From: Peter Zijlstra <peterz@infradead.org>
To: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Valentin Schneider <valentin.schneider@arm.com>,
Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>, Qian Cai <cai@redhat.com>,
Vincent Donnefort <vincent.donnefort@arm.com>,
Dexuan Cui <decui@microsoft.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Steven Rostedt <rostedt@goodmis.org>, Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH 3/4] workqueue: Tag bound workers with KTHREAD_IS_PER_CPU
Date: Sun, 17 Jan 2021 10:54:07 +0100 [thread overview]
Message-ID: <YAQJP+5bmrrXZ6eu@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <YAM0l2WItxyaHr2N@hirez.programming.kicks-ass.net>
On Sat, Jan 16, 2021 at 07:46:47PM +0100, Peter Zijlstra wrote:
> On Sun, Jan 17, 2021 at 12:14:34AM +0800, Lai Jiangshan wrote:
>
> > BP: AP: worker:
> > cpus_write_lock()
> > bringup_cpu() work_item_func()
> > bringup_wait_for_ap get_online_cpus()
> > kthread_park(worker)
>
> Thanks, pictures are easier. Agreed, that a problem.
>
> I've also found another problem I think. rescuer_thread becomes part of
> for_each_pool_worker() between worker_attach_to_pool() and
> worker_detach_from_pool(), so it would try and do kthread_park() on
> rescuer, when things align. And rescuer_thread() doesn't have a
> kthread_parkme().
>
> And we already rely on this 'ugly' thing of first doing
> kthread_set_per_cpu() and fixing up the affinity later for the rescuer.
>
> Let me restart the SRCU-P testing with the below delta applied.
>
> ---
> kernel/workqueue.c | 14 +++++---------
> 1 file changed, 5 insertions(+), 9 deletions(-)
>
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index 1db769b116a1..894bb885b40b 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -2368,7 +2368,6 @@ static int worker_thread(void *__worker)
> /* tell the scheduler that this is a workqueue worker */
> set_pf_worker(true);
> woke_up:
> - kthread_parkme();
> raw_spin_lock_irq(&pool->lock);
>
> /* am I supposed to die? */
> @@ -2426,7 +2425,7 @@ static int worker_thread(void *__worker)
> move_linked_works(work, &worker->scheduled, NULL);
> process_scheduled_works(worker);
> }
> - } while (keep_working(pool) && !kthread_should_park());
> + } while (keep_working(pool));
>
> worker_set_flags(worker, WORKER_PREP);
> sleep:
> @@ -2438,12 +2437,9 @@ static int worker_thread(void *__worker)
> * event.
> */
> worker_enter_idle(worker);
> - set_current_state(TASK_IDLE);
> + __set_current_state(TASK_IDLE);
> raw_spin_unlock_irq(&pool->lock);
> -
> - if (!kthread_should_park())
> - schedule();
> -
> + schedule();
> goto woke_up;
> }
>
> @@ -4979,9 +4975,9 @@ static void rebind_workers(struct worker_pool *pool)
> * from CPU_ONLINE, the following shouldn't fail.
> */
> for_each_pool_worker(worker, pool) {
> - WARN_ON_ONCE(kthread_park(worker->task) < 0);
> kthread_set_per_cpu(worker->task, pool->cpu);
> - kthread_unpark(worker->task);
> + WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
> + pool->attrs->cpumask) < 0);
> }
>
> raw_spin_lock_irq(&pool->lock);
In the roughly 80 instances of 18*SRCU-P since sending this, I've got
one sched_cpu_dying splat about a stray kworker, so somthing isn't
right.
My intention was to not think today, so I'll delay that until tomorrow.
next prev parent reply other threads:[~2021-01-17 9:56 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-12 14:43 [PATCH 0/4] sched: Fix hot-unplug regressions Peter Zijlstra
2021-01-12 14:43 ` [PATCH 2/4] kthread: Extract KTHREAD_IS_PER_CPU Peter Zijlstra
2021-01-12 14:43 ` [PATCH 3/4] workqueue: Tag bound workers with KTHREAD_IS_PER_CPU Peter Zijlstra
2021-01-12 16:36 ` Lai Jiangshan
2021-01-13 11:43 ` Peter Zijlstra
2021-01-12 17:57 ` Valentin Schneider
2021-01-13 13:28 ` Lai Jiangshan
2021-01-13 14:16 ` Valentin Schneider
2021-01-13 17:52 ` Paul E. McKenney
2021-01-13 18:43 ` Valentin Schneider
2021-01-13 18:59 ` Paul E. McKenney
2021-01-14 13:12 ` Peter Zijlstra
2021-01-14 13:21 ` Valentin Schneider
2021-01-14 15:34 ` Peter Zijlstra
2021-01-16 6:27 ` Lai Jiangshan
2021-01-16 12:45 ` Peter Zijlstra
2021-01-16 14:45 ` Lai Jiangshan
2021-01-16 15:16 ` Peter Zijlstra
2021-01-16 16:14 ` Lai Jiangshan
2021-01-16 18:46 ` Peter Zijlstra
2021-01-17 9:54 ` Peter Zijlstra [this message]
2021-01-16 15:13 ` Peter Zijlstra
2021-01-12 14:43 ` [PATCH 4/4] sched: Fix CPU hotplug / tighten is_per_cpu_kthread() 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=YAQJP+5bmrrXZ6eu@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=cai@redhat.com \
--cc=decui@microsoft.com \
--cc=jiangshanlai@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=paulmck@kernel.org \
--cc=rostedt@goodmis.org \
--cc=tglx@linutronix.de \
--cc=tj@kernel.org \
--cc=valentin.schneider@arm.com \
--cc=vincent.donnefort@arm.com \
--cc=vincent.guittot@linaro.org \
/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).