subr_sleepqueue.c revision 262192
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 * 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/* 28 * Implementation of sleep queues used to hold queue of threads blocked on 29 * a wait channel. Sleep queues different from turnstiles in that wait 30 * channels are not owned by anyone, so there is no priority propagation. 31 * Sleep queues can also provide a timeout and can also be interrupted by 32 * signals. That said, there are several similarities between the turnstile 33 * and sleep queue implementations. (Note: turnstiles were implemented 34 * first.) For example, both use a hash table of the same size where each 35 * bucket is referred to as a "chain" that contains both a spin lock and 36 * a linked list of queues. An individual queue is located by using a hash 37 * to pick a chain, locking the chain, and then walking the chain searching 38 * for the queue. This means that a wait channel object does not need to 39 * embed it's queue head just as locks do not embed their turnstile queue 40 * head. Threads also carry around a sleep queue that they lend to the 41 * wait channel when blocking. Just as in turnstiles, the queue includes 42 * a free list of the sleep queues of other threads blocked on the same 43 * wait channel in the case of multiple waiters. 44 * 45 * Some additional functionality provided by sleep queues include the 46 * ability to set a timeout. The timeout is managed using a per-thread 47 * callout that resumes a thread if it is asleep. A thread may also 48 * catch signals while it is asleep (aka an interruptible sleep). The 49 * signal code uses sleepq_abort() to interrupt a sleeping thread. Finally, 50 * sleep queues also provide some extra assertions. One is not allowed to 51 * mix the sleep/wakeup and cv APIs for a given wait channel. Also, one 52 * must consistently use the same lock to synchronize with a wait channel, 53 * though this check is currently only a warning for sleep/wakeup due to 54 * pre-existing abuse of that API. The same lock must also be held when 55 * awakening threads, though that is currently only enforced for condition 56 * variables. 57 */ 58 59#include <sys/cdefs.h> 60__FBSDID("$FreeBSD: stable/10/sys/kern/subr_sleepqueue.c 262192 2014-02-18 20:27:17Z jhb $"); 61 62#include "opt_sleepqueue_profiling.h" 63#include "opt_ddb.h" 64#include "opt_kdtrace.h" 65#include "opt_sched.h" 66 67#include <sys/param.h> 68#include <sys/systm.h> 69#include <sys/lock.h> 70#include <sys/kernel.h> 71#include <sys/ktr.h> 72#include <sys/mutex.h> 73#include <sys/proc.h> 74#include <sys/sbuf.h> 75#include <sys/sched.h> 76#include <sys/sdt.h> 77#include <sys/signalvar.h> 78#include <sys/sleepqueue.h> 79#include <sys/sysctl.h> 80 81#include <vm/uma.h> 82 83#ifdef DDB 84#include <ddb/ddb.h> 85#endif 86 87/* 88 * Constants for the hash table of sleep queue chains. 89 * SC_TABLESIZE must be a power of two for SC_MASK to work properly. 90 */ 91#define SC_TABLESIZE 256 /* Must be power of 2. */ 92#define SC_MASK (SC_TABLESIZE - 1) 93#define SC_SHIFT 8 94#define SC_HASH(wc) ((((uintptr_t)(wc) >> SC_SHIFT) ^ (uintptr_t)(wc)) & \ 95 SC_MASK) 96#define SC_LOOKUP(wc) &sleepq_chains[SC_HASH(wc)] 97#define NR_SLEEPQS 2 98/* 99 * There two different lists of sleep queues. Both lists are connected 100 * via the sq_hash entries. The first list is the sleep queue chain list 101 * that a sleep queue is on when it is attached to a wait channel. The 102 * second list is the free list hung off of a sleep queue that is attached 103 * to a wait channel. 104 * 105 * Each sleep queue also contains the wait channel it is attached to, the 106 * list of threads blocked on that wait channel, flags specific to the 107 * wait channel, and the lock used to synchronize with a wait channel. 108 * The flags are used to catch mismatches between the various consumers 109 * of the sleep queue API (e.g. sleep/wakeup and condition variables). 110 * The lock pointer is only used when invariants are enabled for various 111 * debugging checks. 112 * 113 * Locking key: 114 * c - sleep queue chain lock 115 */ 116struct sleepqueue { 117 TAILQ_HEAD(, thread) sq_blocked[NR_SLEEPQS]; /* (c) Blocked threads. */ 118 u_int sq_blockedcnt[NR_SLEEPQS]; /* (c) N. of 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 int sq_type; /* (c) Queue type. */ 123#ifdef INVARIANTS 124 struct lock_object *sq_lock; /* (c) Associated lock. */ 125#endif 126}; 127 128struct 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 138u_int sleepq_max_depth; 139static SYSCTL_NODE(_debug, OID_AUTO, sleepq, CTLFLAG_RD, 0, "sleepq profiling"); 140static SYSCTL_NODE(_debug_sleepq, OID_AUTO, chains, CTLFLAG_RD, 0, 141 "sleepq chain stats"); 142SYSCTL_UINT(_debug_sleepq, OID_AUTO, max_depth, CTLFLAG_RD, &sleepq_max_depth, 143 0, "maxmimum depth achieved of a single chain"); 144 145static void sleepq_profile(const char *wmesg); 146static int prof_enabled; 147#endif 148static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE]; 149static uma_zone_t sleepq_zone; 150 151/* 152 * Prototypes for non-exported routines. 153 */ 154static int sleepq_catch_signals(void *wchan, int pri); 155static int sleepq_check_signals(void); 156static int sleepq_check_timeout(void); 157#ifdef INVARIANTS 158static void sleepq_dtor(void *mem, int size, void *arg); 159#endif 160static int sleepq_init(void *mem, int size, int flags); 161static int sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, 162 int pri); 163static void sleepq_switch(void *wchan, int pri); 164static void sleepq_timeout(void *arg); 165 166SDT_PROBE_DECLARE(sched, , , sleep); 167SDT_PROBE_DECLARE(sched, , , wakeup); 168 169/* 170 * Early initialization of sleep queues that is called from the sleepinit() 171 * SYSINIT. 172 */ 173void 174init_sleepqueues(void) 175{ 176#ifdef SLEEPQUEUE_PROFILING 177 struct sysctl_oid *chain_oid; 178 char chain_name[10]; 179#endif 180 int i; 181 182 for (i = 0; i < SC_TABLESIZE; i++) { 183 LIST_INIT(&sleepq_chains[i].sc_queues); 184 mtx_init(&sleepq_chains[i].sc_lock, "sleepq chain", NULL, 185 MTX_SPIN | MTX_RECURSE); 186#ifdef SLEEPQUEUE_PROFILING 187 snprintf(chain_name, sizeof(chain_name), "%d", i); 188 chain_oid = SYSCTL_ADD_NODE(NULL, 189 SYSCTL_STATIC_CHILDREN(_debug_sleepq_chains), OID_AUTO, 190 chain_name, CTLFLAG_RD, NULL, "sleepq chain stats"); 191 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO, 192 "depth", CTLFLAG_RD, &sleepq_chains[i].sc_depth, 0, NULL); 193 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO, 194 "max_depth", CTLFLAG_RD, &sleepq_chains[i].sc_max_depth, 0, 195 NULL); 196#endif 197 } 198 sleepq_zone = uma_zcreate("SLEEPQUEUE", sizeof(struct sleepqueue), 199#ifdef INVARIANTS 200 NULL, sleepq_dtor, sleepq_init, NULL, UMA_ALIGN_CACHE, 0); 201#else 202 NULL, NULL, sleepq_init, NULL, UMA_ALIGN_CACHE, 0); 203#endif 204 205 thread0.td_sleepqueue = sleepq_alloc(); 206} 207 208/* 209 * Get a sleep queue for a new thread. 210 */ 211struct sleepqueue * 212sleepq_alloc(void) 213{ 214 215 return (uma_zalloc(sleepq_zone, M_WAITOK)); 216} 217 218/* 219 * Free a sleep queue when a thread is destroyed. 220 */ 221void 222sleepq_free(struct sleepqueue *sq) 223{ 224 225 uma_zfree(sleepq_zone, sq); 226} 227 228/* 229 * Lock the sleep queue chain associated with the specified wait channel. 230 */ 231void 232sleepq_lock(void *wchan) 233{ 234 struct sleepqueue_chain *sc; 235 236 sc = SC_LOOKUP(wchan); 237 mtx_lock_spin(&sc->sc_lock); 238} 239 240/* 241 * Look up the sleep queue associated with a given wait channel in the hash 242 * table locking the associated sleep queue chain. If no queue is found in 243 * the table, NULL is returned. 244 */ 245struct sleepqueue * 246sleepq_lookup(void *wchan) 247{ 248 struct sleepqueue_chain *sc; 249 struct sleepqueue *sq; 250 251 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__)); 252 sc = SC_LOOKUP(wchan); 253 mtx_assert(&sc->sc_lock, MA_OWNED); 254 LIST_FOREACH(sq, &sc->sc_queues, sq_hash) 255 if (sq->sq_wchan == wchan) 256 return (sq); 257 return (NULL); 258} 259 260/* 261 * Unlock the sleep queue chain associated with a given wait channel. 262 */ 263void 264sleepq_release(void *wchan) 265{ 266 struct sleepqueue_chain *sc; 267 268 sc = SC_LOOKUP(wchan); 269 mtx_unlock_spin(&sc->sc_lock); 270} 271 272/* 273 * Places the current thread on the sleep queue for the specified wait 274 * channel. If INVARIANTS is enabled, then it associates the passed in 275 * lock with the sleepq to make sure it is held when that sleep queue is 276 * woken up. 277 */ 278void 279sleepq_add(void *wchan, struct lock_object *lock, const char *wmesg, int flags, 280 int queue) 281{ 282 struct sleepqueue_chain *sc; 283 struct sleepqueue *sq; 284 struct thread *td; 285 286 td = curthread; 287 sc = SC_LOOKUP(wchan); 288 mtx_assert(&sc->sc_lock, MA_OWNED); 289 MPASS(td->td_sleepqueue != NULL); 290 MPASS(wchan != NULL); 291 MPASS((queue >= 0) && (queue < NR_SLEEPQS)); 292 293 /* If this thread is not allowed to sleep, die a horrible death. */ 294 KASSERT(td->td_no_sleeping == 0, 295 ("%s: td %p to sleep on wchan %p with sleeping prohibited", 296 __func__, td, wchan)); 297 298 /* Look up the sleep queue associated with the wait channel 'wchan'. */ 299 sq = sleepq_lookup(wchan); 300 301 /* 302 * If the wait channel does not already have a sleep queue, use 303 * this thread's sleep queue. Otherwise, insert the current thread 304 * into the sleep queue already in use by this wait channel. 305 */ 306 if (sq == NULL) { 307#ifdef INVARIANTS 308 int i; 309 310 sq = td->td_sleepqueue; 311 for (i = 0; i < NR_SLEEPQS; i++) { 312 KASSERT(TAILQ_EMPTY(&sq->sq_blocked[i]), 313 ("thread's sleep queue %d is not empty", i)); 314 KASSERT(sq->sq_blockedcnt[i] == 0, 315 ("thread's sleep queue %d count mismatches", i)); 316 } 317 KASSERT(LIST_EMPTY(&sq->sq_free), 318 ("thread's sleep queue has a non-empty free list")); 319 KASSERT(sq->sq_wchan == NULL, ("stale sq_wchan pointer")); 320 sq->sq_lock = lock; 321#endif 322#ifdef SLEEPQUEUE_PROFILING 323 sc->sc_depth++; 324 if (sc->sc_depth > sc->sc_max_depth) { 325 sc->sc_max_depth = sc->sc_depth; 326 if (sc->sc_max_depth > sleepq_max_depth) 327 sleepq_max_depth = sc->sc_max_depth; 328 } 329#endif 330 sq = td->td_sleepqueue; 331 LIST_INSERT_HEAD(&sc->sc_queues, sq, sq_hash); 332 sq->sq_wchan = wchan; 333 sq->sq_type = flags & SLEEPQ_TYPE; 334 } else { 335 MPASS(wchan == sq->sq_wchan); 336 MPASS(lock == sq->sq_lock); 337 MPASS((flags & SLEEPQ_TYPE) == sq->sq_type); 338 LIST_INSERT_HEAD(&sq->sq_free, td->td_sleepqueue, sq_hash); 339 } 340 thread_lock(td); 341 TAILQ_INSERT_TAIL(&sq->sq_blocked[queue], td, td_slpq); 342 sq->sq_blockedcnt[queue]++; 343 td->td_sleepqueue = NULL; 344 td->td_sqqueue = queue; 345 td->td_wchan = wchan; 346 td->td_wmesg = wmesg; 347 if (flags & SLEEPQ_INTERRUPTIBLE) { 348 td->td_flags |= TDF_SINTR; 349 td->td_flags &= ~TDF_SLEEPABORT; 350 } 351 thread_unlock(td); 352} 353 354/* 355 * Sets a timeout that will remove the current thread from the specified 356 * sleep queue after timo ticks if the thread has not already been awakened. 357 */ 358void 359sleepq_set_timeout_sbt(void *wchan, sbintime_t sbt, sbintime_t pr, 360 int flags) 361{ 362 struct sleepqueue_chain *sc; 363 struct thread *td; 364 365 td = curthread; 366 sc = SC_LOOKUP(wchan); 367 mtx_assert(&sc->sc_lock, MA_OWNED); 368 MPASS(TD_ON_SLEEPQ(td)); 369 MPASS(td->td_sleepqueue == NULL); 370 MPASS(wchan != NULL); 371 callout_reset_sbt_on(&td->td_slpcallout, sbt, pr, 372 sleepq_timeout, td, PCPU_GET(cpuid), flags | C_DIRECT_EXEC); 373} 374 375/* 376 * Return the number of actual sleepers for the specified queue. 377 */ 378u_int 379sleepq_sleepcnt(void *wchan, int queue) 380{ 381 struct sleepqueue *sq; 382 383 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__)); 384 MPASS((queue >= 0) && (queue < NR_SLEEPQS)); 385 sq = sleepq_lookup(wchan); 386 if (sq == NULL) 387 return (0); 388 return (sq->sq_blockedcnt[queue]); 389} 390 391/* 392 * Marks the pending sleep of the current thread as interruptible and 393 * makes an initial check for pending signals before putting a thread 394 * to sleep. Enters and exits with the thread lock held. Thread lock 395 * may have transitioned from the sleepq lock to a run lock. 396 */ 397static int 398sleepq_catch_signals(void *wchan, int pri) 399{ 400 struct sleepqueue_chain *sc; 401 struct sleepqueue *sq; 402 struct thread *td; 403 struct proc *p; 404 struct sigacts *ps; 405 int sig, ret; 406 407 td = curthread; 408 p = curproc; 409 sc = SC_LOOKUP(wchan); 410 mtx_assert(&sc->sc_lock, MA_OWNED); 411 MPASS(wchan != NULL); 412 if ((td->td_pflags & TDP_WAKEUP) != 0) { 413 td->td_pflags &= ~TDP_WAKEUP; 414 ret = EINTR; 415 thread_lock(td); 416 goto out; 417 } 418 419 /* 420 * See if there are any pending signals for this thread. If not 421 * we can switch immediately. Otherwise do the signal processing 422 * directly. 423 */ 424 thread_lock(td); 425 if ((td->td_flags & (TDF_NEEDSIGCHK | TDF_NEEDSUSPCHK)) == 0) { 426 sleepq_switch(wchan, pri); 427 return (0); 428 } 429 thread_unlock(td); 430 mtx_unlock_spin(&sc->sc_lock); 431 CTR3(KTR_PROC, "sleepq catching signals: thread %p (pid %ld, %s)", 432 (void *)td, (long)p->p_pid, td->td_name); 433 PROC_LOCK(p); 434 ps = p->p_sigacts; 435 mtx_lock(&ps->ps_mtx); 436 sig = cursig(td); 437 if (sig == 0) { 438 mtx_unlock(&ps->ps_mtx); 439 ret = thread_suspend_check(1); 440 MPASS(ret == 0 || ret == EINTR || ret == ERESTART); 441 } else { 442 if (SIGISMEMBER(ps->ps_sigintr, sig)) 443 ret = EINTR; 444 else 445 ret = ERESTART; 446 mtx_unlock(&ps->ps_mtx); 447 } 448 /* 449 * Lock the per-process spinlock prior to dropping the PROC_LOCK 450 * to avoid a signal delivery race. PROC_LOCK, PROC_SLOCK, and 451 * thread_lock() are currently held in tdsendsignal(). 452 */ 453 PROC_SLOCK(p); 454 mtx_lock_spin(&sc->sc_lock); 455 PROC_UNLOCK(p); 456 thread_lock(td); 457 PROC_SUNLOCK(p); 458 if (ret == 0) { 459 sleepq_switch(wchan, pri); 460 return (0); 461 } 462out: 463 /* 464 * There were pending signals and this thread is still 465 * on the sleep queue, remove it from the sleep queue. 466 */ 467 if (TD_ON_SLEEPQ(td)) { 468 sq = sleepq_lookup(wchan); 469 if (sleepq_resume_thread(sq, td, 0)) { 470#ifdef INVARIANTS 471 /* 472 * This thread hasn't gone to sleep yet, so it 473 * should not be swapped out. 474 */ 475 panic("not waking up swapper"); 476#endif 477 } 478 } 479 mtx_unlock_spin(&sc->sc_lock); 480 MPASS(td->td_lock != &sc->sc_lock); 481 return (ret); 482} 483 484/* 485 * Switches to another thread if we are still asleep on a sleep queue. 486 * Returns with thread lock. 487 */ 488static void 489sleepq_switch(void *wchan, int pri) 490{ 491 struct sleepqueue_chain *sc; 492 struct sleepqueue *sq; 493 struct thread *td; 494 495 td = curthread; 496 sc = SC_LOOKUP(wchan); 497 mtx_assert(&sc->sc_lock, MA_OWNED); 498 THREAD_LOCK_ASSERT(td, MA_OWNED); 499 500 /* 501 * If we have a sleep queue, then we've already been woken up, so 502 * just return. 503 */ 504 if (td->td_sleepqueue != NULL) { 505 mtx_unlock_spin(&sc->sc_lock); 506 return; 507 } 508 509 /* 510 * If TDF_TIMEOUT is set, then our sleep has been timed out 511 * already but we are still on the sleep queue, so dequeue the 512 * thread and return. 513 */ 514 if (td->td_flags & TDF_TIMEOUT) { 515 MPASS(TD_ON_SLEEPQ(td)); 516 sq = sleepq_lookup(wchan); 517 if (sleepq_resume_thread(sq, td, 0)) { 518#ifdef INVARIANTS 519 /* 520 * This thread hasn't gone to sleep yet, so it 521 * should not be swapped out. 522 */ 523 panic("not waking up swapper"); 524#endif 525 } 526 mtx_unlock_spin(&sc->sc_lock); 527 return; 528 } 529#ifdef SLEEPQUEUE_PROFILING 530 if (prof_enabled) 531 sleepq_profile(td->td_wmesg); 532#endif 533 MPASS(td->td_sleepqueue == NULL); 534 sched_sleep(td, pri); 535 thread_lock_set(td, &sc->sc_lock); 536 SDT_PROBE0(sched, , , sleep); 537 TD_SET_SLEEPING(td); 538 mi_switch(SW_VOL | SWT_SLEEPQ, NULL); 539 KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING")); 540 CTR3(KTR_PROC, "sleepq resume: thread %p (pid %ld, %s)", 541 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name); 542} 543 544/* 545 * Check to see if we timed out. 546 */ 547static int 548sleepq_check_timeout(void) 549{ 550 struct thread *td; 551 552 td = curthread; 553 THREAD_LOCK_ASSERT(td, MA_OWNED); 554 555 /* 556 * If TDF_TIMEOUT is set, we timed out. 557 */ 558 if (td->td_flags & TDF_TIMEOUT) { 559 td->td_flags &= ~TDF_TIMEOUT; 560 return (EWOULDBLOCK); 561 } 562 563 /* 564 * If TDF_TIMOFAIL is set, the timeout ran after we had 565 * already been woken up. 566 */ 567 if (td->td_flags & TDF_TIMOFAIL) 568 td->td_flags &= ~TDF_TIMOFAIL; 569 570 /* 571 * If callout_stop() fails, then the timeout is running on 572 * another CPU, so synchronize with it to avoid having it 573 * accidentally wake up a subsequent sleep. 574 */ 575 else if (callout_stop(&td->td_slpcallout) == 0) { 576 td->td_flags |= TDF_TIMEOUT; 577 TD_SET_SLEEPING(td); 578 mi_switch(SW_INVOL | SWT_SLEEPQTIMO, NULL); 579 } 580 return (0); 581} 582 583/* 584 * Check to see if we were awoken by a signal. 585 */ 586static int 587sleepq_check_signals(void) 588{ 589 struct thread *td; 590 591 td = curthread; 592 THREAD_LOCK_ASSERT(td, MA_OWNED); 593 594 /* We are no longer in an interruptible sleep. */ 595 if (td->td_flags & TDF_SINTR) 596 td->td_flags &= ~TDF_SINTR; 597 598 if (td->td_flags & TDF_SLEEPABORT) { 599 td->td_flags &= ~TDF_SLEEPABORT; 600 return (td->td_intrval); 601 } 602 603 return (0); 604} 605 606/* 607 * Block the current thread until it is awakened from its sleep queue. 608 */ 609void 610sleepq_wait(void *wchan, int pri) 611{ 612 struct thread *td; 613 614 td = curthread; 615 MPASS(!(td->td_flags & TDF_SINTR)); 616 thread_lock(td); 617 sleepq_switch(wchan, pri); 618 thread_unlock(td); 619} 620 621/* 622 * Block the current thread until it is awakened from its sleep queue 623 * or it is interrupted by a signal. 624 */ 625int 626sleepq_wait_sig(void *wchan, int pri) 627{ 628 int rcatch; 629 int rval; 630 631 rcatch = sleepq_catch_signals(wchan, pri); 632 rval = sleepq_check_signals(); 633 thread_unlock(curthread); 634 if (rcatch) 635 return (rcatch); 636 return (rval); 637} 638 639/* 640 * Block the current thread until it is awakened from its sleep queue 641 * or it times out while waiting. 642 */ 643int 644sleepq_timedwait(void *wchan, int pri) 645{ 646 struct thread *td; 647 int rval; 648 649 td = curthread; 650 MPASS(!(td->td_flags & TDF_SINTR)); 651 thread_lock(td); 652 sleepq_switch(wchan, pri); 653 rval = sleepq_check_timeout(); 654 thread_unlock(td); 655 656 return (rval); 657} 658 659/* 660 * Block the current thread until it is awakened from its sleep queue, 661 * it is interrupted by a signal, or it times out waiting to be awakened. 662 */ 663int 664sleepq_timedwait_sig(void *wchan, int pri) 665{ 666 int rcatch, rvalt, rvals; 667 668 rcatch = sleepq_catch_signals(wchan, pri); 669 rvalt = sleepq_check_timeout(); 670 rvals = sleepq_check_signals(); 671 thread_unlock(curthread); 672 if (rcatch) 673 return (rcatch); 674 if (rvals) 675 return (rvals); 676 return (rvalt); 677} 678 679/* 680 * Returns the type of sleepqueue given a waitchannel. 681 */ 682int 683sleepq_type(void *wchan) 684{ 685 struct sleepqueue *sq; 686 int type; 687 688 MPASS(wchan != NULL); 689 690 sleepq_lock(wchan); 691 sq = sleepq_lookup(wchan); 692 if (sq == NULL) { 693 sleepq_release(wchan); 694 return (-1); 695 } 696 type = sq->sq_type; 697 sleepq_release(wchan); 698 return (type); 699} 700 701/* 702 * Removes a thread from a sleep queue and makes it 703 * runnable. 704 */ 705static int 706sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, int pri) 707{ 708 struct sleepqueue_chain *sc; 709 710 MPASS(td != NULL); 711 MPASS(sq->sq_wchan != NULL); 712 MPASS(td->td_wchan == sq->sq_wchan); 713 MPASS(td->td_sqqueue < NR_SLEEPQS && td->td_sqqueue >= 0); 714 THREAD_LOCK_ASSERT(td, MA_OWNED); 715 sc = SC_LOOKUP(sq->sq_wchan); 716 mtx_assert(&sc->sc_lock, MA_OWNED); 717 718 SDT_PROBE2(sched, , , wakeup, td, td->td_proc); 719 720 /* Remove the thread from the queue. */ 721 sq->sq_blockedcnt[td->td_sqqueue]--; 722 TAILQ_REMOVE(&sq->sq_blocked[td->td_sqqueue], td, td_slpq); 723 724 /* 725 * Get a sleep queue for this thread. If this is the last waiter, 726 * use the queue itself and take it out of the chain, otherwise, 727 * remove a queue from the free list. 728 */ 729 if (LIST_EMPTY(&sq->sq_free)) { 730 td->td_sleepqueue = sq; 731#ifdef INVARIANTS 732 sq->sq_wchan = NULL; 733#endif 734#ifdef SLEEPQUEUE_PROFILING 735 sc->sc_depth--; 736#endif 737 } else 738 td->td_sleepqueue = LIST_FIRST(&sq->sq_free); 739 LIST_REMOVE(td->td_sleepqueue, sq_hash); 740 741 td->td_wmesg = NULL; 742 td->td_wchan = NULL; 743 td->td_flags &= ~TDF_SINTR; 744 745 CTR3(KTR_PROC, "sleepq_wakeup: thread %p (pid %ld, %s)", 746 (void *)td, (long)td->td_proc->p_pid, td->td_name); 747 748 /* Adjust priority if requested. */ 749 MPASS(pri == 0 || (pri >= PRI_MIN && pri <= PRI_MAX)); 750 if (pri != 0 && td->td_priority > pri && 751 PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) 752 sched_prio(td, pri); 753 754 /* 755 * Note that thread td might not be sleeping if it is running 756 * sleepq_catch_signals() on another CPU or is blocked on its 757 * proc lock to check signals. There's no need to mark the 758 * thread runnable in that case. 759 */ 760 if (TD_IS_SLEEPING(td)) { 761 TD_CLR_SLEEPING(td); 762 return (setrunnable(td)); 763 } 764 return (0); 765} 766 767#ifdef INVARIANTS 768/* 769 * UMA zone item deallocator. 770 */ 771static void 772sleepq_dtor(void *mem, int size, void *arg) 773{ 774 struct sleepqueue *sq; 775 int i; 776 777 sq = mem; 778 for (i = 0; i < NR_SLEEPQS; i++) { 779 MPASS(TAILQ_EMPTY(&sq->sq_blocked[i])); 780 MPASS(sq->sq_blockedcnt[i] == 0); 781 } 782} 783#endif 784 785/* 786 * UMA zone item initializer. 787 */ 788static int 789sleepq_init(void *mem, int size, int flags) 790{ 791 struct sleepqueue *sq; 792 int i; 793 794 bzero(mem, size); 795 sq = mem; 796 for (i = 0; i < NR_SLEEPQS; i++) { 797 TAILQ_INIT(&sq->sq_blocked[i]); 798 sq->sq_blockedcnt[i] = 0; 799 } 800 LIST_INIT(&sq->sq_free); 801 return (0); 802} 803 804/* 805 * Find the highest priority thread sleeping on a wait channel and resume it. 806 */ 807int 808sleepq_signal(void *wchan, int flags, int pri, int queue) 809{ 810 struct sleepqueue *sq; 811 struct thread *td, *besttd; 812 int wakeup_swapper; 813 814 CTR2(KTR_PROC, "sleepq_signal(%p, %d)", wchan, flags); 815 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__)); 816 MPASS((queue >= 0) && (queue < NR_SLEEPQS)); 817 sq = sleepq_lookup(wchan); 818 if (sq == NULL) 819 return (0); 820 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE), 821 ("%s: mismatch between sleep/wakeup and cv_*", __func__)); 822 823 /* 824 * Find the highest priority thread on the queue. If there is a 825 * tie, use the thread that first appears in the queue as it has 826 * been sleeping the longest since threads are always added to 827 * the tail of sleep queues. 828 */ 829 besttd = NULL; 830 TAILQ_FOREACH(td, &sq->sq_blocked[queue], td_slpq) { 831 if (besttd == NULL || td->td_priority < besttd->td_priority) 832 besttd = td; 833 } 834 MPASS(besttd != NULL); 835 thread_lock(besttd); 836 wakeup_swapper = sleepq_resume_thread(sq, besttd, pri); 837 thread_unlock(besttd); 838 return (wakeup_swapper); 839} 840 841/* 842 * Resume all threads sleeping on a specified wait channel. 843 */ 844int 845sleepq_broadcast(void *wchan, int flags, int pri, int queue) 846{ 847 struct sleepqueue *sq; 848 struct thread *td, *tdn; 849 int wakeup_swapper; 850 851 CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags); 852 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__)); 853 MPASS((queue >= 0) && (queue < NR_SLEEPQS)); 854 sq = sleepq_lookup(wchan); 855 if (sq == NULL) 856 return (0); 857 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE), 858 ("%s: mismatch between sleep/wakeup and cv_*", __func__)); 859 860 /* Resume all blocked threads on the sleep queue. */ 861 wakeup_swapper = 0; 862 TAILQ_FOREACH_SAFE(td, &sq->sq_blocked[queue], td_slpq, tdn) { 863 thread_lock(td); 864 if (sleepq_resume_thread(sq, td, pri)) 865 wakeup_swapper = 1; 866 thread_unlock(td); 867 } 868 return (wakeup_swapper); 869} 870 871/* 872 * Time sleeping threads out. When the timeout expires, the thread is 873 * removed from the sleep queue and made runnable if it is still asleep. 874 */ 875static void 876sleepq_timeout(void *arg) 877{ 878 struct sleepqueue_chain *sc; 879 struct sleepqueue *sq; 880 struct thread *td; 881 void *wchan; 882 int wakeup_swapper; 883 884 td = arg; 885 wakeup_swapper = 0; 886 CTR3(KTR_PROC, "sleepq_timeout: thread %p (pid %ld, %s)", 887 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name); 888 889 /* 890 * First, see if the thread is asleep and get the wait channel if 891 * it is. 892 */ 893 thread_lock(td); 894 if (TD_IS_SLEEPING(td) && TD_ON_SLEEPQ(td)) { 895 wchan = td->td_wchan; 896 sc = SC_LOOKUP(wchan); 897 THREAD_LOCKPTR_ASSERT(td, &sc->sc_lock); 898 sq = sleepq_lookup(wchan); 899 MPASS(sq != NULL); 900 td->td_flags |= TDF_TIMEOUT; 901 wakeup_swapper = sleepq_resume_thread(sq, td, 0); 902 thread_unlock(td); 903 if (wakeup_swapper) 904 kick_proc0(); 905 return; 906 } 907 908 /* 909 * If the thread is on the SLEEPQ but isn't sleeping yet, it 910 * can either be on another CPU in between sleepq_add() and 911 * one of the sleepq_*wait*() routines or it can be in 912 * sleepq_catch_signals(). 913 */ 914 if (TD_ON_SLEEPQ(td)) { 915 td->td_flags |= TDF_TIMEOUT; 916 thread_unlock(td); 917 return; 918 } 919 920 /* 921 * Now check for the edge cases. First, if TDF_TIMEOUT is set, 922 * then the other thread has already yielded to us, so clear 923 * the flag and resume it. If TDF_TIMEOUT is not set, then the 924 * we know that the other thread is not on a sleep queue, but it 925 * hasn't resumed execution yet. In that case, set TDF_TIMOFAIL 926 * to let it know that the timeout has already run and doesn't 927 * need to be canceled. 928 */ 929 if (td->td_flags & TDF_TIMEOUT) { 930 MPASS(TD_IS_SLEEPING(td)); 931 td->td_flags &= ~TDF_TIMEOUT; 932 TD_CLR_SLEEPING(td); 933 wakeup_swapper = setrunnable(td); 934 } else 935 td->td_flags |= TDF_TIMOFAIL; 936 thread_unlock(td); 937 if (wakeup_swapper) 938 kick_proc0(); 939} 940 941/* 942 * Resumes a specific thread from the sleep queue associated with a specific 943 * wait channel if it is on that queue. 944 */ 945void 946sleepq_remove(struct thread *td, void *wchan) 947{ 948 struct sleepqueue *sq; 949 int wakeup_swapper; 950 951 /* 952 * Look up the sleep queue for this wait channel, then re-check 953 * that the thread is asleep on that channel, if it is not, then 954 * bail. 955 */ 956 MPASS(wchan != NULL); 957 sleepq_lock(wchan); 958 sq = sleepq_lookup(wchan); 959 /* 960 * We can not lock the thread here as it may be sleeping on a 961 * different sleepq. However, holding the sleepq lock for this 962 * wchan can guarantee that we do not miss a wakeup for this 963 * channel. The asserts below will catch any false positives. 964 */ 965 if (!TD_ON_SLEEPQ(td) || td->td_wchan != wchan) { 966 sleepq_release(wchan); 967 return; 968 } 969 /* Thread is asleep on sleep queue sq, so wake it up. */ 970 thread_lock(td); 971 MPASS(sq != NULL); 972 MPASS(td->td_wchan == wchan); 973 wakeup_swapper = sleepq_resume_thread(sq, td, 0); 974 thread_unlock(td); 975 sleepq_release(wchan); 976 if (wakeup_swapper) 977 kick_proc0(); 978} 979 980/* 981 * Abort a thread as if an interrupt had occurred. Only abort 982 * interruptible waits (unfortunately it isn't safe to abort others). 983 */ 984int 985sleepq_abort(struct thread *td, int intrval) 986{ 987 struct sleepqueue *sq; 988 void *wchan; 989 990 THREAD_LOCK_ASSERT(td, MA_OWNED); 991 MPASS(TD_ON_SLEEPQ(td)); 992 MPASS(td->td_flags & TDF_SINTR); 993 MPASS(intrval == EINTR || intrval == ERESTART); 994 995 /* 996 * If the TDF_TIMEOUT flag is set, just leave. A 997 * timeout is scheduled anyhow. 998 */ 999 if (td->td_flags & TDF_TIMEOUT) 1000 return (0); 1001 1002 CTR3(KTR_PROC, "sleepq_abort: thread %p (pid %ld, %s)", 1003 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name); 1004 td->td_intrval = intrval; 1005 td->td_flags |= TDF_SLEEPABORT; 1006 /* 1007 * If the thread has not slept yet it will find the signal in 1008 * sleepq_catch_signals() and call sleepq_resume_thread. Otherwise 1009 * we have to do it here. 1010 */ 1011 if (!TD_IS_SLEEPING(td)) 1012 return (0); 1013 wchan = td->td_wchan; 1014 MPASS(wchan != NULL); 1015 sq = sleepq_lookup(wchan); 1016 MPASS(sq != NULL); 1017 1018 /* Thread is asleep on sleep queue sq, so wake it up. */ 1019 return (sleepq_resume_thread(sq, td, 0)); 1020} 1021 1022#ifdef SLEEPQUEUE_PROFILING 1023#define SLEEPQ_PROF_LOCATIONS 1024 1024#define SLEEPQ_SBUFSIZE 512 1025struct sleepq_prof { 1026 LIST_ENTRY(sleepq_prof) sp_link; 1027 const char *sp_wmesg; 1028 long sp_count; 1029}; 1030 1031LIST_HEAD(sqphead, sleepq_prof); 1032 1033struct sqphead sleepq_prof_free; 1034struct sqphead sleepq_hash[SC_TABLESIZE]; 1035static struct sleepq_prof sleepq_profent[SLEEPQ_PROF_LOCATIONS]; 1036static struct mtx sleepq_prof_lock; 1037MTX_SYSINIT(sleepq_prof_lock, &sleepq_prof_lock, "sleepq_prof", MTX_SPIN); 1038 1039static void 1040sleepq_profile(const char *wmesg) 1041{ 1042 struct sleepq_prof *sp; 1043 1044 mtx_lock_spin(&sleepq_prof_lock); 1045 if (prof_enabled == 0) 1046 goto unlock; 1047 LIST_FOREACH(sp, &sleepq_hash[SC_HASH(wmesg)], sp_link) 1048 if (sp->sp_wmesg == wmesg) 1049 goto done; 1050 sp = LIST_FIRST(&sleepq_prof_free); 1051 if (sp == NULL) 1052 goto unlock; 1053 sp->sp_wmesg = wmesg; 1054 LIST_REMOVE(sp, sp_link); 1055 LIST_INSERT_HEAD(&sleepq_hash[SC_HASH(wmesg)], sp, sp_link); 1056done: 1057 sp->sp_count++; 1058unlock: 1059 mtx_unlock_spin(&sleepq_prof_lock); 1060 return; 1061} 1062 1063static void 1064sleepq_prof_reset(void) 1065{ 1066 struct sleepq_prof *sp; 1067 int enabled; 1068 int i; 1069 1070 mtx_lock_spin(&sleepq_prof_lock); 1071 enabled = prof_enabled; 1072 prof_enabled = 0; 1073 for (i = 0; i < SC_TABLESIZE; i++) 1074 LIST_INIT(&sleepq_hash[i]); 1075 LIST_INIT(&sleepq_prof_free); 1076 for (i = 0; i < SLEEPQ_PROF_LOCATIONS; i++) { 1077 sp = &sleepq_profent[i]; 1078 sp->sp_wmesg = NULL; 1079 sp->sp_count = 0; 1080 LIST_INSERT_HEAD(&sleepq_prof_free, sp, sp_link); 1081 } 1082 prof_enabled = enabled; 1083 mtx_unlock_spin(&sleepq_prof_lock); 1084} 1085 1086static int 1087enable_sleepq_prof(SYSCTL_HANDLER_ARGS) 1088{ 1089 int error, v; 1090 1091 v = prof_enabled; 1092 error = sysctl_handle_int(oidp, &v, v, req); 1093 if (error) 1094 return (error); 1095 if (req->newptr == NULL) 1096 return (error); 1097 if (v == prof_enabled) 1098 return (0); 1099 if (v == 1) 1100 sleepq_prof_reset(); 1101 mtx_lock_spin(&sleepq_prof_lock); 1102 prof_enabled = !!v; 1103 mtx_unlock_spin(&sleepq_prof_lock); 1104 1105 return (0); 1106} 1107 1108static int 1109reset_sleepq_prof_stats(SYSCTL_HANDLER_ARGS) 1110{ 1111 int error, v; 1112 1113 v = 0; 1114 error = sysctl_handle_int(oidp, &v, 0, req); 1115 if (error) 1116 return (error); 1117 if (req->newptr == NULL) 1118 return (error); 1119 if (v == 0) 1120 return (0); 1121 sleepq_prof_reset(); 1122 1123 return (0); 1124} 1125 1126static int 1127dump_sleepq_prof_stats(SYSCTL_HANDLER_ARGS) 1128{ 1129 struct sleepq_prof *sp; 1130 struct sbuf *sb; 1131 int enabled; 1132 int error; 1133 int i; 1134 1135 error = sysctl_wire_old_buffer(req, 0); 1136 if (error != 0) 1137 return (error); 1138 sb = sbuf_new_for_sysctl(NULL, NULL, SLEEPQ_SBUFSIZE, req); 1139 sbuf_printf(sb, "\nwmesg\tcount\n"); 1140 enabled = prof_enabled; 1141 mtx_lock_spin(&sleepq_prof_lock); 1142 prof_enabled = 0; 1143 mtx_unlock_spin(&sleepq_prof_lock); 1144 for (i = 0; i < SC_TABLESIZE; i++) { 1145 LIST_FOREACH(sp, &sleepq_hash[i], sp_link) { 1146 sbuf_printf(sb, "%s\t%ld\n", 1147 sp->sp_wmesg, sp->sp_count); 1148 } 1149 } 1150 mtx_lock_spin(&sleepq_prof_lock); 1151 prof_enabled = enabled; 1152 mtx_unlock_spin(&sleepq_prof_lock); 1153 1154 error = sbuf_finish(sb); 1155 sbuf_delete(sb); 1156 return (error); 1157} 1158 1159SYSCTL_PROC(_debug_sleepq, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD, 1160 NULL, 0, dump_sleepq_prof_stats, "A", "Sleepqueue profiling statistics"); 1161SYSCTL_PROC(_debug_sleepq, OID_AUTO, reset, CTLTYPE_INT | CTLFLAG_RW, 1162 NULL, 0, reset_sleepq_prof_stats, "I", 1163 "Reset sleepqueue profiling statistics"); 1164SYSCTL_PROC(_debug_sleepq, OID_AUTO, enable, CTLTYPE_INT | CTLFLAG_RW, 1165 NULL, 0, enable_sleepq_prof, "I", "Enable sleepqueue profiling"); 1166#endif 1167 1168#ifdef DDB 1169DB_SHOW_COMMAND(sleepq, db_show_sleepqueue) 1170{ 1171 struct sleepqueue_chain *sc; 1172 struct sleepqueue *sq; 1173#ifdef INVARIANTS 1174 struct lock_object *lock; 1175#endif 1176 struct thread *td; 1177 void *wchan; 1178 int i; 1179 1180 if (!have_addr) 1181 return; 1182 1183 /* 1184 * First, see if there is an active sleep queue for the wait channel 1185 * indicated by the address. 1186 */ 1187 wchan = (void *)addr; 1188 sc = SC_LOOKUP(wchan); 1189 LIST_FOREACH(sq, &sc->sc_queues, sq_hash) 1190 if (sq->sq_wchan == wchan) 1191 goto found; 1192 1193 /* 1194 * Second, see if there is an active sleep queue at the address 1195 * indicated. 1196 */ 1197 for (i = 0; i < SC_TABLESIZE; i++) 1198 LIST_FOREACH(sq, &sleepq_chains[i].sc_queues, sq_hash) { 1199 if (sq == (struct sleepqueue *)addr) 1200 goto found; 1201 } 1202 1203 db_printf("Unable to locate a sleep queue via %p\n", (void *)addr); 1204 return; 1205found: 1206 db_printf("Wait channel: %p\n", sq->sq_wchan); 1207 db_printf("Queue type: %d\n", sq->sq_type); 1208#ifdef INVARIANTS 1209 if (sq->sq_lock) { 1210 lock = sq->sq_lock; 1211 db_printf("Associated Interlock: %p - (%s) %s\n", lock, 1212 LOCK_CLASS(lock)->lc_name, lock->lo_name); 1213 } 1214#endif 1215 db_printf("Blocked threads:\n"); 1216 for (i = 0; i < NR_SLEEPQS; i++) { 1217 db_printf("\nQueue[%d]:\n", i); 1218 if (TAILQ_EMPTY(&sq->sq_blocked[i])) 1219 db_printf("\tempty\n"); 1220 else 1221 TAILQ_FOREACH(td, &sq->sq_blocked[0], 1222 td_slpq) { 1223 db_printf("\t%p (tid %d, pid %d, \"%s\")\n", td, 1224 td->td_tid, td->td_proc->p_pid, 1225 td->td_name); 1226 } 1227 db_printf("(expected: %u)\n", sq->sq_blockedcnt[i]); 1228 } 1229} 1230 1231/* Alias 'show sleepqueue' to 'show sleepq'. */ 1232DB_SHOW_ALIAS(sleepqueue, db_show_sleepqueue); 1233#endif 1234