <paulmck@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Michael Ellerman <mpe@ellerman.id.au>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
Borislav Petkov <bp@alien8.de>
Subject: Re: Endless soft-lockups for compiling workload since next-20200519
Date: Mon, 25 May 2020 16:38:59 +0200 [thread overview]
Message-ID: <20200525143859.GX325280@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200525140541.GA28923@lenoir>
On Mon, May 25, 2020 at 04:05:49PM +0200, Frederic Weisbecker wrote:
> On Mon, May 25, 2020 at 03:21:05PM +0200, Peter Zijlstra wrote:
> > @@ -2320,7 +2304,7 @@ static void ttwu_queue_remote(struct task_struct *p, int cpu, int wake_flags)
> >
> > if (llist_add(&p->wake_entry, &rq->wake_list)) {
> > if (!set_nr_if_polling(rq->idle))
> > - smp_call_function_single_async(cpu, &rq->wake_csd);
> > + smp_call_function_single_async(cpu, &p->wake_csd);
> > else
> > trace_sched_wake_idle_without_ipi(cpu);
>
> Ok that's of course very unlikely but could it be possible to have the
> following:
>
> CPU 0 CPU 1 CPU 2
> -----
>
> //Wake up A
> ttwu_queue(TASK A, CPU 1) idle_loop {
> ttwu_queue_pending {
> ....
> raw_spin_unlock_irqrestore(rq)
> # VMEXIT (with IPI still pending)
> //task A migrates here
> wait_event(....)
> //sleep
>
> //Wake up A
> ttwu_queue(TASK A, CPU 2) {
> //IPI on CPU 2 ignored
> // due to csd->flags == CSD_LOCK
>
Right you are.
Bah!
More thinking....
next prev parent reply other threads:[~2020-05-25 14:39 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-20 3:58 Endless soft-lockups for compiling workload since next-20200519 Qian Cai
2020-05-20 12:50 ` Peter Zijlstra
2020-05-20 14:06 ` Qian Cai
2020-05-21 0:40 ` Frederic Weisbecker
2020-05-21 9:39 ` Peter Zijlstra
2020-05-21 10:49 ` Peter Zijlstra
2020-05-21 11:00 ` Peter Zijlstra
2020-05-21 12:41 ` Frederic Weisbecker
2020-05-25 13:21 ` Peter Zijlstra
2020-05-25 14:05 ` Frederic Weisbecker
2020-05-25 14:38 ` Peter Zijlstra [this message]
2020-05-25 14:17 ` Peter Zijlstra
2020-05-22 2:00 ` Qian Cai
2020-05-21 10:10 ` 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=20200525143859.GX325280@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=bp@alien8.de \
--cc=cai@lca.pw \
--cc=frederic@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=mpe@ellerman.id.au \
--cc=paulmck@kernel.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