[PATCH 1/2 V7 for-3.6-fixes] workqueue: add POOL_MANAGING_WORKERS

[Lai Jiangshan <laijs@cn.fujitsu.com>]

When hotplug happens, the plug code will also grab the manager_mutex,
it will break too_many_workers()'s assumption, and make too_many_workers()
ugly(kick the timer wrongly, no found bug).

To avoid assumption-coruption, we add the original POOL_MANAGING_WORKERS back.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
 kernel/workqueue.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index dc7b845..383548e 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -66,6 +66,7 @@ enum {
 
 	/* pool flags */
 	POOL_MANAGE_WORKERS	= 1 << 0,	/* need to manage workers */
+	POOL_MANAGING_WORKERS   = 1 << 1,       /* managing workers */
 
 	/* worker flags */
 	WORKER_STARTED		= 1 << 0,	/* started */
@@ -652,7 +653,7 @@ static bool need_to_manage_workers(struct worker_pool *pool)
 /* Do we have too many workers and should some go away? */
 static bool too_many_workers(struct worker_pool *pool)
 {
-	bool managing = mutex_is_locked(&pool->manager_mutex);
+	bool managing = pool->flags & POOL_MANAGING_WORKERS;
 	int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
 	int nr_busy = pool->nr_workers - nr_idle;
 
@@ -1827,6 +1828,7 @@ static bool manage_workers(struct worker *worker)
 	if (!mutex_trylock(&pool->manager_mutex))
 		return ret;
 
+	pool->flags |= POOL_MANAGING_WORKERS;
 	pool->flags &= ~POOL_MANAGE_WORKERS;
 
 	/*
@@ -1836,6 +1838,7 @@ static bool manage_workers(struct worker *worker)
 	ret |= maybe_destroy_workers(pool);
 	ret |= maybe_create_worker(pool);
 
+	pool->flags &= ~POOL_MANAGING_WORKERS;
 	mutex_unlock(&pool->manager_mutex);
 	return ret;
 }
-- 
1.7.4.4