timer: 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.

[ sboyd@codeaurora.org: Remove WARN, intialize timer function]

Signed-off-by: Christine Chan <cschan@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/1320724108-20788-4-git-send-email-sboyd@codeaurora.org
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 48 insertions, 5 deletions

diff --git a/kernel/timer.c b/kernel/timer.c
index 317087d5d5fc..5fc5a766ba1d 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -487,12 +487,40 @@ 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 {
+                        setup_timer(timer, stub_timer, 0);
+                        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)
@@ -515,6 +543,11 @@ 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);
@@ -538,6 +571,7 @@ 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)
@@ -559,6 +593,11 @@ 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)
@@ -909,6 +948,8 @@ 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);
@@ -939,6 +980,8 @@ 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)