workqueues: shift kthread_bind() from CPU_UP_PREPARE to CPU_ONLINE

CPU_UP_PREPARE binds cwq->thread to the new CPU.  So CPU_UP_CANCELED tries to
wake up the task which is bound to the failed CPU.

With this patch we don't bind cwq->thread until CPU becomes online.  The first
wake_up() after kthread_create() is a bit special, make a simple helper for
that.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index e858e93..7d1ebfc 100644 (file)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -668,15 +668,21 @@ static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
 
        cwq->thread = p;
        cwq->should_stop = 0;
-       if (!is_single_threaded(wq))
-               kthread_bind(p, cpu);
-
-       if (is_single_threaded(wq) || cpu_online(cpu))
-               wake_up_process(p);
 
        return 0;
 }
 
+static void start_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
+{
+       struct task_struct *p = cwq->thread;
+
+       if (p != NULL) {
+               if (cpu >= 0)
+                       kthread_bind(p, cpu);
+               wake_up_process(p);
+       }
+}
+
 struct workqueue_struct *__create_workqueue(const char *name,
                                            int singlethread, int freezeable)
 {
@@ -702,6 +708,7 @@ struct workqueue_struct *__create_workqueue(const char *name,
        if (singlethread) {
                cwq = init_cpu_workqueue(wq, singlethread_cpu);
                err = create_workqueue_thread(cwq, singlethread_cpu);
+               start_workqueue_thread(cwq, -1);
        } else {
                mutex_lock(&workqueue_mutex);
                list_add(&wq->list, &workqueues);
@@ -711,6 +718,7 @@ struct workqueue_struct *__create_workqueue(const char *name,
                        if (err || !cpu_online(cpu))
                                continue;
                        err = create_workqueue_thread(cwq, cpu);
+                       start_workqueue_thread(cwq, cpu);
                }
                mutex_unlock(&workqueue_mutex);
        }
@@ -808,12 +816,11 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
                        return NOTIFY_BAD;
 
                case CPU_ONLINE:
-                       wake_up_process(cwq->thread);
+                       start_workqueue_thread(cwq, cpu);
                        break;
 
                case CPU_UP_CANCELED:
-                       if (cwq->thread)
-                               wake_up_process(cwq->thread);
+                       start_workqueue_thread(cwq, -1);
                case CPU_DEAD:
                        cleanup_workqueue_thread(cwq, cpu);
                        break;