From: Peter Zijlstra <peterz@infradead.org>
To: mingo@kernel.org, tglx@linutronix.de
Cc: linux-kernel@vger.kernel.org, jiangshanlai@gmail.com,
valentin.schneider@arm.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: [PATCH 5/8] workqueue: Tag bound workers with KTHREAD_IS_PER_CPU
Date: Sat, 16 Jan 2021 12:30:38 +0100 [thread overview]
Message-ID: <20210116113919.933156564@infradead.org> (raw)
In-Reply-To: 20210116113033.608340773@infradead.org
Mark the per-cpu workqueue workers as KTHREAD_IS_PER_CPU.
Workqueues have unfortunate semantics in that per-cpu workers are not
default flushed and parked during hotplug, however a subset does
manual flush on hotplug and hard relies on them for correctness.
Therefore play silly games..
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
kernel/workqueue.c | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1861,6 +1861,8 @@ static void worker_attach_to_pool(struct
*/
if (pool->flags & POOL_DISASSOCIATED)
worker->flags |= WORKER_UNBOUND;
+ else
+ kthread_set_per_cpu(worker->task, pool->cpu);
list_add_tail(&worker->node, &pool->workers);
worker->pool = pool;
@@ -1883,6 +1885,7 @@ static void worker_detach_from_pool(stru
mutex_lock(&wq_pool_attach_mutex);
+ kthread_set_per_cpu(worker->task, -1);
list_del(&worker->node);
worker->pool = NULL;
@@ -2368,6 +2371,7 @@ 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? */
@@ -2425,7 +2429,7 @@ static int worker_thread(void *__worker)
move_linked_works(work, &worker->scheduled, NULL);
process_scheduled_works(worker);
}
- } while (keep_working(pool));
+ } while (keep_working(pool) && !kthread_should_park());
worker_set_flags(worker, WORKER_PREP);
sleep:
@@ -2437,9 +2441,12 @@ 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);
- schedule();
+
+ if (!kthread_should_park())
+ schedule();
+
goto woke_up;
}
@@ -4919,8 +4926,10 @@ static void unbind_workers(int cpu)
raw_spin_unlock_irq(&pool->lock);
- for_each_pool_worker(worker, pool)
+ for_each_pool_worker(worker, pool) {
+ kthread_set_per_cpu(worker->task, -1);
WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, cpu_possible_mask) < 0);
+ }
mutex_unlock(&wq_pool_attach_mutex);
@@ -4972,9 +4981,11 @@ 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)
- WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
- pool->attrs->cpumask) < 0);
+ 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);
+ }
raw_spin_lock_irq(&pool->lock);
next prev parent reply other threads:[~2021-01-16 11:44 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-16 11:30 [PATCH 0/8] sched: Fix hot-unplug regressions Peter Zijlstra
2021-01-16 11:30 ` [PATCH 1/8] sched/core: Print out straggler tasks in sched_cpu_dying() Peter Zijlstra
2021-01-16 11:30 ` [PATCH 2/8] workqueue: Use cpu_possible_mask instead of cpu_active_mask to break affinity Peter Zijlstra
2021-01-16 11:30 ` [PATCH 3/8] sched: Dont run cpu-online with balance_push() enabled Peter Zijlstra
2021-01-16 15:27 ` Peter Zijlstra
2021-01-16 11:30 ` [PATCH 4/8] kthread: Extract KTHREAD_IS_PER_CPU Peter Zijlstra
2021-01-16 11:30 ` Peter Zijlstra [this message]
2021-01-16 11:30 ` [PATCH 6/8] workqueue: Restrict affinity change to rescuer Peter Zijlstra
2021-01-16 11:30 ` [PATCH 7/8] sched: Fix CPU hotplug / tighten is_per_cpu_kthread() Peter Zijlstra
2021-01-17 16:57 ` Valentin Schneider
2021-01-18 9:30 ` Peter Zijlstra
2021-01-16 11:30 ` [PATCH 8/8] sched: Relax the set_cpus_allowed_ptr() semantics Peter Zijlstra
2021-01-16 14:39 ` Lai Jiangshan
2021-01-16 15:19 ` Peter Zijlstra
2021-01-16 15:25 ` [PATCH 0/8] sched: Fix hot-unplug regressions Peter Zijlstra
2021-01-16 15:45 ` Paul E. McKenney
2021-01-16 18:51 ` Peter Zijlstra
2021-01-16 15:48 ` Paul E. McKenney
2021-01-18 5:28 ` Paul E. McKenney
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