From ba92e10cb8a623a5c59305b51f8ef364998cd871 Mon Sep 17 00:00:00 2001
From: Martin Mares <mj@ucw.cz>
Date: Fri, 8 Dec 2006 17:47:16 +0100
Subject: [PATCH] workqueue: Added non-blocking wait functions.

---
 lib/workqueue.c | 41 +++++++++++++++++++++++++++++++++++------
 lib/workqueue.h |  2 ++
 2 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/lib/workqueue.c b/lib/workqueue.c
index a5ea7b8d..a015e878 100644
--- a/lib/workqueue.c
+++ b/lib/workqueue.c
@@ -117,10 +117,9 @@ raw_queue_put(struct raw_queue *q, struct work *w)
   sem_post(q->queue_sem);
 }
 
-struct work *
-raw_queue_get(struct raw_queue *q)
+static inline struct work *
+raw_queue_do_get(struct raw_queue *q)
 {
-  sem_wait(q->queue_sem);
   pthread_mutex_lock(&q->queue_mutex);
   struct work *w = clist_head(&q->queue);
   ASSERT(w);
@@ -129,6 +128,22 @@ raw_queue_get(struct raw_queue *q)
   return w;
 }
 
+struct work *
+raw_queue_get(struct raw_queue *q)
+{
+  sem_wait(q->queue_sem);
+  return raw_queue_do_get(q);
+}
+
+struct work *
+raw_queue_try_get(struct raw_queue *q)
+{
+  if (!sem_trywait(q->queue_sem))
+    return raw_queue_do_get(q);
+  else
+    return NULL;
+}
+
 void
 work_queue_init(struct worker_pool *p, struct work_queue *q)
 {
@@ -153,12 +168,14 @@ work_submit(struct work_queue *q, struct work *w)
   q->nr_running++;
 }
 
-struct work *
-work_wait(struct work_queue *q)
+static struct work *
+work_do_wait(struct work_queue *q, int try)
 {
   while (q->nr_running)
     {
-      struct work *w = raw_queue_get(&q->finished);
+      struct work *w = (try ? raw_queue_try_get : raw_queue_get)(&q->finished);
+      if (!w)
+	return NULL;
       q->nr_running--;
       if (w->returned)
 	w->returned(q, w);
@@ -168,6 +185,18 @@ work_wait(struct work_queue *q)
   return NULL;
 }
 
+struct work *
+work_wait(struct work_queue *q)
+{
+  return work_do_wait(q, 0);
+}
+
+struct work *
+work_try_wait(struct work_queue *q)
+{
+  return work_do_wait(q, 1);
+}
+
 #ifdef TEST
 
 #include <unistd.h>
diff --git a/lib/workqueue.h b/lib/workqueue.h
index 32ea19fc..5f8b5fcd 100644
--- a/lib/workqueue.h
+++ b/lib/workqueue.h
@@ -76,10 +76,12 @@ void raw_queue_init(struct raw_queue *q);
 void raw_queue_cleanup(struct raw_queue *q);
 void raw_queue_put(struct raw_queue *q, struct work *w);
 struct work *raw_queue_get(struct raw_queue *q);
+struct work *raw_queue_try_get(struct raw_queue *q);
 
 void work_queue_init(struct worker_pool *p, struct work_queue *q);
 void work_queue_cleanup(struct work_queue *q);
 void work_submit(struct work_queue *q, struct work *w);
 struct work *work_wait(struct work_queue *q);
+struct work *work_try_wait(struct work_queue *q);
 
 #endif	/* !_UCW_WORKQUEUE_H */
-- 
2.39.2