locking/rwlock, spinlock: Support Clang's context analysis

Add support for Clang's context analysis for raw_spinlock_t,
spinlock_t, and rwlock. This wholesale conversion is required because
all three of them are interdependent.

To avoid warnings in constructors, the initialization functions mark a
lock as acquired when initialized before guarded variables.

The test verifies that common patterns do not generate false positives.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20251219154418.3592607-9-elver@google.com

1 files changed, 24 insertions, 11 deletions

diff --git a/include/linux/rwlock_rt.h b/include/linux/rwlock_rt.h
index 7d81fc6918ee..f64d6d319a47 100644
--- a/include/linux/rwlock_rt.h
+++ b/include/linux/rwlock_rt.h
@@ -22,28 +22,32 @@ do {							\
 							\
 	init_rwbase_rt(&(rwl)->rwbase);			\
 	__rt_rwlock_init(rwl, #rwl, &__key);		\
+	__assume_ctx_lock(rwl);				\
 } while (0)
 
-extern void rt_read_lock(rwlock_t *rwlock)	__acquires(rwlock);
+extern void rt_read_lock(rwlock_t *rwlock)	__acquires_shared(rwlock);
 extern int rt_read_trylock(rwlock_t *rwlock);
-extern void rt_read_unlock(rwlock_t *rwlock)	__releases(rwlock);
+extern void rt_read_unlock(rwlock_t *rwlock)	__releases_shared(rwlock);
 extern void rt_write_lock(rwlock_t *rwlock)	__acquires(rwlock);
 extern void rt_write_lock_nested(rwlock_t *rwlock, int subclass)	__acquires(rwlock);
 extern int rt_write_trylock(rwlock_t *rwlock);
 extern void rt_write_unlock(rwlock_t *rwlock)	__releases(rwlock);
 
 static __always_inline void read_lock(rwlock_t *rwlock)
+	__acquires_shared(rwlock)
 {
 	rt_read_lock(rwlock);
 }
 
 static __always_inline void read_lock_bh(rwlock_t *rwlock)
+	__acquires_shared(rwlock)
 {
 	local_bh_disable();
 	rt_read_lock(rwlock);
 }
 
 static __always_inline void read_lock_irq(rwlock_t *rwlock)
+	__acquires_shared(rwlock)
 {
 	rt_read_lock(rwlock);
 }
@@ -55,37 +59,43 @@ static __always_inline void read_lock_irq(rwlock_t *rwlock)
 		flags = 0;				\
 	} while (0)
 
-#define read_trylock(lock)	__cond_lock(lock, rt_read_trylock(lock))
+#define read_trylock(lock)	__cond_lock_shared(lock, rt_read_trylock(lock))
 
 static __always_inline void read_unlock(rwlock_t *rwlock)
+	__releases_shared(rwlock)
 {
 	rt_read_unlock(rwlock);
 }
 
 static __always_inline void read_unlock_bh(rwlock_t *rwlock)
+	__releases_shared(rwlock)
 {
 	rt_read_unlock(rwlock);
 	local_bh_enable();
 }
 
 static __always_inline void read_unlock_irq(rwlock_t *rwlock)
+	__releases_shared(rwlock)
 {
 	rt_read_unlock(rwlock);
 }
 
 static __always_inline void read_unlock_irqrestore(rwlock_t *rwlock,
 						   unsigned long flags)
+	__releases_shared(rwlock)
 {
 	rt_read_unlock(rwlock);
 }
 
 static __always_inline void write_lock(rwlock_t *rwlock)
+	__acquires(rwlock)
 {
 	rt_write_lock(rwlock);
 }
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 static __always_inline void write_lock_nested(rwlock_t *rwlock, int subclass)
+	__acquires(rwlock)
 {
 	rt_write_lock_nested(rwlock, subclass);
 }
@@ -94,12 +104,14 @@ static __always_inline void write_lock_nested(rwlock_t *rwlock, int subclass)
 #endif
 
 static __always_inline void write_lock_bh(rwlock_t *rwlock)
+	__acquires(rwlock)
 {
 	local_bh_disable();
 	rt_write_lock(rwlock);
 }
 
 static __always_inline void write_lock_irq(rwlock_t *rwlock)
+	__acquires(rwlock)
 {
 	rt_write_lock(rwlock);
 }
@@ -114,33 +126,34 @@ static __always_inline void write_lock_irq(rwlock_t *rwlock)
 #define write_trylock(lock)	__cond_lock(lock, rt_write_trylock(lock))
 
 #define write_trylock_irqsave(lock, flags)		\
-({							\
-	int __locked;					\
-							\
-	typecheck(unsigned long, flags);		\
-	flags = 0;					\
-	__locked = write_trylock(lock);			\
-	__locked;					\
-})
+	__cond_lock(lock, ({				\
+		typecheck(unsigned long, flags);	\
+		flags = 0;				\
+		rt_write_trylock(lock);			\
+	}))
 
 static __always_inline void write_unlock(rwlock_t *rwlock)
+	__releases(rwlock)
 {
 	rt_write_unlock(rwlock);
 }
 
 static __always_inline void write_unlock_bh(rwlock_t *rwlock)
+	__releases(rwlock)
 {
 	rt_write_unlock(rwlock);
 	local_bh_enable();
 }
 
 static __always_inline void write_unlock_irq(rwlock_t *rwlock)
+	__releases(rwlock)
 {
 	rt_write_unlock(rwlock);
 }
 
 static __always_inline void write_unlock_irqrestore(rwlock_t *rwlock,
 						    unsigned long flags)
+	__releases(rwlock)
 {
 	rt_write_unlock(rwlock);
 }