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workqueue: Tag bound workers with KTHREAD_IS_PER_CPU

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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>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Tested-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210121103506.693465814@infradead.org
This commit is contained in:
Peter Zijlstra 2021-01-12 11:26:49 +01:00
parent ac687e6e8c
commit 5c25b5ff89
1 changed files with 9 additions and 2 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

11
kernel/workqueue.c
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@ -1861,6 +1861,8 @@ static void worker_attach_to_pool(struct worker *worker,
*/
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(struct worker *worker)
mutex_lock(&wq_pool_attach_mutex);
kthread_set_per_cpu(worker->task, -1);
list_del(&worker->node);
worker->pool = NULL;
@ -4919,8 +4922,10 @@ 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 +4977,11 @@ static void rebind_workers(struct worker_pool *pool)
* 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);
}
raw_spin_lock_irq(&pool->lock);