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>

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index c1458fe..1e327bb 100644 (file)
--- 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)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 589d763..cff580a 100644 (file)
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3188,7 +3188,7 @@ print_lock_nested_lock_not_held(struct task_struct *curr,
        return 0;
 }
 
-static int __lock_is_held(struct lockdep_map *lock);
+static int __lock_is_held(struct lockdep_map *lock, int read);
 
 /*
  * This gets called for every mutex_lock*()/spin_lock*() operation.
@@ -3329,7 +3329,7 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
        }
        chain_key = iterate_chain_key(chain_key, class_idx);
 
-       if (nest_lock && !__lock_is_held(nest_lock))
+       if (nest_lock && !__lock_is_held(nest_lock, -1))
                return print_lock_nested_lock_not_held(curr, hlock, ip);
 
        if (!validate_chain(curr, lock, hlock, chain_head, chain_key))
@@ -3576,7 +3576,7 @@ found_it:
        return 1;
 }
 
-static int __lock_is_held(struct lockdep_map *lock)
+static int __lock_is_held(struct lockdep_map *lock, int read)
 {
        struct task_struct *curr = current;
        int i;
@@ -3584,8 +3584,12 @@ static int __lock_is_held(struct lockdep_map *lock)
        for (i = 0; i < curr->lockdep_depth; i++) {
                struct held_lock *hlock = curr->held_locks + i;
 
-               if (match_held_lock(hlock, lock))
-                       return 1;
+               if (match_held_lock(hlock, lock)) {
+                       if (read == -1 || hlock->read == read)
+                               return 1;
+
+                       return 0;
+               }
        }
 
        return 0;
@@ -3769,7 +3773,7 @@ void lock_release(struct lockdep_map *lock, int nested,
 }
 EXPORT_SYMBOL_GPL(lock_release);
 
-int lock_is_held(struct lockdep_map *lock)
+int lock_is_held_type(struct lockdep_map *lock, int read)
 {
        unsigned long flags;
        int ret = 0;
@@ -3781,13 +3785,13 @@ int lock_is_held(struct lockdep_map *lock)
        check_flags(flags);
 
        current->lockdep_recursion = 1;
-       ret = __lock_is_held(lock);
+       ret = __lock_is_held(lock, read);
        current->lockdep_recursion = 0;
        raw_local_irq_restore(flags);
 
        return ret;
 }
-EXPORT_SYMBOL_GPL(lock_is_held);
+EXPORT_SYMBOL_GPL(lock_is_held_type);
 
 struct pin_cookie lock_pin_lock(struct lockdep_map *lock)
 {