[PATCH] locking/arch: Rewrite local_add_unless as static inline function

* [PATCH] locking/arch: Rewrite local_add_unless as static inline function
@ 2023-07-31  8:42 Uros Bizjak
  2023-08-07 16:13 ` Christophe Leroy
  2023-10-04 15:46 ` [tip: locking/core] locking/local, arch: Rewrite local_add_unless() as a " tip-bot2 for Uros Bizjak
  0 siblings, 2 replies; 4+ messages in thread
From: Uros Bizjak @ 2023-07-31  8:42 UTC (permalink / raw)
  To: loongarch, linux-mips, x86, linux-arch, linux-kernel
  Cc: Uros Bizjak, Will Deacon, Peter Zijlstra, Boqun Feng,
	Mark Rutland, Richard Henderson, Ivan Kokshaysky, Matt Turner,
	Huacai Chen, WANG Xuerui, Jiaxun Yang, Jun Yi,
	Thomas Bogendoerfer, Michael Ellerman, Nicholas Piggin,
	Christophe Leroy, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
	Dave Hansen, H. Peter Anvin

Rewrite local_add_unless as a static inline function with boolean
return value, similar to arch_atomic_add_unless arch fallbacks.

The function is currently unused.

Cc: Will Deacon <will@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: Jun Yi <yijun@loongson.cn>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
---
 arch/alpha/include/asm/local.h     | 33 +++++++++++++++---------------
 arch/loongarch/include/asm/local.h | 27 ++++++++++++++----------
 arch/mips/include/asm/local.h      | 27 ++++++++++++++----------
 arch/powerpc/include/asm/local.h   | 12 +++++------
 arch/x86/include/asm/local.h       | 33 +++++++++++++++---------------
 5 files changed, 70 insertions(+), 62 deletions(-)

diff --git a/arch/alpha/include/asm/local.h b/arch/alpha/include/asm/local.h
index 0fcaad642cc3..88eb398947a5 100644
--- a/arch/alpha/include/asm/local.h
+++ b/arch/alpha/include/asm/local.h
@@ -65,28 +65,27 @@ static __inline__ bool local_try_cmpxchg(local_t *l, long *old, long new)
 #define local_xchg(l, n) (xchg_local(&((l)->a.counter), (n)))
 
 /**
- * local_add_unless - add unless the number is a given value
+ * local_add_unless - add unless the number is already a given value
  * @l: pointer of type local_t
  * @a: the amount to add to l...
  * @u: ...unless l is equal to u.
  *
- * Atomically adds @a to @l, so long as it was not @u.
- * Returns non-zero if @l was not @u, and zero otherwise.
+ * Atomically adds @a to @l, if @v was not already @u.
+ * Returns true if the addition was done.
  */
-#define local_add_unless(l, a, u)				\
-({								\
-	long c, old;						\
-	c = local_read(l);					\
-	for (;;) {						\
-		if (unlikely(c == (u)))				\
-			break;					\
-		old = local_cmpxchg((l), c, c + (a));	\
-		if (likely(old == c))				\
-			break;					\
-		c = old;					\
-	}							\
-	c != (u);						\
-})
+static __inline__ bool
+local_add_unless(local_t *l, long a, long u)
+{
+	long c = local_read(l);
+
+	do {
+		if (unlikely(c == u))
+			return false;
+	} while (!local_try_cmpxchg(l, &c, c + a));
+
+	return true;
+}
+
 #define local_inc_not_zero(l) local_add_unless((l), 1, 0)
 
 #define local_add_negative(a, l) (local_add_return((a), (l)) < 0)
diff --git a/arch/loongarch/include/asm/local.h b/arch/loongarch/include/asm/local.h
index 83e995b30e47..15bc3579f16c 100644
--- a/arch/loongarch/include/asm/local.h
+++ b/arch/loongarch/include/asm/local.h
@@ -70,22 +70,27 @@ static inline bool local_try_cmpxchg(local_t *l, long *old, long new)
 #define local_xchg(l, n) (atomic_long_xchg((&(l)->a), (n)))
 
 /**
- * local_add_unless - add unless the number is a given value
+ * local_add_unless - add unless the number is already a given value
  * @l: pointer of type local_t
  * @a: the amount to add to l...
  * @u: ...unless l is equal to u.
  *
- * Atomically adds @a to @l, so long as it was not @u.
- * Returns non-zero if @l was not @u, and zero otherwise.
+ * Atomically adds @a to @l, if @v was not already @u.
+ * Returns true if the addition was done.
  */
-#define local_add_unless(l, a, u)				\
-({								\
-	long c, old;						\
-	c = local_read(l);					\
-	while (c != (u) && (old = local_cmpxchg((l), c, c + (a))) != c) \
-		c = old;					\
-	c != (u);						\
-})
+static inline bool
+local_add_unless(local_t *l, long a, long u)
+{
+	long c = local_read(l);
+
+	do {
+		if (unlikely(c == u))
+			return false;
+	} while (!local_try_cmpxchg(l, &c, c + a));
+
+	return true;
+}
+
 #define local_inc_not_zero(l) local_add_unless((l), 1, 0)
 
 #define local_dec_return(l) local_sub_return(1, (l))
diff --git a/arch/mips/include/asm/local.h b/arch/mips/include/asm/local.h
index 5daf6fe8e3e9..90435158a083 100644
--- a/arch/mips/include/asm/local.h
+++ b/arch/mips/include/asm/local.h
@@ -108,22 +108,27 @@ static __inline__ bool local_try_cmpxchg(local_t *l, long *old, long new)
 #define local_xchg(l, n) (atomic_long_xchg((&(l)->a), (n)))
 
 /**
- * local_add_unless - add unless the number is a given value
+ * local_add_unless - add unless the number is already a given value
  * @l: pointer of type local_t
  * @a: the amount to add to l...
  * @u: ...unless l is equal to u.
  *
- * Atomically adds @a to @l, so long as it was not @u.
- * Returns non-zero if @l was not @u, and zero otherwise.
+ * Atomically adds @a to @l, if @v was not already @u.
+ * Returns true if the addition was done.
  */
-#define local_add_unless(l, a, u)				\
-({								\
-	long c, old;						\
-	c = local_read(l);					\
-	while (c != (u) && (old = local_cmpxchg((l), c, c + (a))) != c) \
-		c = old;					\
-	c != (u);						\
-})
+static __inline__ bool
+local_add_unless(local_t *l, long a, long u)
+{
+	long c = local_read(l);
+
+	do {
+		if (unlikely(c == u))
+			return false;
+	} while (!local_try_cmpxchg(l, &c, c + a));
+
+	return true;
+}
+
 #define local_inc_not_zero(l) local_add_unless((l), 1, 0)
 
 #define local_dec_return(l) local_sub_return(1, (l))
diff --git a/arch/powerpc/include/asm/local.h b/arch/powerpc/include/asm/local.h
index 45492fb5bf22..ec6ced6d7ced 100644
--- a/arch/powerpc/include/asm/local.h
+++ b/arch/powerpc/include/asm/local.h
@@ -115,23 +115,23 @@ static __inline__ long local_xchg(local_t *l, long n)
 }
 
 /**
- * local_add_unless - add unless the number is a given value
+ * local_add_unless - add unless the number is already a given value
  * @l: pointer of type local_t
  * @a: the amount to add to v...
  * @u: ...unless v is equal to u.
  *
- * Atomically adds @a to @l, so long as it was not @u.
- * Returns non-zero if @l was not @u, and zero otherwise.
+ * Atomically adds @a to @l, if @v was not already @u.
+ * Returns true if the addition was done.
  */
-static __inline__ int local_add_unless(local_t *l, long a, long u)
+static __inline__ bool local_add_unless(local_t *l, long a, long u)
 {
 	unsigned long flags;
-	int ret = 0;
+	bool ret = false;
 
 	powerpc_local_irq_pmu_save(flags);
 	if (l->v != u) {
 		l->v += a;
-		ret = 1;
+		ret = true;
 	}
 	powerpc_local_irq_pmu_restore(flags);
 
diff --git a/arch/x86/include/asm/local.h b/arch/x86/include/asm/local.h
index 56d4ef604b91..46ce92d4e556 100644
--- a/arch/x86/include/asm/local.h
+++ b/arch/x86/include/asm/local.h
@@ -135,28 +135,27 @@ static inline bool local_try_cmpxchg(local_t *l, long *old, long new)
 #define local_xchg(l, n) (xchg(&((l)->a.counter), (n)))
 
 /**
- * local_add_unless - add unless the number is a given value
+ * local_add_unless - add unless the number is already a given value
  * @l: pointer of type local_t
  * @a: the amount to add to l...
  * @u: ...unless l is equal to u.
  *
- * Atomically adds @a to @l, so long as it was not @u.
- * Returns non-zero if @l was not @u, and zero otherwise.
+ * Atomically adds @a to @l, if @v was not already @u.
+ * Returns true if the addition was done.
  */
-#define local_add_unless(l, a, u)				\
-({								\
-	long c, old;						\
-	c = local_read((l));					\
-	for (;;) {						\
-		if (unlikely(c == (u)))				\
-			break;					\
-		old = local_cmpxchg((l), c, c + (a));		\
-		if (likely(old == c))				\
-			break;					\
-		c = old;					\
-	}							\
-	c != (u);						\
-})
+static __always_inline bool
+local_add_unless(local_t *l, long a, long u)
+{
+	long c = local_read(l);
+
+	do {
+		if (unlikely(c == u))
+			return false;
+	} while (!local_try_cmpxchg(l, &c, c + a));
+
+	return true;
+}
+
 #define local_inc_not_zero(l) local_add_unless((l), 1, 0)
 
 /* On x86_32, these are no better than the atomic variants.
-- 
2.41.0


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