Merge tag 'locking-core-2023-05-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking updates from Ingo Molnar:

 - Introduce local{,64}_try_cmpxchg() - a slightly more optimal
   primitive, which will be used in perf events ring-buffer code

 - Simplify/modify rwsems on PREEMPT_RT, to address writer starvation

 - Misc cleanups/fixes

* tag 'locking-core-2023-05-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/atomic: Correct (cmp)xchg() instrumentation
  locking/x86: Define arch_try_cmpxchg_local()
  locking/arch: Wire up local_try_cmpxchg()
  locking/generic: Wire up local{,64}_try_cmpxchg()
  locking/atomic: Add generic try_cmpxchg{,64}_local() support
  locking/rwbase: Mitigate indefinite writer starvation
  locking/arch: Rename all internal __xchg() names to __arch_xchg()

2 files changed, 15 insertions, 7 deletions

diff --git a/arch/alpha/include/asm/cmpxchg.h b/arch/alpha/include/asm/cmpxchg.h
index 6e0a850aa9d3..91d4a4d9258c 100644
--- a/arch/alpha/include/asm/cmpxchg.h
+++ b/arch/alpha/include/asm/cmpxchg.h
@@ -6,15 +6,15 @@
  * Atomic exchange routines.
  */
 
-#define ____xchg(type, args...)		__xchg ## type ## _local(args)
+#define ____xchg(type, args...)		__arch_xchg ## type ## _local(args)
 #define ____cmpxchg(type, args...)	__cmpxchg ## type ## _local(args)
 #include <asm/xchg.h>
 
 #define xchg_local(ptr, x)						\
 ({									\
 	__typeof__(*(ptr)) _x_ = (x);					\
-	(__typeof__(*(ptr))) __xchg_local((ptr), (unsigned long)_x_,	\
-				       sizeof(*(ptr)));			\
+	(__typeof__(*(ptr))) __arch_xchg_local((ptr), (unsigned long)_x_,\
+					       sizeof(*(ptr)));		\
 })
 
 #define arch_cmpxchg_local(ptr, o, n)					\
@@ -34,7 +34,7 @@
 
 #undef ____xchg
 #undef ____cmpxchg
-#define ____xchg(type, args...)		__xchg ##type(args)
+#define ____xchg(type, args...)		__arch_xchg ##type(args)
 #define ____cmpxchg(type, args...)	__cmpxchg ##type(args)
 #include <asm/xchg.h>
 
@@ -48,7 +48,7 @@
 	__typeof__(*(ptr)) _x_ = (x);					\
 	smp_mb();							\
 	__ret = (__typeof__(*(ptr)))					\
-		__xchg((ptr), (unsigned long)_x_, sizeof(*(ptr)));	\
+		__arch_xchg((ptr), (unsigned long)_x_, sizeof(*(ptr)));	\
 	smp_mb();							\
 	__ret;								\
 })
diff --git a/arch/alpha/include/asm/local.h b/arch/alpha/include/asm/local.h
index fab26a1c93d5..0fcaad642cc3 100644
--- a/arch/alpha/include/asm/local.h
+++ b/arch/alpha/include/asm/local.h
@@ -52,8 +52,16 @@ static __inline__ long local_sub_return(long i, local_t * l)
 	return result;
 }
 
-#define local_cmpxchg(l, o, n) \
-	(cmpxchg_local(&((l)->a.counter), (o), (n)))
+static __inline__ long local_cmpxchg(local_t *l, long old, long new)
+{
+	return cmpxchg_local(&l->a.counter, old, new);
+}
+
+static __inline__ bool local_try_cmpxchg(local_t *l, long *old, long new)
+{
+	return try_cmpxchg_local(&l->a.counter, (s64 *)old, new);
+}
+
 #define local_xchg(l, n) (xchg_local(&((l)->a.counter), (n)))
 
 /**