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authorLai Jiangshan <laijs@cn.fujitsu.com>2012-09-10 10:03:33 -0700
committerTejun Heo <tj@kernel.org>2012-09-10 10:04:54 -0700
commit552a37e9360a293cd20e7f8ff1fb326a244c5f1e (patch)
tree00d89d5778d4ab8320f6bf24d81e33a290f9fcb1 /kernel
parentec58815ab0409a921a7c9744eb4ca44866b14d71 (diff)
workqueue: restore POOL_MANAGING_WORKERS
This patch restores POOL_MANAGING_WORKERS which was replaced by pool->manager_mutex by 6037315269 "workqueue: use mutex for global_cwq manager exclusion". There's a subtle idle worker depletion bug across CPU hotplug events and we need to distinguish an actual manager and CPU hotplug preventing management. POOL_MANAGING_WORKERS will be used for the former and manager_mutex the later. This patch just lays POOL_MANAGING_WORKERS on top of the existing manager_mutex and doesn't introduce any synchronization changes. The next patch will update it. Note that this patch fixes a non-critical anomaly where too_many_workers() may return %true spuriously while CPU hotplug is in progress. While the issue could schedule idle timer spuriously, it didn't trigger any actual misbehavior. tj: Rewrote patch description. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/workqueue.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index dc7b8458e27..383548ed0b5 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;
}