src/sched_policies: do not lock all workers when selecting a victim with ws

Locking all workers before selecting a victim is useless because if the
stolen job is consumed by an other worker before that one, we look for local
tasks. Otherwise, we try to select an other victim. This is similar to lws.

src/sched_policies/work_stealing_policy.c

@@ -314,28 +314,17 @@ int ws_push_task(struct starpu_task *task)
 
 	int workerid = starpu_worker_get_id();
 
-	unsigned worker = 0;
-	struct starpu_worker_collection *workers = starpu_sched_ctx_get_worker_collection(sched_ctx_id);
-	struct starpu_sched_ctx_iterator it;
-	
-	workers->init_iterator(workers, &it);
-	/* !! C'est ballot de tout locker! */
-	while(workers->has_next(workers, &it))
-	{
-		worker = workers->get_next(workers, &it);
-		starpu_pthread_mutex_t *sched_mutex;
-		starpu_pthread_cond_t *sched_cond;
-		starpu_worker_get_sched_condition(worker, &sched_mutex, &sched_cond);
-		STARPU_PTHREAD_MUTEX_LOCK(sched_mutex);
-	}
-	
-	
 	/* If the current thread is not a worker but
 	 * the main thread (-1), we find the better one to
 	 * put task on its queue */
 	if (workerid == -1)
 		workerid = select_worker(sched_ctx_id);
 
+	starpu_pthread_mutex_t *sched_mutex;
+	starpu_pthread_cond_t *sched_cond;
+	starpu_worker_get_sched_condition(workerid, &sched_mutex, &sched_cond);
+	STARPU_PTHREAD_MUTEX_LOCK(sched_mutex);
+
 #ifdef HAVE_AYUDAME_H
 	struct _starpu_job *j = _starpu_get_job_associated_to_task(task);
 	if (AYU_event)
@@ -349,19 +338,17 @@ int ws_push_task(struct starpu_task *task)
 
 	starpu_push_task_end(task);
 
+	STARPU_PTHREAD_MUTEX_UNLOCK(sched_mutex);
+
+#if !defined(STARPU_NON_BLOCKING_DRIVERS) || defined(STARPU_SIMGRID)
+	/* TODO: implement fine-grain signaling, similar to what eager does */
+	struct starpu_worker_collection *workers = starpu_sched_ctx_get_worker_collection(sched_ctx_id);
+	struct starpu_sched_ctx_iterator it;
+
 	workers->init_iterator(workers, &it);
 	while(workers->has_next(workers, &it))
-	{
-		worker = workers->get_next(workers, &it);
-		starpu_pthread_mutex_t *sched_mutex;
-		starpu_pthread_cond_t *sched_cond;
-		starpu_worker_get_sched_condition(worker, &sched_mutex, &sched_cond);
-#if !defined(STARPU_NON_BLOCKING_DRIVERS) || defined(STARPU_SIMGRID)
-		starpu_wakeup_worker_locked(worker, sched_cond, sched_mutex);
+		starpu_wake_worker(workers->get_next(workers, &it));
 #endif
-		STARPU_PTHREAD_MUTEX_UNLOCK(sched_mutex);
-	}
-		
 	return 0;
 }