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| author | Lai Jiangshan <laijs@cn.fujitsu.com> | 2012-09-10 10:03:33 -0700 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2012-09-10 10:04:54 -0700 |
| commit | 552a37e9360a293cd20e7f8ff1fb326a244c5f1e (patch) | |
| tree | 00d89d5778d4ab8320f6bf24d81e33a290f9fcb1 /kernel | |
| parent | ec58815ab0409a921a7c9744eb4ca44866b14d71 (diff) | |
| download | lwn-552a37e9360a293cd20e7f8ff1fb326a244c5f1e.tar.gz lwn-552a37e9360a293cd20e7f8ff1fb326a244c5f1e.zip | |
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.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index dc7b8458e275..383548ed0b54 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; } |