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 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 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