From: Frederic Weisbecker <frederic@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Qian Cai <cai@lca.pw>, Borislav Petkov <bp@alien8.de>,
Thomas Gleixner <tglx@linutronix.de>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: Endless soft-lockups for compiling workload since next-20200519
Date: Mon, 25 May 2020 16:05:49 +0200 [thread overview]
Message-ID: <20200525140541.GA28923@lenoir> (raw)
In-Reply-To: <20200525132105.GW325280@hirez.programming.kicks-ass.net>
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
WARNING: multiple messages have this Message-ID (diff)
From: Frederic Weisbecker <frederic@kernel.org>
To: Peter Zijlstra <peterz@infradead.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 16:05:49 +0200 [thread overview]
Message-ID: <20200525140541.GA28923@lenoir> (raw)
In-Reply-To: <20200525132105.GW325280@hirez.programming.kicks-ass.net>
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
next prev parent reply other threads:[~2020-05-25 14:11 UTC|newest]
Thread overview: 28+ 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 3:58 ` Qian Cai
2020-05-20 12:50 ` Peter Zijlstra
2020-05-20 12:50 ` Peter Zijlstra
2020-05-20 14:06 ` Qian Cai
2020-05-20 14:06 ` Qian Cai
2020-05-21 0:40 ` Frederic Weisbecker
2020-05-21 0:40 ` Frederic Weisbecker
2020-05-21 9:39 ` Peter Zijlstra
2020-05-21 9:39 ` Peter Zijlstra
2020-05-21 10:49 ` Peter Zijlstra
2020-05-21 10:49 ` Peter Zijlstra
2020-05-21 11:00 ` Peter Zijlstra
2020-05-21 11:00 ` Peter Zijlstra
2020-05-21 12:41 ` Frederic Weisbecker
2020-05-21 12:41 ` Frederic Weisbecker
2020-05-25 13:21 ` Peter Zijlstra
2020-05-25 13:21 ` Peter Zijlstra
2020-05-25 14:05 ` Frederic Weisbecker [this message]
2020-05-25 14:05 ` Frederic Weisbecker
2020-05-25 14:38 ` Peter Zijlstra
2020-05-25 14:38 ` Peter Zijlstra
2020-05-25 14:17 ` Peter Zijlstra
2020-05-25 14:17 ` Peter Zijlstra
2020-05-22 2:00 ` Qian Cai
2020-05-22 2:00 ` Qian Cai
2020-05-21 10:10 ` Peter Zijlstra
2020-05-21 10:10 ` Peter Zijlstra
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