Implement FETCH-OP atomic primitives, these are very similar to the
existing OP-RETURN primitives we already have, except they return the
value of the atomic variable _before_ modification.
This is especially useful for irreversible operations -- such as
bitops (because it becomes impossible to reconstruct the state prior
to modification).
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
arch/x86/include/asm/atomic.h | 37 ++++++++++++++++++++++++++++++++++---
arch/x86/include/asm/atomic64_32.h | 25 ++++++++++++++++++++++---
arch/x86/include/asm/atomic64_64.h | 35 ++++++++++++++++++++++++++++++++---
3 files changed, 88 insertions(+), 9 deletions(-)
--- a/arch/x86/include/asm/atomic.h
+++ b/arch/x86/include/asm/atomic.h
@@ -171,6 +171,16 @@ static __always_inline int atomic_sub_re
#define atomic_inc_return(v) (atomic_add_return(1, v))
#define atomic_dec_return(v) (atomic_sub_return(1, v))
+static __always_inline int atomic_fetch_add(int i, atomic_t *v)
+{
+ return xadd(&v->counter, i);
+}
+
+static __always_inline int atomic_fetch_sub(int i, atomic_t *v)
+{
+ return xadd(&v->counter, -i);
+}
+
static __always_inline int atomic_cmpxchg(atomic_t *v, int old, int new)
{
return cmpxchg(&v->counter, old, new);
@@ -190,10 +200,31 @@ static inline void atomic_##op(int i, at
: "memory"); \
}
-ATOMIC_OP(and)
-ATOMIC_OP(or)
-ATOMIC_OP(xor)
+#define ATOMIC_FETCH_OP(op, c_op) \
+static inline int atomic_fetch_##op(int i, atomic_t *v) \
+{ \
+ int old, val = atomic_read(v); \
+ for (;;) { \
+ old = atomic_cmpxchg(v, val, val c_op i); \
+ if (old == val) \
+ break; \
+ val = old; \
+ } \
+ return old; \
+}
+
+#define ATOMIC_OPS(op, c_op) \
+ ATOMIC_OP(op) \
+ ATOMIC_FETCH_OP(op, c_op)
+
+#define atomic_fetch_or atomic_fetch_or
+
+ATOMIC_OPS(and, &)
+ATOMIC_OPS(or , |)
+ATOMIC_OPS(xor, ^)
+#undef ATOMIC_OPS
+#undef ATOMIC_FETCH_OP
#undef ATOMIC_OP
/**
--- a/arch/x86/include/asm/atomic64_32.h
+++ b/arch/x86/include/asm/atomic64_32.h
@@ -320,10 +320,29 @@ static inline void atomic64_##op(long lo
c = old; \
}
-ATOMIC64_OP(and, &)
-ATOMIC64_OP(or, |)
-ATOMIC64_OP(xor, ^)
+#define ATOMIC64_FETCH_OP(op, c_op) \
+static inline long long atomic64_fetch_##op(long long i, atomic64_t *v) \
+{ \
+ long long old, c = 0; \
+ while ((old = atomic64_cmpxchg(v, c, c c_op i)) != c) \
+ c = old; \
+ return old; \
+}
+
+ATOMIC64_FETCH_OP(add, +)
+
+#define atomic64_fetch_sub(i, v) atomic64_fetch_add(-(i), (v))
+
+#define ATOMIC64_OPS(op, c_op) \
+ ATOMIC64_OP(op, c_op) \
+ ATOMIC64_FETCH_OP(op, c_op)
+
+ATOMIC64_OPS(and, &)
+ATOMIC64_OPS(or, |)
+ATOMIC64_OPS(xor, ^)
+#undef ATOMIC64_OPS
+#undef ATOMIC64_FETCH_OP
#undef ATOMIC64_OP
#endif /* _ASM_X86_ATOMIC64_32_H */
--- a/arch/x86/include/asm/atomic64_64.h
+++ b/arch/x86/include/asm/atomic64_64.h
@@ -158,6 +158,16 @@ static inline long atomic64_sub_return(l
return atomic64_add_return(-i, v);
}
+static inline long atomic64_fetch_add(long i, atomic64_t *v)
+{
+ return xadd(&v->counter, i);
+}
+
+static inline long atomic64_fetch_sub(long i, atomic64_t *v)
+{
+ return xadd(&v->counter, -i);
+}
+
#define atomic64_inc_return(v) (atomic64_add_return(1, (v)))
#define atomic64_dec_return(v) (atomic64_sub_return(1, (v)))
@@ -229,10 +239,29 @@ static inline void atomic64_##op(long i,
: "memory"); \
}
-ATOMIC64_OP(and)
-ATOMIC64_OP(or)
-ATOMIC64_OP(xor)
+#define ATOMIC64_FETCH_OP(op, c_op) \
+static inline long atomic64_fetch_##op(long i, atomic64_t *v) \
+{ \
+ long old, val = atomic64_read(v); \
+ for (;;) { \
+ old = atomic64_cmpxchg(v, val, val c_op i); \
+ if (old == val) \
+ break; \
+ val = old; \
+ } \
+ return old; \
+}
+
+#define ATOMIC64_OPS(op, c_op) \
+ ATOMIC64_OP(op) \
+ ATOMIC64_FETCH_OP(op, c_op)
+
+ATOMIC64_OPS(and, &)
+ATOMIC64_OPS(or, |)
+ATOMIC64_OPS(xor, ^)
+#undef ATOMIC64_OPS
+#undef ATOMIC64_FETCH_OP
#undef ATOMIC64_OP
#endif /* _ASM_X86_ATOMIC64_64_H */
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