lockdep: add might_lock() / might_lock_read()

useful to establish a lock dependency in case the actual dependency is
rare or hard to trigger.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 18 insertions, 0 deletions

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 331e5f1c2d8..0aa657aa8a1 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -480,4 +480,22 @@ static inline void print_irqtrace_events(struct task_struct *curr)
 # define lock_map_release(l)                    do { } while (0)
 #endif
 
+#ifdef CONFIG_PROVE_LOCKING
+# define might_lock(lock)                                               \
+do {                                                                    \
+        typecheck(struct lockdep_map *, &(lock)->dep_map);              \
+        lock_acquire(&(lock)->dep_map, 0, 0, 0, 2, NULL, _THIS_IP_);    \
+        lock_release(&(lock)->dep_map, 0, _THIS_IP_);                   \
+} while (0)
+# define might_lock_read(lock)                                          \
+do {                                                                    \
+        typecheck(struct lockdep_map *, &(lock)->dep_map);              \
+        lock_acquire(&(lock)->dep_map, 0, 0, 1, 2, NULL, _THIS_IP_);    \
+        lock_release(&(lock)->dep_map, 0, _THIS_IP_);                   \
+} while (0)
+#else
+# define might_lock(lock) do { } while (0)
+# define might_lock_read(lock) do { } while (0)
+#endif
+
 #endif /* __LINUX_LOCKDEP_H */