lockdep: spin_lock_nest_lock()

Expose the new lock protection lock.

This can be used to annotate places where we take multiple locks of the
same class and avoid deadlocks by always taking another (top-level) lock
first.

NOTE: we're still bound to the MAX_LOCK_DEPTH (48) limit.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h
index 61e5610ad165..e0c0fccced46 100644
--- a/include/linux/spinlock.h
+++ b/include/linux/spinlock.h
@@ -183,8 +183,14 @@ do {								\
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 # define spin_lock_nested(lock, subclass) _spin_lock_nested(lock, subclass)
+# define spin_lock_nest_lock(lock, nest_lock)                           \
+         do {                                                           \
+                 typecheck(struct lockdep_map *, &(nest_lock)->dep_map);\
+                 _spin_lock_nest_lock(lock, &(nest_lock)->dep_map);     \
+         } while (0)
 #else
 # define spin_lock_nested(lock, subclass) _spin_lock(lock)
+# define spin_lock_nest_lock(lock, nest_lock) _spin_lock(lock)
 #endif
 
 #define write_lock(lock)                _write_lock(lock)