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>

1 files changed, 84 insertions, 9 deletions

diff --git a/include/linux/timer.h b/include/linux/timer.h
index daf9685b861c..51774eb87cc6 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -5,6 +5,7 @@
 #include <linux/ktime.h>
 #include <linux/stddef.h>
 #include <linux/debugobjects.h>
+#include <linux/stringify.h>
 
 struct tvec_base;
 
@@ -21,52 +22,126 @@ struct timer_list {
         char start_comm[16];
         int start_pid;
 #endif
+#ifdef CONFIG_LOCKDEP
+        struct lockdep_map lockdep_map;
+#endif
 };
 
 extern struct tvec_base boot_tvec_bases;
 
+#ifdef CONFIG_LOCKDEP
+/*
+ * NB: because we have to copy the lockdep_map, setting the lockdep_map key
+ * (second argument) here is required, otherwise it could be initialised to
+ * the copy of the lockdep_map later! We use the pointer to and the string
+ * "<file>:<line>" as the key resp. the name of the lockdep_map.
+ */
+#define __TIMER_LOCKDEP_MAP_INITIALIZER(_kn)                            \
+        .lockdep_map = STATIC_LOCKDEP_MAP_INIT(_kn, &_kn),
+#else
+#define __TIMER_LOCKDEP_MAP_INITIALIZER(_kn)
+#endif
+
 #define TIMER_INITIALIZER(_function, _expires, _data) {         \
                 .entry = { .prev = TIMER_ENTRY_STATIC },        \
                 .function = (_function),                        \
                 .expires = (_expires),                          \
                 .data = (_data),                                \
                 .base = &boot_tvec_bases,                       \
+                __TIMER_LOCKDEP_MAP_INITIALIZER(                \
+                        __FILE__ ":" __stringify(__LINE__))     \
         }
 
 #define DEFINE_TIMER(_name, _function, _expires, _data)         \
         struct timer_list _name =                               \
                 TIMER_INITIALIZER(_function, _expires, _data)
 
-void init_timer(struct timer_list *timer);
-void init_timer_deferrable(struct timer_list *timer);
+void init_timer_key(struct timer_list *timer,
+                    const char *name,
+                    struct lock_class_key *key);
+void init_timer_deferrable_key(struct timer_list *timer,
+                               const char *name,
+                               struct lock_class_key *key);
+
+#ifdef CONFIG_LOCKDEP
+#define init_timer(timer)                                               \
+        do {                                                            \
+                static struct lock_class_key __key;                     \
+                init_timer_key((timer), #timer, &__key);                \
+        } while (0)
+
+#define init_timer_deferrable(timer)                                    \
+        do {                                                            \
+                static struct lock_class_key __key;                     \
+                init_timer_deferrable_key((timer), #timer, &__key);     \
+        } while (0)
+
+#define init_timer_on_stack(timer)                                      \
+        do {                                                            \
+                static struct lock_class_key __key;                     \
+                init_timer_on_stack_key((timer), #timer, &__key);       \
+        } while (0)
+
+#define setup_timer(timer, fn, data)                                    \
+        do {                                                            \
+                static struct lock_class_key __key;                     \
+                setup_timer_key((timer), #timer, &__key, (fn), (data));\
+        } while (0)
+
+#define setup_timer_on_stack(timer, fn, data)                           \
+        do {                                                            \
+                static struct lock_class_key __key;                     \
+                setup_timer_on_stack_key((timer), #timer, &__key,       \
+                                         (fn), (data));                 \
+        } while (0)
+#else
+#define init_timer(timer)\
+        init_timer_key((timer), NULL, NULL)
+#define init_timer_deferrable(timer)\
+        init_timer_deferrable_key((timer), NULL, NULL)
+#define init_timer_on_stack(timer)\
+        init_timer_on_stack_key((timer), NULL, NULL)
+#define setup_timer(timer, fn, data)\
+        setup_timer_key((timer), NULL, NULL, (fn), (data))
+#define setup_timer_on_stack(timer, fn, data)\
+        setup_timer_on_stack_key((timer), NULL, NULL, (fn), (data))
+#endif
 
 #ifdef CONFIG_DEBUG_OBJECTS_TIMERS
-extern void init_timer_on_stack(struct timer_list *timer);
+extern void init_timer_on_stack_key(struct timer_list *timer,
+                                    const char *name,
+                                    struct lock_class_key *key);
 extern void destroy_timer_on_stack(struct timer_list *timer);
 #else
 static inline void destroy_timer_on_stack(struct timer_list *timer) { }
-static inline void init_timer_on_stack(struct timer_list *timer)
+static inline void init_timer_on_stack_key(struct timer_list *timer,
+                                           const char *name,
+                                           struct lock_class_key *key)
 {
-        init_timer(timer);
+        init_timer_key(timer, name, key);
 }
 #endif
 
-static inline void setup_timer(struct timer_list * timer,
+static inline void setup_timer_key(struct timer_list * timer,
+                                const char *name,
+                                struct lock_class_key *key,
                                 void (*function)(unsigned long),
                                 unsigned long data)
 {
         timer->function = function;
         timer->data = data;
-        init_timer(timer);
+        init_timer_key(timer, name, key);
 }
 
-static inline void setup_timer_on_stack(struct timer_list *timer,
+static inline void setup_timer_on_stack_key(struct timer_list *timer,
+                                        const char *name,
+                                        struct lock_class_key *key,
                                         void (*function)(unsigned long),
                                         unsigned long data)
 {
         timer->function = function;
         timer->data = data;
-        init_timer_on_stack(timer);
+        init_timer_on_stack_key(timer, name, key);
 }
 
 /**