kern_condvar.c revision 183352
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 183352 2008-09-25 13:42:19Z 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, lock, 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((lock) != NULL, ("%s: lock NULL", __func__)); \ 57} while (0) 58 59/* 60 * Initialize a condition variable. Must be called before use. 61 */ 62void 63cv_init(struct cv *cvp, const char *desc) 64{ 65 66 cvp->cv_description = desc; 67 cvp->cv_waiters = 0; 68} 69 70/* 71 * Destroy a condition variable. The condition variable must be re-initialized 72 * in order to be re-used. 73 */ 74void 75cv_destroy(struct cv *cvp) 76{ 77#ifdef INVARIANTS 78 struct sleepqueue *sq; 79 80 sleepq_lock(cvp); 81 sq = sleepq_lookup(cvp); 82 sleepq_release(cvp); 83 KASSERT(sq == NULL, ("%s: associated sleep queue non-empty", __func__)); 84#endif 85} 86 87/* 88 * Wait on a condition variable. The current thread is placed on the condition 89 * variable's wait queue and suspended. A cv_signal or cv_broadcast on the same 90 * condition variable will resume the thread. The mutex is released before 91 * sleeping and will be held on return. It is recommended that the mutex be 92 * held when cv_signal or cv_broadcast are called. 93 */ 94void 95_cv_wait(struct cv *cvp, struct lock_object *lock) 96{ 97 WITNESS_SAVE_DECL(lock_witness); 98 struct lock_class *class; 99 struct thread *td; 100 int lock_state; 101 102 td = curthread; 103 lock_state = 0; 104#ifdef KTRACE 105 if (KTRPOINT(td, KTR_CSW)) 106 ktrcsw(1, 0); 107#endif 108 CV_ASSERT(cvp, lock, td); 109 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 110 "Waiting on \"%s\"", cvp->cv_description); 111 class = LOCK_CLASS(lock); 112 113 if (cold || panicstr) { 114 /* 115 * During autoconfiguration, just give interrupts 116 * a chance, then just return. Don't run any other 117 * thread or panic below, in case this is the idle 118 * process and already asleep. 119 */ 120 return; 121 } 122 123 sleepq_lock(cvp); 124 125 cvp->cv_waiters++; 126 if (lock == &Giant.lock_object) 127 mtx_assert(&Giant, MA_OWNED); 128 DROP_GIANT(); 129 130 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0); 131 if (lock != &Giant.lock_object) { 132 if (class->lc_flags & LC_SLEEPABLE) 133 sleepq_release(cvp); 134 WITNESS_SAVE(lock, lock_witness); 135 lock_state = class->lc_unlock(lock); 136 if (class->lc_flags & LC_SLEEPABLE) 137 sleepq_lock(cvp); 138 } 139 sleepq_wait(cvp, 0); 140 141#ifdef KTRACE 142 if (KTRPOINT(td, KTR_CSW)) 143 ktrcsw(0, 0); 144#endif 145 PICKUP_GIANT(); 146 if (lock != &Giant.lock_object) { 147 class->lc_lock(lock, lock_state); 148 WITNESS_RESTORE(lock, lock_witness); 149 } 150} 151 152/* 153 * Wait on a condition variable. This function differs from cv_wait by 154 * not aquiring the mutex after condition variable was signaled. 155 */ 156void 157_cv_wait_unlock(struct cv *cvp, struct lock_object *lock) 158{ 159 struct lock_class *class; 160 struct thread *td; 161 162 td = curthread; 163#ifdef KTRACE 164 if (KTRPOINT(td, KTR_CSW)) 165 ktrcsw(1, 0); 166#endif 167 CV_ASSERT(cvp, lock, td); 168 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 169 "Waiting on \"%s\"", cvp->cv_description); 170 KASSERT(lock != &Giant.lock_object, 171 ("cv_wait_unlock cannot be used with Giant")); 172 class = LOCK_CLASS(lock); 173 174 if (cold || panicstr) { 175 /* 176 * During autoconfiguration, just give interrupts 177 * a chance, then just return. Don't run any other 178 * thread or panic below, in case this is the idle 179 * process and already asleep. 180 */ 181 class->lc_unlock(lock); 182 return; 183 } 184 185 sleepq_lock(cvp); 186 187 cvp->cv_waiters++; 188 DROP_GIANT(); 189 190 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0); 191 if (class->lc_flags & LC_SLEEPABLE) 192 sleepq_release(cvp); 193 class->lc_unlock(lock); 194 if (class->lc_flags & LC_SLEEPABLE) 195 sleepq_lock(cvp); 196 sleepq_wait(cvp, 0); 197 198#ifdef KTRACE 199 if (KTRPOINT(td, KTR_CSW)) 200 ktrcsw(0, 0); 201#endif 202 PICKUP_GIANT(); 203} 204 205/* 206 * Wait on a condition variable, allowing interruption by signals. Return 0 if 207 * the thread was resumed with cv_signal or cv_broadcast, EINTR or ERESTART if 208 * a signal was caught. If ERESTART is returned the system call should be 209 * restarted if possible. 210 */ 211int 212_cv_wait_sig(struct cv *cvp, struct lock_object *lock) 213{ 214 WITNESS_SAVE_DECL(lock_witness); 215 struct lock_class *class; 216 struct thread *td; 217 struct proc *p; 218 int lock_state, rval; 219 220 td = curthread; 221 p = td->td_proc; 222 lock_state = 0; 223#ifdef KTRACE 224 if (KTRPOINT(td, KTR_CSW)) 225 ktrcsw(1, 0); 226#endif 227 CV_ASSERT(cvp, lock, td); 228 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 229 "Waiting on \"%s\"", cvp->cv_description); 230 class = LOCK_CLASS(lock); 231 232 if (cold || panicstr) { 233 /* 234 * After a panic, or during autoconfiguration, just give 235 * interrupts a chance, then just return; don't run any other 236 * procs or panic below, in case this is the idle process and 237 * already asleep. 238 */ 239 return (0); 240 } 241 242 sleepq_lock(cvp); 243 244 cvp->cv_waiters++; 245 if (lock == &Giant.lock_object) 246 mtx_assert(&Giant, MA_OWNED); 247 DROP_GIANT(); 248 249 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR | 250 SLEEPQ_INTERRUPTIBLE, 0); 251 if (lock != &Giant.lock_object) { 252 if (class->lc_flags & LC_SLEEPABLE) 253 sleepq_release(cvp); 254 WITNESS_SAVE(lock, lock_witness); 255 lock_state = class->lc_unlock(lock); 256 if (class->lc_flags & LC_SLEEPABLE) 257 sleepq_lock(cvp); 258 } 259 rval = sleepq_wait_sig(cvp, 0); 260 261#ifdef KTRACE 262 if (KTRPOINT(td, KTR_CSW)) 263 ktrcsw(0, 0); 264#endif 265 PICKUP_GIANT(); 266 if (lock != &Giant.lock_object) { 267 class->lc_lock(lock, lock_state); 268 WITNESS_RESTORE(lock, lock_witness); 269 } 270 271 return (rval); 272} 273 274/* 275 * Wait on a condition variable for at most timo/hz seconds. Returns 0 if the 276 * process was resumed by cv_signal or cv_broadcast, EWOULDBLOCK if the timeout 277 * expires. 278 */ 279int 280_cv_timedwait(struct cv *cvp, struct lock_object *lock, int timo) 281{ 282 WITNESS_SAVE_DECL(lock_witness); 283 struct lock_class *class; 284 struct thread *td; 285 int lock_state, rval; 286 287 td = curthread; 288 rval = 0; 289 lock_state = 0; 290#ifdef KTRACE 291 if (KTRPOINT(td, KTR_CSW)) 292 ktrcsw(1, 0); 293#endif 294 CV_ASSERT(cvp, lock, td); 295 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 296 "Waiting on \"%s\"", cvp->cv_description); 297 class = LOCK_CLASS(lock); 298 299 if (cold || panicstr) { 300 /* 301 * After a panic, or during autoconfiguration, just give 302 * interrupts a chance, then just return; don't run any other 303 * thread or panic below, in case this is the idle process and 304 * already asleep. 305 */ 306 return 0; 307 } 308 309 sleepq_lock(cvp); 310 311 cvp->cv_waiters++; 312 if (lock == &Giant.lock_object) 313 mtx_assert(&Giant, MA_OWNED); 314 DROP_GIANT(); 315 316 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0); 317 sleepq_set_timeout(cvp, timo); 318 if (lock != &Giant.lock_object) { 319 if (class->lc_flags & LC_SLEEPABLE) 320 sleepq_release(cvp); 321 WITNESS_SAVE(lock, lock_witness); 322 lock_state = class->lc_unlock(lock); 323 if (class->lc_flags & LC_SLEEPABLE) 324 sleepq_lock(cvp); 325 } 326 rval = sleepq_timedwait(cvp, 0); 327 328#ifdef KTRACE 329 if (KTRPOINT(td, KTR_CSW)) 330 ktrcsw(0, 0); 331#endif 332 PICKUP_GIANT(); 333 if (lock != &Giant.lock_object) { 334 class->lc_lock(lock, lock_state); 335 WITNESS_RESTORE(lock, lock_witness); 336 } 337 338 return (rval); 339} 340 341/* 342 * Wait on a condition variable for at most timo/hz seconds, allowing 343 * interruption by signals. Returns 0 if the thread was resumed by cv_signal 344 * or cv_broadcast, EWOULDBLOCK if the timeout expires, and EINTR or ERESTART if 345 * a signal was caught. 346 */ 347int 348_cv_timedwait_sig(struct cv *cvp, struct lock_object *lock, int timo) 349{ 350 WITNESS_SAVE_DECL(lock_witness); 351 struct lock_class *class; 352 struct thread *td; 353 struct proc *p; 354 int lock_state, rval; 355 356 td = curthread; 357 p = td->td_proc; 358 rval = 0; 359 lock_state = 0; 360#ifdef KTRACE 361 if (KTRPOINT(td, KTR_CSW)) 362 ktrcsw(1, 0); 363#endif 364 CV_ASSERT(cvp, lock, td); 365 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 366 "Waiting on \"%s\"", cvp->cv_description); 367 class = LOCK_CLASS(lock); 368 369 if (cold || panicstr) { 370 /* 371 * After a panic, or during autoconfiguration, just give 372 * interrupts a chance, then just return; don't run any other 373 * thread or panic below, in case this is the idle process and 374 * already asleep. 375 */ 376 return 0; 377 } 378 379 sleepq_lock(cvp); 380 381 cvp->cv_waiters++; 382 if (lock == &Giant.lock_object) 383 mtx_assert(&Giant, MA_OWNED); 384 DROP_GIANT(); 385 386 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR | 387 SLEEPQ_INTERRUPTIBLE, 0); 388 sleepq_set_timeout(cvp, timo); 389 if (lock != &Giant.lock_object) { 390 if (class->lc_flags & LC_SLEEPABLE) 391 sleepq_release(cvp); 392 WITNESS_SAVE(lock, lock_witness); 393 lock_state = class->lc_unlock(lock); 394 if (class->lc_flags & LC_SLEEPABLE) 395 sleepq_lock(cvp); 396 } 397 rval = sleepq_timedwait_sig(cvp, 0); 398 399#ifdef KTRACE 400 if (KTRPOINT(td, KTR_CSW)) 401 ktrcsw(0, 0); 402#endif 403 PICKUP_GIANT(); 404 if (lock != &Giant.lock_object) { 405 class->lc_lock(lock, lock_state); 406 WITNESS_RESTORE(lock, lock_witness); 407 } 408 409 return (rval); 410} 411 412/* 413 * Signal a condition variable, wakes up one waiting thread. Will also wakeup 414 * the swapper if the process is not in memory, so that it can bring the 415 * sleeping process in. Note that this may also result in additional threads 416 * being made runnable. Should be called with the same mutex as was passed to 417 * cv_wait held. 418 */ 419void 420cv_signal(struct cv *cvp) 421{ 422 int wakeup_swapper; 423 424 wakeup_swapper = 0; 425 sleepq_lock(cvp); 426 if (cvp->cv_waiters > 0) { 427 cvp->cv_waiters--; 428 wakeup_swapper = sleepq_signal(cvp, SLEEPQ_CONDVAR, 0, 0); 429 } 430 sleepq_release(cvp); 431 if (wakeup_swapper) 432 kick_proc0(); 433} 434 435/* 436 * Broadcast a signal to a condition variable. Wakes up all waiting threads. 437 * Should be called with the same mutex as was passed to cv_wait held. 438 */ 439void 440cv_broadcastpri(struct cv *cvp, int pri) 441{ 442 int wakeup_swapper; 443 444 /* 445 * XXX sleepq_broadcast pri argument changed from -1 meaning 446 * no pri to 0 meaning no pri. 447 */ 448 wakeup_swapper = 0; 449 if (pri == -1) 450 pri = 0; 451 sleepq_lock(cvp); 452 if (cvp->cv_waiters > 0) { 453 cvp->cv_waiters = 0; 454 wakeup_swapper = sleepq_broadcast(cvp, SLEEPQ_CONDVAR, pri, 0); 455 } 456 sleepq_release(cvp); 457 if (wakeup_swapper) 458 kick_proc0(); 459} 460