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Message-Id: <20230126173354.13250-1-jmaselbas@kalray.eu>
Date: Thu, 26 Jan 2023 18:33:54 +0100
From: Jules Maselbas <jmaselbas@...ray.eu>
To: Will Deacon <will@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Boqun Feng <boqun.feng@...il.com>,
Mark Rutland <mark.rutland@....com>,
Arnd Bergmann <arnd@...db.de>
Cc: linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
Jules Maselbas <jmaselbas@...ray.eu>
Subject: [PATCH] locking/atomic: atomic: Use arch_atomic_{read,set} in generic atomic ops
Reading and setting the atomic counter should be done through
arch_atomic_{read,set} macros, which respectively uses {READ,WRITE}_ONCE
macros.
This is to avoid the compiler from potentially replay the read access.
Suggested-by: Mark Rutland <mark.rutland@....com>
Signed-off-by: Jules Maselbas <jmaselbas@...ray.eu>
---
include/asm-generic/atomic.h | 31 +++++++++++++++++--------------
1 file changed, 17 insertions(+), 14 deletions(-)
diff --git a/include/asm-generic/atomic.h b/include/asm-generic/atomic.h
index 04b8be9f1a77..711e408af581 100644
--- a/include/asm-generic/atomic.h
+++ b/include/asm-generic/atomic.h
@@ -12,6 +12,9 @@
#include <asm/cmpxchg.h>
#include <asm/barrier.h>
+#define arch_atomic_read(v) READ_ONCE((v)->counter)
+#define arch_atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
+
#ifdef CONFIG_SMP
/* we can build all atomic primitives from cmpxchg */
@@ -21,7 +24,7 @@ static inline void generic_atomic_##op(int i, atomic_t *v) \
{ \
int c, old; \
\
- c = v->counter; \
+ c = arch_atomic_read(v); \
while ((old = arch_cmpxchg(&v->counter, c, c c_op i)) != c) \
c = old; \
}
@@ -31,7 +34,7 @@ static inline int generic_atomic_##op##_return(int i, atomic_t *v) \
{ \
int c, old; \
\
- c = v->counter; \
+ c = arch_atomic_read(v); \
while ((old = arch_cmpxchg(&v->counter, c, c c_op i)) != c) \
c = old; \
\
@@ -43,7 +46,7 @@ static inline int generic_atomic_fetch_##op(int i, atomic_t *v) \
{ \
int c, old; \
\
- c = v->counter; \
+ c = arch_atomic_read(v); \
while ((old = arch_cmpxchg(&v->counter, c, c c_op i)) != c) \
c = old; \
\
@@ -58,9 +61,11 @@ static inline int generic_atomic_fetch_##op(int i, atomic_t *v) \
static inline void generic_atomic_##op(int i, atomic_t *v) \
{ \
unsigned long flags; \
+ int c; \
\
raw_local_irq_save(flags); \
- v->counter = v->counter c_op i; \
+ c = arch_atomic_read(v); \
+ arch_atomic_set(v, c c_op i); \
raw_local_irq_restore(flags); \
}
@@ -68,27 +73,28 @@ static inline void generic_atomic_##op(int i, atomic_t *v) \
static inline int generic_atomic_##op##_return(int i, atomic_t *v) \
{ \
unsigned long flags; \
- int ret; \
+ int c; \
\
raw_local_irq_save(flags); \
- ret = (v->counter = v->counter c_op i); \
+ c = arch_atomic_read(v); \
+ arch_atomic_set(v, c c_op i); \
raw_local_irq_restore(flags); \
\
- return ret; \
+ return c c_op i; \
}
#define ATOMIC_FETCH_OP(op, c_op) \
static inline int generic_atomic_fetch_##op(int i, atomic_t *v) \
{ \
unsigned long flags; \
- int ret; \
+ int c; \
\
raw_local_irq_save(flags); \
- ret = v->counter; \
- v->counter = v->counter c_op i; \
+ c = arch_atomic_read(v); \
+ arch_atomic_set(v, c c_op i); \
raw_local_irq_restore(flags); \
\
- return ret; \
+ return c; \
}
#endif /* CONFIG_SMP */
@@ -127,9 +133,6 @@ ATOMIC_OP(xor, ^)
#define arch_atomic_or generic_atomic_or
#define arch_atomic_xor generic_atomic_xor
-#define arch_atomic_read(v) READ_ONCE((v)->counter)
-#define arch_atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
-
#define arch_atomic_xchg(ptr, v) (arch_xchg(&(ptr)->counter, (v)))
#define arch_atomic_cmpxchg(v, old, new) (arch_cmpxchg(&((v)->counter), (old), (new)))
--
2.17.1
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