2 * Copyright (C) 2005 Internet Systems Consortium, Inc. ("ISC")
4 * Permission to use, copy, modify, and 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 1.2.2.3 2005/07/27 04:23:33 marka 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
47 * This routine atomically stores the value 'val' in 'p'.
50 isc_atomic_store(isc_int32_t *p, isc_int32_t val) {
52 #ifdef ISC_PLATFORM_USETHREADS
54 * xchg should automatically lock memory, but we add it
55 * explicitly just in case (it at least doesn't harm)
67 * This routine atomically replaces the value in 'p' with 'val', if the
68 * original value is equal to 'cmpval'. The original value is returned in any
71 static inline isc_int32_t
72 isc_atomic_cmpxchg(isc_int32_t *p, isc_int32_t cmpval, isc_int32_t val) {
74 #ifdef ISC_PLATFORM_USETHREADS
79 : "r"(val), "m"(*p), "a"(cmpval)
85 #elif defined(ISC_PLATFORM_USESTDASM)
87 * The followings are "generic" assembly code which implements the same
88 * functionality in case the gcc extension cannot be used. It should be
89 * better to avoid inlining below, since we directly refer to specific
90 * positions of the stack frame, which would not actually point to the
91 * intended address in the embedded mnemonic.
93 #include <isc/util.h> /* for 'UNUSED' macro */
96 isc_atomic_xadd(isc_int32_t *p, isc_int32_t val) {
101 "movl 8(%ebp), %ecx\n"
102 "movl 12(%ebp), %edx\n"
103 #ifdef ISC_PLATFORM_USETHREADS
106 "xadd %edx, (%ecx)\n"
109 * set the return value directly in the register so that we
110 * can avoid guessing the correct position in the stack for a
118 isc_atomic_store(isc_int32_t *p, isc_int32_t val) {
123 "movl 8(%ebp), %ecx\n"
124 "movl 12(%ebp), %edx\n"
125 #ifdef ISC_PLATFORM_USETHREADS
128 "xchgl (%ecx), %edx\n"
133 isc_atomic_cmpxchg(isc_int32_t *p, isc_int32_t cmpval, isc_int32_t val) {
139 "movl 8(%ebp), %ecx\n"
140 "movl 12(%ebp), %eax\n" /* must be %eax for cmpxchgl */
141 "movl 16(%ebp), %edx\n"
142 #ifdef ISC_PLATFORM_USETHREADS
147 * If (%ecx) == %eax then (%ecx) := %edx.
148 % %eax is set to old (%ecx), which will be the return value.
150 "cmpxchgl %edx, (%ecx)"
153 #else /* !ISC_PLATFORM_USEGCCASM && !ISC_PLATFORM_USESTDASM */
155 #error "unsupported compiler. disable atomic ops by --disable-atomic"
158 #endif /* ISC_ATOMIC_H */