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 * $DragonFly: src/lib/libthread_xu/thread/thr_umtx.c,v 1.4 2008/04/14 20:12:41 dillon Exp $ 29 */ 30 31 #include <assert.h> 32 #include <errno.h> 33 #include <unistd.h> 34 #include <sys/time.h> 35 36 #include "sysvipc_lock_generic.h" 37 38 /* 39 * This function is used to acquire a contested lock. 40 */ 41 int 42 __sysv_umtx_lock(volatile umtx_t *mtx, int timo) 43 { 44 int v, errval, ret = 0; 45 46 /* contested */ 47 do { 48 v = *mtx; 49 if (v == 2 || atomic_cmpset_acq_int(mtx, 1, 2)) { 50 if (timo == 0) 51 umtx_sleep(mtx, 2, timo); 52 else if ( (errval = umtx_sleep(mtx, 2, timo)) > 0) { 53 if (errval == EAGAIN) { 54 if (atomic_cmpset_acq_int(mtx, 0, 2)) 55 ret = 0; 56 else 57 ret = ETIMEDOUT; 58 break; 59 } 60 } 61 } 62 } while (!atomic_cmpset_acq_int(mtx, 0, 2)); 63 64 return (ret); 65 } 66 67 void 68 __sysv_umtx_unlock(volatile umtx_t *mtx) 69 { 70 int v; 71 72 for (;;) { 73 v = *mtx; 74 if (atomic_cmpset_acq_int(mtx, v, v-1)) { 75 if (v != 1) { 76 *mtx = 0; 77 umtx_wakeup(mtx, 1); 78 } 79 break; 80 } 81 } 82 } 83