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: Sat, 16 Jan 2021 19:46:47 +0100 [thread overview]
Message-ID: <YAM0l2WItxyaHr2N@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CAJhGHyBKexR+UmR2Hzf-OU9_9zfc0V6r=s2rS=N8sc+2VnN3mw@mail.gmail.com>
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);
next prev parent reply other threads:[~2021-01-16 18:49 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 [this message]
2021-01-17 9:54 ` Peter Zijlstra
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
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