locking/rwsem: Add context analysis

Add compiler context analysis annotations.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260306101417.GT1282955@noisy.programming.kicks-ass.net

diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index e7829531c4baa1ef401f67cd1b4495603cadab0b..6a1a7bae5f811d0877b714ab9f4c7253f7ea4970 100644 (file)
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -57,7 +57,7 @@ context_lock_struct(rw_semaphore) {
        struct optimistic_spin_queue osq; /* spinner MCS lock */
 #endif
        raw_spinlock_t wait_lock;
-       struct rwsem_waiter *first_waiter;
+       struct rwsem_waiter *first_waiter __guarded_by(&wait_lock);
 #ifdef CONFIG_DEBUG_RWSEMS
        void *magic;
 #endif
@@ -131,7 +131,7 @@ do {                                                                \
  */
 static inline bool rwsem_is_contended(struct rw_semaphore *sem)
 {
-       return sem->first_waiter != NULL;
+       return data_race(sem->first_waiter != NULL);
 }
 
 #if defined(CONFIG_DEBUG_RWSEMS) || defined(CONFIG_DETECT_HUNG_TASK_BLOCKER)

diff --git a/kernel/locking/Makefile b/kernel/locking/Makefile
index 0c07de79388c97b3ac6e0d825b84d80ab1297b0d..cee1901d4cff8d9d2a865560911abae0090b047b 100644 (file)
--- a/kernel/locking/Makefile
+++ b/kernel/locking/Makefile
@@ -6,6 +6,7 @@ KCOV_INSTRUMENT         := n
 CONTEXT_ANALYSIS_mutex.o := y
 CONTEXT_ANALYSIS_rtmutex_api.o := y
 CONTEXT_ANALYSIS_ww_rt_mutex.o := y
+CONTEXT_ANALYSIS_rwsem.o := y
 
 obj-y += mutex.o semaphore.o rwsem.o percpu-rwsem.o
 

diff --git a/kernel/locking/rwbase_rt.c b/kernel/locking/rwbase_rt.c
index 9f4322c074862295b3767dcded344196a0336306..82e078c0665ac4afb52250a33fd6f7b5a90c628d 100644 (file)
--- a/kernel/locking/rwbase_rt.c
+++ b/kernel/locking/rwbase_rt.c
@@ -186,6 +186,7 @@ static __always_inline void rwbase_read_unlock(struct rwbase_rt *rwb,
 
 static inline void __rwbase_write_unlock(struct rwbase_rt *rwb, int bias,
                                         unsigned long flags)
+       __releases(&rwb->rtmutex.wait_lock)
 {
        struct rt_mutex_base *rtm = &rwb->rtmutex;
 

diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index e66f37ebc6f61798dcc758ecdc8d88a12509679f..ba4cb74de06449d91a632dd820c1edb7bbfdcc07 100644 (file)
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -72,7 +72,7 @@
                #c, atomic_long_read(&(sem)->count),            \
                (unsigned long) sem->magic,                     \
                atomic_long_read(&(sem)->owner), (long)current, \
-               (sem)->first_waiter ? "" : "not "))             \
+               rwsem_is_contended(sem) ? "" : "not "))         \
                        debug_locks_off();                      \
        } while (0)
 #else
@@ -320,9 +320,10 @@ void __init_rwsem(struct rw_semaphore *sem, const char *name,
        sem->magic = sem;
 #endif
        atomic_long_set(&sem->count, RWSEM_UNLOCKED_VALUE);
-       raw_spin_lock_init(&sem->wait_lock);
-       sem->first_waiter = NULL;
        atomic_long_set(&sem->owner, 0L);
+       scoped_guard (raw_spinlock_init, &sem->wait_lock) {
+               sem->first_waiter = NULL;
+       }
 #ifdef CONFIG_RWSEM_SPIN_ON_OWNER
        osq_lock_init(&sem->osq);
 #endif
@@ -365,6 +366,7 @@ enum rwsem_wake_type {
 
 static inline
 bool __rwsem_del_waiter(struct rw_semaphore *sem, struct rwsem_waiter *waiter)
+       __must_hold(&sem->wait_lock)
 {
        if (list_empty(&waiter->list)) {
                sem->first_waiter = NULL;
@@ -401,6 +403,7 @@ rwsem_del_waiter(struct rw_semaphore *sem, struct rwsem_waiter *waiter)
 static inline
 struct rwsem_waiter *next_waiter(const struct rw_semaphore *sem,
                                 const struct rwsem_waiter *waiter)
+       __must_hold(&sem->wait_lock)
 {
        struct rwsem_waiter *next = list_first_entry(&waiter->list,
                                                     struct rwsem_waiter, list);
@@ -621,6 +624,7 @@ rwsem_del_wake_waiter(struct rw_semaphore *sem, struct rwsem_waiter *waiter,
  */
 static inline bool rwsem_try_write_lock(struct rw_semaphore *sem,
                                        struct rwsem_waiter *waiter)
+       __must_hold(&sem->wait_lock)
 {
        struct rwsem_waiter *first = sem->first_waiter;
        long count, new;
@@ -1558,6 +1562,7 @@ static inline bool is_rwsem_reader_owned(struct rw_semaphore *sem)
  * lock for reading
  */
 void __sched down_read(struct rw_semaphore *sem)
+       __no_context_analysis
 {
        might_sleep();
        rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
@@ -1567,6 +1572,7 @@ void __sched down_read(struct rw_semaphore *sem)
 EXPORT_SYMBOL(down_read);
 
 int __sched down_read_interruptible(struct rw_semaphore *sem)
+       __no_context_analysis
 {
        might_sleep();
        rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
@@ -1581,6 +1587,7 @@ int __sched down_read_interruptible(struct rw_semaphore *sem)
 EXPORT_SYMBOL(down_read_interruptible);
 
 int __sched down_read_killable(struct rw_semaphore *sem)
+       __no_context_analysis
 {
        might_sleep();
        rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
@@ -1598,6 +1605,7 @@ EXPORT_SYMBOL(down_read_killable);
  * trylock for reading -- returns 1 if successful, 0 if contention
  */
 int down_read_trylock(struct rw_semaphore *sem)
+       __no_context_analysis
 {
        int ret = __down_read_trylock(sem);
 
@@ -1611,6 +1619,7 @@ EXPORT_SYMBOL(down_read_trylock);
  * lock for writing
  */
 void __sched down_write(struct rw_semaphore *sem)
+       __no_context_analysis
 {
        might_sleep();
        rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
@@ -1622,6 +1631,7 @@ EXPORT_SYMBOL(down_write);
  * lock for writing
  */
 int __sched down_write_killable(struct rw_semaphore *sem)
+       __no_context_analysis
 {
        might_sleep();
        rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
@@ -1640,6 +1650,7 @@ EXPORT_SYMBOL(down_write_killable);
  * trylock for writing -- returns 1 if successful, 0 if contention
  */
 int down_write_trylock(struct rw_semaphore *sem)
+       __no_context_analysis
 {
        int ret = __down_write_trylock(sem);
 
@@ -1654,6 +1665,7 @@ EXPORT_SYMBOL(down_write_trylock);
  * release a read lock
  */
 void up_read(struct rw_semaphore *sem)
+       __no_context_analysis
 {
        rwsem_release(&sem->dep_map, _RET_IP_);
        __up_read(sem);
@@ -1664,6 +1676,7 @@ EXPORT_SYMBOL(up_read);
  * release a write lock
  */
 void up_write(struct rw_semaphore *sem)
+       __no_context_analysis
 {
        rwsem_release(&sem->dep_map, _RET_IP_);
        __up_write(sem);
@@ -1674,6 +1687,7 @@ EXPORT_SYMBOL(up_write);
  * downgrade write lock to read lock
  */
 void downgrade_write(struct rw_semaphore *sem)
+       __no_context_analysis
 {
        lock_downgrade(&sem->dep_map, _RET_IP_);
        __downgrade_write(sem);
@@ -1683,6 +1697,7 @@ EXPORT_SYMBOL(downgrade_write);
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 
 void down_read_nested(struct rw_semaphore *sem, int subclass)
+       __no_context_analysis
 {
        might_sleep();
        rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
@@ -1691,6 +1706,7 @@ void down_read_nested(struct rw_semaphore *sem, int subclass)
 EXPORT_SYMBOL(down_read_nested);
 
 int down_read_killable_nested(struct rw_semaphore *sem, int subclass)
+       __no_context_analysis
 {
        might_sleep();
        rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
@@ -1705,6 +1721,7 @@ int down_read_killable_nested(struct rw_semaphore *sem, int subclass)
 EXPORT_SYMBOL(down_read_killable_nested);
 
 void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest)
+       __no_context_analysis
 {
        might_sleep();
        rwsem_acquire_nest(&sem->dep_map, 0, 0, nest, _RET_IP_);
@@ -1713,6 +1730,7 @@ void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest)
 EXPORT_SYMBOL(_down_write_nest_lock);
 
 void down_read_non_owner(struct rw_semaphore *sem)
+       __no_context_analysis
 {
        might_sleep();
        __down_read(sem);
@@ -1727,6 +1745,7 @@ void down_read_non_owner(struct rw_semaphore *sem)
 EXPORT_SYMBOL(down_read_non_owner);
 
 void down_write_nested(struct rw_semaphore *sem, int subclass)
+       __no_context_analysis
 {
        might_sleep();
        rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
@@ -1735,6 +1754,7 @@ void down_write_nested(struct rw_semaphore *sem, int subclass)
 EXPORT_SYMBOL(down_write_nested);
 
 int __sched down_write_killable_nested(struct rw_semaphore *sem, int subclass)
+       __no_context_analysis
 {
        might_sleep();
        rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
@@ -1750,6 +1770,7 @@ int __sched down_write_killable_nested(struct rw_semaphore *sem, int subclass)
 EXPORT_SYMBOL(down_write_killable_nested);
 
 void up_read_non_owner(struct rw_semaphore *sem)
+       __no_context_analysis
 {
        DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem);
        __up_read(sem);