Messages in this thread | | | Date | Tue, 13 May 2014 14:32:52 +0800 | From | Lai Jiangshan <> | Subject | Re: [PATCH 03/10 V2] workqueue: async worker destruction |
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On 05/13/2014 05:20 AM, Tejun Heo wrote: > On Mon, May 12, 2014 at 02:56:15PM +0800, Lai Jiangshan wrote: >> /** >> + * worker_detach_from_pool() - detach the worker from the pool >> + * @worker: worker which is attached to its pool >> + * @pool: attached pool >> + * >> + * Undo the attaching which had been done in create_worker(). >> + * The caller worker shouldn't access to the pool after detached >> + * except it has other reference to the pool. >> + */ >> +static void worker_detach_from_pool(struct worker *worker, >> + struct worker_pool *pool) >> +{ >> + struct completion *detach_completion = NULL; >> + >> + mutex_lock(&pool->manager_mutex); >> + idr_remove(&pool->worker_idr, worker->id); >> + if (idr_is_empty(&pool->worker_idr)) >> + detach_completion = pool->detach_completion; >> + mutex_unlock(&pool->manager_mutex); >> + >> + if (detach_completion) >> + complete(detach_completion); >> +} > > Are we gonna use this function from somewhere else too?
it is called from worker_thread().
I don't want to unfold it into worker_thread(), it is better readability when it is wrapped and it will be called in patch10 for rescuer.
> >> @@ -2289,6 +2298,10 @@ woke_up: >> spin_unlock_irq(&pool->lock); >> WARN_ON_ONCE(!list_empty(&worker->entry)); >> worker->task->flags &= ~PF_WQ_WORKER; >> + >> + set_task_comm(worker->task, "kworker_dying"); > > Given how other kworkers are named, maybe a better name is > "kworker/dying" or "kworker/detached"? > >> + worker_detach_from_pool(worker, pool); >> + kfree(worker); >> return 0; >> } >> >> @@ -3561,6 +3574,7 @@ static void rcu_free_pool(struct rcu_head *rcu) >> static void put_unbound_pool(struct worker_pool *pool) >> { >> struct worker *worker; >> + DECLARE_COMPLETION_ONSTACK(detach_completion); > > I think it's conventional to put initialized ones (especially the ones > require initializing macros) before uninitialized vars. > >> @@ -3579,19 +3593,24 @@ static void put_unbound_pool(struct worker_pool *pool) >> >> /* >> * Become the manager and destroy all workers. Grabbing >> - * manager_arb prevents @pool's workers from blocking on >> - * manager_mutex. >> + * manager_arb ensures manage_workers() finish and enter idle. > > I don't follow what the above comment update is trying to say.
If a pool is destroying, the worker will not call manage_workers(). but the existing manage_workers() may be still running.
mutex_lock(&manager_arb) in put_unbound_pool() should wait this manage_workers() finished due to the manager-worker (non-idle-worker) can't be destroyed.
> > Thanks. >
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