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workqueue/hotplug: simplify workqueue_offline_cpu() 

Since the recent cpu/hotplug refactoring, workqueue_offline_cpu() is
guaranteed to run on the local cpu which is going offline.

This also fixes the following deadlock by removing work item
scheduling and flushing from CPU hotplug path.

 http://lkml.kernel.org/r/1504764252-29091-1-git-send-email-prsood@codeaurora.org

tj: Description update.

Signed-off-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Lai Jiangshan 2017-12-01 22:20:36 +08:00 committed by Tejun Heo
parent c98a980509
commit e8b3f8db7a
1 changed files with 6 additions and 9 deletions
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15
kernel/workqueue.c
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@ -1635,7 +1635,7 @@ static void worker_enter_idle(struct worker *worker)
mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
/*
* Sanity check nr_running. Because wq_unbind_fn() releases
* Sanity check nr_running. Because unbind_workers() releases
* pool->lock between setting %WORKER_UNBOUND and zapping
* nr_running, the warning may trigger spuriously. Check iff
* unbind is not in progress.
@ -4511,9 +4511,8 @@ void show_workqueue_state(void)
* cpu comes back online.
*/
static void wq_unbind_fn(struct work_struct *work)
static void unbind_workers(int cpu)
{
int cpu = smp_processor_id();
struct worker_pool *pool;
struct worker *worker;
@ -4710,12 +4709,13 @@ int workqueue_online_cpu(unsigned int cpu)
int workqueue_offline_cpu(unsigned int cpu)
{
struct work_struct unbind_work;
struct workqueue_struct *wq;
/* unbinding per-cpu workers should happen on the local CPU */
INIT_WORK_ONSTACK(&unbind_work, wq_unbind_fn);
queue_work_on(cpu, system_highpri_wq, &unbind_work);
if (WARN_ON(cpu != smp_processor_id()))
return -1;
unbind_workers(cpu);
/* update NUMA affinity of unbound workqueues */
mutex_lock(&wq_pool_mutex);
@ -4723,9 +4723,6 @@ int workqueue_offline_cpu(unsigned int cpu)
wq_update_unbound_numa(wq, cpu, false);
mutex_unlock(&wq_pool_mutex);
/* wait for per-cpu unbinding to finish */
flush_work(&unbind_work);
destroy_work_on_stack(&unbind_work);
return 0;
}