From: Andrew Morton Cc: Oleg Nesterov Cc: Srivatsa Vaddagiri Cc: Gautham Shenoy Signed-off-by: Andrew Morton --- kernel/workqueue.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) diff -puN kernel/workqueue.c~flush_workqueue-use-preempt_disable-to-hold-off-cpu-hotplug kernel/workqueue.c --- a/kernel/workqueue.c~flush_workqueue-use-preempt_disable-to-hold-off-cpu-hotplug +++ a/kernel/workqueue.c @@ -419,18 +419,22 @@ static void flush_cpu_workqueue(struct c * Probably keventd trying to flush its own queue. So simply run * it by hand rather than deadlocking. */ - mutex_unlock(&workqueue_mutex); + preempt_enable(); + /* + * We can still touch *cwq here because we are keventd, and + * hot-unplug will be waiting us to exit. + */ run_workqueue(cwq); - mutex_lock(&workqueue_mutex); + preempt_disable(); } else { struct wq_barrier barr; init_wq_barrier(&barr); __queue_work(cwq, &barr.work); - mutex_unlock(&workqueue_mutex); + preempt_enable(); /* Can no longer touch *cwq */ wait_for_completion(&barr.done); - mutex_lock(&workqueue_mutex); + preempt_disable(); } } @@ -449,7 +453,7 @@ static void flush_cpu_workqueue(struct c */ void fastcall flush_workqueue(struct workqueue_struct *wq) { - mutex_lock(&workqueue_mutex); + preempt_disable(); /* CPU hotplug */ if (is_single_threaded(wq)) { /* Always use first cpu's area. */ flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, singlethread_cpu)); @@ -459,7 +463,7 @@ void fastcall flush_workqueue(struct wor for_each_online_cpu(cpu) flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu)); } - mutex_unlock(&workqueue_mutex); + preempt_enable(); } EXPORT_SYMBOL_GPL(flush_workqueue); _