timer: implement lockdep deadlock detection
This modifies the timer code in a way to allow lockdep to detect
deadlocks resulting from a lock being taken in the timer function
as well as around the del_timer_sync() call.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
diff --git a/kernel/timer.c b/kernel/timer.c
index 13dd64f..ef1c385 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -491,14 +491,18 @@
debug_object_free(timer, &timer_debug_descr);
}
-static void __init_timer(struct timer_list *timer);
+static void __init_timer(struct timer_list *timer,
+ const char *name,
+ struct lock_class_key *key);
-void init_timer_on_stack(struct timer_list *timer)
+void init_timer_on_stack_key(struct timer_list *timer,
+ const char *name,
+ struct lock_class_key *key)
{
debug_object_init_on_stack(timer, &timer_debug_descr);
- __init_timer(timer);
+ __init_timer(timer, name, key);
}
-EXPORT_SYMBOL_GPL(init_timer_on_stack);
+EXPORT_SYMBOL_GPL(init_timer_on_stack_key);
void destroy_timer_on_stack(struct timer_list *timer)
{
@@ -512,7 +516,9 @@
static inline void debug_timer_deactivate(struct timer_list *timer) { }
#endif
-static void __init_timer(struct timer_list *timer)
+static void __init_timer(struct timer_list *timer,
+ const char *name,
+ struct lock_class_key *key)
{
timer->entry.next = NULL;
timer->base = __raw_get_cpu_var(tvec_bases);
@@ -521,6 +527,7 @@
timer->start_pid = -1;
memset(timer->start_comm, 0, TASK_COMM_LEN);
#endif
+ lockdep_init_map(&timer->lockdep_map, name, key, 0);
}
/**
@@ -530,19 +537,23 @@
* init_timer() must be done to a timer prior calling *any* of the
* other timer functions.
*/
-void init_timer(struct timer_list *timer)
+void init_timer_key(struct timer_list *timer,
+ const char *name,
+ struct lock_class_key *key)
{
debug_timer_init(timer);
- __init_timer(timer);
+ __init_timer(timer, name, key);
}
-EXPORT_SYMBOL(init_timer);
+EXPORT_SYMBOL(init_timer_key);
-void init_timer_deferrable(struct timer_list *timer)
+void init_timer_deferrable_key(struct timer_list *timer,
+ const char *name,
+ struct lock_class_key *key)
{
- init_timer(timer);
+ init_timer_key(timer, name, key);
timer_set_deferrable(timer);
}
-EXPORT_SYMBOL(init_timer_deferrable);
+EXPORT_SYMBOL(init_timer_deferrable_key);
static inline void detach_timer(struct timer_list *timer,
int clear_pending)
@@ -789,6 +800,15 @@
*/
int del_timer_sync(struct timer_list *timer)
{
+#ifdef CONFIG_LOCKDEP
+ unsigned long flags;
+
+ local_irq_save(flags);
+ lock_map_acquire(&timer->lockdep_map);
+ lock_map_release(&timer->lockdep_map);
+ local_irq_restore(flags);
+#endif
+
for (;;) {
int ret = try_to_del_timer_sync(timer);
if (ret >= 0)
@@ -861,10 +881,36 @@
set_running_timer(base, timer);
detach_timer(timer, 1);
+
spin_unlock_irq(&base->lock);
{
int preempt_count = preempt_count();
+
+#ifdef CONFIG_LOCKDEP
+ /*
+ * It is permissible to free the timer from
+ * inside the function that is called from
+ * it, this we need to take into account for
+ * lockdep too. To avoid bogus "held lock
+ * freed" warnings as well as problems when
+ * looking into timer->lockdep_map, make a
+ * copy and use that here.
+ */
+ struct lockdep_map lockdep_map =
+ timer->lockdep_map;
+#endif
+ /*
+ * Couple the lock chain with the lock chain at
+ * del_timer_sync() by acquiring the lock_map
+ * around the fn() call here and in
+ * del_timer_sync().
+ */
+ lock_map_acquire(&lockdep_map);
+
fn(data);
+
+ lock_map_release(&lockdep_map);
+
if (preempt_count != preempt_count()) {
printk(KERN_ERR "huh, entered %p "
"with preempt_count %08x, exited"