locking/rtmutex: Add context analysis

Add compiler context analysis annotations.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260121111213.851599178@infradead.org

include/linux/rtmutex.h

@@ -22,8 +22,8 @@ extern int max_lock_depth;
 
 struct rt_mutex_base {
 	raw_spinlock_t		wait_lock;
-	struct rb_root_cached   waiters;
-	struct task_struct	*owner;
+	struct rb_root_cached   waiters __guarded_by(&wait_lock);
+	struct task_struct	*owner  __guarded_by(&wait_lock);
 };
 
 #define __RT_MUTEX_BASE_INITIALIZER(rtbasename)				\
@@ -41,7 +41,7 @@ struct rt_mutex_base {
  */
 static inline bool rt_mutex_base_is_locked(struct rt_mutex_base *lock)
 {
-	return READ_ONCE(lock->owner) != NULL;
+	return data_race(READ_ONCE(lock->owner) != NULL);
 }
 
 #ifdef CONFIG_RT_MUTEXES
@@ -49,7 +49,7 @@ static inline bool rt_mutex_base_is_locked(struct rt_mutex_base *lock)
 
 static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
 {
-	unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
+	unsigned long owner = (unsigned long) data_race(READ_ONCE(lock->owner));
 
 	return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
 }

kernel/locking/Makefile

@@ -4,6 +4,8 @@
 KCOV_INSTRUMENT		:= n
 
 CONTEXT_ANALYSIS_mutex.o := y
+CONTEXT_ANALYSIS_rtmutex_api.o := y
+CONTEXT_ANALYSIS_ww_rt_mutex.o := y
 
 obj-y += mutex.o semaphore.o rwsem.o percpu-rwsem.o
 

kernel/locking/rtmutex.c

@@ -94,6 +94,7 @@ static inline int __ww_mutex_check_kill(struct rt_mutex *lock,
 
 static __always_inline struct task_struct *
 rt_mutex_owner_encode(struct rt_mutex_base *lock, struct task_struct *owner)
+	__must_hold(&lock->wait_lock)
 {
 	unsigned long val = (unsigned long)owner;
 
@@ -105,6 +106,7 @@ rt_mutex_owner_encode(struct rt_mutex_base *lock, struct task_struct *owner)
 
 static __always_inline void
 rt_mutex_set_owner(struct rt_mutex_base *lock, struct task_struct *owner)
+	__must_hold(&lock->wait_lock)
 {
 	/*
 	 * lock->wait_lock is held but explicit acquire semantics are needed
@@ -114,12 +116,14 @@ rt_mutex_set_owner(struct rt_mutex_base *lock, struct task_struct *owner)
 }
 
 static __always_inline void rt_mutex_clear_owner(struct rt_mutex_base *lock)
+	__must_hold(&lock->wait_lock)
 {
 	/* lock->wait_lock is held so the unlock provides release semantics. */
 	WRITE_ONCE(lock->owner, rt_mutex_owner_encode(lock, NULL));
 }
 
 static __always_inline void clear_rt_mutex_waiters(struct rt_mutex_base *lock)
+	__must_hold(&lock->wait_lock)
 {
 	lock->owner = (struct task_struct *)
 			((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS);
@@ -127,6 +131,7 @@ static __always_inline void clear_rt_mutex_waiters(struct rt_mutex_base *lock)
 
 static __always_inline void
 fixup_rt_mutex_waiters(struct rt_mutex_base *lock, bool acquire_lock)
+	__must_hold(&lock->wait_lock)
 {
 	unsigned long owner, *p = (unsigned long *) &lock->owner;
 
@@ -328,6 +333,7 @@ static __always_inline bool rt_mutex_cmpxchg_release(struct rt_mutex_base *lock,
 }
 
 static __always_inline void mark_rt_mutex_waiters(struct rt_mutex_base *lock)
+	__must_hold(&lock->wait_lock)
 {
 	lock->owner = (struct task_struct *)
 			((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS);
@@ -1206,6 +1212,7 @@ static int __sched task_blocks_on_rt_mutex(struct rt_mutex_base *lock,
 					   struct ww_acquire_ctx *ww_ctx,
 					   enum rtmutex_chainwalk chwalk,
 					   struct wake_q_head *wake_q)
+	__must_hold(&lock->wait_lock)
 {
 	struct task_struct *owner = rt_mutex_owner(lock);
 	struct rt_mutex_waiter *top_waiter = waiter;
@@ -1249,6 +1256,7 @@ static int __sched task_blocks_on_rt_mutex(struct rt_mutex_base *lock,
 
 		/* Check whether the waiter should back out immediately */
 		rtm = container_of(lock, struct rt_mutex, rtmutex);
+		__assume_ctx_lock(&rtm->rtmutex.wait_lock);
 		res = __ww_mutex_add_waiter(waiter, rtm, ww_ctx, wake_q);
 		if (res) {
 			raw_spin_lock(&task->pi_lock);
@@ -1356,6 +1364,7 @@ static void __sched mark_wakeup_next_waiter(struct rt_wake_q_head *wqh,
 }
 
 static int __sched __rt_mutex_slowtrylock(struct rt_mutex_base *lock)
+	__must_hold(&lock->wait_lock)
 {
 	int ret = try_to_take_rt_mutex(lock, current, NULL);
 
@@ -1505,7 +1514,7 @@ static bool rtmutex_spin_on_owner(struct rt_mutex_base *lock,
 		 *  - the VCPU on which owner runs is preempted
 		 */
 		if (!owner_on_cpu(owner) || need_resched() ||
-		    !rt_mutex_waiter_is_top_waiter(lock, waiter)) {
+		    !data_race(rt_mutex_waiter_is_top_waiter(lock, waiter))) {
 			res = false;
 			break;
 		}
@@ -1538,6 +1547,7 @@ static bool rtmutex_spin_on_owner(struct rt_mutex_base *lock,
  */
 static void __sched remove_waiter(struct rt_mutex_base *lock,
 				  struct rt_mutex_waiter *waiter)
+	__must_hold(&lock->wait_lock)
 {
 	bool is_top_waiter = (waiter == rt_mutex_top_waiter(lock));
 	struct task_struct *owner = rt_mutex_owner(lock);
@@ -1613,6 +1623,8 @@ static int __sched rt_mutex_slowlock_block(struct rt_mutex_base *lock,
 	struct task_struct *owner;
 	int ret = 0;
 
+	__assume_ctx_lock(&rtm->rtmutex.wait_lock);
+
 	lockevent_inc(rtmutex_slow_block);
 	for (;;) {
 		/* Try to acquire the lock: */
@@ -1658,6 +1670,7 @@ static int __sched rt_mutex_slowlock_block(struct rt_mutex_base *lock,
 static void __sched rt_mutex_handle_deadlock(int res, int detect_deadlock,
 					     struct rt_mutex_base *lock,
 					     struct rt_mutex_waiter *w)
+	__must_hold(&lock->wait_lock)
 {
 	/*
 	 * If the result is not -EDEADLOCK or the caller requested
@@ -1694,11 +1707,13 @@ static int __sched __rt_mutex_slowlock(struct rt_mutex_base *lock,
 				       enum rtmutex_chainwalk chwalk,
 				       struct rt_mutex_waiter *waiter,
 				       struct wake_q_head *wake_q)
+	__must_hold(&lock->wait_lock)
 {
 	struct rt_mutex *rtm = container_of(lock, struct rt_mutex, rtmutex);
 	struct ww_mutex *ww = ww_container_of(rtm);
 	int ret;
 
+	__assume_ctx_lock(&rtm->rtmutex.wait_lock);
 	lockdep_assert_held(&lock->wait_lock);
 	lockevent_inc(rtmutex_slowlock);
 
@@ -1750,6 +1765,7 @@ static inline int __rt_mutex_slowlock_locked(struct rt_mutex_base *lock,
 					     struct ww_acquire_ctx *ww_ctx,
 					     unsigned int state,
 					     struct wake_q_head *wake_q)
+	__must_hold(&lock->wait_lock)
 {
 	struct rt_mutex_waiter waiter;
 	int ret;

kernel/locking/rtmutex_api.c

@@ -526,6 +526,7 @@ static __always_inline int __mutex_lock_common(struct mutex *lock,
 					       unsigned int subclass,
 					       struct lockdep_map *nest_lock,
 					       unsigned long ip)
+	__acquires(lock) __no_context_analysis
 {
 	int ret;
 
@@ -647,6 +648,7 @@ EXPORT_SYMBOL(mutex_trylock);
 #endif /* !CONFIG_DEBUG_LOCK_ALLOC */
 
 void __sched mutex_unlock(struct mutex *lock)
+	__releases(lock) __no_context_analysis
 {
 	mutex_release(&lock->dep_map, _RET_IP_);
 	__rt_mutex_unlock(&lock->rtmutex);

kernel/locking/rtmutex_common.h

@@ -79,12 +79,18 @@ struct rt_wake_q_head {
  * PI-futex support (proxy locking functions, etc.):
  */
 extern void rt_mutex_init_proxy_locked(struct rt_mutex_base *lock,
-				       struct task_struct *proxy_owner);
-extern void rt_mutex_proxy_unlock(struct rt_mutex_base *lock);
+				       struct task_struct *proxy_owner)
+	__must_hold(&lock->wait_lock);
+
+extern void rt_mutex_proxy_unlock(struct rt_mutex_base *lock)
+	__must_hold(&lock->wait_lock);
+
 extern int __rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
 				     struct rt_mutex_waiter *waiter,
 				     struct task_struct *task,
-				     struct wake_q_head *);
+				     struct wake_q_head *)
+	__must_hold(&lock->wait_lock);
+
 extern int rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
 				     struct rt_mutex_waiter *waiter,
 				     struct task_struct *task);
@@ -94,8 +100,9 @@ extern int rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock,
 extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex_base *lock,
 				 struct rt_mutex_waiter *waiter);
 
-extern int rt_mutex_futex_trylock(struct rt_mutex_base *l);
-extern int __rt_mutex_futex_trylock(struct rt_mutex_base *l);
+extern int rt_mutex_futex_trylock(struct rt_mutex_base *lock);
+extern int __rt_mutex_futex_trylock(struct rt_mutex_base *lock)
+	__must_hold(&lock->wait_lock);
 
 extern void rt_mutex_futex_unlock(struct rt_mutex_base *lock);
 extern bool __rt_mutex_futex_unlock(struct rt_mutex_base *lock,
@@ -109,6 +116,7 @@ extern void rt_mutex_postunlock(struct rt_wake_q_head *wqh);
  */
 #ifdef CONFIG_RT_MUTEXES
 static inline int rt_mutex_has_waiters(struct rt_mutex_base *lock)
+	__must_hold(&lock->wait_lock)
 {
 	return !RB_EMPTY_ROOT(&lock->waiters.rb_root);
 }
@@ -120,6 +128,7 @@ static inline int rt_mutex_has_waiters(struct rt_mutex_base *lock)
  */
 static inline bool rt_mutex_waiter_is_top_waiter(struct rt_mutex_base *lock,
 						 struct rt_mutex_waiter *waiter)
+	__must_hold(&lock->wait_lock)
 {
 	struct rb_node *leftmost = rb_first_cached(&lock->waiters);
 
@@ -127,6 +136,7 @@ static inline bool rt_mutex_waiter_is_top_waiter(struct rt_mutex_base *lock,
 }
 
 static inline struct rt_mutex_waiter *rt_mutex_top_waiter(struct rt_mutex_base *lock)
+	__must_hold(&lock->wait_lock)
 {
 	struct rb_node *leftmost = rb_first_cached(&lock->waiters);
 	struct rt_mutex_waiter *w = NULL;
@@ -170,9 +180,10 @@ enum rtmutex_chainwalk {
 
 static inline void __rt_mutex_base_init(struct rt_mutex_base *lock)
 {
-	raw_spin_lock_init(&lock->wait_lock);
-	lock->waiters = RB_ROOT_CACHED;
-	lock->owner = NULL;
+	scoped_guard (raw_spinlock_init, &lock->wait_lock) {
+		lock->waiters = RB_ROOT_CACHED;
+		lock->owner = NULL;
+	}
 }
 
 /* Debug functions */

kernel/locking/ww_mutex.h

@@ -4,6 +4,7 @@
 
 #define MUTEX		mutex
 #define MUTEX_WAITER	mutex_waiter
+#define WAIT_LOCK	wait_lock
 
 static inline struct mutex_waiter *
 __ww_waiter_first(struct mutex *lock)
@@ -86,9 +87,11 @@ static inline void lockdep_assert_wait_lock_held(struct mutex *lock)
 
 #define MUTEX		rt_mutex
 #define MUTEX_WAITER	rt_mutex_waiter
+#define WAIT_LOCK	rtmutex.wait_lock
 
 static inline struct rt_mutex_waiter *
 __ww_waiter_first(struct rt_mutex *lock)
+	__must_hold(&lock->rtmutex.wait_lock)
 {
 	struct rb_node *n = rb_first(&lock->rtmutex.waiters.rb_root);
 	if (!n)
@@ -116,6 +119,7 @@ __ww_waiter_prev(struct rt_mutex *lock, struct rt_mutex_waiter *w)
 
 static inline struct rt_mutex_waiter *
 __ww_waiter_last(struct rt_mutex *lock)
+	__must_hold(&lock->rtmutex.wait_lock)
 {
 	struct rb_node *n = rb_last(&lock->rtmutex.waiters.rb_root);
 	if (!n)
@@ -137,21 +141,25 @@ __ww_mutex_owner(struct rt_mutex *lock)
 
 static inline bool
 __ww_mutex_has_waiters(struct rt_mutex *lock)
+	__must_hold(&lock->rtmutex.wait_lock)
 {
 	return rt_mutex_has_waiters(&lock->rtmutex);
 }
 
 static inline void lock_wait_lock(struct rt_mutex *lock, unsigned long *flags)
+	__acquires(&lock->rtmutex.wait_lock)
 {
 	raw_spin_lock_irqsave(&lock->rtmutex.wait_lock, *flags);
 }
 
 static inline void unlock_wait_lock(struct rt_mutex *lock, unsigned long *flags)
+	__releases(&lock->rtmutex.wait_lock)
 {
 	raw_spin_unlock_irqrestore(&lock->rtmutex.wait_lock, *flags);
 }
 
 static inline void lockdep_assert_wait_lock_held(struct rt_mutex *lock)
+	__must_hold(&lock->rtmutex.wait_lock)
 {
 	lockdep_assert_held(&lock->rtmutex.wait_lock);
 }
@@ -304,7 +312,7 @@ static bool __ww_mutex_wound(struct MUTEX *lock,
 			     struct ww_acquire_ctx *ww_ctx,
 			     struct ww_acquire_ctx *hold_ctx,
 			     struct wake_q_head *wake_q)
-	__must_hold(&lock->wait_lock)
+	__must_hold(&lock->WAIT_LOCK)
 {
 	struct task_struct *owner = __ww_mutex_owner(lock);
 
@@ -369,7 +377,7 @@ static bool __ww_mutex_wound(struct MUTEX *lock,
 static void
 __ww_mutex_check_waiters(struct MUTEX *lock, struct ww_acquire_ctx *ww_ctx,
 			 struct wake_q_head *wake_q)
-	__must_hold(&lock->wait_lock)
+	__must_hold(&lock->WAIT_LOCK)
 {
 	struct MUTEX_WAITER *cur;
 
@@ -396,6 +404,7 @@ ww_mutex_set_context_fastpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
 {
 	DEFINE_WAKE_Q(wake_q);
 	unsigned long flags;
+	bool has_waiters;
 
 	ww_mutex_lock_acquired(lock, ctx);
 
@@ -417,7 +426,8 @@ ww_mutex_set_context_fastpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
 	 * __ww_mutex_add_waiter() and makes sure we either observe ww->ctx
 	 * and/or !empty list.
 	 */
-	if (likely(!__ww_mutex_has_waiters(&lock->base)))
+	has_waiters = data_race(__ww_mutex_has_waiters(&lock->base));
+	if (likely(!has_waiters))
 		return;
 
 	/*
@@ -463,7 +473,7 @@ __ww_mutex_kill(struct MUTEX *lock, struct ww_acquire_ctx *ww_ctx)
 static inline int
 __ww_mutex_check_kill(struct MUTEX *lock, struct MUTEX_WAITER *waiter,
 		      struct ww_acquire_ctx *ctx)
-	__must_hold(&lock->wait_lock)
+	__must_hold(&lock->WAIT_LOCK)
 {
 	struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
 	struct ww_acquire_ctx *hold_ctx = READ_ONCE(ww->ctx);
@@ -514,7 +524,7 @@ __ww_mutex_add_waiter(struct MUTEX_WAITER *waiter,
 		      struct MUTEX *lock,
 		      struct ww_acquire_ctx *ww_ctx,
 		      struct wake_q_head *wake_q)
-	__must_hold(&lock->wait_lock)
+	__must_hold(&lock->WAIT_LOCK)
 {
 	struct MUTEX_WAITER *cur, *pos = NULL;
 	bool is_wait_die;

kernel/locking/ww_rt_mutex.c

@@ -90,6 +90,7 @@ ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
 EXPORT_SYMBOL(ww_mutex_lock_interruptible);
 
 void __sched ww_mutex_unlock(struct ww_mutex *lock)
+	__no_context_analysis
 {
 	struct rt_mutex *rtm = &lock->base;
 

scripts/context-analysis-suppression.txt

@@ -24,6 +24,7 @@ src:*include/linux/mutex*.h=emit
 src:*include/linux/rcupdate.h=emit
 src:*include/linux/refcount.h=emit
 src:*include/linux/rhashtable.h=emit
+src:*include/linux/rtmutex*.h=emit
 src:*include/linux/rwlock*.h=emit
 src:*include/linux/rwsem.h=emit
 src:*include/linux/sched*=emit