[PATCH v2 10/34] locking/mutex: Support Clang's capability analysis

Marco Elver
2025-03-04T09:25:37Z

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 ddda3dc0d8d3..0000214056c2 100644
--- a/Documentation/dev-tools/capability-analysis.rst
+++ b/Documentation/dev-tools/capability-analysis.rst
@@ -79,7 +79,7 @@ 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..f71ad9ec96d0 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(true, 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(true, 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 84060bace61d..286723b47328 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 __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++;
+ }
+}