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.
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| @@ -1635,7 +1635,7 @@ static void worker_enter_idle(struct worker *worker) · 1634 unmodified lines | ||
| 1635 | 1635 | mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT); |
| 1636 | 1636 | |
| 1637 | 1637 | /* |
| 1638 | − * Sanity check nr_running. Because wq_unbind_fn() releases | |
| 1638 | + * Sanity check nr_running. Because unbind_workers() releases | |
| 1639 | 1639 | * pool->lock between setting %WORKER_UNBOUND and zapping |
| 1640 | 1640 | * nr_running, the warning may trigger spuriously. Check iff |
| 1641 | 1641 | * unbind is not in progress. |
| @@ -4511,9 +4511,8 @@ void show_workqueue_state(void) · 2869 unmodified lines | ||
| 4511 | 4511 | * cpu comes back online. |
| 4512 | 4512 | */ |
| 4513 | 4513 | |
| 4514 | −static void wq_unbind_fn(struct work_struct *work) | |
| 4514 | +static void unbind_workers(int cpu) | |
| 4515 | 4515 | { |
| 4516 | − int cpu = smp_processor_id(); | |
| 4517 | 4516 | struct worker_pool *pool; |
| 4518 | 4517 | struct worker *worker; |
| 4519 | 4518 | |
| @@ -4710,12 +4709,13 @@ int workqueue_online_cpu(unsigned int cpu) · 190 unmodified lines | ||
| 4710 | 4709 | |
| 4711 | 4710 | int workqueue_offline_cpu(unsigned int cpu) |
| 4712 | 4711 | { |
| 4713 | − struct work_struct unbind_work; | |
| 4714 | 4712 | struct workqueue_struct *wq; |
| 4715 | 4713 | |
| 4716 | 4714 | /* unbinding per-cpu workers should happen on the local CPU */ |
| 4717 | − INIT_WORK_ONSTACK(&unbind_work, wq_unbind_fn); | |
| 4718 | − queue_work_on(cpu, system_highpri_wq, &unbind_work); | |
| 4715 | + if (WARN_ON(cpu != smp_processor_id())) | |
| 4716 | + return -1; | |
| 4717 | + | |
| 4718 | + unbind_workers(cpu); | |
| 4719 | 4719 | |
| 4720 | 4720 | /* update NUMA affinity of unbound workqueues */ |
| 4721 | 4721 | mutex_lock(&wq_pool_mutex); |
| @@ -4723,9 +4723,6 @@ int workqueue_offline_cpu(unsigned int cpu) · 1 unmodified line | ||
| 4723 | 4723 | wq_update_unbound_numa(wq, cpu, false); |
| 4724 | 4724 | mutex_unlock(&wq_pool_mutex); |
| 4725 | 4725 | |
| 4726 | − /* wait for per-cpu unbinding to finish */ | |
| 4727 | − flush_work(&unbind_work); | |
| 4728 | − destroy_work_on_stack(&unbind_work); | |
| 4729 | 4726 | return 0; |
| 4730 | 4727 | } |
| 4731 | 4728 | |