1 /*- 2 * Copyright (c) 2004 John Baldwin <jhb@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 * 3. Neither the name of the author nor the names of any co-contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 */ 29 30 /* 31 * Implementation of sleep queues used to hold queue of threads blocked on 32 * a wait channel. Sleep queues different from turnstiles in that wait 33 * channels are not owned by anyone, so there is no priority propagation. 34 * Sleep queues can also provide a timeout and can also be interrupted by 35 * signals. That said, there are several similarities between the turnstile 36 * and sleep queue implementations. (Note: turnstiles were implemented 37 * first.) For example, both use a hash table of the same size where each 38 * bucket is referred to as a "chain" that contains both a spin lock and 39 * a linked list of queues. An individual queue is located by using a hash 40 * to pick a chain, locking the chain, and then walking the chain searching 41 * for the queue. This means that a wait channel object does not need to 42 * embed it's queue head just as locks do not embed their turnstile queue 43 * head. Threads also carry around a sleep queue that they lend to the 44 * wait channel when blocking. Just as in turnstiles, the queue includes 45 * a free list of the sleep queues of other threads blocked on the same 46 * wait channel in the case of multiple waiters. 47 * 48 * Some additional functionality provided by sleep queues include the 49 * ability to set a timeout. The timeout is managed using a per-thread 50 * callout that resumes a thread if it is asleep. A thread may also 51 * catch signals while it is asleep (aka an interruptible sleep). The 52 * signal code uses sleepq_abort() to interrupt a sleeping thread. Finally, 53 * sleep queues also provide some extra assertions. One is not allowed to 54 * mix the sleep/wakeup and cv APIs for a given wait channel. Also, one 55 * must consistently use the same lock to synchronize with a wait channel, 56 * though this check is currently only a warning for sleep/wakeup due to 57 * pre-existing abuse of that API. The same lock must also be held when 58 * awakening threads, though that is currently only enforced for condition 59 * variables. 60 */ 61 62 #include <sys/cdefs.h> 63 __FBSDID("$FreeBSD$"); 64 65 #include "opt_sleepqueue_profiling.h" 66 #include "opt_ddb.h" 67 68 #include <sys/param.h> 69 #include <sys/systm.h> 70 #include <sys/lock.h> 71 #include <sys/kernel.h> 72 #include <sys/ktr.h> 73 #include <sys/mutex.h> 74 #include <sys/proc.h> 75 #include <sys/sched.h> 76 #include <sys/signalvar.h> 77 #include <sys/sleepqueue.h> 78 #include <sys/sysctl.h> 79 80 #include <vm/uma.h> 81 82 #ifdef DDB 83 #include <ddb/ddb.h> 84 #endif 85 86 /* 87 * Constants for the hash table of sleep queue chains. These constants are 88 * the same ones that 4BSD (and possibly earlier versions of BSD) used. 89 * Basically, we ignore the lower 8 bits of the address since most wait 90 * channel pointers are aligned and only look at the next 7 bits for the 91 * hash. SC_TABLESIZE must be a power of two for SC_MASK to work properly. 92 */ 93 #define SC_TABLESIZE 128 /* Must be power of 2. */ 94 #define SC_MASK (SC_TABLESIZE - 1) 95 #define SC_SHIFT 8 96 #define SC_HASH(wc) (((uintptr_t)(wc) >> SC_SHIFT) & SC_MASK) 97 #define SC_LOOKUP(wc) &sleepq_chains[SC_HASH(wc)] 98 #define NR_SLEEPQS 2 99 /* 100 * There two different lists of sleep queues. Both lists are connected 101 * via the sq_hash entries. The first list is the sleep queue chain list 102 * that a sleep queue is on when it is attached to a wait channel. The 103 * second list is the free list hung off of a sleep queue that is attached 104 * to a wait channel. 105 * 106 * Each sleep queue also contains the wait channel it is attached to, the 107 * list of threads blocked on that wait channel, flags specific to the 108 * wait channel, and the lock used to synchronize with a wait channel. 109 * The flags are used to catch mismatches between the various consumers 110 * of the sleep queue API (e.g. sleep/wakeup and condition variables). 111 * The lock pointer is only used when invariants are enabled for various 112 * debugging checks. 113 * 114 * Locking key: 115 * c - sleep queue chain lock 116 */ 117 struct sleepqueue { 118 TAILQ_HEAD(, thread) sq_blocked[NR_SLEEPQS]; /* (c) Blocked threads. */ 119 LIST_ENTRY(sleepqueue) sq_hash; /* (c) Chain and free list. */ 120 LIST_HEAD(, sleepqueue) sq_free; /* (c) Free queues. */ 121 void *sq_wchan; /* (c) Wait channel. */ 122 #ifdef INVARIANTS 123 int sq_type; /* (c) Queue type. */ 124 struct lock_object *sq_lock; /* (c) Associated lock. */ 125 #endif 126 }; 127 128 struct sleepqueue_chain { 129 LIST_HEAD(, sleepqueue) sc_queues; /* List of sleep queues. */ 130 struct mtx sc_lock; /* Spin lock for this chain. */ 131 #ifdef SLEEPQUEUE_PROFILING 132 u_int sc_depth; /* Length of sc_queues. */ 133 u_int sc_max_depth; /* Max length of sc_queues. */ 134 #endif 135 }; 136 137 #ifdef SLEEPQUEUE_PROFILING 138 u_int sleepq_max_depth; 139 SYSCTL_NODE(_debug, OID_AUTO, sleepq, CTLFLAG_RD, 0, "sleepq profiling"); 140 SYSCTL_NODE(_debug_sleepq, OID_AUTO, chains, CTLFLAG_RD, 0, 141 "sleepq chain stats"); 142 SYSCTL_UINT(_debug_sleepq, OID_AUTO, max_depth, CTLFLAG_RD, &sleepq_max_depth, 143 0, "maxmimum depth achieved of a single chain"); 144 #endif 145 static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE]; 146 static uma_zone_t sleepq_zone; 147 148 /* 149 * Prototypes for non-exported routines. 150 */ 151 static int sleepq_catch_signals(void *wchan); 152 static int sleepq_check_signals(void); 153 static int sleepq_check_timeout(void); 154 #ifdef INVARIANTS 155 static void sleepq_dtor(void *mem, int size, void *arg); 156 #endif 157 static int sleepq_init(void *mem, int size, int flags); 158 static void sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, 159 int pri); 160 static void sleepq_switch(void *wchan); 161 static void sleepq_timeout(void *arg); 162 163 /* 164 * Early initialization of sleep queues that is called from the sleepinit() 165 * SYSINIT. 166 */ 167 void 168 init_sleepqueues(void) 169 { 170 #ifdef SLEEPQUEUE_PROFILING 171 struct sysctl_oid *chain_oid; 172 char chain_name[10]; 173 #endif 174 int i; 175 176 for (i = 0; i < SC_TABLESIZE; i++) { 177 LIST_INIT(&sleepq_chains[i].sc_queues); 178 mtx_init(&sleepq_chains[i].sc_lock, "sleepq chain", NULL, 179 MTX_SPIN); 180 #ifdef SLEEPQUEUE_PROFILING 181 snprintf(chain_name, sizeof(chain_name), "%d", i); 182 chain_oid = SYSCTL_ADD_NODE(NULL, 183 SYSCTL_STATIC_CHILDREN(_debug_sleepq_chains), OID_AUTO, 184 chain_name, CTLFLAG_RD, NULL, "sleepq chain stats"); 185 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO, 186 "depth", CTLFLAG_RD, &sleepq_chains[i].sc_depth, 0, NULL); 187 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO, 188 "max_depth", CTLFLAG_RD, &sleepq_chains[i].sc_max_depth, 0, 189 NULL); 190 #endif 191 } 192 sleepq_zone = uma_zcreate("SLEEPQUEUE", sizeof(struct sleepqueue), 193 #ifdef INVARIANTS 194 NULL, sleepq_dtor, sleepq_init, NULL, UMA_ALIGN_CACHE, 0); 195 #else 196 NULL, NULL, sleepq_init, NULL, UMA_ALIGN_CACHE, 0); 197 #endif 198 199 thread0.td_sleepqueue = sleepq_alloc(); 200 } 201 202 /* 203 * Get a sleep queue for a new thread. 204 */ 205 struct sleepqueue * 206 sleepq_alloc(void) 207 { 208 209 return (uma_zalloc(sleepq_zone, M_WAITOK)); 210 } 211 212 /* 213 * Free a sleep queue when a thread is destroyed. 214 */ 215 void 216 sleepq_free(struct sleepqueue *sq) 217 { 218 219 uma_zfree(sleepq_zone, sq); 220 } 221 222 /* 223 * Lock the sleep queue chain associated with the specified wait channel. 224 */ 225 void 226 sleepq_lock(void *wchan) 227 { 228 struct sleepqueue_chain *sc; 229 230 sc = SC_LOOKUP(wchan); 231 mtx_lock_spin(&sc->sc_lock); 232 } 233 234 /* 235 * Look up the sleep queue associated with a given wait channel in the hash 236 * table locking the associated sleep queue chain. If no queue is found in 237 * the table, NULL is returned. 238 */ 239 struct sleepqueue * 240 sleepq_lookup(void *wchan) 241 { 242 struct sleepqueue_chain *sc; 243 struct sleepqueue *sq; 244 245 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__)); 246 sc = SC_LOOKUP(wchan); 247 mtx_assert(&sc->sc_lock, MA_OWNED); 248 LIST_FOREACH(sq, &sc->sc_queues, sq_hash) 249 if (sq->sq_wchan == wchan) 250 return (sq); 251 return (NULL); 252 } 253 254 /* 255 * Unlock the sleep queue chain associated with a given wait channel. 256 */ 257 void 258 sleepq_release(void *wchan) 259 { 260 struct sleepqueue_chain *sc; 261 262 sc = SC_LOOKUP(wchan); 263 mtx_unlock_spin(&sc->sc_lock); 264 } 265 266 /* 267 * Places the current thread on the sleep queue for the specified wait 268 * channel. If INVARIANTS is enabled, then it associates the passed in 269 * lock with the sleepq to make sure it is held when that sleep queue is 270 * woken up. 271 */ 272 void 273 sleepq_add(void *wchan, struct lock_object *lock, const char *wmesg, int flags, 274 int queue) 275 { 276 struct sleepqueue_chain *sc; 277 struct sleepqueue *sq; 278 struct thread *td; 279 280 td = curthread; 281 sc = SC_LOOKUP(wchan); 282 mtx_assert(&sc->sc_lock, MA_OWNED); 283 MPASS(td->td_sleepqueue != NULL); 284 MPASS(wchan != NULL); 285 MPASS((queue >= 0) && (queue < NR_SLEEPQS)); 286 287 /* If this thread is not allowed to sleep, die a horrible death. */ 288 KASSERT(!(td->td_pflags & TDP_NOSLEEPING), 289 ("Trying sleep, but thread marked as sleeping prohibited")); 290 291 /* Look up the sleep queue associated with the wait channel 'wchan'. */ 292 sq = sleepq_lookup(wchan); 293 294 /* 295 * If the wait channel does not already have a sleep queue, use 296 * this thread's sleep queue. Otherwise, insert the current thread 297 * into the sleep queue already in use by this wait channel. 298 */ 299 if (sq == NULL) { 300 #ifdef INVARIANTS 301 int i; 302 303 sq = td->td_sleepqueue; 304 for (i = 0; i < NR_SLEEPQS; i++) 305 KASSERT(TAILQ_EMPTY(&sq->sq_blocked[i]), 306 ("thread's sleep queue %d is not empty", i)); 307 KASSERT(LIST_EMPTY(&sq->sq_free), 308 ("thread's sleep queue has a non-empty free list")); 309 KASSERT(sq->sq_wchan == NULL, ("stale sq_wchan pointer")); 310 sq->sq_lock = lock; 311 sq->sq_type = flags & SLEEPQ_TYPE; 312 #endif 313 #ifdef SLEEPQUEUE_PROFILING 314 sc->sc_depth++; 315 if (sc->sc_depth > sc->sc_max_depth) { 316 sc->sc_max_depth = sc->sc_depth; 317 if (sc->sc_max_depth > sleepq_max_depth) 318 sleepq_max_depth = sc->sc_max_depth; 319 } 320 #endif 321 sq = td->td_sleepqueue; 322 LIST_INSERT_HEAD(&sc->sc_queues, sq, sq_hash); 323 sq->sq_wchan = wchan; 324 } else { 325 MPASS(wchan == sq->sq_wchan); 326 MPASS(lock == sq->sq_lock); 327 MPASS((flags & SLEEPQ_TYPE) == sq->sq_type); 328 LIST_INSERT_HEAD(&sq->sq_free, td->td_sleepqueue, sq_hash); 329 } 330 TAILQ_INSERT_TAIL(&sq->sq_blocked[queue], td, td_slpq); 331 td->td_sleepqueue = NULL; 332 mtx_lock_spin(&sched_lock); 333 td->td_sqqueue = queue; 334 td->td_wchan = wchan; 335 td->td_wmesg = wmesg; 336 if (flags & SLEEPQ_INTERRUPTIBLE) { 337 td->td_flags |= TDF_SINTR; 338 td->td_flags &= ~TDF_SLEEPABORT; 339 } 340 mtx_unlock_spin(&sched_lock); 341 } 342 343 /* 344 * Sets a timeout that will remove the current thread from the specified 345 * sleep queue after timo ticks if the thread has not already been awakened. 346 */ 347 void 348 sleepq_set_timeout(void *wchan, int timo) 349 { 350 struct sleepqueue_chain *sc; 351 struct thread *td; 352 353 td = curthread; 354 sc = SC_LOOKUP(wchan); 355 mtx_assert(&sc->sc_lock, MA_OWNED); 356 MPASS(TD_ON_SLEEPQ(td)); 357 MPASS(td->td_sleepqueue == NULL); 358 MPASS(wchan != NULL); 359 callout_reset(&td->td_slpcallout, timo, sleepq_timeout, td); 360 } 361 362 /* 363 * Marks the pending sleep of the current thread as interruptible and 364 * makes an initial check for pending signals before putting a thread 365 * to sleep. Return with sleep queue and scheduler lock held. 366 */ 367 static int 368 sleepq_catch_signals(void *wchan) 369 { 370 struct sleepqueue_chain *sc; 371 struct sleepqueue *sq; 372 struct thread *td; 373 struct proc *p; 374 struct sigacts *ps; 375 int sig, ret; 376 377 td = curthread; 378 p = curproc; 379 sc = SC_LOOKUP(wchan); 380 mtx_assert(&sc->sc_lock, MA_OWNED); 381 MPASS(wchan != NULL); 382 CTR3(KTR_PROC, "sleepq catching signals: thread %p (pid %ld, %s)", 383 (void *)td, (long)p->p_pid, p->p_comm); 384 385 MPASS(td->td_flags & TDF_SINTR); 386 mtx_unlock_spin(&sc->sc_lock); 387 388 /* See if there are any pending signals for this thread. */ 389 PROC_LOCK(p); 390 ps = p->p_sigacts; 391 mtx_lock(&ps->ps_mtx); 392 sig = cursig(td); 393 if (sig == 0) { 394 mtx_unlock(&ps->ps_mtx); 395 ret = thread_suspend_check(1); 396 MPASS(ret == 0 || ret == EINTR || ret == ERESTART); 397 } else { 398 if (SIGISMEMBER(ps->ps_sigintr, sig)) 399 ret = EINTR; 400 else 401 ret = ERESTART; 402 mtx_unlock(&ps->ps_mtx); 403 } 404 405 if (ret == 0) { 406 mtx_lock_spin(&sc->sc_lock); 407 /* 408 * Lock sched_lock before unlocking proc lock, 409 * without this, we could lose a race. 410 */ 411 mtx_lock_spin(&sched_lock); 412 PROC_UNLOCK(p); 413 if (!(td->td_flags & TDF_INTERRUPT)) 414 return (0); 415 /* KSE threads tried unblocking us. */ 416 ret = td->td_intrval; 417 mtx_unlock_spin(&sched_lock); 418 MPASS(ret == EINTR || ret == ERESTART); 419 } else { 420 PROC_UNLOCK(p); 421 mtx_lock_spin(&sc->sc_lock); 422 } 423 /* 424 * There were pending signals and this thread is still 425 * on the sleep queue, remove it from the sleep queue. 426 */ 427 sq = sleepq_lookup(wchan); 428 mtx_lock_spin(&sched_lock); 429 if (TD_ON_SLEEPQ(td)) 430 sleepq_resume_thread(sq, td, -1); 431 return (ret); 432 } 433 434 /* 435 * Switches to another thread if we are still asleep on a sleep queue and 436 * drop the lock on the sleep queue chain. Returns with sched_lock held. 437 */ 438 static void 439 sleepq_switch(void *wchan) 440 { 441 struct sleepqueue_chain *sc; 442 struct thread *td; 443 444 td = curthread; 445 sc = SC_LOOKUP(wchan); 446 mtx_assert(&sc->sc_lock, MA_OWNED); 447 mtx_assert(&sched_lock, MA_OWNED); 448 449 /* 450 * If we have a sleep queue, then we've already been woken up, so 451 * just return. 452 */ 453 if (td->td_sleepqueue != NULL) { 454 MPASS(!TD_ON_SLEEPQ(td)); 455 mtx_unlock_spin(&sc->sc_lock); 456 return; 457 } 458 459 /* 460 * Otherwise, actually go to sleep. 461 */ 462 mtx_unlock_spin(&sc->sc_lock); 463 sched_sleep(td); 464 TD_SET_SLEEPING(td); 465 mi_switch(SW_VOL, NULL); 466 KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING")); 467 CTR3(KTR_PROC, "sleepq resume: thread %p (pid %ld, %s)", 468 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm); 469 } 470 471 /* 472 * Check to see if we timed out. 473 */ 474 static int 475 sleepq_check_timeout(void) 476 { 477 struct thread *td; 478 479 mtx_assert(&sched_lock, MA_OWNED); 480 td = curthread; 481 482 /* 483 * If TDF_TIMEOUT is set, we timed out. 484 */ 485 if (td->td_flags & TDF_TIMEOUT) { 486 td->td_flags &= ~TDF_TIMEOUT; 487 return (EWOULDBLOCK); 488 } 489 490 /* 491 * If TDF_TIMOFAIL is set, the timeout ran after we had 492 * already been woken up. 493 */ 494 if (td->td_flags & TDF_TIMOFAIL) 495 td->td_flags &= ~TDF_TIMOFAIL; 496 497 /* 498 * If callout_stop() fails, then the timeout is running on 499 * another CPU, so synchronize with it to avoid having it 500 * accidentally wake up a subsequent sleep. 501 */ 502 else if (callout_stop(&td->td_slpcallout) == 0) { 503 td->td_flags |= TDF_TIMEOUT; 504 TD_SET_SLEEPING(td); 505 mi_switch(SW_INVOL, NULL); 506 } 507 return (0); 508 } 509 510 /* 511 * Check to see if we were awoken by a signal. 512 */ 513 static int 514 sleepq_check_signals(void) 515 { 516 struct thread *td; 517 518 mtx_assert(&sched_lock, MA_OWNED); 519 td = curthread; 520 521 /* We are no longer in an interruptible sleep. */ 522 if (td->td_flags & TDF_SINTR) 523 td->td_flags &= ~TDF_SINTR; 524 525 if (td->td_flags & TDF_SLEEPABORT) { 526 td->td_flags &= ~TDF_SLEEPABORT; 527 return (td->td_intrval); 528 } 529 530 if (td->td_flags & TDF_INTERRUPT) 531 return (td->td_intrval); 532 533 return (0); 534 } 535 536 /* 537 * Block the current thread until it is awakened from its sleep queue. 538 */ 539 void 540 sleepq_wait(void *wchan) 541 { 542 543 MPASS(!(curthread->td_flags & TDF_SINTR)); 544 mtx_lock_spin(&sched_lock); 545 sleepq_switch(wchan); 546 mtx_unlock_spin(&sched_lock); 547 } 548 549 /* 550 * Block the current thread until it is awakened from its sleep queue 551 * or it is interrupted by a signal. 552 */ 553 int 554 sleepq_wait_sig(void *wchan) 555 { 556 int rcatch; 557 int rval; 558 559 rcatch = sleepq_catch_signals(wchan); 560 if (rcatch == 0) 561 sleepq_switch(wchan); 562 else 563 sleepq_release(wchan); 564 rval = sleepq_check_signals(); 565 mtx_unlock_spin(&sched_lock); 566 if (rcatch) 567 return (rcatch); 568 return (rval); 569 } 570 571 /* 572 * Block the current thread until it is awakened from its sleep queue 573 * or it times out while waiting. 574 */ 575 int 576 sleepq_timedwait(void *wchan) 577 { 578 int rval; 579 580 MPASS(!(curthread->td_flags & TDF_SINTR)); 581 mtx_lock_spin(&sched_lock); 582 sleepq_switch(wchan); 583 rval = sleepq_check_timeout(); 584 mtx_unlock_spin(&sched_lock); 585 return (rval); 586 } 587 588 /* 589 * Block the current thread until it is awakened from its sleep queue, 590 * it is interrupted by a signal, or it times out waiting to be awakened. 591 */ 592 int 593 sleepq_timedwait_sig(void *wchan) 594 { 595 int rcatch, rvalt, rvals; 596 597 rcatch = sleepq_catch_signals(wchan); 598 if (rcatch == 0) 599 sleepq_switch(wchan); 600 else 601 sleepq_release(wchan); 602 rvalt = sleepq_check_timeout(); 603 rvals = sleepq_check_signals(); 604 mtx_unlock_spin(&sched_lock); 605 if (rcatch) 606 return (rcatch); 607 if (rvals) 608 return (rvals); 609 return (rvalt); 610 } 611 612 /* 613 * Removes a thread from a sleep queue and makes it 614 * runnable. 615 */ 616 static void 617 sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, int pri) 618 { 619 struct sleepqueue_chain *sc; 620 621 MPASS(td != NULL); 622 MPASS(sq->sq_wchan != NULL); 623 MPASS(td->td_wchan == sq->sq_wchan); 624 MPASS(td->td_sqqueue < NR_SLEEPQS && td->td_sqqueue >= 0); 625 sc = SC_LOOKUP(sq->sq_wchan); 626 mtx_assert(&sc->sc_lock, MA_OWNED); 627 mtx_assert(&sched_lock, MA_OWNED); 628 629 /* Remove the thread from the queue. */ 630 TAILQ_REMOVE(&sq->sq_blocked[td->td_sqqueue], td, td_slpq); 631 632 /* 633 * Get a sleep queue for this thread. If this is the last waiter, 634 * use the queue itself and take it out of the chain, otherwise, 635 * remove a queue from the free list. 636 */ 637 if (LIST_EMPTY(&sq->sq_free)) { 638 td->td_sleepqueue = sq; 639 #ifdef INVARIANTS 640 sq->sq_wchan = NULL; 641 #endif 642 #ifdef SLEEPQUEUE_PROFILING 643 sc->sc_depth--; 644 #endif 645 } else 646 td->td_sleepqueue = LIST_FIRST(&sq->sq_free); 647 LIST_REMOVE(td->td_sleepqueue, sq_hash); 648 649 td->td_wmesg = NULL; 650 td->td_wchan = NULL; 651 td->td_flags &= ~TDF_SINTR; 652 653 /* 654 * Note that thread td might not be sleeping if it is running 655 * sleepq_catch_signals() on another CPU or is blocked on 656 * its proc lock to check signals. It doesn't hurt to clear 657 * the sleeping flag if it isn't set though, so we just always 658 * do it. However, we can't assert that it is set. 659 */ 660 CTR3(KTR_PROC, "sleepq_wakeup: thread %p (pid %ld, %s)", 661 (void *)td, (long)td->td_proc->p_pid, td->td_proc->p_comm); 662 TD_CLR_SLEEPING(td); 663 664 /* Adjust priority if requested. */ 665 MPASS(pri == -1 || (pri >= PRI_MIN && pri <= PRI_MAX)); 666 if (pri != -1 && td->td_priority > pri) 667 sched_prio(td, pri); 668 setrunnable(td); 669 } 670 671 #ifdef INVARIANTS 672 /* 673 * UMA zone item deallocator. 674 */ 675 static void 676 sleepq_dtor(void *mem, int size, void *arg) 677 { 678 struct sleepqueue *sq; 679 int i; 680 681 sq = mem; 682 for (i = 0; i < NR_SLEEPQS; i++) 683 MPASS(TAILQ_EMPTY(&sq->sq_blocked[i])); 684 } 685 #endif 686 687 /* 688 * UMA zone item initializer. 689 */ 690 static int 691 sleepq_init(void *mem, int size, int flags) 692 { 693 struct sleepqueue *sq; 694 int i; 695 696 bzero(mem, size); 697 sq = mem; 698 for (i = 0; i < NR_SLEEPQS; i++) 699 TAILQ_INIT(&sq->sq_blocked[i]); 700 LIST_INIT(&sq->sq_free); 701 return (0); 702 } 703 704 /* 705 * Find the highest priority thread sleeping on a wait channel and resume it. 706 */ 707 void 708 sleepq_signal(void *wchan, int flags, int pri, int queue) 709 { 710 struct sleepqueue *sq; 711 struct thread *td, *besttd; 712 713 CTR2(KTR_PROC, "sleepq_signal(%p, %d)", wchan, flags); 714 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__)); 715 MPASS((queue >= 0) && (queue < NR_SLEEPQS)); 716 sq = sleepq_lookup(wchan); 717 if (sq == NULL) { 718 sleepq_release(wchan); 719 return; 720 } 721 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE), 722 ("%s: mismatch between sleep/wakeup and cv_*", __func__)); 723 724 /* 725 * Find the highest priority thread on the queue. If there is a 726 * tie, use the thread that first appears in the queue as it has 727 * been sleeping the longest since threads are always added to 728 * the tail of sleep queues. 729 */ 730 besttd = NULL; 731 TAILQ_FOREACH(td, &sq->sq_blocked[queue], td_slpq) { 732 if (besttd == NULL || td->td_priority < besttd->td_priority) 733 besttd = td; 734 } 735 MPASS(besttd != NULL); 736 mtx_lock_spin(&sched_lock); 737 sleepq_resume_thread(sq, besttd, pri); 738 mtx_unlock_spin(&sched_lock); 739 sleepq_release(wchan); 740 } 741 742 /* 743 * Resume all threads sleeping on a specified wait channel. 744 */ 745 void 746 sleepq_broadcast(void *wchan, int flags, int pri, int queue) 747 { 748 struct sleepqueue *sq; 749 750 CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags); 751 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__)); 752 MPASS((queue >= 0) && (queue < NR_SLEEPQS)); 753 sq = sleepq_lookup(wchan); 754 if (sq == NULL) { 755 sleepq_release(wchan); 756 return; 757 } 758 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE), 759 ("%s: mismatch between sleep/wakeup and cv_*", __func__)); 760 761 /* Resume all blocked threads on the sleep queue. */ 762 mtx_lock_spin(&sched_lock); 763 while (!TAILQ_EMPTY(&sq->sq_blocked[queue])) 764 sleepq_resume_thread(sq, TAILQ_FIRST(&sq->sq_blocked[queue]), 765 pri); 766 mtx_unlock_spin(&sched_lock); 767 sleepq_release(wchan); 768 } 769 770 /* 771 * Time sleeping threads out. When the timeout expires, the thread is 772 * removed from the sleep queue and made runnable if it is still asleep. 773 */ 774 static void 775 sleepq_timeout(void *arg) 776 { 777 struct sleepqueue *sq; 778 struct thread *td; 779 void *wchan; 780 781 td = arg; 782 CTR3(KTR_PROC, "sleepq_timeout: thread %p (pid %ld, %s)", 783 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm); 784 785 /* 786 * First, see if the thread is asleep and get the wait channel if 787 * it is. 788 */ 789 mtx_lock_spin(&sched_lock); 790 if (TD_ON_SLEEPQ(td)) { 791 wchan = td->td_wchan; 792 mtx_unlock_spin(&sched_lock); 793 sleepq_lock(wchan); 794 sq = sleepq_lookup(wchan); 795 mtx_lock_spin(&sched_lock); 796 } else { 797 wchan = NULL; 798 sq = NULL; 799 } 800 801 /* 802 * At this point, if the thread is still on the sleep queue, 803 * we have that sleep queue locked as it cannot migrate sleep 804 * queues while we dropped sched_lock. If it had resumed and 805 * was on another CPU while the lock was dropped, it would have 806 * seen that TDF_TIMEOUT and TDF_TIMOFAIL are clear and the 807 * call to callout_stop() to stop this routine would have failed 808 * meaning that it would have already set TDF_TIMEOUT to 809 * synchronize with this function. 810 */ 811 if (TD_ON_SLEEPQ(td)) { 812 MPASS(td->td_wchan == wchan); 813 MPASS(sq != NULL); 814 td->td_flags |= TDF_TIMEOUT; 815 sleepq_resume_thread(sq, td, -1); 816 mtx_unlock_spin(&sched_lock); 817 sleepq_release(wchan); 818 return; 819 } else if (wchan != NULL) 820 sleepq_release(wchan); 821 822 /* 823 * Now check for the edge cases. First, if TDF_TIMEOUT is set, 824 * then the other thread has already yielded to us, so clear 825 * the flag and resume it. If TDF_TIMEOUT is not set, then the 826 * we know that the other thread is not on a sleep queue, but it 827 * hasn't resumed execution yet. In that case, set TDF_TIMOFAIL 828 * to let it know that the timeout has already run and doesn't 829 * need to be canceled. 830 */ 831 if (td->td_flags & TDF_TIMEOUT) { 832 MPASS(TD_IS_SLEEPING(td)); 833 td->td_flags &= ~TDF_TIMEOUT; 834 TD_CLR_SLEEPING(td); 835 setrunnable(td); 836 } else 837 td->td_flags |= TDF_TIMOFAIL; 838 mtx_unlock_spin(&sched_lock); 839 } 840 841 /* 842 * Resumes a specific thread from the sleep queue associated with a specific 843 * wait channel if it is on that queue. 844 */ 845 void 846 sleepq_remove(struct thread *td, void *wchan) 847 { 848 struct sleepqueue *sq; 849 850 /* 851 * Look up the sleep queue for this wait channel, then re-check 852 * that the thread is asleep on that channel, if it is not, then 853 * bail. 854 */ 855 MPASS(wchan != NULL); 856 sleepq_lock(wchan); 857 sq = sleepq_lookup(wchan); 858 mtx_lock_spin(&sched_lock); 859 if (!TD_ON_SLEEPQ(td) || td->td_wchan != wchan) { 860 mtx_unlock_spin(&sched_lock); 861 sleepq_release(wchan); 862 return; 863 } 864 MPASS(sq != NULL); 865 866 /* Thread is asleep on sleep queue sq, so wake it up. */ 867 sleepq_resume_thread(sq, td, -1); 868 sleepq_release(wchan); 869 mtx_unlock_spin(&sched_lock); 870 } 871 872 /* 873 * Abort a thread as if an interrupt had occurred. Only abort 874 * interruptible waits (unfortunately it isn't safe to abort others). 875 * 876 * XXX: What in the world does the comment below mean? 877 * Also, whatever the signal code does... 878 */ 879 void 880 sleepq_abort(struct thread *td, int intrval) 881 { 882 void *wchan; 883 884 mtx_assert(&sched_lock, MA_OWNED); 885 MPASS(TD_ON_SLEEPQ(td)); 886 MPASS(td->td_flags & TDF_SINTR); 887 MPASS(intrval == EINTR || intrval == ERESTART); 888 889 /* 890 * If the TDF_TIMEOUT flag is set, just leave. A 891 * timeout is scheduled anyhow. 892 */ 893 if (td->td_flags & TDF_TIMEOUT) 894 return; 895 896 CTR3(KTR_PROC, "sleepq_abort: thread %p (pid %ld, %s)", 897 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm); 898 wchan = td->td_wchan; 899 if (wchan != NULL) { 900 td->td_intrval = intrval; 901 td->td_flags |= TDF_SLEEPABORT; 902 } 903 mtx_unlock_spin(&sched_lock); 904 sleepq_remove(td, wchan); 905 mtx_lock_spin(&sched_lock); 906 } 907 908 #ifdef DDB 909 DB_SHOW_COMMAND(sleepq, db_show_sleepqueue) 910 { 911 struct sleepqueue_chain *sc; 912 struct sleepqueue *sq; 913 #ifdef INVARIANTS 914 struct lock_object *lock; 915 #endif 916 struct thread *td; 917 void *wchan; 918 int i; 919 920 if (!have_addr) 921 return; 922 923 /* 924 * First, see if there is an active sleep queue for the wait channel 925 * indicated by the address. 926 */ 927 wchan = (void *)addr; 928 sc = SC_LOOKUP(wchan); 929 LIST_FOREACH(sq, &sc->sc_queues, sq_hash) 930 if (sq->sq_wchan == wchan) 931 goto found; 932 933 /* 934 * Second, see if there is an active sleep queue at the address 935 * indicated. 936 */ 937 for (i = 0; i < SC_TABLESIZE; i++) 938 LIST_FOREACH(sq, &sleepq_chains[i].sc_queues, sq_hash) { 939 if (sq == (struct sleepqueue *)addr) 940 goto found; 941 } 942 943 db_printf("Unable to locate a sleep queue via %p\n", (void *)addr); 944 return; 945 found: 946 db_printf("Wait channel: %p\n", sq->sq_wchan); 947 #ifdef INVARIANTS 948 db_printf("Queue type: %d\n", sq->sq_type); 949 if (sq->sq_lock) { 950 lock = sq->sq_lock; 951 db_printf("Associated Interlock: %p - (%s) %s\n", lock, 952 LOCK_CLASS(lock)->lc_name, lock->lo_name); 953 } 954 #endif 955 db_printf("Blocked threads:\n"); 956 for (i = 0; i < NR_SLEEPQS; i++) { 957 db_printf("\nQueue[%d]:\n", i); 958 if (TAILQ_EMPTY(&sq->sq_blocked[i])) 959 db_printf("\tempty\n"); 960 else 961 TAILQ_FOREACH(td, &sq->sq_blocked[0], 962 td_slpq) { 963 db_printf("\t%p (tid %d, pid %d, \"%s\")\n", td, 964 td->td_tid, td->td_proc->p_pid, 965 td->td_name[i] != '\0' ? td->td_name : 966 td->td_proc->p_comm); 967 } 968 } 969 } 970 971 /* Alias 'show sleepqueue' to 'show sleepq'. */ 972 DB_SET(sleepqueue, db_show_sleepqueue, db_show_cmd_set, 0, NULL); 973 #endif 974