kern_condvar.c revision 136445
1/*- 2 * Copyright (c) 2000 Jake Burkholder <jake@freebsd.org>. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 */ 26 27#include <sys/cdefs.h> 28__FBSDID("$FreeBSD: head/sys/kern/kern_condvar.c 136445 2004-10-12 18:36:20Z jhb $"); 29 30#include "opt_ktrace.h" 31 32#include <sys/param.h> 33#include <sys/systm.h> 34#include <sys/lock.h> 35#include <sys/mutex.h> 36#include <sys/proc.h> 37#include <sys/kernel.h> 38#include <sys/ktr.h> 39#include <sys/condvar.h> 40#include <sys/sched.h> 41#include <sys/signalvar.h> 42#include <sys/sleepqueue.h> 43#include <sys/resourcevar.h> 44#ifdef KTRACE 45#include <sys/uio.h> 46#include <sys/ktrace.h> 47#endif 48 49/* 50 * Common sanity checks for cv_wait* functions. 51 */ 52#define CV_ASSERT(cvp, mp, td) do { \ 53 KASSERT((td) != NULL, ("%s: curthread NULL", __func__)); \ 54 KASSERT(TD_IS_RUNNING(td), ("%s: not TDS_RUNNING", __func__)); \ 55 KASSERT((cvp) != NULL, ("%s: cvp NULL", __func__)); \ 56 KASSERT((mp) != NULL, ("%s: mp NULL", __func__)); \ 57 mtx_assert((mp), MA_OWNED | MA_NOTRECURSED); \ 58} while (0) 59 60/* 61 * Initialize a condition variable. Must be called before use. 62 */ 63void 64cv_init(struct cv *cvp, const char *desc) 65{ 66 67 cvp->cv_description = desc; 68 cvp->cv_waiters = 0; 69} 70 71/* 72 * Destroy a condition variable. The condition variable must be re-initialized 73 * in order to be re-used. 74 */ 75void 76cv_destroy(struct cv *cvp) 77{ 78#ifdef INVARIANTS 79 struct sleepqueue *sq; 80 81 sleepq_lock(cvp); 82 sq = sleepq_lookup(cvp); 83 sleepq_release(cvp); 84 KASSERT(sq == NULL, ("%s: associated sleep queue non-empty", __func__)); 85#endif 86} 87 88/* 89 * Wait on a condition variable. The current thread is placed on the condition 90 * variable's wait queue and suspended. A cv_signal or cv_broadcast on the same 91 * condition variable will resume the thread. The mutex is released before 92 * sleeping and will be held on return. It is recommended that the mutex be 93 * held when cv_signal or cv_broadcast are called. 94 */ 95void 96cv_wait(struct cv *cvp, struct mtx *mp) 97{ 98 struct thread *td; 99 WITNESS_SAVE_DECL(mp); 100 101 td = curthread; 102#ifdef KTRACE 103 if (KTRPOINT(td, KTR_CSW)) 104 ktrcsw(1, 0); 105#endif 106 CV_ASSERT(cvp, mp, td); 107 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, &mp->mtx_object, 108 "Waiting on \"%s\"", cvp->cv_description); 109 WITNESS_SAVE(&mp->mtx_object, mp); 110 111 if (cold || panicstr) { 112 /* 113 * During autoconfiguration, just give interrupts 114 * a chance, then just return. Don't run any other 115 * thread or panic below, in case this is the idle 116 * process and already asleep. 117 */ 118 return; 119 } 120 121 sleepq_lock(cvp); 122 123 cvp->cv_waiters++; 124 DROP_GIANT(); 125 mtx_unlock(mp); 126 127 sleepq_add(cvp, mp, cvp->cv_description, SLEEPQ_CONDVAR); 128 sleepq_wait(cvp); 129 130#ifdef KTRACE 131 if (KTRPOINT(td, KTR_CSW)) 132 ktrcsw(0, 0); 133#endif 134 PICKUP_GIANT(); 135 mtx_lock(mp); 136 WITNESS_RESTORE(&mp->mtx_object, mp); 137} 138 139/* 140 * Wait on a condition variable, allowing interruption by signals. Return 0 if 141 * the thread was resumed with cv_signal or cv_broadcast, EINTR or ERESTART if 142 * a signal was caught. If ERESTART is returned the system call should be 143 * restarted if possible. 144 */ 145int 146cv_wait_sig(struct cv *cvp, struct mtx *mp) 147{ 148 struct thread *td; 149 struct proc *p; 150 int rval, sig; 151 WITNESS_SAVE_DECL(mp); 152 153 td = curthread; 154 p = td->td_proc; 155#ifdef KTRACE 156 if (KTRPOINT(td, KTR_CSW)) 157 ktrcsw(1, 0); 158#endif 159 CV_ASSERT(cvp, mp, td); 160 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, &mp->mtx_object, 161 "Waiting on \"%s\"", cvp->cv_description); 162 WITNESS_SAVE(&mp->mtx_object, mp); 163 164 if (cold || panicstr) { 165 /* 166 * After a panic, or during autoconfiguration, just give 167 * interrupts a chance, then just return; don't run any other 168 * procs or panic below, in case this is the idle process and 169 * already asleep. 170 */ 171 return (0); 172 } 173 174 sleepq_lock(cvp); 175 176 /* 177 * Don't bother sleeping if we are exiting and not the exiting 178 * thread or if our thread is marked as interrupted. 179 */ 180 mtx_lock_spin(&sched_lock); 181 rval = thread_sleep_check(td); 182 mtx_unlock_spin(&sched_lock); 183 if (rval != 0) { 184 sleepq_release(cvp); 185 return (rval); 186 } 187 188 cvp->cv_waiters++; 189 DROP_GIANT(); 190 mtx_unlock(mp); 191 192 sleepq_add(cvp, mp, cvp->cv_description, SLEEPQ_CONDVAR | 193 SLEEPQ_INTERRUPTIBLE); 194 sig = sleepq_catch_signals(cvp); 195 rval = sleepq_wait_sig(cvp); 196 if (rval == 0) 197 rval = sleepq_calc_signal_retval(sig); 198 199#ifdef KTRACE 200 if (KTRPOINT(td, KTR_CSW)) 201 ktrcsw(0, 0); 202#endif 203 PICKUP_GIANT(); 204 mtx_lock(mp); 205 WITNESS_RESTORE(&mp->mtx_object, mp); 206 207 return (rval); 208} 209 210/* 211 * Wait on a condition variable for at most timo/hz seconds. Returns 0 if the 212 * process was resumed by cv_signal or cv_broadcast, EWOULDBLOCK if the timeout 213 * expires. 214 */ 215int 216cv_timedwait(struct cv *cvp, struct mtx *mp, int timo) 217{ 218 struct thread *td; 219 int rval; 220 WITNESS_SAVE_DECL(mp); 221 222 td = curthread; 223 rval = 0; 224#ifdef KTRACE 225 if (KTRPOINT(td, KTR_CSW)) 226 ktrcsw(1, 0); 227#endif 228 CV_ASSERT(cvp, mp, td); 229 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, &mp->mtx_object, 230 "Waiting on \"%s\"", cvp->cv_description); 231 WITNESS_SAVE(&mp->mtx_object, mp); 232 233 if (cold || panicstr) { 234 /* 235 * After a panic, or during autoconfiguration, just give 236 * interrupts a chance, then just return; don't run any other 237 * thread or panic below, in case this is the idle process and 238 * already asleep. 239 */ 240 return 0; 241 } 242 243 sleepq_lock(cvp); 244 245 cvp->cv_waiters++; 246 DROP_GIANT(); 247 mtx_unlock(mp); 248 249 sleepq_add(cvp, mp, cvp->cv_description, SLEEPQ_CONDVAR); 250 sleepq_set_timeout(cvp, timo); 251 rval = sleepq_timedwait(cvp); 252 253#ifdef KTRACE 254 if (KTRPOINT(td, KTR_CSW)) 255 ktrcsw(0, 0); 256#endif 257 PICKUP_GIANT(); 258 mtx_lock(mp); 259 WITNESS_RESTORE(&mp->mtx_object, mp); 260 261 return (rval); 262} 263 264/* 265 * Wait on a condition variable for at most timo/hz seconds, allowing 266 * interruption by signals. Returns 0 if the thread was resumed by cv_signal 267 * or cv_broadcast, EWOULDBLOCK if the timeout expires, and EINTR or ERESTART if 268 * a signal was caught. 269 */ 270int 271cv_timedwait_sig(struct cv *cvp, struct mtx *mp, int timo) 272{ 273 struct thread *td; 274 struct proc *p; 275 int rval; 276 int sig; 277 WITNESS_SAVE_DECL(mp); 278 279 td = curthread; 280 p = td->td_proc; 281 rval = 0; 282#ifdef KTRACE 283 if (KTRPOINT(td, KTR_CSW)) 284 ktrcsw(1, 0); 285#endif 286 CV_ASSERT(cvp, mp, td); 287 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, &mp->mtx_object, 288 "Waiting on \"%s\"", cvp->cv_description); 289 WITNESS_SAVE(&mp->mtx_object, mp); 290 291 if (cold || panicstr) { 292 /* 293 * After a panic, or during autoconfiguration, just give 294 * interrupts a chance, then just return; don't run any other 295 * thread or panic below, in case this is the idle process and 296 * already asleep. 297 */ 298 return 0; 299 } 300 301 sleepq_lock(cvp); 302 303 /* 304 * Don't bother sleeping if we are exiting and not the exiting 305 * thread or if our thread is marked as interrupted. 306 */ 307 mtx_lock_spin(&sched_lock); 308 rval = thread_sleep_check(td); 309 mtx_unlock_spin(&sched_lock); 310 if (rval != 0) { 311 sleepq_release(cvp); 312 return (rval); 313 } 314 315 cvp->cv_waiters++; 316 DROP_GIANT(); 317 mtx_unlock(mp); 318 319 sleepq_add(cvp, mp, cvp->cv_description, SLEEPQ_CONDVAR | 320 SLEEPQ_INTERRUPTIBLE); 321 sleepq_set_timeout(cvp, timo); 322 sig = sleepq_catch_signals(cvp); 323 rval = sleepq_timedwait_sig(cvp, sig != 0); 324 if (rval == 0) 325 rval = sleepq_calc_signal_retval(sig); 326 327#ifdef KTRACE 328 if (KTRPOINT(td, KTR_CSW)) 329 ktrcsw(0, 0); 330#endif 331 PICKUP_GIANT(); 332 mtx_lock(mp); 333 WITNESS_RESTORE(&mp->mtx_object, mp); 334 335 return (rval); 336} 337 338/* 339 * Signal a condition variable, wakes up one waiting thread. Will also wakeup 340 * the swapper if the process is not in memory, so that it can bring the 341 * sleeping process in. Note that this may also result in additional threads 342 * being made runnable. Should be called with the same mutex as was passed to 343 * cv_wait held. 344 */ 345void 346cv_signal(struct cv *cvp) 347{ 348 349 sleepq_lock(cvp); 350 if (cvp->cv_waiters > 0) { 351 cvp->cv_waiters--; 352 sleepq_signal(cvp, SLEEPQ_CONDVAR, -1); 353 } else 354 sleepq_release(cvp); 355} 356 357/* 358 * Broadcast a signal to a condition variable. Wakes up all waiting threads. 359 * Should be called with the same mutex as was passed to cv_wait held. 360 */ 361void 362cv_broadcastpri(struct cv *cvp, int pri) 363{ 364 365 sleepq_lock(cvp); 366 if (cvp->cv_waiters > 0) { 367 cvp->cv_waiters = 0; 368 sleepq_broadcast(cvp, SLEEPQ_CONDVAR, pri); 369 } else 370 sleepq_release(cvp); 371} 372