1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright (c) 2000 Jake Burkholder <jake@freebsd.org>. 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 <sys/cdefs.h> 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 */ 74 void 75 cv_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 */ 86 void 87 cv_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 */ 106 void 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 */ 161 void 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 */ 210 int 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 */ 270 int 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 */ 332 int 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 */ 395 void 396 cv_signal(struct cv *cvp) 397 { 398 399 if (cvp->cv_waiters == 0) 400 return; 401 sleepq_lock(cvp); 402 if (cvp->cv_waiters == 0) { 403 sleepq_release(cvp); 404 return; 405 } 406 if (cvp->cv_waiters == CV_WAITERS_BOUND && sleepq_lookup(cvp) == NULL) { 407 cvp->cv_waiters = 0; 408 sleepq_release(cvp); 409 } else { 410 if (cvp->cv_waiters < CV_WAITERS_BOUND) 411 cvp->cv_waiters--; 412 if (sleepq_signal(cvp, SLEEPQ_CONDVAR | SLEEPQ_DROP, 0, 0)) 413 kick_proc0(); 414 } 415 } 416 417 /* 418 * Broadcast a signal to a condition variable. Wakes up all waiting threads. 419 * Should be called with the same mutex as was passed to cv_wait held. 420 */ 421 void 422 cv_broadcastpri(struct cv *cvp, int pri) 423 { 424 int wakeup_swapper; 425 426 if (cvp->cv_waiters == 0) 427 return; 428 /* 429 * XXX sleepq_broadcast pri argument changed from -1 meaning 430 * no pri to 0 meaning no pri. 431 */ 432 wakeup_swapper = 0; 433 if (pri == -1) 434 pri = 0; 435 sleepq_lock(cvp); 436 if (cvp->cv_waiters > 0) { 437 cvp->cv_waiters = 0; 438 wakeup_swapper = sleepq_broadcast(cvp, SLEEPQ_CONDVAR, pri, 0); 439 } 440 sleepq_release(cvp); 441 if (wakeup_swapper) 442 kick_proc0(); 443 } 444