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Subjectatomic64_t proposal
I'm proposing the creation of an atomic64_t variable, which is a 64-bit
version of atomic_t, and the usage of the __typeof__ keyword in macro versions
of the atomic operations to enable them to operate on either type (atomic_t and
atomic64_t).

I submitted the following patch to David Mosberger to be considered for
inclusion in the IA-64 linux kernel. He suggested that I bring the topic up
on this list so that the other 64-bit platform maintainers can commment.

Thanks,
Dean


==============================================================================
diff -Naur 2.4.18-ia64/linux/include/asm-ia64/atomic.h linux/linux/include/asm-ia64/atomic.h
--- 2.4.18-ia64/linux/include/asm-ia64/atomic.h Wed Jul 17 07:12:34 2002
+++ linux/linux/include/asm-ia64/atomic.h Wed Aug 21 18:12:13 2002
@@ -5,10 +5,6 @@
* Atomic operations that C can't guarantee us. Useful for
* resource counting etc..
*
- * NOTE: don't mess with the types below! The "unsigned long" and
- * "int" types were carefully placed so as to ensure proper operation
- * of the macros.
- *
* Copyright (C) 1998, 1999, 2002 Hewlett-Packard Co
* David Mosberger-Tang <davidm@hpl.hp.com>
*/
@@ -21,63 +17,59 @@
* memory accesses are ordered.
*/
typedef struct { volatile __s32 counter; } atomic_t;
+typedef struct { volatile __s64 counter; } atomic64_t;

#define ATOMIC_INIT(i) ((atomic_t) { (i) })
+#define ATOMIC64_INIT(i) ((atomic64_t) { (i) })

#define atomic_read(v) ((v)->counter)
#define atomic_set(v,i) (((v)->counter) = (i))

-static __inline__ int
-ia64_atomic_add (int i, atomic_t *v)
-{
- __s32 old, new;
- CMPXCHG_BUGCHECK_DECL
-
- do {
- CMPXCHG_BUGCHECK(v);
- old = atomic_read(v);
- new = old + i;
- } while (ia64_cmpxchg("acq", v, old, old + i, sizeof(atomic_t)) != old);
- return new;
-}
-
-static __inline__ int
-ia64_atomic_sub (int i, atomic_t *v)
-{
- __s32 old, new;
- CMPXCHG_BUGCHECK_DECL
-
- do {
- CMPXCHG_BUGCHECK(v);
- old = atomic_read(v);
- new = old - i;
- } while (ia64_cmpxchg("acq", v, old, new, sizeof(atomic_t)) != old);
- return new;
-}
+#define ia64_atomic_add(i,v) \
+({ \
+ __typeof__((v)->counter) _old, _new; \
+ CMPXCHG_BUGCHECK_DECL \
+ \
+ do { \
+ CMPXCHG_BUGCHECK(v); \
+ _old = atomic_read(v); \
+ _new = _old + (i); \
+ } while (ia64_cmpxchg("acq", (v), _old, _new, sizeof(*(v))) != _old); \
+ (__typeof__((v)->counter)) _new; /* return new value */ \
+})
+
+#define ia64_atomic_sub(i,v) \
+({ \
+ __typeof__((v)->counter) _old, _new; \
+ CMPXCHG_BUGCHECK_DECL \
+ \
+ do { \
+ CMPXCHG_BUGCHECK(v); \
+ _old = atomic_read(v); \
+ _new = _old - (i); \
+ } while (ia64_cmpxchg("acq", (v), _old, _new, sizeof(*(v))) != _old); \
+ (__typeof__((v)->counter)) _new; /* return new value */ \
+})

/*
* Atomically add I to V and return TRUE if the resulting value is
* negative.
*/
-static __inline__ int
-atomic_add_negative (int i, atomic_t *v)
-{
- return ia64_atomic_add(i, v) < 0;
-}
+#define atomic_add_negative(i,v) (ia64_atomic_add((i), (v)) < 0)

#define atomic_add_return(i,v) \
((__builtin_constant_p(i) && \
( (i == 1) || (i == 4) || (i == 8) || (i == 16) \
|| (i == -1) || (i == -4) || (i == -8) || (i == -16))) \
? ia64_fetch_and_add(i, &(v)->counter) \
- : ia64_atomic_add(i, v))
+ : ia64_atomic_add((i), (v)))

#define atomic_sub_return(i,v) \
((__builtin_constant_p(i) && \
( (i == 1) || (i == 4) || (i == 8) || (i == 16) \
|| (i == -1) || (i == -4) || (i == -8) || (i == -16))) \
? ia64_fetch_and_add(-(i), &(v)->counter) \
- : ia64_atomic_sub(i, v))
+ : ia64_atomic_sub((i), (v)))

#define atomic_dec_return(v) atomic_sub_return(1, (v))
#define atomic_inc_return(v) atomic_add_return(1, (v))
==============================================================================
-
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