workqueue: Rework while loop locking

Reduce the number of pthread_mutex_lock() and unlock calls by moving
these outside while loops. Other than protecting the all_sw_idle() call with
the wq->flush_lock, this patch does not change any functionality.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>

diff --git a/workqueue.c b/workqueue.c
index b59595124913338bc59dc20fb6a036c895b4f1f1..254bf6b6505fd8e047021fc819b99e567d5722e4 100644 (file)
--- a/workqueue.c
+++ b/workqueue.c
@@ -85,15 +85,14 @@ static bool all_sw_idle(struct workqueue *wq)
  */
 void workqueue_flush(struct workqueue *wq)
 {
+       pthread_mutex_lock(&wq->flush_lock);
        wq->wake_idle = 1;
 
-       while (!all_sw_idle(wq)) {
-               pthread_mutex_lock(&wq->flush_lock);
+       while (!all_sw_idle(wq))
                pthread_cond_wait(&wq->flush_cond, &wq->flush_lock);
-               pthread_mutex_unlock(&wq->flush_lock);
-       }
 
        wq->wake_idle = 0;
+       pthread_mutex_unlock(&wq->flush_lock);
 }
 
 /*
@@ -159,12 +158,10 @@ static void *worker_thread(void *data)
        if (sw->flags & SW_F_ERROR)
                goto done;
 
+       pthread_mutex_lock(&sw->lock);
        while (1) {
-               pthread_mutex_lock(&sw->lock);
-
                if (flist_empty(&sw->work_list)) {
                        if (sw->flags & SW_F_EXIT) {
-                               pthread_mutex_unlock(&sw->lock);
                                break;
                        }
 
@@ -182,7 +179,6 @@ static void *worker_thread(void *data)
                                goto handle_work;
 
                        if (sw->flags & SW_F_EXIT) {
-                               pthread_mutex_unlock(&sw->lock);
                                break;
                        } else if (!(sw->flags & SW_F_IDLE)) {
                                sw->flags |= SW_F_IDLE;
@@ -200,7 +196,9 @@ handle_work:
                handle_list(sw, &local_list);
                if (wq->ops.update_acct_fn)
                        wq->ops.update_acct_fn(sw);
+               pthread_mutex_lock(&sw->lock);
        }
+       pthread_mutex_unlock(&sw->lock);
 
 done:
        sk_out_drop();
@@ -336,11 +334,11 @@ int workqueue_init(struct thread_data *td, struct workqueue *wq,
         * Wait for them all to be started and initialized
         */
        error = 0;
+       pthread_mutex_lock(&wq->flush_lock);
        do {
                struct submit_worker *sw;
 
                running = 0;
-               pthread_mutex_lock(&wq->flush_lock);
                for (i = 0; i < wq->max_workers; i++) {
                        sw = &wq->workers[i];
                        pthread_mutex_lock(&sw->lock);
@@ -351,14 +349,12 @@ int workqueue_init(struct thread_data *td, struct workqueue *wq,
                        pthread_mutex_unlock(&sw->lock);
                }
 
-               if (error || running == wq->max_workers) {
-                       pthread_mutex_unlock(&wq->flush_lock);
+               if (error || running == wq->max_workers)
                        break;
-               }
 
                pthread_cond_wait(&wq->flush_cond, &wq->flush_lock);
-               pthread_mutex_unlock(&wq->flush_lock);
        } while (1);
+       pthread_mutex_unlock(&wq->flush_lock);
 
        if (!error)
                return 0;