2 * Copyright (C) 2005, 2007, 2008 Internet Systems Consortium, Inc. ("ISC")
4 * Permission to use, copy, modify, and/or distribute this software for any
5 * purpose with or without fee is hereby granted, provided that the above
6 * copyright notice and this permission notice appear in all copies.
8 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
9 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
10 * AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
11 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
12 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
13 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
14 * PERFORMANCE OF THIS SOFTWARE.
17 /* $Id: atomic.h,v 1.10 2008/01/24 23:47:00 tbox Exp $ */
20 #define ISC_ATOMIC_H 1
22 #include <isc/platform.h>
23 #include <isc/types.h>
25 #ifdef ISC_PLATFORM_USEGCCASM
27 * This routine atomically increments the value stored in 'p' by 'val', and
28 * returns the previous value.
30 static __inline__ isc_int32_t
31 isc_atomic_xadd(isc_int32_t *p, isc_int32_t val) {
32 isc_int32_t prev = val;
35 #ifdef ISC_PLATFORM_USETHREADS
46 #ifdef ISC_PLATFORM_HAVEXADDQ
47 static __inline__ isc_int64_t
48 isc_atomic_xaddq(isc_int64_t *p, isc_int64_t val) {
49 isc_int64_t prev = val;
52 #ifdef ISC_PLATFORM_USETHREADS
62 #endif /* ISC_PLATFORM_HAVEXADDQ */
65 * This routine atomically stores the value 'val' in 'p'.
67 static __inline__ void
68 isc_atomic_store(isc_int32_t *p, isc_int32_t val) {
70 #ifdef ISC_PLATFORM_USETHREADS
72 * xchg should automatically lock memory, but we add it
73 * explicitly just in case (it at least doesn't harm)
85 * This routine atomically replaces the value in 'p' with 'val', if the
86 * original value is equal to 'cmpval'. The original value is returned in any
89 static __inline__ isc_int32_t
90 isc_atomic_cmpxchg(isc_int32_t *p, isc_int32_t cmpval, isc_int32_t val) {
92 #ifdef ISC_PLATFORM_USETHREADS
97 : "r"(val), "m"(*p), "a"(cmpval)
103 #elif defined(ISC_PLATFORM_USESTDASM)
105 * The followings are "generic" assembly code which implements the same
106 * functionality in case the gcc extension cannot be used. It should be
107 * better to avoid inlining below, since we directly refer to specific
108 * positions of the stack frame, which would not actually point to the
109 * intended address in the embedded mnemonic.
111 #include <isc/util.h> /* for 'UNUSED' macro */
114 isc_atomic_xadd(isc_int32_t *p, isc_int32_t val) {
119 "movl 8(%ebp), %ecx\n"
120 "movl 12(%ebp), %edx\n"
121 #ifdef ISC_PLATFORM_USETHREADS
124 "xadd %edx, (%ecx)\n"
127 * set the return value directly in the register so that we
128 * can avoid guessing the correct position in the stack for a
136 isc_atomic_store(isc_int32_t *p, isc_int32_t val) {
141 "movl 8(%ebp), %ecx\n"
142 "movl 12(%ebp), %edx\n"
143 #ifdef ISC_PLATFORM_USETHREADS
146 "xchgl (%ecx), %edx\n"
151 isc_atomic_cmpxchg(isc_int32_t *p, isc_int32_t cmpval, isc_int32_t val) {
157 "movl 8(%ebp), %ecx\n"
158 "movl 12(%ebp), %eax\n" /* must be %eax for cmpxchgl */
159 "movl 16(%ebp), %edx\n"
160 #ifdef ISC_PLATFORM_USETHREADS
165 * If (%ecx) == %eax then (%ecx) := %edx.
166 % %eax is set to old (%ecx), which will be the return value.
168 "cmpxchgl %edx, (%ecx)"
171 #else /* !ISC_PLATFORM_USEGCCASM && !ISC_PLATFORM_USESTDASM */
173 #error "unsupported compiler. disable atomic ops by --disable-atomic"
176 #endif /* ISC_ATOMIC_H */