1 /*-
2 * Copyright (c) 2005 David Xu <davidxu@freebsd.org>
3 * Copyright (c) 2005 Matthew Dillon <dillon@backplane.com>
4 *
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #include <assert.h>
30 #include <errno.h>
31 #include <unistd.h>
32 #include <sys/time.h>
33
34 #include "sysvipc_lock_generic.h"
35
36 /*
37 * This function is used to acquire a contested lock.
38 */
39 int
__sysv_umtx_lock(volatile umtx_t * mtx,int timo)40 __sysv_umtx_lock(volatile umtx_t *mtx, int timo)
41 {
42 int v, errval, ret = 0;
43
44 /* contested */
45 do {
46 v = *mtx;
47 if (v == 2 || atomic_cmpset_acq_int(mtx, 1, 2)) {
48 if (timo == 0)
49 umtx_sleep(mtx, 2, timo);
50 else if ( (errval = umtx_sleep(mtx, 2, timo)) > 0) {
51 if (errval == EAGAIN) {
52 if (atomic_cmpset_acq_int(mtx, 0, 2))
53 ret = 0;
54 else
55 ret = ETIMEDOUT;
56 break;
57 }
58 }
59 }
60 } while (!atomic_cmpset_acq_int(mtx, 0, 2));
61
62 return (ret);
63 }
64
65 void
__sysv_umtx_unlock(volatile umtx_t * mtx)66 __sysv_umtx_unlock(volatile umtx_t *mtx)
67 {
68 int v;
69
70 for (;;) {
71 v = *mtx;
72 if (atomic_cmpset_acq_int(mtx, v, v-1)) {
73 if (v != 1) {
74 *mtx = 0;
75 umtx_wakeup(mtx, 1);
76 }
77 break;
78 }
79 }
80 }
81