locking/lockdep: Provide a type check for lock_is_held

Christoph requested lockdep_assert_held() variants that distinguish
between held-for-read or held-for-write.

Provide:

  int lock_is_held_type(struct lockdep_map *lock, int read)

which takes the same argument as lock_acquire(.read) and matches it to
the held_lock instance.

Use of this function should be gated by the debug_locks variable. When
that is 0 the return value of the lock_is_held_type() function is
undefined. This is done to allow both negative and positive tests for
holding locks.

By default we provide (positive) lockdep_assert_held{,_exclusive,_read}()
macros.

Requested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Jens Axboe <axboe@fb.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

1 files changed, 23 insertions, 2 deletions

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index c1458fede1f9..1e327bb80838 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -338,9 +338,18 @@ extern void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 extern void lock_release(struct lockdep_map *lock, int nested,
                          unsigned long ip);
 
-#define lockdep_is_held(lock)   lock_is_held(&(lock)->dep_map)
+/*
+ * Same "read" as for lock_acquire(), except -1 means any.
+ */
+extern int lock_is_held_type(struct lockdep_map *lock, int read);
+
+static inline int lock_is_held(struct lockdep_map *lock)
+{
+        return lock_is_held_type(lock, -1);
+}
 
-extern int lock_is_held(struct lockdep_map *lock);
+#define lockdep_is_held(lock)           lock_is_held(&(lock)->dep_map)
+#define lockdep_is_held_type(lock, r)   lock_is_held_type(&(lock)->dep_map, (r))
 
 extern void lock_set_class(struct lockdep_map *lock, const char *name,
                            struct lock_class_key *key, unsigned int subclass,
@@ -372,6 +381,14 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
                 WARN_ON(debug_locks && !lockdep_is_held(l));    \
         } while (0)
 
+#define lockdep_assert_held_exclusive(l)        do {                    \
+                WARN_ON(debug_locks && !lockdep_is_held_type(l, 0));    \
+        } while (0)
+
+#define lockdep_assert_held_read(l)     do {                            \
+                WARN_ON(debug_locks && !lockdep_is_held_type(l, 1));    \
+        } while (0)
+
 #define lockdep_assert_held_once(l)     do {                            \
                 WARN_ON_ONCE(debug_locks && !lockdep_is_held(l));       \
         } while (0)
@@ -428,7 +445,11 @@ struct lock_class_key { };
 
 #define lockdep_depth(tsk)      (0)
 
+#define lockdep_is_held_type(l, r)              (1)
+
 #define lockdep_assert_held(l)                  do { (void)(l); } while (0)
+#define lockdep_assert_held_exclusive(l)        do { (void)(l); } while (0)
+#define lockdep_assert_held_read(l)             do { (void)(l); } while (0)
 #define lockdep_assert_held_once(l)             do { (void)(l); } while (0)
 
 #define lockdep_recursing(tsk)                  (0)