defer freeing empty buckets where it is safe to walk

Author: Hannes Gredler

code/common/src/timer.c

@@ -188,29 +188,17 @@ timer_enqueue_bucket(timer_root_s *root, timer_s *timer, time_t sec, long nsec)
 static void
 timer_dequeue_bucket(timer_s *timer)
 {
-    timer_root_s *timer_root;
     timer_bucket_s *timer_bucket;
 
     timer_bucket = timer->timer_bucket;
-    timer_root = timer_bucket->timer_root;
 
     CIRCLEQ_REMOVE(&timer_bucket->timer_qhead, timer, timer_qnode);
     timer_bucket->timers--;
     timer->timer_bucket = NULL;
 
-    /* If the last timer of a bucket is gone, 
-     * remove the bucket as well. */
-    if(!timer_bucket->timers) {
-        CIRCLEQ_REMOVE(&timer_root->timer_bucket_qhead, timer_bucket, timer_bucket_qnode);
-
-#ifdef BNGBLASTER_TIMER_LOGGING
-        LOG(TIMER_DETAIL, "  Delete timer bucket %lu.%06lus\n",
-            timer_bucket->sec, timer_bucket->nsec/1000);
-#endif
-
-        free(timer_bucket);
-        timer_root->buckets--;
-    }
+    /*
+     * Defer deleting empty buckets to timer_process_changes().
+     */
 }
 
 static void
@@ -357,11 +345,14 @@ static void
 timer_process_changes(timer_root_s *root)
 {
     timer_s *timer;
-    timer_bucket_s *timer_bucket;
+    timer_bucket_s *timer_bucket, *timer_bucket_next;
 
     struct timespec now;
     clock_gettime(CLOCK_MONOTONIC, &now);
 
+    /*
+     * First work the chnaged timer list.
+     */
     while(!CIRCLEQ_EMPTY(&root->timer_change_qhead)) {
         timer = CIRCLEQ_FIRST(&root->timer_change_qhead);
         timer_bucket = timer->timer_bucket;
@@ -388,6 +379,27 @@ timer_process_changes(timer_root_s *root)
             continue;
         }
     }
+
+    /*
+     * Some buckets may be empty by now.
+     * Trash them here where it is safe.
+     */
+    CIRCLEQ_FOREACH_SAFE(timer_bucket, &root->timer_bucket_qhead,
+			 timer_bucket_qnode, timer_bucket_next) {
+
+	/* If the bucket is empty, remove it. */
+	if(!timer_bucket->timers) {
+	    CIRCLEQ_REMOVE(&root->timer_bucket_qhead, timer_bucket, timer_bucket_qnode);
+
+#ifdef BNGBLASTER_TIMER_LOGGING
+	    LOG(TIMER_DETAIL, "  Delete timer bucket %lu.%06lus\n",
+		timer_bucket->sec, timer_bucket->nsec/1000);
+#endif
+
+	    free(timer_bucket);
+	    root->buckets--;
+	}
+    }
 }
 
 /**
@@ -629,4 +641,4 @@ timer_flush_root(timer_root_s *timer_root)
         timer_root->gc--;
         free(timer);
     }
-}
+}

code/common/src/timer.h

@@ -15,6 +15,14 @@
 #define MSEC100 100000000UL     /* 100 million nanoseconds == 100 milliseconds */
 #define SEC     1000000000UL    /* 1 billion nanoseconds == 1 second */
 
+#ifndef CIRCLEQ_FOREACH_SAFE
+#define CIRCLEQ_FOREACH_SAFE(var, head, field, tvar)                      \
+    for ((var) = CIRCLEQ_FIRST((head));                                   \
+        (var) != (void *)(head) &&                                        \
+        ((tvar) = CIRCLEQ_NEXT((var), field), 1);                         \
+        (var) = (tvar))
+#endif
+
 /*  Top level data structure for timers. */
 typedef struct timer_root_
 {