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: stable/11/sys/kern/kern_condvar.c 315386 2017-03-16 07:10:08Z mjg $"); 29 30#include "opt_ktrace.h" 31 32#include <sys/param.h> 33#include <sys/systm.h> 34#include <sys/limits.h> 35#include <sys/lock.h> 36#include <sys/mutex.h> 37#include <sys/proc.h> 38#include <sys/kernel.h> 39#include <sys/ktr.h> 40#include <sys/condvar.h> 41#include <sys/sched.h> 42#include <sys/signalvar.h> 43#include <sys/sleepqueue.h> 44#include <sys/resourcevar.h> 45#ifdef KTRACE 46#include <sys/uio.h> 47#include <sys/ktrace.h> 48#endif 49 50/* 51 * A bound below which cv_waiters is valid. Once cv_waiters reaches this bound, 52 * cv_signal must manually check the wait queue for threads. 53 */ 54#define CV_WAITERS_BOUND INT_MAX 55 56#define CV_WAITERS_INC(cvp) do { \ 57 if ((cvp)->cv_waiters < CV_WAITERS_BOUND) \ 58 (cvp)->cv_waiters++; \ 59} while (0) 60 61/* 62 * Common sanity checks for cv_wait* functions. 63 */ 64#define CV_ASSERT(cvp, lock, td) do { \ 65 KASSERT((td) != NULL, ("%s: td NULL", __func__)); \ 66 KASSERT(TD_IS_RUNNING(td), ("%s: not TDS_RUNNING", __func__)); \ 67 KASSERT((cvp) != NULL, ("%s: cvp NULL", __func__)); \ 68 KASSERT((lock) != NULL, ("%s: lock NULL", __func__)); \ 69} while (0) 70 71/* 72 * Initialize a condition variable. Must be called before use. 73 */ 74void 75cv_init(struct cv *cvp, const char *desc) 76{ 77 78 cvp->cv_description = desc; 79 cvp->cv_waiters = 0; 80} 81 82/* 83 * Destroy a condition variable. The condition variable must be re-initialized 84 * in order to be re-used. 85 */ 86void 87cv_destroy(struct cv *cvp) 88{ 89#ifdef INVARIANTS 90 struct sleepqueue *sq; 91 92 sleepq_lock(cvp); 93 sq = sleepq_lookup(cvp); 94 sleepq_release(cvp); 95 KASSERT(sq == NULL, ("%s: associated sleep queue non-empty", __func__)); 96#endif 97} 98 99/* 100 * Wait on a condition variable. The current thread is placed on the condition 101 * variable's wait queue and suspended. A cv_signal or cv_broadcast on the same 102 * condition variable will resume the thread. The mutex is released before 103 * sleeping and will be held on return. It is recommended that the mutex be 104 * held when cv_signal or cv_broadcast are called. 105 */ 106void 107_cv_wait(struct cv *cvp, struct lock_object *lock) 108{ 109 WITNESS_SAVE_DECL(lock_witness); 110 struct lock_class *class; 111 struct thread *td; 112 uintptr_t lock_state; 113 114 td = curthread; 115 lock_state = 0; 116#ifdef KTRACE 117 if (KTRPOINT(td, KTR_CSW)) 118 ktrcsw(1, 0, cv_wmesg(cvp)); 119#endif 120 CV_ASSERT(cvp, lock, td); 121 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 122 "Waiting on \"%s\"", cvp->cv_description); 123 class = LOCK_CLASS(lock); 124 125 if (SCHEDULER_STOPPED_TD(td)) 126 return; 127 128 sleepq_lock(cvp); 129 130 CV_WAITERS_INC(cvp); 131 if (lock == &Giant.lock_object) 132 mtx_assert(&Giant, MA_OWNED); 133 DROP_GIANT(); 134 135 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0); 136 if (lock != &Giant.lock_object) { 137 if (class->lc_flags & LC_SLEEPABLE) 138 sleepq_release(cvp); 139 WITNESS_SAVE(lock, lock_witness); 140 lock_state = class->lc_unlock(lock); 141 if (class->lc_flags & LC_SLEEPABLE) 142 sleepq_lock(cvp); 143 } 144 sleepq_wait(cvp, 0); 145 146#ifdef KTRACE 147 if (KTRPOINT(td, KTR_CSW)) 148 ktrcsw(0, 0, cv_wmesg(cvp)); 149#endif 150 PICKUP_GIANT(); 151 if (lock != &Giant.lock_object) { 152 class->lc_lock(lock, lock_state); 153 WITNESS_RESTORE(lock, lock_witness); 154 } 155} 156 157/* 158 * Wait on a condition variable. This function differs from cv_wait by 159 * not acquiring the mutex after condition variable was signaled. 160 */ 161void 162_cv_wait_unlock(struct cv *cvp, struct lock_object *lock) 163{ 164 struct lock_class *class; 165 struct thread *td; 166 167 td = curthread; 168#ifdef KTRACE 169 if (KTRPOINT(td, KTR_CSW)) 170 ktrcsw(1, 0, cv_wmesg(cvp)); 171#endif 172 CV_ASSERT(cvp, lock, td); 173 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 174 "Waiting on \"%s\"", cvp->cv_description); 175 KASSERT(lock != &Giant.lock_object, 176 ("cv_wait_unlock cannot be used with Giant")); 177 class = LOCK_CLASS(lock); 178 179 if (SCHEDULER_STOPPED_TD(td)) { 180 class->lc_unlock(lock); 181 return; 182 } 183 184 sleepq_lock(cvp); 185 186 CV_WAITERS_INC(cvp); 187 DROP_GIANT(); 188 189 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0); 190 if (class->lc_flags & LC_SLEEPABLE) 191 sleepq_release(cvp); 192 class->lc_unlock(lock); 193 if (class->lc_flags & LC_SLEEPABLE) 194 sleepq_lock(cvp); 195 sleepq_wait(cvp, 0); 196 197#ifdef KTRACE 198 if (KTRPOINT(td, KTR_CSW)) 199 ktrcsw(0, 0, cv_wmesg(cvp)); 200#endif 201 PICKUP_GIANT(); 202} 203 204/* 205 * Wait on a condition variable, allowing interruption by signals. Return 0 if 206 * the thread was resumed with cv_signal or cv_broadcast, EINTR or ERESTART if 207 * a signal was caught. If ERESTART is returned the system call should be 208 * restarted if possible. 209 */ 210int 211_cv_wait_sig(struct cv *cvp, struct lock_object *lock) 212{ 213 WITNESS_SAVE_DECL(lock_witness); 214 struct lock_class *class; 215 struct thread *td; 216 uintptr_t lock_state; 217 int rval; 218 219 td = curthread; 220 lock_state = 0; 221#ifdef KTRACE 222 if (KTRPOINT(td, KTR_CSW)) 223 ktrcsw(1, 0, cv_wmesg(cvp)); 224#endif 225 CV_ASSERT(cvp, lock, td); 226 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 227 "Waiting on \"%s\"", cvp->cv_description); 228 class = LOCK_CLASS(lock); 229 230 if (SCHEDULER_STOPPED_TD(td)) 231 return (0); 232 233 sleepq_lock(cvp); 234 235 CV_WAITERS_INC(cvp); 236 if (lock == &Giant.lock_object) 237 mtx_assert(&Giant, MA_OWNED); 238 DROP_GIANT(); 239 240 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR | 241 SLEEPQ_INTERRUPTIBLE, 0); 242 if (lock != &Giant.lock_object) { 243 if (class->lc_flags & LC_SLEEPABLE) 244 sleepq_release(cvp); 245 WITNESS_SAVE(lock, lock_witness); 246 lock_state = class->lc_unlock(lock); 247 if (class->lc_flags & LC_SLEEPABLE) 248 sleepq_lock(cvp); 249 } 250 rval = sleepq_wait_sig(cvp, 0); 251 252#ifdef KTRACE 253 if (KTRPOINT(td, KTR_CSW)) 254 ktrcsw(0, 0, cv_wmesg(cvp)); 255#endif 256 PICKUP_GIANT(); 257 if (lock != &Giant.lock_object) { 258 class->lc_lock(lock, lock_state); 259 WITNESS_RESTORE(lock, lock_witness); 260 } 261 262 return (rval); 263} 264 265/* 266 * Wait on a condition variable for (at most) the value specified in sbt 267 * argument. Returns 0 if the process was resumed by cv_signal or cv_broadcast, 268 * EWOULDBLOCK if the timeout expires. 269 */ 270int 271_cv_timedwait_sbt(struct cv *cvp, struct lock_object *lock, sbintime_t sbt, 272 sbintime_t pr, int flags) 273{ 274 WITNESS_SAVE_DECL(lock_witness); 275 struct lock_class *class; 276 struct thread *td; 277 int lock_state, rval; 278 279 td = curthread; 280 lock_state = 0; 281#ifdef KTRACE 282 if (KTRPOINT(td, KTR_CSW)) 283 ktrcsw(1, 0, cv_wmesg(cvp)); 284#endif 285 CV_ASSERT(cvp, lock, td); 286 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 287 "Waiting on \"%s\"", cvp->cv_description); 288 class = LOCK_CLASS(lock); 289 290 if (SCHEDULER_STOPPED_TD(td)) 291 return (0); 292 293 sleepq_lock(cvp); 294 295 CV_WAITERS_INC(cvp); 296 if (lock == &Giant.lock_object) 297 mtx_assert(&Giant, MA_OWNED); 298 DROP_GIANT(); 299 300 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0); 301 sleepq_set_timeout_sbt(cvp, sbt, pr, flags); 302 if (lock != &Giant.lock_object) { 303 if (class->lc_flags & LC_SLEEPABLE) 304 sleepq_release(cvp); 305 WITNESS_SAVE(lock, lock_witness); 306 lock_state = class->lc_unlock(lock); 307 if (class->lc_flags & LC_SLEEPABLE) 308 sleepq_lock(cvp); 309 } 310 rval = sleepq_timedwait(cvp, 0); 311 312#ifdef KTRACE 313 if (KTRPOINT(td, KTR_CSW)) 314 ktrcsw(0, 0, cv_wmesg(cvp)); 315#endif 316 PICKUP_GIANT(); 317 if (lock != &Giant.lock_object) { 318 class->lc_lock(lock, lock_state); 319 WITNESS_RESTORE(lock, lock_witness); 320 } 321 322 return (rval); 323} 324 325/* 326 * Wait on a condition variable for (at most) the value specified in sbt 327 * argument, allowing interruption by signals. 328 * Returns 0 if the thread was resumed by cv_signal or cv_broadcast, 329 * EWOULDBLOCK if the timeout expires, and EINTR or ERESTART if a signal 330 * was caught. 331 */ 332int 333_cv_timedwait_sig_sbt(struct cv *cvp, struct lock_object *lock, 334 sbintime_t sbt, sbintime_t pr, int flags) 335{ 336 WITNESS_SAVE_DECL(lock_witness); 337 struct lock_class *class; 338 struct thread *td; 339 int lock_state, rval; 340 341 td = curthread; 342 lock_state = 0; 343#ifdef KTRACE 344 if (KTRPOINT(td, KTR_CSW)) 345 ktrcsw(1, 0, cv_wmesg(cvp)); 346#endif 347 CV_ASSERT(cvp, lock, td); 348 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 349 "Waiting on \"%s\"", cvp->cv_description); 350 class = LOCK_CLASS(lock); 351 352 if (SCHEDULER_STOPPED_TD(td)) 353 return (0); 354 355 sleepq_lock(cvp); 356 357 CV_WAITERS_INC(cvp); 358 if (lock == &Giant.lock_object) 359 mtx_assert(&Giant, MA_OWNED); 360 DROP_GIANT(); 361 362 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR | 363 SLEEPQ_INTERRUPTIBLE, 0); 364 sleepq_set_timeout_sbt(cvp, sbt, pr, flags); 365 if (lock != &Giant.lock_object) { 366 if (class->lc_flags & LC_SLEEPABLE) 367 sleepq_release(cvp); 368 WITNESS_SAVE(lock, lock_witness); 369 lock_state = class->lc_unlock(lock); 370 if (class->lc_flags & LC_SLEEPABLE) 371 sleepq_lock(cvp); 372 } 373 rval = sleepq_timedwait_sig(cvp, 0); 374 375#ifdef KTRACE 376 if (KTRPOINT(td, KTR_CSW)) 377 ktrcsw(0, 0, cv_wmesg(cvp)); 378#endif 379 PICKUP_GIANT(); 380 if (lock != &Giant.lock_object) { 381 class->lc_lock(lock, lock_state); 382 WITNESS_RESTORE(lock, lock_witness); 383 } 384 385 return (rval); 386} 387 388/* 389 * Signal a condition variable, wakes up one waiting thread. Will also wakeup 390 * the swapper if the process is not in memory, so that it can bring the 391 * sleeping process in. Note that this may also result in additional threads 392 * being made runnable. Should be called with the same mutex as was passed to 393 * cv_wait held. 394 */ 395void 396cv_signal(struct cv *cvp) 397{ 398 int wakeup_swapper; 399 400 if (cvp->cv_waiters == 0) 401 return; 402 wakeup_swapper = 0; 403 sleepq_lock(cvp); 404 if (cvp->cv_waiters > 0) { 405 if (cvp->cv_waiters == CV_WAITERS_BOUND && 406 sleepq_lookup(cvp) == NULL) { 407 cvp->cv_waiters = 0; 408 } else { 409 if (cvp->cv_waiters < CV_WAITERS_BOUND) 410 cvp->cv_waiters--; 411 wakeup_swapper = sleepq_signal(cvp, SLEEPQ_CONDVAR, 0, 412 0); 413 } 414 } 415 sleepq_release(cvp); 416 if (wakeup_swapper) 417 kick_proc0(); 418} 419 420/* 421 * Broadcast a signal to a condition variable. Wakes up all waiting threads. 422 * Should be called with the same mutex as was passed to cv_wait held. 423 */ 424void 425cv_broadcastpri(struct cv *cvp, int pri) 426{ 427 int wakeup_swapper; 428 429 if (cvp->cv_waiters == 0) 430 return; 431 /* 432 * XXX sleepq_broadcast pri argument changed from -1 meaning 433 * no pri to 0 meaning no pri. 434 */ 435 wakeup_swapper = 0; 436 if (pri == -1) 437 pri = 0; 438 sleepq_lock(cvp); 439 if (cvp->cv_waiters > 0) { 440 cvp->cv_waiters = 0; 441 wakeup_swapper = sleepq_broadcast(cvp, SLEEPQ_CONDVAR, pri, 0); 442 } 443 sleepq_release(cvp); 444 if (wakeup_swapper) 445 kick_proc0(); 446} 447