[PATCH RFC 11/24] locking/mutex: Support Clang's capability analysis

[Marco Elver <elver@google.com>]

Add support for Clang's capability analysis for mutex.

Signed-off-by: Marco Elver <elver@google.com>
---
 .../dev-tools/capability-analysis.rst         |  2 +-
 include/linux/mutex.h                         | 29 +++++----
 include/linux/mutex_types.h                   |  4 +-
 lib/test_capability-analysis.c                | 64 +++++++++++++++++++
 4 files changed, 82 insertions(+), 17 deletions(-)

diff --git a/Documentation/dev-tools/capability-analysis.rst b/Documentation/dev-tools/capability-analysis.rst
index 904448605a77..31f76e877be5 100644
--- a/Documentation/dev-tools/capability-analysis.rst
+++ b/Documentation/dev-tools/capability-analysis.rst
@@ -85,7 +85,7 @@ Supported Kernel Primitives
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Currently the following synchronization primitives are supported:
-`raw_spinlock_t`, `spinlock_t`, `rwlock_t`.
+`raw_spinlock_t`, `spinlock_t`, `rwlock_t`, `mutex`.
 
 For capabilities with an initialization function (e.g., `spin_lock_init()`),
 calling this function on the capability instance before initializing any
diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 2bf91b57591b..09ee3b89d342 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -62,6 +62,7 @@ do {									\
 	static struct lock_class_key __key;				\
 									\
 	__mutex_init((mutex), #mutex, &__key);				\
+	__assert_cap(mutex);						\
 } while (0)
 
 /**
@@ -154,14 +155,14 @@ static inline int __devm_mutex_init(struct device *dev, struct mutex *lock)
  * Also see Documentation/locking/mutex-design.rst.
  */
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
-extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
+extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass) __acquires(lock);
 extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);
 
 extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
-					unsigned int subclass);
+					unsigned int subclass) __cond_acquires(0, lock);
 extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
-					unsigned int subclass);
-extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass);
+					unsigned int subclass) __cond_acquires(0, lock);
+extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass) __acquires(lock);
 
 #define mutex_lock(lock) mutex_lock_nested(lock, 0)
 #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
@@ -175,10 +176,10 @@ do {									\
 } while (0)
 
 #else
-extern void mutex_lock(struct mutex *lock);
-extern int __must_check mutex_lock_interruptible(struct mutex *lock);
-extern int __must_check mutex_lock_killable(struct mutex *lock);
-extern void mutex_lock_io(struct mutex *lock);
+extern void mutex_lock(struct mutex *lock) __acquires(lock);
+extern int __must_check mutex_lock_interruptible(struct mutex *lock) __cond_acquires(0, lock);
+extern int __must_check mutex_lock_killable(struct mutex *lock) __cond_acquires(0, lock);
+extern void mutex_lock_io(struct mutex *lock) __acquires(lock);
 
 # define mutex_lock_nested(lock, subclass) mutex_lock(lock)
 # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
@@ -193,13 +194,13 @@ extern void mutex_lock_io(struct mutex *lock);
  *
  * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
  */
-extern int mutex_trylock(struct mutex *lock);
-extern void mutex_unlock(struct mutex *lock);
+extern int mutex_trylock(struct mutex *lock) __cond_acquires(1, lock);
+extern void mutex_unlock(struct mutex *lock) __releases(lock);
 
-extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
+extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock) __cond_acquires(1, lock);
 
-DEFINE_GUARD(mutex, struct mutex *, mutex_lock(_T), mutex_unlock(_T))
-DEFINE_GUARD_COND(mutex, _try, mutex_trylock(_T))
-DEFINE_GUARD_COND(mutex, _intr, mutex_lock_interruptible(_T) == 0)
+DEFINE_LOCK_GUARD_1(mutex, struct mutex, mutex_lock(_T->lock), mutex_unlock(_T->lock))
+DEFINE_LOCK_GUARD_1_COND(mutex, _try, mutex_trylock(_T->lock))
+DEFINE_LOCK_GUARD_1_COND(mutex, _intr, mutex_lock_interruptible(_T->lock) == 0)
 
 #endif /* __LINUX_MUTEX_H */
diff --git a/include/linux/mutex_types.h b/include/linux/mutex_types.h
index fdf7f515fde8..e1a5ea12d53c 100644
--- a/include/linux/mutex_types.h
+++ b/include/linux/mutex_types.h
@@ -38,7 +38,7 @@
  * - detects multi-task circular deadlocks and prints out all affected
  *   locks and tasks (and only those tasks)
  */
-struct mutex {
+struct_with_capability(mutex) {
 	atomic_long_t		owner;
 	raw_spinlock_t		wait_lock;
 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
@@ -59,7 +59,7 @@ struct mutex {
  */
 #include <linux/rtmutex.h>
 
-struct mutex {
+struct_with_capability(mutex) {
 	struct rt_mutex_base	rtmutex;
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 	struct lockdep_map	dep_map;
diff --git a/lib/test_capability-analysis.c b/lib/test_capability-analysis.c
index f63980e134cf..3410c04c2b76 100644
--- a/lib/test_capability-analysis.c
+++ b/lib/test_capability-analysis.c
@@ -5,6 +5,7 @@
  */
 
 #include <linux/build_bug.h>
+#include <linux/mutex.h>
 #include <linux/spinlock.h>
 
 /*
@@ -144,3 +145,66 @@ TEST_SPINLOCK_COMMON(read_lock,
 		     read_unlock,
 		     read_trylock,
 		     TEST_OP_RO);
+
+struct test_mutex_data {
+	struct mutex mtx;
+	int counter __var_guarded_by(&mtx);
+};
+
+static void __used test_mutex_init(struct test_mutex_data *d)
+{
+	mutex_init(&d->mtx);
+	d->counter = 0;
+}
+
+static void __used test_mutex_lock(struct test_mutex_data *d)
+{
+	mutex_lock(&d->mtx);
+	d->counter++;
+	mutex_unlock(&d->mtx);
+	mutex_lock_io(&d->mtx);
+	d->counter++;
+	mutex_unlock(&d->mtx);
+}
+
+static void __used test_mutex_trylock(struct test_mutex_data *d, atomic_t *a)
+{
+	if (!mutex_lock_interruptible(&d->mtx)) {
+		d->counter++;
+		mutex_unlock(&d->mtx);
+	}
+	if (!mutex_lock_killable(&d->mtx)) {
+		d->counter++;
+		mutex_unlock(&d->mtx);
+	}
+	if (mutex_trylock(&d->mtx)) {
+		d->counter++;
+		mutex_unlock(&d->mtx);
+	}
+	if (atomic_dec_and_mutex_lock(a, &d->mtx)) {
+		d->counter++;
+		mutex_unlock(&d->mtx);
+	}
+}
+
+static void __used test_mutex_assert(struct test_mutex_data *d)
+{
+	lockdep_assert_held(&d->mtx);
+	d->counter++;
+}
+
+static void __used test_mutex_guard(struct test_mutex_data *d)
+{
+	guard(mutex)(&d->mtx);
+	d->counter++;
+}
+
+static void __used test_mutex_cond_guard(struct test_mutex_data *d)
+{
+	scoped_cond_guard(mutex_try, return, &d->mtx) {
+		d->counter++;
+	}
+	scoped_cond_guard(mutex_intr, return, &d->mtx) {
+		d->counter++;
+	}
+}
-- 
2.48.1.502.g6dc24dfdaf-goog