kern_condvar.c revision 177085
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 177085 2008-03-12 06:31:06Z jeff $"); 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#ifdef KTRACE 104 if (KTRPOINT(td, KTR_CSW)) 105 ktrcsw(1, 0); 106#endif 107 CV_ASSERT(cvp, lock, td); 108 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 109 "Waiting on \"%s\"", cvp->cv_description); 110 WITNESS_SAVE(lock, lock_witness); 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 DROP_GIANT(); 127 128 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0); 129 if (class->lc_flags & LC_SLEEPABLE) 130 sleepq_release(cvp); 131 lock_state = class->lc_unlock(lock); 132 if (class->lc_flags & LC_SLEEPABLE) 133 sleepq_lock(cvp); 134 sleepq_wait(cvp, 0); 135 136#ifdef KTRACE 137 if (KTRPOINT(td, KTR_CSW)) 138 ktrcsw(0, 0); 139#endif 140 PICKUP_GIANT(); 141 class->lc_lock(lock, lock_state); 142 WITNESS_RESTORE(lock, lock_witness); 143} 144 145/* 146 * Wait on a condition variable. This function differs from cv_wait by 147 * not aquiring the mutex after condition variable was signaled. 148 */ 149void 150_cv_wait_unlock(struct cv *cvp, struct lock_object *lock) 151{ 152 struct lock_class *class; 153 struct thread *td; 154 155 td = curthread; 156#ifdef KTRACE 157 if (KTRPOINT(td, KTR_CSW)) 158 ktrcsw(1, 0); 159#endif 160 CV_ASSERT(cvp, lock, td); 161 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 162 "Waiting on \"%s\"", cvp->cv_description); 163 class = LOCK_CLASS(lock); 164 165 if (cold || panicstr) { 166 /* 167 * During autoconfiguration, just give interrupts 168 * a chance, then just return. Don't run any other 169 * thread or panic below, in case this is the idle 170 * process and already asleep. 171 */ 172 class->lc_unlock(lock); 173 return; 174 } 175 176 sleepq_lock(cvp); 177 178 cvp->cv_waiters++; 179 DROP_GIANT(); 180 181 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0); 182 if (class->lc_flags & LC_SLEEPABLE) 183 sleepq_release(cvp); 184 class->lc_unlock(lock); 185 if (class->lc_flags & LC_SLEEPABLE) 186 sleepq_lock(cvp); 187 sleepq_wait(cvp, 0); 188 189#ifdef KTRACE 190 if (KTRPOINT(td, KTR_CSW)) 191 ktrcsw(0, 0); 192#endif 193 PICKUP_GIANT(); 194} 195 196/* 197 * Wait on a condition variable, allowing interruption by signals. Return 0 if 198 * the thread was resumed with cv_signal or cv_broadcast, EINTR or ERESTART if 199 * a signal was caught. If ERESTART is returned the system call should be 200 * restarted if possible. 201 */ 202int 203_cv_wait_sig(struct cv *cvp, struct lock_object *lock) 204{ 205 WITNESS_SAVE_DECL(lock_witness); 206 struct lock_class *class; 207 struct thread *td; 208 struct proc *p; 209 int lock_state, rval; 210 211 td = curthread; 212 p = td->td_proc; 213#ifdef KTRACE 214 if (KTRPOINT(td, KTR_CSW)) 215 ktrcsw(1, 0); 216#endif 217 CV_ASSERT(cvp, lock, td); 218 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 219 "Waiting on \"%s\"", cvp->cv_description); 220 WITNESS_SAVE(lock, lock_witness); 221 class = LOCK_CLASS(lock); 222 223 if (cold || panicstr) { 224 /* 225 * After a panic, or during autoconfiguration, just give 226 * interrupts a chance, then just return; don't run any other 227 * procs or panic below, in case this is the idle process and 228 * already asleep. 229 */ 230 return (0); 231 } 232 233 sleepq_lock(cvp); 234 235 cvp->cv_waiters++; 236 DROP_GIANT(); 237 238 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR | 239 SLEEPQ_INTERRUPTIBLE, 0); 240 if (class->lc_flags & LC_SLEEPABLE) 241 sleepq_release(cvp); 242 lock_state = class->lc_unlock(lock); 243 if (class->lc_flags & LC_SLEEPABLE) 244 sleepq_lock(cvp); 245 rval = sleepq_wait_sig(cvp, 0); 246 247#ifdef KTRACE 248 if (KTRPOINT(td, KTR_CSW)) 249 ktrcsw(0, 0); 250#endif 251 PICKUP_GIANT(); 252 class->lc_lock(lock, lock_state); 253 WITNESS_RESTORE(lock, lock_witness); 254 255 return (rval); 256} 257 258/* 259 * Wait on a condition variable for at most timo/hz seconds. Returns 0 if the 260 * process was resumed by cv_signal or cv_broadcast, EWOULDBLOCK if the timeout 261 * expires. 262 */ 263int 264_cv_timedwait(struct cv *cvp, struct lock_object *lock, int timo) 265{ 266 WITNESS_SAVE_DECL(lock_witness); 267 struct lock_class *class; 268 struct thread *td; 269 int lock_state, rval; 270 271 td = curthread; 272 rval = 0; 273#ifdef KTRACE 274 if (KTRPOINT(td, KTR_CSW)) 275 ktrcsw(1, 0); 276#endif 277 CV_ASSERT(cvp, lock, td); 278 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 279 "Waiting on \"%s\"", cvp->cv_description); 280 WITNESS_SAVE(lock, lock_witness); 281 class = LOCK_CLASS(lock); 282 283 if (cold || panicstr) { 284 /* 285 * After a panic, or during autoconfiguration, just give 286 * interrupts a chance, then just return; don't run any other 287 * thread or panic below, in case this is the idle process and 288 * already asleep. 289 */ 290 return 0; 291 } 292 293 sleepq_lock(cvp); 294 295 cvp->cv_waiters++; 296 DROP_GIANT(); 297 298 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0); 299 sleepq_set_timeout(cvp, timo); 300 if (class->lc_flags & LC_SLEEPABLE) 301 sleepq_release(cvp); 302 lock_state = class->lc_unlock(lock); 303 if (class->lc_flags & LC_SLEEPABLE) 304 sleepq_lock(cvp); 305 rval = sleepq_timedwait(cvp, 0); 306 307#ifdef KTRACE 308 if (KTRPOINT(td, KTR_CSW)) 309 ktrcsw(0, 0); 310#endif 311 PICKUP_GIANT(); 312 class->lc_lock(lock, lock_state); 313 WITNESS_RESTORE(lock, lock_witness); 314 315 return (rval); 316} 317 318/* 319 * Wait on a condition variable for at most timo/hz seconds, allowing 320 * interruption by signals. Returns 0 if the thread was resumed by cv_signal 321 * or cv_broadcast, EWOULDBLOCK if the timeout expires, and EINTR or ERESTART if 322 * a signal was caught. 323 */ 324int 325_cv_timedwait_sig(struct cv *cvp, struct lock_object *lock, int timo) 326{ 327 WITNESS_SAVE_DECL(lock_witness); 328 struct lock_class *class; 329 struct thread *td; 330 struct proc *p; 331 int lock_state, rval; 332 333 td = curthread; 334 p = td->td_proc; 335 rval = 0; 336#ifdef KTRACE 337 if (KTRPOINT(td, KTR_CSW)) 338 ktrcsw(1, 0); 339#endif 340 CV_ASSERT(cvp, lock, td); 341 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 342 "Waiting on \"%s\"", cvp->cv_description); 343 WITNESS_SAVE(lock, lock_witness); 344 class = LOCK_CLASS(lock); 345 346 if (cold || panicstr) { 347 /* 348 * After a panic, or during autoconfiguration, just give 349 * interrupts a chance, then just return; don't run any other 350 * thread or panic below, in case this is the idle process and 351 * already asleep. 352 */ 353 return 0; 354 } 355 356 sleepq_lock(cvp); 357 358 cvp->cv_waiters++; 359 DROP_GIANT(); 360 361 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR | 362 SLEEPQ_INTERRUPTIBLE, 0); 363 sleepq_set_timeout(cvp, timo); 364 if (class->lc_flags & LC_SLEEPABLE) 365 sleepq_release(cvp); 366 lock_state = class->lc_unlock(lock); 367 if (class->lc_flags & LC_SLEEPABLE) 368 sleepq_lock(cvp); 369 rval = sleepq_timedwait_sig(cvp, 0); 370 371#ifdef KTRACE 372 if (KTRPOINT(td, KTR_CSW)) 373 ktrcsw(0, 0); 374#endif 375 PICKUP_GIANT(); 376 class->lc_lock(lock, lock_state); 377 WITNESS_RESTORE(lock, lock_witness); 378 379 return (rval); 380} 381 382/* 383 * Signal a condition variable, wakes up one waiting thread. Will also wakeup 384 * the swapper if the process is not in memory, so that it can bring the 385 * sleeping process in. Note that this may also result in additional threads 386 * being made runnable. Should be called with the same mutex as was passed to 387 * cv_wait held. 388 */ 389void 390cv_signal(struct cv *cvp) 391{ 392 393 sleepq_lock(cvp); 394 if (cvp->cv_waiters > 0) { 395 cvp->cv_waiters--; 396 sleepq_signal(cvp, SLEEPQ_CONDVAR, 0, 0); 397 } 398 sleepq_release(cvp); 399} 400 401/* 402 * Broadcast a signal to a condition variable. Wakes up all waiting threads. 403 * Should be called with the same mutex as was passed to cv_wait held. 404 */ 405void 406cv_broadcastpri(struct cv *cvp, int pri) 407{ 408 /* 409 * XXX sleepq_broadcast pri argument changed from -1 meaning 410 * no pri to 0 meaning no pri. 411 */ 412 if (pri == -1) 413 pri = 0; 414 sleepq_lock(cvp); 415 if (cvp->cv_waiters > 0) { 416 cvp->cv_waiters = 0; 417 sleepq_broadcast(cvp, SLEEPQ_CONDVAR, pri, 0); 418 } 419 sleepq_release(cvp); 420} 421