From: Valentin Schneider <valentin.schneider@arm.com>
To: Peter Zijlstra <peterz@infradead.org>,
mingo@kernel.org, tglx@linutronix.de
Cc: linux-kernel@vger.kernel.org, jiangshanlai@gmail.com,
cai@redhat.com, vincent.donnefort@arm.com, decui@microsoft.com,
paulmck@kernel.org, vincent.guittot@linaro.org,
rostedt@goodmis.org, tj@kernel.org, peterz@infradead.org
Subject: Re: [PATCH -v3 5/9] workqueue: Tag bound workers with KTHREAD_IS_PER_CPU
Date: Thu, 21 Jan 2021 14:31:20 +0000 [thread overview]
Message-ID: <jhja6t2mkef.mognet@arm.com> (raw)
In-Reply-To: <20210121103506.693465814@infradead.org>
On 21/01/21 11:17, Peter Zijlstra wrote:
> @@ -4972,9 +4977,11 @@ static void rebind_workers(struct worker
> * of all workers first and then clear UNBOUND. As we're called
> * from CPU_ONLINE, the following shouldn't fail.
> */
> - for_each_pool_worker(worker, pool)
> + for_each_pool_worker(worker, pool) {
> + kthread_set_per_cpu(worker->task, pool->cpu);
> WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
> pool->attrs->cpumask) < 0);
At the end of this series, is_cpu_allowed() allows kthreads with
KTHREAD_IS_PER_CPU on any online CPU, even if it isn't the designated
kthread->cpu.
I thought there might be a race here, given this gives us a window where a
pcpu kworker has the flag but is still affined to cpus_possible_mask. Now,
given cpus_write_lock(), we can't have a CPU going up while another goes
down. So I think it's actually fine, and I've been chasing ghosts yet again.
> + }
>
> raw_spin_lock_irq(&pool->lock);
>
next prev parent reply other threads:[~2021-01-21 14:44 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-21 10:17 [PATCH -v3 0/9] sched: Fix hot-unplug regression Peter Zijlstra
2021-01-21 10:17 ` [PATCH -v3 1/9] sched/core: Print out straggler tasks in sched_cpu_dying() Peter Zijlstra
2021-01-21 10:17 ` [PATCH -v3 2/9] workqueue: Use cpu_possible_mask instead of cpu_active_mask to break affinity Peter Zijlstra
2021-01-21 10:17 ` [PATCH -v3 3/9] sched: Dont run cpu-online with balance_push() enabled Peter Zijlstra
2021-01-21 14:00 ` Valentin Schneider
2021-01-21 14:14 ` Peter Zijlstra
2021-01-22 17:41 ` [tip: sched/urgent] sched: Don't " tip-bot2 for Peter Zijlstra
2021-01-21 10:17 ` [PATCH -v3 4/9] kthread: Extract KTHREAD_IS_PER_CPU Peter Zijlstra
2021-01-22 17:41 ` [tip: sched/urgent] " tip-bot2 for Peter Zijlstra
2021-01-21 10:17 ` [PATCH -v3 5/9] workqueue: Tag bound workers with KTHREAD_IS_PER_CPU Peter Zijlstra
2021-01-21 14:31 ` Valentin Schneider [this message]
2021-01-22 17:41 ` [tip: sched/urgent] " tip-bot2 for Peter Zijlstra
2021-01-21 10:17 ` [PATCH -v3 6/9] workqueue: Restrict affinity change to rescuer Peter Zijlstra
2021-01-22 17:41 ` [tip: sched/urgent] " tip-bot2 for Peter Zijlstra
2021-01-21 10:17 ` [PATCH -v3 7/9] sched: Prepare to use balance_push in ttwu() Peter Zijlstra
2021-01-22 17:41 ` [tip: sched/urgent] " tip-bot2 for Peter Zijlstra
2021-01-21 10:17 ` [PATCH -v3 8/9] sched: Fix CPU hotplug / tighten is_per_cpu_kthread() Peter Zijlstra
2021-01-21 14:01 ` Valentin Schneider
2021-01-21 14:18 ` Peter Zijlstra
2021-01-21 14:36 ` Valentin Schneider
2021-01-22 17:41 ` [tip: sched/urgent] " tip-bot2 for Peter Zijlstra
2021-01-21 10:17 ` [PATCH -v3 9/9] sched: Relax the set_cpus_allowed_ptr() semantics Peter Zijlstra
2021-01-22 17:41 ` [tip: sched/urgent] " tip-bot2 for Peter Zijlstra
2021-01-21 14:36 ` [PATCH -v3 0/9] sched: Fix hot-unplug regression Valentin Schneider
2021-01-21 19:56 ` Paul E. McKenney
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