workqueue: WORKER_REBIND is no longer necessary for idle rebinding
Now both worker destruction and idle rebinding remove the worker from
idle list while it's still idle, so list_empty(&worker->entry) can be
used to test whether either is pending and WORKER_DIE to distinguish
between the two instead making WORKER_REBIND unnecessary.
Use list_empty(&worker->entry) to determine whether destruction or
rebinding is pending. This simplifies worker state transitions.
WORKER_REBIND is not needed anymore. Remove it.
tj: Updated comments and description.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 794724e..cdc6bfc 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -73,11 +73,10 @@
WORKER_DIE = 1 << 1, /* die die die */
WORKER_IDLE = 1 << 2, /* is idle */
WORKER_PREP = 1 << 3, /* preparing to run works */
- WORKER_REBIND = 1 << 5, /* mom is home, come back */
WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
WORKER_UNBOUND = 1 << 7, /* worker is unbound */
- WORKER_NOT_RUNNING = WORKER_PREP | WORKER_REBIND | WORKER_UNBOUND |
+ WORKER_NOT_RUNNING = WORKER_PREP | WORKER_UNBOUND |
WORKER_CPU_INTENSIVE,
NR_WORKER_POOLS = 2, /* # worker pools per gcwq */
@@ -1618,20 +1617,15 @@
/*
* Rebind an idle @worker to its CPU. worker_thread() will test
- * %WORKER_REBIND before leaving idle and call this function.
+ * list_empty(@worker->entry) before leaving idle and call this function.
*/
static void idle_worker_rebind(struct worker *worker)
{
struct global_cwq *gcwq = worker->pool->gcwq;
- /*
- * CPU may go down again inbetween. If rebinding fails, reinstate
- * UNBOUND. We're off idle_list and nobody else can do it for us.
- */
- if (!worker_maybe_bind_and_lock(worker))
- worker->flags |= WORKER_UNBOUND;
-
- worker_clr_flags(worker, WORKER_REBIND);
+ /* CPU may go down again inbetween, clear UNBOUND only on success */
+ if (worker_maybe_bind_and_lock(worker))
+ worker_clr_flags(worker, WORKER_UNBOUND);
/* rebind complete, become available again */
list_add(&worker->entry, &worker->pool->idle_list);
@@ -1689,16 +1683,9 @@
for_each_worker_pool(pool, gcwq)
lockdep_assert_held(&pool->manager_mutex);
- /* set REBIND and kick idle ones */
+ /* dequeue and kick idle ones */
for_each_worker_pool(pool, gcwq) {
list_for_each_entry_safe(worker, n, &pool->idle_list, entry) {
- unsigned long worker_flags = worker->flags;
-
- /* morph UNBOUND to REBIND atomically */
- worker_flags &= ~WORKER_UNBOUND;
- worker_flags |= WORKER_REBIND;
- ACCESS_ONCE(worker->flags) = worker_flags;
-
/*
* idle workers should be off @pool->idle_list
* until rebind is complete to avoid receiving
@@ -1706,7 +1693,10 @@
*/
list_del_init(&worker->entry);
- /* worker_thread() will call idle_worker_rebind() */
+ /*
+ * worker_thread() will see the above dequeuing
+ * and call idle_worker_rebind().
+ */
wake_up_process(worker->task);
}
}
@@ -2176,7 +2166,7 @@
* necessary to avoid spurious warnings from rescuers servicing the
* unbound or a disassociated gcwq.
*/
- WARN_ON_ONCE(!(worker->flags & (WORKER_UNBOUND | WORKER_REBIND)) &&
+ WARN_ON_ONCE(!(worker->flags & WORKER_UNBOUND) &&
!(gcwq->flags & GCWQ_DISASSOCIATED) &&
raw_smp_processor_id() != gcwq->cpu);
@@ -2300,18 +2290,17 @@
woke_up:
spin_lock_irq(&gcwq->lock);
- /*
- * DIE can be set only while idle and REBIND set while busy has
- * @worker->rebind_work scheduled. Checking here is enough.
- */
- if (unlikely(worker->flags & (WORKER_REBIND | WORKER_DIE))) {
+ /* we are off idle list if destruction or rebind is requested */
+ if (unlikely(list_empty(&worker->entry))) {
spin_unlock_irq(&gcwq->lock);
+ /* if DIE is set, destruction is requested */
if (worker->flags & WORKER_DIE) {
worker->task->flags &= ~PF_WQ_WORKER;
return 0;
}
+ /* otherwise, rebind */
idle_worker_rebind(worker);
goto woke_up;
}