workqueue: fix GCWQ_DISASSOCIATED initialization

init_workqueues() incorrectly marks workqueues for all possible CPUs
associated.  Combined with mayday_mask initialization bug, this can
make rescuers keep trying to bind to an offline gcwq indefinitely.
Fix init_workqueues() such that only online CPUs have their gcwqs have
GCWQ_DISASSOCIATED cleared.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: CAI Qian <caiqian@redhat.com>

kernel/workqueue.c

@@ -3558,8 +3558,7 @@ static int __init init_workqueues(void)
 		spin_lock_init(&gcwq->lock);
 		INIT_LIST_HEAD(&gcwq->worklist);
 		gcwq->cpu = cpu;
-		if (cpu == WORK_CPU_UNBOUND)
-			gcwq->flags |= GCWQ_DISASSOCIATED;
+		gcwq->flags |= GCWQ_DISASSOCIATED;
 
 		INIT_LIST_HEAD(&gcwq->idle_list);
 		for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++)
@@ -3583,6 +3582,8 @@ static int __init init_workqueues(void)
 		struct global_cwq *gcwq = get_gcwq(cpu);
 		struct worker *worker;
 
+		if (cpu != WORK_CPU_UNBOUND)
+			gcwq->flags &= ~GCWQ_DISASSOCIATED;
 		worker = create_worker(gcwq, true);
 		BUG_ON(!worker);
 		spin_lock_irq(&gcwq->lock);