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/*
* Copyright (C) 2005, 2007, 2008 Internet Systems Consortium, Inc. ("ISC")
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
* REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
* INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
* LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
* OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
* PERFORMANCE OF THIS SOFTWARE.
*/
/* $Id: atomic.h,v 1.10 2008/01/24 23:47:00 tbox Exp $ */
#ifndef ISC_ATOMIC_H
#define ISC_ATOMIC_H 1
#include <isc/platform.h>
#include <isc/types.h>
#ifdef ISC_PLATFORM_USEGCCASM
/*
* This routine atomically increments the value stored in 'p' by 'val', and
* returns the previous value.
*/
static __inline__ isc_int32_t
isc_atomic_xadd(isc_int32_t *p, isc_int32_t val) {
isc_int32_t prev = val;
__asm__ volatile(
#ifdef ISC_PLATFORM_USETHREADS
"lock;"
#endif
"xadd %0, %1"
:"=q"(prev)
:"m"(*p), "0"(prev)
:"memory", "cc");
return (prev);
}
#ifdef ISC_PLATFORM_HAVEXADDQ
static __inline__ isc_int64_t
isc_atomic_xaddq(isc_int64_t *p, isc_int64_t val) {
isc_int64_t prev = val;
__asm__ volatile(
#ifdef ISC_PLATFORM_USETHREADS
"lock;"
#endif
"xaddq %0, %1"
:"=q"(prev)
:"m"(*p), "0"(prev)
:"memory", "cc");
return (prev);
}
#endif /* ISC_PLATFORM_HAVEXADDQ */
/*
* This routine atomically stores the value 'val' in 'p'.
*/
static __inline__ void
isc_atomic_store(isc_int32_t *p, isc_int32_t val) {
__asm__ volatile(
#ifdef ISC_PLATFORM_USETHREADS
/*
* xchg should automatically lock memory, but we add it
* explicitly just in case (it at least doesn't harm)
*/
"lock;"
#endif
"xchgl %1, %0"
:
: "r"(val), "m"(*p)
: "memory");
}
/*
* This routine atomically replaces the value in 'p' with 'val', if the
* original value is equal to 'cmpval'. The original value is returned in any
* case.
*/
static __inline__ isc_int32_t
isc_atomic_cmpxchg(isc_int32_t *p, isc_int32_t cmpval, isc_int32_t val) {
__asm__ volatile(
#ifdef ISC_PLATFORM_USETHREADS
"lock;"
#endif
"cmpxchgl %1, %2"
: "=a"(cmpval)
: "r"(val), "m"(*p), "a"(cmpval)
: "memory");
return (cmpval);
}
#elif defined(ISC_PLATFORM_USESTDASM)
/*
* The followings are "generic" assembly code which implements the same
* functionality in case the gcc extension cannot be used. It should be
* better to avoid inlining below, since we directly refer to specific
* positions of the stack frame, which would not actually point to the
* intended address in the embedded mnemonic.
*/
#include <isc/util.h> /* for 'UNUSED' macro */
static isc_int32_t
isc_atomic_xadd(isc_int32_t *p, isc_int32_t val) {
UNUSED(p);
UNUSED(val);
__asm (
"movl 8(%ebp), %ecx\n"
"movl 12(%ebp), %edx\n"
#ifdef ISC_PLATFORM_USETHREADS
"lock;"
#endif
"xadd %edx, (%ecx)\n"
/*
* set the return value directly in the register so that we
* can avoid guessing the correct position in the stack for a
* local variable.
*/
"movl %edx, %eax"
);
}
static void
isc_atomic_store(isc_int32_t *p, isc_int32_t val) {
UNUSED(p);
UNUSED(val);
__asm (
"movl 8(%ebp), %ecx\n"
"movl 12(%ebp), %edx\n"
#ifdef ISC_PLATFORM_USETHREADS
"lock;"
#endif
"xchgl (%ecx), %edx\n"
);
}
static isc_int32_t
isc_atomic_cmpxchg(isc_int32_t *p, isc_int32_t cmpval, isc_int32_t val) {
UNUSED(p);
UNUSED(cmpval);
UNUSED(val);
__asm (
"movl 8(%ebp), %ecx\n"
"movl 12(%ebp), %eax\n" /* must be %eax for cmpxchgl */
"movl 16(%ebp), %edx\n"
#ifdef ISC_PLATFORM_USETHREADS
"lock;"
#endif
/*
* If (%ecx) == %eax then (%ecx) := %edx.
% %eax is set to old (%ecx), which will be the return value.
*/
"cmpxchgl %edx, (%ecx)"
);
}
#else /* !ISC_PLATFORM_USEGCCASM && !ISC_PLATFORM_USESTDASM */
#error "unsupported compiler. disable atomic ops by --disable-atomic"
#endif
#endif /* ISC_ATOMIC_H */
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