nailed it. once we've got the sleep mutex, make sure there's nothing in 'our'...

nailed it. once we've got the sleep mutex, make sure there's nothing in 'our' queue before taking a nap.

src/scheduler.c

@@ -28,7 +28,6 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <unistd.h>
 
 /* MPI headers. */
 #ifdef WITH_MPI
@@ -1279,7 +1278,7 @@ struct task *scheduler_gettask(struct scheduler *s, int qid,
         if (res != NULL) break;
       }
     }
-
+    
 /* If we failed, take a short nap. */
 #ifdef WITH_MPI
     if (res == NULL && qid > 1) {
@@ -1287,7 +1286,10 @@ struct task *scheduler_gettask(struct scheduler *s, int qid,
     if (res == NULL) {
 #endif
       pthread_mutex_lock(&s->sleep_mutex);
-      if (s->waiting > 0) pthread_cond_wait(&s->sleep_cond, &s->sleep_mutex);
+      res = queue_gettask(&s->queues[qid], prev, 0);
+      if (res == NULL && s->waiting > 0) {
+        pthread_cond_wait(&s->sleep_cond, &s->sleep_mutex);
+      }
       pthread_mutex_unlock(&s->sleep_mutex);
     }
   }