Add support for multi-priority workqueues

Each piece of queued work now has an associated priority value; each
priority goes on a separate queue.

With probability (N-1)/N, the workers will take work from the highest
priority nonempty queue.  Otherwise, they'll look for work in a
queue of lower priority.  This behavior is meant to prevent
starvation for lower-priority tasks.

1 files changed, 14 insertions, 0 deletions

diff --git a/src/common/workqueue.h b/src/common/workqueue.h
index 7b483eb7ac..d2508f5329 100644
--- a/src/common/workqueue.h
+++ b/src/common/workqueue.h
@@ -22,6 +22,20 @@ typedef enum workqueue_reply_t {
   WQ_RPL_SHUTDOWN = 2, /** indicates thread is shutting down */
 } workqueue_reply_t;
 
+/** Possible priorities for work.  Lower numeric values are more important. */
+typedef enum workqueue_priority_t {
+  WQ_PRI_HIGH = 0,
+  WQ_PRI_MED  = 1,
+  WQ_PRI_LOW  = 2,
+} workqueue_priority_t;
+
+workqueue_entry_t *threadpool_queue_work_priority(threadpool_t *pool,
+                                    workqueue_priority_t prio,
+                                    workqueue_reply_t (*fn)(void *,
+                                                            void *),
+                                    void (*reply_fn)(void *),
+                                    void *arg);
+
 workqueue_entry_t *threadpool_queue_work(threadpool_t *pool,
                                          workqueue_reply_t (*fn)(void *,
                                                                  void *),