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authorPeter Zijlstra <peterz@infradead.org>2016-04-18 02:16:03 +0300
committerIngo Molnar <mingo@kernel.org>2016-06-16 11:48:31 +0300
commita8bcccaba162632c3963259b8a442c6b490f4c68 (patch)
treed44f5e4ab5ff4f56e444352a18fd00716a69a7af /arch/x86/include/asm/atomic64_64.h
parent1af5de9af138941fb8638cf126293b16f3387de4 (diff)
downloadlinux-a8bcccaba162632c3963259b8a442c6b490f4c68.tar.xz
locking/atomic, arch/x86: Implement atomic{,64}_fetch_{add,sub,and,or,xor}()
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@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-arch@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/include/asm/atomic64_64.h')
-rw-r--r--arch/x86/include/asm/atomic64_64.h35
1 files changed, 32 insertions, 3 deletions
diff --git a/arch/x86/include/asm/atomic64_64.h b/arch/x86/include/asm/atomic64_64.h
index 037351022f54..70eed0e14553 100644
--- 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(long i, atomic64_t *v)
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, atomic64_t *v) \
: "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 */