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 1.2 2005/03/15 11:24:23 davidxu Exp $ 29 */ 30 31 /* 32 * Part of these code is derived from /usr/src/test/debug/umtx.c. 33 */ 34 35 #include <assert.h> 36 #include <errno.h> 37 #include <unistd.h> 38 #include <sys/time.h> 39 40 #include "thr_private.h" 41 42 static int get_contested(volatile umtx_t *mtx, int timo); 43 44 int 45 __thr_umtx_lock(volatile umtx_t *mtx, int timo) 46 { 47 int v; 48 int ret; 49 50 for (;;) { 51 v = *mtx; 52 if ((v & UMTX_LOCKED) == 0) { 53 /* not locked, attempt to lock. */ 54 if (atomic_cmpset_acq_int(mtx, v, v | UMTX_LOCKED)) { 55 ret = 0; 56 break; 57 } 58 } else { 59 /* 60 * Locked, bump the contested count and obtain 61 * the contested mutex. 62 */ 63 if (atomic_cmpset_acq_int(mtx, v, v + 1)) { 64 ret = get_contested(mtx, timo); 65 break; 66 } 67 } 68 } 69 70 return (ret); 71 } 72 73 static int 74 get_contested(volatile umtx_t *mtx, int timo) 75 { 76 int ret = 0; 77 int v; 78 79 for (;;) { 80 v = *mtx; 81 assert(v & ~UMTX_LOCKED); /* our contesting count still there */ 82 if ((v & UMTX_LOCKED) == 0) { 83 /* 84 * Not locked, attempt to remove our contested 85 * count and lock at the same time. 86 */ 87 if (atomic_cmpset_acq_int(mtx, v, (v - 1) | UMTX_LOCKED)) { 88 ret = 0; 89 break; 90 } 91 } else { 92 /* 93 * Retried after resuming from umtx_sleep, try to leave if there 94 * was error, e.g, timeout. 95 */ 96 if (ret) { 97 if (atomic_cmpset_acq_int(mtx, v, v - 1)) 98 break; 99 else 100 continue; 101 } 102 103 /* 104 * Still locked, sleep and try again. 105 */ 106 if (timo == 0) { 107 umtx_sleep(mtx, v, 0); 108 } else { 109 if (umtx_sleep(mtx, v, timo) < 0) { 110 if (errno == EAGAIN) 111 ret = ETIMEDOUT; 112 } 113 } 114 } 115 } 116 117 return (ret); 118 } 119 120 void 121 __thr_umtx_unlock(volatile umtx_t *mtx) 122 { 123 int v; 124 125 for (;;) { 126 v = *mtx; 127 assert(v & UMTX_LOCKED); /* we still have it locked */ 128 if (v == UMTX_LOCKED) { 129 /* 130 * We hold an uncontested lock, try to set to an unlocked 131 * state. 132 */ 133 if (atomic_cmpset_acq_int(mtx, UMTX_LOCKED, 0)) 134 return; 135 } else { 136 /* 137 * We hold a contested lock, unlock and wakeup exactly 138 * one sleeper. It is possible for this to race a new 139 * thread obtaining a lock, in which case any contested 140 * sleeper we wake up will simply go back to sleep. 141 */ 142 if (atomic_cmpset_acq_int(mtx, v, v & ~UMTX_LOCKED)) { 143 umtx_wakeup(mtx, 1); 144 return; 145 } 146 } 147 } 148 } 149 150 int 151 __thr_umtx_timedlock(volatile umtx_t *mtx, const struct timespec *timeout) 152 { 153 struct timespec ts, ts2, ts3; 154 int timo, ret; 155 156 if ((timeout->tv_sec < 0) || 157 (timeout->tv_sec == 0 && timeout->tv_nsec <= 0)) 158 return (ETIMEDOUT); 159 160 /* XXX there should have MONO timer! */ 161 clock_gettime(CLOCK_REALTIME, &ts); 162 TIMESPEC_ADD(&ts, &ts, timeout); 163 ts2 = *timeout; 164 165 for (;;) { 166 if (ts2.tv_nsec) { 167 timo = (int)(ts2.tv_nsec / 1000); 168 if (timo == 0) 169 timo = 1; 170 } else { 171 timo = 1000000; 172 } 173 ret = __thr_umtx_lock(mtx, timo); 174 if (ret != ETIMEDOUT) 175 break; 176 clock_gettime(CLOCK_REALTIME, &ts3); 177 TIMESPEC_SUB(&ts2, &ts, &ts3); 178 if (ts2.tv_sec < 0 || (ts2.tv_sec == 0 && ts2.tv_nsec <= 0)) { 179 ret = ETIMEDOUT; 180 break; 181 } 182 } 183 return (ret); 184 } 185 186 int 187 _thr_umtx_wait(volatile umtx_t *mtx, int exp, const struct timespec *timeout, 188 int clockid) 189 { 190 struct timespec ts, ts2, ts3; 191 int timo, ret = 0; 192 193 if (*mtx != exp) 194 return (0); 195 196 if (timeout == NULL) { 197 if (umtx_sleep(mtx, exp, 0) < 0) { 198 if (errno == EINTR) 199 ret = EINTR; 200 } 201 return (ret); 202 } 203 204 if ((timeout->tv_sec < 0) || 205 (timeout->tv_sec == 0 && timeout->tv_nsec <= 0)) 206 return (ETIMEDOUT); 207 208 clock_gettime(clockid, &ts); 209 TIMESPEC_ADD(&ts, &ts, timeout); 210 ts2 = *timeout; 211 212 for (;;) { 213 if (ts2.tv_nsec) { 214 timo = (int)(ts2.tv_nsec / 1000); 215 if (timo == 0) 216 timo = 1; 217 } else { 218 timo = 1000000; 219 } 220 if (umtx_sleep(mtx, exp, timo) < 0) { 221 if (errno == EBUSY) { 222 ret = 0; 223 break; 224 } else if (errno == EINTR) { 225 ret = EINTR; 226 break; 227 } 228 } 229 clock_gettime(clockid, &ts3); 230 TIMESPEC_SUB(&ts2, &ts, &ts3); 231 if (ts2.tv_sec < 0 || (ts2.tv_sec == 0 && ts2.tv_nsec <= 0)) { 232 ret = ETIMEDOUT; 233 break; 234 } 235 } 236 return (ret); 237 } 238 239 void _thr_umtx_wake(volatile umtx_t *mtx, int count) 240 { 241 umtx_wakeup(mtx, count); 242 } 243