timer: brute force corruption fix.

[ccan] / ccan / timer / timer.c

diff --git a/ccan/timer/timer.c b/ccan/timer/timer.c
index 208d8e6988f1a2d8871ecf40aecb64b8f7f4e282..2c58a4e5238df00b7bd88abc8cee76feb284eab2 100644 (file)
--- a/ccan/timer/timer.c
+++ b/ccan/timer/timer.c
@@ -148,73 +148,50 @@ static const struct timer *find_first(const struct list_head *list,
        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, -1U, 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;
-               if (off != 0)
-                       /* We need *next* bucket: we've started reusing the
-                        * one above */
-                       base++;
-               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. */
-       found = find_first(h, level, NULL);
-
-       while (need_next) {
-               need_next = false;
-               if (!timers->level[level+1]) {
-                       found = find_first(&timers->far, -1U, found);
-               } else {
-                       /* Current upper bucket has emptied into this
-                        * bucket; we want *next* one. */
-                       base >>= TIMER_LEVEL_BITS;
-                       base++;
-                       off = base % PER_LEVEL;
-
-                       if (off == 0) {
-                               need_next = true;
-                       } else {
-                               h = &timers->level[level+1]->list[off];
-                               found = find_first(h, level+1, found);
-                       }
+       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
+               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)