]> git.ozlabs.org Git - ccan/blobdiff - ccan/timer/timer.c
timer: brute force corruption fix.
[ccan] / ccan / timer / timer.c
index f0e017ba6ed8decba4ac4abcf0ecce07f01abf48..2c58a4e5238df00b7bd88abc8cee76feb284eab2 100644 (file)
@@ -131,7 +131,10 @@ static void add_level(struct timers *timers, unsigned int level)
                timer_add_raw(timers, t);
 }
 
+/* We don't need to search past the first at level 0, since the
+ * bucket range is 1; they're all the same. */
 static const struct timer *find_first(const struct list_head *list,
+                                     unsigned int level,
                                      const struct timer *prev)
 {
        struct timer *t;
@@ -139,67 +142,56 @@ static const struct timer *find_first(const struct list_head *list,
        list_for_each(list, t, list) {
                if (!prev || t->time < prev->time)
                        prev = t;
+               if (level == 0)
+                       break;
        }
        return prev;
 }
 
-static const struct timer *get_first(const struct timers *timers)
+/* FIXME: Suboptimal */
+static const struct timer *brute_force_first(const struct timers *timers)
 {
-       unsigned int level, i, off;
-       bool need_next;
-       uint64_t base;
+       unsigned int l, i;
        const struct timer *found = NULL;
-       struct list_head *h;
-
-       if (timers->first < timers->base) {
-               base = timers->base;
-               level = 0;
-       } else {
-               /* May not be accurate, due to timer_del / expiry. */
-               level = level_of(timers, timers->first);
-               base = timers->first >> (TIMER_LEVEL_BITS * level);
-       }
-
-next:
-       if (!timers->level[level])
-               return find_first(&timers->far, NULL);
-
-       need_next = false;
-       off = base % PER_LEVEL;
-       for (i = 0; i < PER_LEVEL; i++) {
-               h = &timers->level[level]->list[(i+off) % PER_LEVEL];
-
-               if (!list_empty(h))
-                       break;
 
-               /* We haven't cascaded yet, so if we wrap, we'll need to
-                * check next level, too. */
-               if (i + off == PER_LEVEL)
-                       need_next = true;
-       }
-       if (i == PER_LEVEL) {
-               level++;
-               base >>= TIMER_LEVEL_BITS;
-               goto next;
+       for (l = 0; l < ARRAY_SIZE(timers->level) && timers->level[l]; l++) {
+               for (i = 0; i < PER_LEVEL; i++)
+                       found = find_first(&timers->level[l]->list[i], l,
+                                          found);
        }
 
-       /* Level 0 is exact, so they're all the same. */
-       if (level == 0)
-               found = list_top(h, struct timer, list);
+       found = find_first(&timers->far, -1U, found);
+       return found;
+}
+                       
+static const struct timer *get_first(const struct timers *timers)
+{
+       uint64_t time;
+       
+       /* Where can we start from? */
+       if (timers->first < timers->base)
+               time = timers->base;
        else
-               found = find_first(h, NULL);
-
-       if (need_next) {
-               if (!timers->level[level+1]) {
-                       found = find_first(&timers->far, found);
-               } else {
-                       base >>= TIMER_LEVEL_BITS;
-                       off = base % PER_LEVEL;
-                       h = &timers->level[level+1]->list[off];
-                       found = find_first(h, found);
+               time = timers->first;
+
+       /* We can have just far timers, for example. */
+       if (timers->level[0]) {
+               /* First search rest of lower buckets; we've already spilled
+                * so if we find one there we don't need to search further. */
+               unsigned int i, off = time % PER_LEVEL;
+
+               for (i = off; i < PER_LEVEL; i++) {
+                       struct list_head *h = &timers->level[0]->list[i];
+                       if (!list_empty(h))
+                               return find_first(h, 0, NULL);
                }
        }
-       return found;
+
+       /* From here on, we're searching non-normalized parts of the
+        * data structure, which is much subtler.
+        *
+        * So we brute force. */
+       return brute_force_first(timers);
 }
 
 static bool update_first(struct timers *timers)