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--- a/src/scheduler.c Mon Aug 25 20:23:24 2008 +0200
+++ b/src/scheduler.c Mon Aug 25 23:02:29 2008 +0200
@@ -63,7 +63,6 @@ clock_t now_times; /* current id
/* Hashed root of all timers */
struct list_node timer_wheel[TIMER_WHEEL_SLOTS];
clock_t timer_last_run; /* remember the last timeslot walk */
-struct list_node *timer_walk_list_node = NULL; /* used for timeslot walk */
/* Pool of timers to avoid malloc() churn */
struct list_node free_timer_list;
@@ -317,6 +316,35 @@ olsr_init_timers(void)
timers_running = 0;
}
+/*
+ * olsr_get_next_list_entry
+ *
+ * Get the next list node in a hash bucket.
+ * The listnode of the timer in may be subject to getting removed from
+ * this timer bucket in olsr_change_timer() and olsr_stop_timer(), which
+ * means that we can miss our walking context.
+ * By caching the previous node we can figure out if the current node
+ * has been removed from the hash bucket and compute the next node.
+ */
+static struct list_node *
+olsr_get_next_list_entry (struct list_node **prev_node,
+ struct list_node *current_node)
+{
+ if ((*prev_node)->next == current_node) {
+
+ /*
+ * No change in the list, normal traversal, update the previous node.
+ */
+ *prev_node = current_node;
+ return (current_node->next);
+ } else {
+
+ /*
+ * List change. Recompute the walking context.
+ */
+ return ((*prev_node)->next);
+ }
+}
/**
* Walk through the timer list and check if any timer is ready to fire.
@@ -326,7 +354,7 @@ olsr_walk_timers(clock_t * last_run)
olsr_walk_timers(clock_t * last_run)
{
static struct timer_entry *timer;
- struct list_node *timer_head_node;
+ struct list_node *timer_head_node, *timer_walk_node, *timer_walk_prev_node;
unsigned int timers_walked, timers_fired;
unsigned int total_timers_walked, total_timers_fired;
unsigned int wheel_slot_walks = 0;
@@ -347,12 +375,15 @@ olsr_walk_timers(clock_t * last_run)
/* Get the hash slot for this clocktick */
timer_head_node = &timer_wheel[*last_run & TIMER_WHEEL_MASK];
+ timer_walk_prev_node = timer_head_node;
/* Walk all entries hanging off this hash bucket */
- for (timer_walk_list_node = timer_head_node->next; timer_walk_list_node != timer_head_node; /* circular list */
- timer_walk_list_node = timer_walk_list_node->next) {
-
- timer = list2timer(timer_walk_list_node);
+ for (timer_walk_node = timer_head_node->next;
+ timer_walk_node != timer_head_node; /* circular list */
+ timer_walk_node = olsr_get_next_list_entry(&timer_walk_prev_node,
+ timer_walk_node)) {
+
+ timer = list2timer(timer_walk_node);
timers_walked++;
@@ -403,11 +434,6 @@ olsr_walk_timers(clock_t * last_run)
/* Increment the time slot and wheel slot walk iteration */
(*last_run)++;
wheel_slot_walks++;
-
- /*
- * Mark the timer walk context unused.
- */
- timer_walk_list_node = NULL;
}
#ifdef DEBUG
@@ -581,21 +607,6 @@ olsr_start_timer(unsigned int rel_time,
return timer;
}
-/*
- * Check if there is a timer walk in progress and advance the
- * walking context if so. Keep in mind we are about to delete
- * the timer from a list and this will destroy the walking context.
- */
-
-static inline void
-olsr_update_timer_walk_ctx(struct timer_entry *timer)
-{
- if (timer_walk_list_node == &timer->timer_list) {
- timer_walk_list_node = timer_walk_list_node->next;
- }
-}
-
-
/**
* Delete a timer.
*
@@ -615,8 +626,6 @@ olsr_stop_timer(struct timer_entry *time
olsr_cookie_name(timer->timer_cookie),
timer, timer->timer_cb_context);
#endif
-
- olsr_update_timer_walk_ctx(timer);
/*
* Carve out of the existing wheel_slot and return to the pool
@@ -658,8 +667,6 @@ olsr_change_timer(struct timer_entry *ti
timer->timer_clock = olsr_jitter(rel_time, jitter_pct, timer->timer_random);
timer->timer_jitter_pct = jitter_pct;
- olsr_update_timer_walk_ctx(timer);
-
/*
* Changes are easy: Remove timer from the exisiting timer_wheel slot
* and reinsert into the new slot.
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