kernel/timer.c: use debugobjects to catch deletion of uninitialized timers

del_timer_sync() calls debug_object_assert_init() to assert that a timer
has been initialized before calling lock_timer_base().  lock_timer_base()
would spin forever on a NULL(uninit-ed) base.  The check is added to
del_timer() to prevent silent failure, even though it would not get stuck
in an infinite loop.

Signed-off-by: Christine Chan <cschan@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/kernel/timer.c b/kernel/timer.c
index dbaa62422b13c057754252d986f97440ec7dd3af..42d02c1e877d3aa211a82eff0eb2f755ffebad93 100644 (file)
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -480,12 +480,41 @@ static int timer_fixup_free(void *addr, enum debug_obj_state state)
        }
 }
 
+/*
+ * fixup_assert_init is called when:
+ * - an untracked/uninit-ed object is found
+ */
+static int timer_fixup_assert_init(void *addr, enum debug_obj_state state)
+{
+       struct timer_list *timer = addr;
+
+       switch (state) {
+       case ODEBUG_STATE_NOTAVAILABLE:
+               if (timer->entry.prev == TIMER_ENTRY_STATIC) {
+                       /*
+                        * This is not really a fixup. The timer was
+                        * statically initialized. We just make sure that it
+                        * is tracked in the object tracker.
+                        */
+                       debug_object_init(timer, &timer_debug_descr);
+                       return 0;
+               } else {
+                       WARN_ON(1);
+                       init_timer(timer);
+                       return 1;
+               }
+       default:
+               return 0;
+       }
+}
+
 static struct debug_obj_descr timer_debug_descr = {
-       .name           = "timer_list",
-       .debug_hint     = timer_debug_hint,
-       .fixup_init     = timer_fixup_init,
-       .fixup_activate = timer_fixup_activate,
-       .fixup_free     = timer_fixup_free,
+       .name                   = "timer_list",
+       .debug_hint             = timer_debug_hint,
+       .fixup_init             = timer_fixup_init,
+       .fixup_activate         = timer_fixup_activate,
+       .fixup_free             = timer_fixup_free,
+       .fixup_assert_init      = timer_fixup_assert_init,
 };
 
 static inline void debug_timer_init(struct timer_list *timer)
@@ -508,6 +537,11 @@ static inline void debug_timer_free(struct timer_list *timer)
        debug_object_free(timer, &timer_debug_descr);
 }
 
+static inline void debug_timer_assert_init(struct timer_list *timer)
+{
+       debug_object_assert_init(timer, &timer_debug_descr);
+}
+
 static void __init_timer(struct timer_list *timer,
                         const char *name,
                         struct lock_class_key *key);
@@ -531,6 +565,7 @@ EXPORT_SYMBOL_GPL(destroy_timer_on_stack);
 static inline void debug_timer_init(struct timer_list *timer) { }
 static inline void debug_timer_activate(struct timer_list *timer) { }
 static inline void debug_timer_deactivate(struct timer_list *timer) { }
+static inline void debug_timer_assert_init(struct timer_list *timer) { }
 #endif
 
 static inline void debug_init(struct timer_list *timer)
@@ -552,6 +587,11 @@ static inline void debug_deactivate(struct timer_list *timer)
        trace_timer_cancel(timer);
 }
 
+static inline void debug_assert_init(struct timer_list *timer)
+{
+       debug_timer_assert_init(timer);
+}
+
 static void __init_timer(struct timer_list *timer,
                         const char *name,
                         struct lock_class_key *key)
@@ -902,6 +942,8 @@ int del_timer(struct timer_list *timer)
        unsigned long flags;
        int ret = 0;
 
+       debug_assert_init(timer);
+
        timer_stats_timer_clear_start_info(timer);
        if (timer_pending(timer)) {
                base = lock_timer_base(timer, &flags);
@@ -932,6 +974,8 @@ int try_to_del_timer_sync(struct timer_list *timer)
        unsigned long flags;
        int ret = -1;
 
+       debug_assert_init(timer);
+
        base = lock_timer_base(timer, &flags);
 
        if (base->running_timer == timer)