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authorLai Jiangshan <laijs@cn.fujitsu.com>2014-05-22 11:01:16 (GMT)
committerTejun Heo <tj@kernel.org>2014-05-22 15:35:51 (GMT)
commit74b414ead1133972817d3ce7b934356150d03a7d (patch)
tree8942db6fda58c213804b66f8825fd736366b1597 /kernel/workqueue.c
parent1037de36edae30f1ddc0a2532decd50f92ac4901 (diff)
downloadlinux-74b414ead1133972817d3ce7b934356150d03a7d.tar.xz
workqueue: remove the confusing POOL_FREEZING
Currently, the global freezing state is propagated to worker_pools via POOL_FREEZING and then to each workqueue; however, the middle step - propagation through worker_pools - can be skipped as long as one or more max_active adjustments happens for each workqueue after the update to the global state is visible. The global workqueue freezing state and the max_active adjustments during workqueue creation and [un]freezing are serialized with wq_pool_mutex, so it's trivial to guarantee that max_actives stay in sync with global freezing state. POOL_FREEZING is unnecessary and makes the code more confusing and complicates freeze_workqueues_begin() and thaw_workqueues() by requiring them to walk through all pools. Remove POOL_FREEZING and use workqueue_freezing directly instead. tj: Description and comment updates. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel/workqueue.c')
-rw-r--r--kernel/workqueue.c32
1 files changed, 7 insertions, 25 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index dd107b8..bc3c188 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -69,7 +69,6 @@ enum {
* worker_attach_to_pool() is in progress.
*/
POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
- POOL_FREEZING = 1 << 3, /* freeze in progress */
/* worker flags */
WORKER_DIE = 1 << 1, /* die die die */
@@ -3533,9 +3532,6 @@ static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
if (!pool || init_worker_pool(pool) < 0)
goto fail;
- if (workqueue_freezing)
- pool->flags |= POOL_FREEZING;
-
lockdep_set_subclass(&pool->lock, 1); /* see put_pwq() */
copy_workqueue_attrs(pool->attrs, attrs);
@@ -3642,7 +3638,12 @@ static void pwq_adjust_max_active(struct pool_workqueue *pwq)
spin_lock_irq(&pwq->pool->lock);
- if (!freezable || !(pwq->pool->flags & POOL_FREEZING)) {
+ /*
+ * During [un]freezing, the caller is responsible for ensuring that
+ * this function is called at least once after @workqueue_freezing
+ * is updated and visible.
+ */
+ if (!freezable || !workqueue_freezing) {
pwq->max_active = wq->saved_max_active;
while (!list_empty(&pwq->delayed_works) &&
@@ -4751,24 +4752,14 @@ EXPORT_SYMBOL_GPL(work_on_cpu);
*/
void freeze_workqueues_begin(void)
{
- struct worker_pool *pool;
struct workqueue_struct *wq;
struct pool_workqueue *pwq;
- int pi;
mutex_lock(&wq_pool_mutex);
WARN_ON_ONCE(workqueue_freezing);
workqueue_freezing = true;
- /* set FREEZING */
- for_each_pool(pool, pi) {
- spin_lock_irq(&pool->lock);
- WARN_ON_ONCE(pool->flags & POOL_FREEZING);
- pool->flags |= POOL_FREEZING;
- spin_unlock_irq(&pool->lock);
- }
-
list_for_each_entry(wq, &workqueues, list) {
mutex_lock(&wq->mutex);
for_each_pwq(pwq, wq)
@@ -4838,21 +4829,13 @@ void thaw_workqueues(void)
{
struct workqueue_struct *wq;
struct pool_workqueue *pwq;
- struct worker_pool *pool;
- int pi;
mutex_lock(&wq_pool_mutex);
if (!workqueue_freezing)
goto out_unlock;
- /* clear FREEZING */
- for_each_pool(pool, pi) {
- spin_lock_irq(&pool->lock);
- WARN_ON_ONCE(!(pool->flags & POOL_FREEZING));
- pool->flags &= ~POOL_FREEZING;
- spin_unlock_irq(&pool->lock);
- }
+ workqueue_freezing = false;
/* restore max_active and repopulate worklist */
list_for_each_entry(wq, &workqueues, list) {
@@ -4862,7 +4845,6 @@ void thaw_workqueues(void)
mutex_unlock(&wq->mutex);
}
- workqueue_freezing = false;
out_unlock:
mutex_unlock(&wq_pool_mutex);
}