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Date: Wed, 20 Mar 2013 03:28:14 +0800
From: Lai Jiangshan <laijs@...fujitsu.com>
To: Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org
Cc: Lai Jiangshan <laijs@...fujitsu.com>
Subject: [PATCH 14/21] workqueue: add wq->freezing and remove POOL_FREEZING
freezing is nothing related to pools, but POOL_FREEZING adds a connection.
it causes:
workqueue_freezing is protected by both wqs_mutex and pools_mutex.
freeze_workqueues_begin() and thaw_workqueues() are very complicated.
Since freezing is workqueue instance attribute, so we introduce wq->freezing
instead and remove POOL_FREEZING. all the problem are solved.
Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
---
kernel/workqueue.c | 49 +++++++++++++++----------------------------------
1 files changed, 15 insertions(+), 34 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index e45f038..db08b63 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -66,7 +66,6 @@ enum {
*/
POOL_MANAGE_WORKERS = 1 << 0, /* need to manage workers */
POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
- POOL_FREEZING = 1 << 3, /* freeze in progress */
/* worker flags */
WORKER_STARTED = 1 << 0, /* started */
@@ -243,6 +242,7 @@ struct workqueue_struct {
int nr_drainers; /* Q: drain in progress */
int saved_max_active; /* Q: saved pwq max_active */
+ bool freezing; /* Q&QS: the wq is freezing */
#ifdef CONFIG_SYSFS
struct wq_device *wq_dev; /* I: for sysfs interface */
@@ -260,7 +260,7 @@ static DEFINE_MUTEX(pools_mutex); /* protects pools */
static DEFINE_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
static LIST_HEAD(workqueues); /* QS: list of all workqueues */
-static bool workqueue_freezing; /* QS&PS: have wqs started freezing? */
+static bool workqueue_freezing; /* QS: have wqs started freezing? */
/* the per-cpu worker pools */
static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS],
@@ -3495,9 +3495,6 @@ 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);
@@ -3573,18 +3570,17 @@ static void pwq_adjust_max_active(struct pool_workqueue *pwq)
struct workqueue_struct *wq = pwq->wq;
bool freezable = wq->flags & WQ_FREEZABLE;
- /* for @wq->saved_max_active */
+ /* for @wq->saved_max_active and @wq->freezing */
lockdep_assert_held(&wq->mutex);
/* fast exit for non-freezable wqs */
if (!freezable && pwq->max_active == wq->saved_max_active)
return;
- spin_lock_irq(&pwq->pool->lock);
-
- if (freezable && (pwq->pool->flags & POOL_FREEZING)) {
+ if (freezable && wq->freezing) {
pwq->max_active = 0;
} else {
+ spin_lock_irq(&pwq->pool->lock);
pwq->max_active = wq->saved_max_active;
while (!list_empty(&pwq->delayed_works) &&
@@ -3598,9 +3594,8 @@ static void pwq_adjust_max_active(struct pool_workqueue *pwq)
* But this function is slowpath, wake up worker unconditionally
*/
wake_up_worker(pwq->pool);
+ spin_unlock_irq(&pwq->pool->lock);
}
-
- spin_unlock_irq(&pwq->pool->lock);
}
static void init_and_link_pwq(struct pool_workqueue *pwq,
@@ -3798,6 +3793,7 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
mutex_lock(&wqs_mutex);
mutex_lock(&wq->mutex);
+ wq->freezing = workqueue_freezing;
for_each_pwq(pwq, wq)
pwq_adjust_max_active(pwq);
mutex_unlock(&wq->mutex);
@@ -4285,28 +4281,20 @@ 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(&wqs_mutex);
/* set FREEZING */
- mutex_lock(&pools_mutex);
WARN_ON_ONCE(workqueue_freezing);
workqueue_freezing = true;
- 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);
- }
- mutex_unlock(&pools_mutex);
-
list_for_each_entry(wq, &workqueues, list) {
mutex_lock(&wq->mutex);
+ /* set FREEZING */
+ WARN_ON_ONCE(wq->freezing);
+ wq->freezing = true;
for_each_pwq(pwq, wq)
pwq_adjust_max_active(pwq);
mutex_unlock(&wq->mutex);
@@ -4374,28 +4362,21 @@ void thaw_workqueues(void)
{
struct workqueue_struct *wq;
struct pool_workqueue *pwq;
- struct worker_pool *pool;
- int pi;
mutex_lock(&wqs_mutex);
if (!workqueue_freezing)
goto out_unlock;
- /* clear FREEZING */
- mutex_lock(&pools_mutex);
workqueue_freezing = false;
- 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);
- }
- mutex_unlock(&pools_mutex);
- /* restore max_active and repopulate worklist */
list_for_each_entry(wq, &workqueues, list) {
mutex_lock(&wq->mutex);
+ /* clear FREEZING */
+ WARN_ON_ONCE(!wq->freezing);
+ wq->freezing = false;
+
+ /* restore max_active and repopulate worklist */
for_each_pwq(pwq, wq)
pwq_adjust_max_active(pwq);
mutex_unlock(&wq->mutex);
--
1.7.7.6
--
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