POOL_MANAGING_WORKERS is used to synchronize the manager role.
Synchronizing among workers doesn't need blocking and that's why it's
implemented as a flag.
It got converted to a mutex a while back to add blocking wait from CPU
hotplug path -
6037315269 ("workqueue: use mutex for global_cwq
manager exclusion"). Later it turned out that synchronization among
workers and cpu hotplug need to be done separately. Eventually,
POOL_MANAGING_WORKERS is restored and workqueue->manager_mutex got
morphed into workqueue->assoc_mutex -
552a37e936 ("workqueue: restore
POOL_MANAGING_WORKERS") and
b2eb83d123 ("workqueue: rename
manager_mutex to assoc_mutex").
Now, we're gonna need to be able to lock out managers from
destroy_workqueue() to support multiple unbound pools with custom
attributes making it again necessary to be able to block on the
manager role. This patch replaces POOL_MANAGING_WORKERS with
worker_pool->manager_arb.
This patch doesn't introduce any behavior changes.
v2: s/manager_mutex/manager_arb/
Signed-off-by: Tejun Heo <tj@kernel.org>
* create_worker() is in progress.
*/
POOL_MANAGE_WORKERS = 1 << 0, /* need to manage workers */
* create_worker() is in progress.
*/
POOL_MANAGE_WORKERS = 1 << 0, /* need to manage workers */
- POOL_MANAGING_WORKERS = 1 << 1, /* managing workers */
POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
POOL_FREEZING = 1 << 3, /* freeze in progress */
POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
POOL_FREEZING = 1 << 3, /* freeze in progress */
DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
/* L: hash of busy workers */
DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
/* L: hash of busy workers */
+ struct mutex manager_arb; /* manager arbitration */
struct mutex assoc_mutex; /* protect POOL_DISASSOCIATED */
struct ida worker_ida; /* L: for worker IDs */
struct mutex assoc_mutex; /* protect POOL_DISASSOCIATED */
struct ida worker_ida; /* L: for worker IDs */
/* Do we have too many workers and should some go away? */
static bool too_many_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 = pool->flags & POOL_MANAGING_WORKERS;
+ bool managing = mutex_is_locked(&pool->manager_arb);
int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
int nr_busy = pool->nr_workers - nr_idle;
int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
int nr_busy = pool->nr_workers - nr_idle;
struct worker_pool *pool = worker->pool;
bool ret = false;
struct worker_pool *pool = worker->pool;
bool ret = false;
- if (pool->flags & POOL_MANAGING_WORKERS)
+ if (!mutex_trylock(&pool->manager_arb))
- pool->flags |= POOL_MANAGING_WORKERS;
-
/*
* To simplify both worker management and CPU hotplug, hold off
* management while hotplug is in progress. CPU hotplug path can't
/*
* To simplify both worker management and CPU hotplug, hold off
* management while hotplug is in progress. CPU hotplug path can't
- * grab %POOL_MANAGING_WORKERS to achieve this because that can
- * lead to idle worker depletion (all become busy thinking someone
- * else is managing) which in turn can result in deadlock under
- * extreme circumstances. Use @pool->assoc_mutex to synchronize
- * manager against CPU hotplug.
+ * grab @pool->manager_arb to achieve this because that can lead to
+ * idle worker depletion (all become busy thinking someone else is
+ * managing) which in turn can result in deadlock under extreme
+ * circumstances. Use @pool->assoc_mutex to synchronize manager
+ * against CPU hotplug.
*
* assoc_mutex would always be free unless CPU hotplug is in
* progress. trylock first without dropping @pool->lock.
*
* assoc_mutex would always be free unless CPU hotplug is in
* progress. trylock first without dropping @pool->lock.
ret |= maybe_destroy_workers(pool);
ret |= maybe_create_worker(pool);
ret |= maybe_destroy_workers(pool);
ret |= maybe_create_worker(pool);
- pool->flags &= ~POOL_MANAGING_WORKERS;
mutex_unlock(&pool->assoc_mutex);
mutex_unlock(&pool->assoc_mutex);
+ mutex_unlock(&pool->manager_arb);
setup_timer(&pool->mayday_timer, pool_mayday_timeout,
(unsigned long)pool);
setup_timer(&pool->mayday_timer, pool_mayday_timeout,
(unsigned long)pool);
+ mutex_init(&pool->manager_arb);
mutex_init(&pool->assoc_mutex);
ida_init(&pool->worker_ida);
mutex_init(&pool->assoc_mutex);
ida_init(&pool->worker_ida);