From b1a1c262e4b0e713e52c63bd3233f1b9d6f2f056 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 15 Jan 2021 19:08:36 +0100 Subject: workqueue: Restrict affinity change to rescuer [ Upstream commit 640f17c82460e9724fd256f0a1f5d99e7ff0bda4 ] create_worker() will already set the right affinity using kthread_bind_mask(), this means only the rescuer will need to change it's affinity. Howveer, while in cpu-hot-unplug a regular task is not allowed to run on online&&!active as it would be pushed away quite agressively. We need KTHREAD_IS_PER_CPU to survive in that environment. Therefore set the affinity after getting that magic flag. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Valentin Schneider Tested-by: Valentin Schneider Link: https://lkml.kernel.org/r/20210121103506.826629830@infradead.org Signed-off-by: Sasha Levin --- kernel/workqueue.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 28e52657e093..29c36c029062 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1847,12 +1847,6 @@ static void worker_attach_to_pool(struct worker *worker, { mutex_lock(&wq_pool_attach_mutex); - /* - * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any - * online CPUs. It'll be re-applied when any of the CPUs come up. - */ - set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask); - /* * The wq_pool_attach_mutex ensures %POOL_DISASSOCIATED remains * stable across this function. See the comments above the flag @@ -1861,6 +1855,9 @@ static void worker_attach_to_pool(struct worker *worker, if (pool->flags & POOL_DISASSOCIATED) worker->flags |= WORKER_UNBOUND; + if (worker->rescue_wq) + set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask); + list_add_tail(&worker->node, &pool->workers); worker->pool = pool; -- cgit v1.2.3