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("$FreeBSD$"); 61 62 #include "opt_sleepqueue_profiling.h" 63 #include "opt_ddb.h" 64 #include "opt_sched.h" 65 66 #include <sys/param.h> 67 #include <sys/systm.h> 68 #include <sys/lock.h> 69 #include <sys/kernel.h> 70 #include <sys/ktr.h> 71 #include <sys/mutex.h> 72 #include <sys/proc.h> 73 #include <sys/sbuf.h> 74 #include <sys/sched.h> 75 #include <sys/sdt.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. 88 * SC_TABLESIZE must be a power of two for SC_MASK to work properly. 89 */ 90 #define SC_TABLESIZE 256 /* Must be power of 2. */ 91 #define SC_MASK (SC_TABLESIZE - 1) 92 #define SC_SHIFT 8 93 #define SC_HASH(wc) ((((uintptr_t)(wc) >> SC_SHIFT) ^ (uintptr_t)(wc)) & \ 94 SC_MASK) 95 #define SC_LOOKUP(wc) &sleepq_chains[SC_HASH(wc)] 96 #define NR_SLEEPQS 2 97 /* 98 * There two different lists of sleep queues. Both lists are connected 99 * via the sq_hash entries. The first list is the sleep queue chain list 100 * that a sleep queue is on when it is attached to a wait channel. The 101 * second list is the free list hung off of a sleep queue that is attached 102 * to a wait channel. 103 * 104 * Each sleep queue also contains the wait channel it is attached to, the 105 * list of threads blocked on that wait channel, flags specific to the 106 * wait channel, and the lock used to synchronize with a wait channel. 107 * The flags are used to catch mismatches between the various consumers 108 * of the sleep queue API (e.g. sleep/wakeup and condition variables). 109 * The lock pointer is only used when invariants are enabled for various 110 * debugging checks. 111 * 112 * Locking key: 113 * c - sleep queue chain lock 114 */ 115 struct sleepqueue { 116 TAILQ_HEAD(, thread) sq_blocked[NR_SLEEPQS]; /* (c) Blocked threads. */ 117 u_int sq_blockedcnt[NR_SLEEPQS]; /* (c) N. of blocked threads. */ 118 LIST_ENTRY(sleepqueue) sq_hash; /* (c) Chain and free list. */ 119 LIST_HEAD(, sleepqueue) sq_free; /* (c) Free queues. */ 120 void *sq_wchan; /* (c) Wait channel. */ 121 int sq_type; /* (c) Queue type. */ 122 #ifdef INVARIANTS 123 struct lock_object *sq_lock; /* (c) Associated lock. */ 124 #endif 125 }; 126 127 struct sleepqueue_chain { 128 LIST_HEAD(, sleepqueue) sc_queues; /* List of sleep queues. */ 129 struct mtx sc_lock; /* Spin lock for this chain. */ 130 #ifdef SLEEPQUEUE_PROFILING 131 u_int sc_depth; /* Length of sc_queues. */ 132 u_int sc_max_depth; /* Max length of sc_queues. */ 133 #endif 134 }; 135 136 #ifdef SLEEPQUEUE_PROFILING 137 u_int sleepq_max_depth; 138 static SYSCTL_NODE(_debug, OID_AUTO, sleepq, CTLFLAG_RD, 0, "sleepq profiling"); 139 static SYSCTL_NODE(_debug_sleepq, OID_AUTO, chains, CTLFLAG_RD, 0, 140 "sleepq chain stats"); 141 SYSCTL_UINT(_debug_sleepq, OID_AUTO, max_depth, CTLFLAG_RD, &sleepq_max_depth, 142 0, "maxmimum depth achieved of a single chain"); 143 144 static void sleepq_profile(const char *wmesg); 145 static int prof_enabled; 146 #endif 147 static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE]; 148 static uma_zone_t sleepq_zone; 149 150 /* 151 * Prototypes for non-exported routines. 152 */ 153 static int sleepq_catch_signals(void *wchan, int pri); 154 static int sleepq_check_signals(void); 155 static int sleepq_check_timeout(void); 156 #ifdef INVARIANTS 157 static void sleepq_dtor(void *mem, int size, void *arg); 158 #endif 159 static int sleepq_init(void *mem, int size, int flags); 160 static int sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, 161 int pri); 162 static void sleepq_switch(void *wchan, int pri); 163 static void sleepq_timeout(void *arg); 164 165 SDT_PROBE_DECLARE(sched, , , sleep); 166 SDT_PROBE_DECLARE(sched, , , wakeup); 167 168 /* 169 * Initialize SLEEPQUEUE_PROFILING specific sysctl nodes. 170 * Note that it must happen after sleepinit() has been fully executed, so 171 * it must happen after SI_SUB_KMEM SYSINIT() subsystem setup. 172 */ 173 #ifdef SLEEPQUEUE_PROFILING 174 static void 175 init_sleepqueue_profiling(void) 176 { 177 char chain_name[10]; 178 struct sysctl_oid *chain_oid; 179 u_int i; 180 181 for (i = 0; i < SC_TABLESIZE; i++) { 182 snprintf(chain_name, sizeof(chain_name), "%u", i); 183 chain_oid = SYSCTL_ADD_NODE(NULL, 184 SYSCTL_STATIC_CHILDREN(_debug_sleepq_chains), OID_AUTO, 185 chain_name, CTLFLAG_RD, NULL, "sleepq chain stats"); 186 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO, 187 "depth", CTLFLAG_RD, &sleepq_chains[i].sc_depth, 0, NULL); 188 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO, 189 "max_depth", CTLFLAG_RD, &sleepq_chains[i].sc_max_depth, 0, 190 NULL); 191 } 192 } 193 194 SYSINIT(sleepqueue_profiling, SI_SUB_LOCK, SI_ORDER_ANY, 195 init_sleepqueue_profiling, NULL); 196 #endif 197 198 /* 199 * Early initialization of sleep queues that is called from the sleepinit() 200 * SYSINIT. 201 */ 202 void 203 init_sleepqueues(void) 204 { 205 int i; 206 207 for (i = 0; i < SC_TABLESIZE; i++) { 208 LIST_INIT(&sleepq_chains[i].sc_queues); 209 mtx_init(&sleepq_chains[i].sc_lock, "sleepq chain", NULL, 210 MTX_SPIN | MTX_RECURSE); 211 } 212 sleepq_zone = uma_zcreate("SLEEPQUEUE", sizeof(struct sleepqueue), 213 #ifdef INVARIANTS 214 NULL, sleepq_dtor, sleepq_init, NULL, UMA_ALIGN_CACHE, 0); 215 #else 216 NULL, NULL, sleepq_init, NULL, UMA_ALIGN_CACHE, 0); 217 #endif 218 219 thread0.td_sleepqueue = sleepq_alloc(); 220 } 221 222 /* 223 * Get a sleep queue for a new thread. 224 */ 225 struct sleepqueue * 226 sleepq_alloc(void) 227 { 228 229 return (uma_zalloc(sleepq_zone, M_WAITOK)); 230 } 231 232 /* 233 * Free a sleep queue when a thread is destroyed. 234 */ 235 void 236 sleepq_free(struct sleepqueue *sq) 237 { 238 239 uma_zfree(sleepq_zone, sq); 240 } 241 242 /* 243 * Lock the sleep queue chain associated with the specified wait channel. 244 */ 245 void 246 sleepq_lock(void *wchan) 247 { 248 struct sleepqueue_chain *sc; 249 250 sc = SC_LOOKUP(wchan); 251 mtx_lock_spin(&sc->sc_lock); 252 } 253 254 /* 255 * Look up the sleep queue associated with a given wait channel in the hash 256 * table locking the associated sleep queue chain. If no queue is found in 257 * the table, NULL is returned. 258 */ 259 struct sleepqueue * 260 sleepq_lookup(void *wchan) 261 { 262 struct sleepqueue_chain *sc; 263 struct sleepqueue *sq; 264 265 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__)); 266 sc = SC_LOOKUP(wchan); 267 mtx_assert(&sc->sc_lock, MA_OWNED); 268 LIST_FOREACH(sq, &sc->sc_queues, sq_hash) 269 if (sq->sq_wchan == wchan) 270 return (sq); 271 return (NULL); 272 } 273 274 /* 275 * Unlock the sleep queue chain associated with a given wait channel. 276 */ 277 void 278 sleepq_release(void *wchan) 279 { 280 struct sleepqueue_chain *sc; 281 282 sc = SC_LOOKUP(wchan); 283 mtx_unlock_spin(&sc->sc_lock); 284 } 285 286 /* 287 * Places the current thread on the sleep queue for the specified wait 288 * channel. If INVARIANTS is enabled, then it associates the passed in 289 * lock with the sleepq to make sure it is held when that sleep queue is 290 * woken up. 291 */ 292 void 293 sleepq_add(void *wchan, struct lock_object *lock, const char *wmesg, int flags, 294 int queue) 295 { 296 struct sleepqueue_chain *sc; 297 struct sleepqueue *sq; 298 struct thread *td; 299 300 td = curthread; 301 sc = SC_LOOKUP(wchan); 302 mtx_assert(&sc->sc_lock, MA_OWNED); 303 MPASS(td->td_sleepqueue != NULL); 304 MPASS(wchan != NULL); 305 MPASS((queue >= 0) && (queue < NR_SLEEPQS)); 306 307 /* If this thread is not allowed to sleep, die a horrible death. */ 308 KASSERT(td->td_no_sleeping == 0, 309 ("%s: td %p to sleep on wchan %p with sleeping prohibited", 310 __func__, td, wchan)); 311 312 /* Look up the sleep queue associated with the wait channel 'wchan'. */ 313 sq = sleepq_lookup(wchan); 314 315 /* 316 * If the wait channel does not already have a sleep queue, use 317 * this thread's sleep queue. Otherwise, insert the current thread 318 * into the sleep queue already in use by this wait channel. 319 */ 320 if (sq == NULL) { 321 #ifdef INVARIANTS 322 int i; 323 324 sq = td->td_sleepqueue; 325 for (i = 0; i < NR_SLEEPQS; i++) { 326 KASSERT(TAILQ_EMPTY(&sq->sq_blocked[i]), 327 ("thread's sleep queue %d is not empty", i)); 328 KASSERT(sq->sq_blockedcnt[i] == 0, 329 ("thread's sleep queue %d count mismatches", i)); 330 } 331 KASSERT(LIST_EMPTY(&sq->sq_free), 332 ("thread's sleep queue has a non-empty free list")); 333 KASSERT(sq->sq_wchan == NULL, ("stale sq_wchan pointer")); 334 sq->sq_lock = lock; 335 #endif 336 #ifdef SLEEPQUEUE_PROFILING 337 sc->sc_depth++; 338 if (sc->sc_depth > sc->sc_max_depth) { 339 sc->sc_max_depth = sc->sc_depth; 340 if (sc->sc_max_depth > sleepq_max_depth) 341 sleepq_max_depth = sc->sc_max_depth; 342 } 343 #endif 344 sq = td->td_sleepqueue; 345 LIST_INSERT_HEAD(&sc->sc_queues, sq, sq_hash); 346 sq->sq_wchan = wchan; 347 sq->sq_type = flags & SLEEPQ_TYPE; 348 } else { 349 MPASS(wchan == sq->sq_wchan); 350 MPASS(lock == sq->sq_lock); 351 MPASS((flags & SLEEPQ_TYPE) == sq->sq_type); 352 LIST_INSERT_HEAD(&sq->sq_free, td->td_sleepqueue, sq_hash); 353 } 354 thread_lock(td); 355 TAILQ_INSERT_TAIL(&sq->sq_blocked[queue], td, td_slpq); 356 sq->sq_blockedcnt[queue]++; 357 td->td_sleepqueue = NULL; 358 td->td_sqqueue = queue; 359 td->td_wchan = wchan; 360 td->td_wmesg = wmesg; 361 if (flags & SLEEPQ_INTERRUPTIBLE) { 362 td->td_flags |= TDF_SINTR; 363 td->td_flags &= ~TDF_SLEEPABORT; 364 } 365 thread_unlock(td); 366 } 367 368 /* 369 * Sets a timeout that will remove the current thread from the specified 370 * sleep queue after timo ticks if the thread has not already been awakened. 371 */ 372 void 373 sleepq_set_timeout_sbt(void *wchan, sbintime_t sbt, sbintime_t pr, 374 int flags) 375 { 376 struct sleepqueue_chain *sc; 377 struct thread *td; 378 379 td = curthread; 380 sc = SC_LOOKUP(wchan); 381 mtx_assert(&sc->sc_lock, MA_OWNED); 382 MPASS(TD_ON_SLEEPQ(td)); 383 MPASS(td->td_sleepqueue == NULL); 384 MPASS(wchan != NULL); 385 callout_reset_sbt_on(&td->td_slpcallout, sbt, pr, 386 sleepq_timeout, td, PCPU_GET(cpuid), flags | C_DIRECT_EXEC); 387 } 388 389 /* 390 * Return the number of actual sleepers for the specified queue. 391 */ 392 u_int 393 sleepq_sleepcnt(void *wchan, int queue) 394 { 395 struct sleepqueue *sq; 396 397 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__)); 398 MPASS((queue >= 0) && (queue < NR_SLEEPQS)); 399 sq = sleepq_lookup(wchan); 400 if (sq == NULL) 401 return (0); 402 return (sq->sq_blockedcnt[queue]); 403 } 404 405 /* 406 * Marks the pending sleep of the current thread as interruptible and 407 * makes an initial check for pending signals before putting a thread 408 * to sleep. Enters and exits with the thread lock held. Thread lock 409 * may have transitioned from the sleepq lock to a run lock. 410 */ 411 static int 412 sleepq_catch_signals(void *wchan, int pri) 413 { 414 struct sleepqueue_chain *sc; 415 struct sleepqueue *sq; 416 struct thread *td; 417 struct proc *p; 418 struct sigacts *ps; 419 int sig, ret; 420 421 td = curthread; 422 p = curproc; 423 sc = SC_LOOKUP(wchan); 424 mtx_assert(&sc->sc_lock, MA_OWNED); 425 MPASS(wchan != NULL); 426 if ((td->td_pflags & TDP_WAKEUP) != 0) { 427 td->td_pflags &= ~TDP_WAKEUP; 428 ret = EINTR; 429 thread_lock(td); 430 goto out; 431 } 432 433 /* 434 * See if there are any pending signals for this thread. If not 435 * we can switch immediately. Otherwise do the signal processing 436 * directly. 437 */ 438 thread_lock(td); 439 if ((td->td_flags & (TDF_NEEDSIGCHK | TDF_NEEDSUSPCHK)) == 0) { 440 sleepq_switch(wchan, pri); 441 return (0); 442 } 443 thread_unlock(td); 444 mtx_unlock_spin(&sc->sc_lock); 445 CTR3(KTR_PROC, "sleepq catching signals: thread %p (pid %ld, %s)", 446 (void *)td, (long)p->p_pid, td->td_name); 447 PROC_LOCK(p); 448 ps = p->p_sigacts; 449 mtx_lock(&ps->ps_mtx); 450 sig = cursig(td); 451 if (sig == 0) { 452 mtx_unlock(&ps->ps_mtx); 453 ret = thread_suspend_check(1); 454 MPASS(ret == 0 || ret == EINTR || ret == ERESTART); 455 } else { 456 if (SIGISMEMBER(ps->ps_sigintr, sig)) 457 ret = EINTR; 458 else 459 ret = ERESTART; 460 mtx_unlock(&ps->ps_mtx); 461 } 462 /* 463 * Lock the per-process spinlock prior to dropping the PROC_LOCK 464 * to avoid a signal delivery race. PROC_LOCK, PROC_SLOCK, and 465 * thread_lock() are currently held in tdsendsignal(). 466 */ 467 PROC_SLOCK(p); 468 mtx_lock_spin(&sc->sc_lock); 469 PROC_UNLOCK(p); 470 thread_lock(td); 471 PROC_SUNLOCK(p); 472 if (ret == 0) { 473 sleepq_switch(wchan, pri); 474 return (0); 475 } 476 out: 477 /* 478 * There were pending signals and this thread is still 479 * on the sleep queue, remove it from the sleep queue. 480 */ 481 if (TD_ON_SLEEPQ(td)) { 482 sq = sleepq_lookup(wchan); 483 if (sleepq_resume_thread(sq, td, 0)) { 484 #ifdef INVARIANTS 485 /* 486 * This thread hasn't gone to sleep yet, so it 487 * should not be swapped out. 488 */ 489 panic("not waking up swapper"); 490 #endif 491 } 492 } 493 mtx_unlock_spin(&sc->sc_lock); 494 MPASS(td->td_lock != &sc->sc_lock); 495 return (ret); 496 } 497 498 /* 499 * Switches to another thread if we are still asleep on a sleep queue. 500 * Returns with thread lock. 501 */ 502 static void 503 sleepq_switch(void *wchan, int pri) 504 { 505 struct sleepqueue_chain *sc; 506 struct sleepqueue *sq; 507 struct thread *td; 508 509 td = curthread; 510 sc = SC_LOOKUP(wchan); 511 mtx_assert(&sc->sc_lock, MA_OWNED); 512 THREAD_LOCK_ASSERT(td, MA_OWNED); 513 514 /* 515 * If we have a sleep queue, then we've already been woken up, so 516 * just return. 517 */ 518 if (td->td_sleepqueue != NULL) { 519 mtx_unlock_spin(&sc->sc_lock); 520 return; 521 } 522 523 /* 524 * If TDF_TIMEOUT is set, then our sleep has been timed out 525 * already but we are still on the sleep queue, so dequeue the 526 * thread and return. 527 */ 528 if (td->td_flags & TDF_TIMEOUT) { 529 MPASS(TD_ON_SLEEPQ(td)); 530 sq = sleepq_lookup(wchan); 531 if (sleepq_resume_thread(sq, td, 0)) { 532 #ifdef INVARIANTS 533 /* 534 * This thread hasn't gone to sleep yet, so it 535 * should not be swapped out. 536 */ 537 panic("not waking up swapper"); 538 #endif 539 } 540 mtx_unlock_spin(&sc->sc_lock); 541 return; 542 } 543 #ifdef SLEEPQUEUE_PROFILING 544 if (prof_enabled) 545 sleepq_profile(td->td_wmesg); 546 #endif 547 MPASS(td->td_sleepqueue == NULL); 548 sched_sleep(td, pri); 549 thread_lock_set(td, &sc->sc_lock); 550 SDT_PROBE0(sched, , , sleep); 551 TD_SET_SLEEPING(td); 552 mi_switch(SW_VOL | SWT_SLEEPQ, NULL); 553 KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING")); 554 CTR3(KTR_PROC, "sleepq resume: thread %p (pid %ld, %s)", 555 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name); 556 } 557 558 /* 559 * Check to see if we timed out. 560 */ 561 static int 562 sleepq_check_timeout(void) 563 { 564 struct thread *td; 565 566 td = curthread; 567 THREAD_LOCK_ASSERT(td, MA_OWNED); 568 569 /* 570 * If TDF_TIMEOUT is set, we timed out. 571 */ 572 if (td->td_flags & TDF_TIMEOUT) { 573 td->td_flags &= ~TDF_TIMEOUT; 574 return (EWOULDBLOCK); 575 } 576 577 /* 578 * If TDF_TIMOFAIL is set, the timeout ran after we had 579 * already been woken up. 580 */ 581 if (td->td_flags & TDF_TIMOFAIL) 582 td->td_flags &= ~TDF_TIMOFAIL; 583 584 /* 585 * If callout_stop() fails, then the timeout is running on 586 * another CPU, so synchronize with it to avoid having it 587 * accidentally wake up a subsequent sleep. 588 */ 589 else if (_callout_stop_safe(&td->td_slpcallout, CS_MIGRBLOCK, NULL) 590 == 0) { 591 td->td_flags |= TDF_TIMEOUT; 592 TD_SET_SLEEPING(td); 593 mi_switch(SW_INVOL | SWT_SLEEPQTIMO, NULL); 594 } 595 return (0); 596 } 597 598 /* 599 * Check to see if we were awoken by a signal. 600 */ 601 static int 602 sleepq_check_signals(void) 603 { 604 struct thread *td; 605 606 td = curthread; 607 THREAD_LOCK_ASSERT(td, MA_OWNED); 608 609 /* We are no longer in an interruptible sleep. */ 610 if (td->td_flags & TDF_SINTR) 611 td->td_flags &= ~TDF_SINTR; 612 613 if (td->td_flags & TDF_SLEEPABORT) { 614 td->td_flags &= ~TDF_SLEEPABORT; 615 return (td->td_intrval); 616 } 617 618 return (0); 619 } 620 621 /* 622 * Block the current thread until it is awakened from its sleep queue. 623 */ 624 void 625 sleepq_wait(void *wchan, int pri) 626 { 627 struct thread *td; 628 629 td = curthread; 630 MPASS(!(td->td_flags & TDF_SINTR)); 631 thread_lock(td); 632 sleepq_switch(wchan, pri); 633 thread_unlock(td); 634 } 635 636 /* 637 * Block the current thread until it is awakened from its sleep queue 638 * or it is interrupted by a signal. 639 */ 640 int 641 sleepq_wait_sig(void *wchan, int pri) 642 { 643 int rcatch; 644 int rval; 645 646 rcatch = sleepq_catch_signals(wchan, pri); 647 rval = sleepq_check_signals(); 648 thread_unlock(curthread); 649 if (rcatch) 650 return (rcatch); 651 return (rval); 652 } 653 654 /* 655 * Block the current thread until it is awakened from its sleep queue 656 * or it times out while waiting. 657 */ 658 int 659 sleepq_timedwait(void *wchan, int pri) 660 { 661 struct thread *td; 662 int rval; 663 664 td = curthread; 665 MPASS(!(td->td_flags & TDF_SINTR)); 666 thread_lock(td); 667 sleepq_switch(wchan, pri); 668 rval = sleepq_check_timeout(); 669 thread_unlock(td); 670 671 return (rval); 672 } 673 674 /* 675 * Block the current thread until it is awakened from its sleep queue, 676 * it is interrupted by a signal, or it times out waiting to be awakened. 677 */ 678 int 679 sleepq_timedwait_sig(void *wchan, int pri) 680 { 681 int rcatch, rvalt, rvals; 682 683 rcatch = sleepq_catch_signals(wchan, pri); 684 rvalt = sleepq_check_timeout(); 685 rvals = sleepq_check_signals(); 686 thread_unlock(curthread); 687 if (rcatch) 688 return (rcatch); 689 if (rvals) 690 return (rvals); 691 return (rvalt); 692 } 693 694 /* 695 * Returns the type of sleepqueue given a waitchannel. 696 */ 697 int 698 sleepq_type(void *wchan) 699 { 700 struct sleepqueue *sq; 701 int type; 702 703 MPASS(wchan != NULL); 704 705 sleepq_lock(wchan); 706 sq = sleepq_lookup(wchan); 707 if (sq == NULL) { 708 sleepq_release(wchan); 709 return (-1); 710 } 711 type = sq->sq_type; 712 sleepq_release(wchan); 713 return (type); 714 } 715 716 /* 717 * Removes a thread from a sleep queue and makes it 718 * runnable. 719 */ 720 static int 721 sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, int pri) 722 { 723 struct sleepqueue_chain *sc; 724 725 MPASS(td != NULL); 726 MPASS(sq->sq_wchan != NULL); 727 MPASS(td->td_wchan == sq->sq_wchan); 728 MPASS(td->td_sqqueue < NR_SLEEPQS && td->td_sqqueue >= 0); 729 THREAD_LOCK_ASSERT(td, MA_OWNED); 730 sc = SC_LOOKUP(sq->sq_wchan); 731 mtx_assert(&sc->sc_lock, MA_OWNED); 732 733 SDT_PROBE2(sched, , , wakeup, td, td->td_proc); 734 735 /* Remove the thread from the queue. */ 736 sq->sq_blockedcnt[td->td_sqqueue]--; 737 TAILQ_REMOVE(&sq->sq_blocked[td->td_sqqueue], td, td_slpq); 738 739 /* 740 * Get a sleep queue for this thread. If this is the last waiter, 741 * use the queue itself and take it out of the chain, otherwise, 742 * remove a queue from the free list. 743 */ 744 if (LIST_EMPTY(&sq->sq_free)) { 745 td->td_sleepqueue = sq; 746 #ifdef INVARIANTS 747 sq->sq_wchan = NULL; 748 #endif 749 #ifdef SLEEPQUEUE_PROFILING 750 sc->sc_depth--; 751 #endif 752 } else 753 td->td_sleepqueue = LIST_FIRST(&sq->sq_free); 754 LIST_REMOVE(td->td_sleepqueue, sq_hash); 755 756 td->td_wmesg = NULL; 757 td->td_wchan = NULL; 758 td->td_flags &= ~TDF_SINTR; 759 760 CTR3(KTR_PROC, "sleepq_wakeup: thread %p (pid %ld, %s)", 761 (void *)td, (long)td->td_proc->p_pid, td->td_name); 762 763 /* Adjust priority if requested. */ 764 MPASS(pri == 0 || (pri >= PRI_MIN && pri <= PRI_MAX)); 765 if (pri != 0 && td->td_priority > pri && 766 PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) 767 sched_prio(td, pri); 768 769 /* 770 * Note that thread td might not be sleeping if it is running 771 * sleepq_catch_signals() on another CPU or is blocked on its 772 * proc lock to check signals. There's no need to mark the 773 * thread runnable in that case. 774 */ 775 if (TD_IS_SLEEPING(td)) { 776 TD_CLR_SLEEPING(td); 777 return (setrunnable(td)); 778 } 779 return (0); 780 } 781 782 #ifdef INVARIANTS 783 /* 784 * UMA zone item deallocator. 785 */ 786 static void 787 sleepq_dtor(void *mem, int size, void *arg) 788 { 789 struct sleepqueue *sq; 790 int i; 791 792 sq = mem; 793 for (i = 0; i < NR_SLEEPQS; i++) { 794 MPASS(TAILQ_EMPTY(&sq->sq_blocked[i])); 795 MPASS(sq->sq_blockedcnt[i] == 0); 796 } 797 } 798 #endif 799 800 /* 801 * UMA zone item initializer. 802 */ 803 static int 804 sleepq_init(void *mem, int size, int flags) 805 { 806 struct sleepqueue *sq; 807 int i; 808 809 bzero(mem, size); 810 sq = mem; 811 for (i = 0; i < NR_SLEEPQS; i++) { 812 TAILQ_INIT(&sq->sq_blocked[i]); 813 sq->sq_blockedcnt[i] = 0; 814 } 815 LIST_INIT(&sq->sq_free); 816 return (0); 817 } 818 819 /* 820 * Find the highest priority thread sleeping on a wait channel and resume it. 821 */ 822 int 823 sleepq_signal(void *wchan, int flags, int pri, int queue) 824 { 825 struct sleepqueue *sq; 826 struct thread *td, *besttd; 827 int wakeup_swapper; 828 829 CTR2(KTR_PROC, "sleepq_signal(%p, %d)", wchan, flags); 830 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__)); 831 MPASS((queue >= 0) && (queue < NR_SLEEPQS)); 832 sq = sleepq_lookup(wchan); 833 if (sq == NULL) 834 return (0); 835 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE), 836 ("%s: mismatch between sleep/wakeup and cv_*", __func__)); 837 838 /* 839 * Find the highest priority thread on the queue. If there is a 840 * tie, use the thread that first appears in the queue as it has 841 * been sleeping the longest since threads are always added to 842 * the tail of sleep queues. 843 */ 844 besttd = NULL; 845 TAILQ_FOREACH(td, &sq->sq_blocked[queue], td_slpq) { 846 if (besttd == NULL || td->td_priority < besttd->td_priority) 847 besttd = td; 848 } 849 MPASS(besttd != NULL); 850 thread_lock(besttd); 851 wakeup_swapper = sleepq_resume_thread(sq, besttd, pri); 852 thread_unlock(besttd); 853 return (wakeup_swapper); 854 } 855 856 /* 857 * Resume all threads sleeping on a specified wait channel. 858 */ 859 int 860 sleepq_broadcast(void *wchan, int flags, int pri, int queue) 861 { 862 struct sleepqueue *sq; 863 struct thread *td, *tdn; 864 int wakeup_swapper; 865 866 CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags); 867 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__)); 868 MPASS((queue >= 0) && (queue < NR_SLEEPQS)); 869 sq = sleepq_lookup(wchan); 870 if (sq == NULL) 871 return (0); 872 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE), 873 ("%s: mismatch between sleep/wakeup and cv_*", __func__)); 874 875 /* Resume all blocked threads on the sleep queue. */ 876 wakeup_swapper = 0; 877 TAILQ_FOREACH_SAFE(td, &sq->sq_blocked[queue], td_slpq, tdn) { 878 thread_lock(td); 879 if (sleepq_resume_thread(sq, td, pri)) 880 wakeup_swapper = 1; 881 thread_unlock(td); 882 } 883 return (wakeup_swapper); 884 } 885 886 /* 887 * Time sleeping threads out. When the timeout expires, the thread is 888 * removed from the sleep queue and made runnable if it is still asleep. 889 */ 890 static void 891 sleepq_timeout(void *arg) 892 { 893 struct sleepqueue_chain *sc; 894 struct sleepqueue *sq; 895 struct thread *td; 896 void *wchan; 897 int wakeup_swapper; 898 899 td = arg; 900 wakeup_swapper = 0; 901 CTR3(KTR_PROC, "sleepq_timeout: thread %p (pid %ld, %s)", 902 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name); 903 904 /* 905 * First, see if the thread is asleep and get the wait channel if 906 * it is. 907 */ 908 thread_lock(td); 909 if (TD_IS_SLEEPING(td) && TD_ON_SLEEPQ(td)) { 910 wchan = td->td_wchan; 911 sc = SC_LOOKUP(wchan); 912 THREAD_LOCKPTR_ASSERT(td, &sc->sc_lock); 913 sq = sleepq_lookup(wchan); 914 MPASS(sq != NULL); 915 td->td_flags |= TDF_TIMEOUT; 916 wakeup_swapper = sleepq_resume_thread(sq, td, 0); 917 thread_unlock(td); 918 if (wakeup_swapper) 919 kick_proc0(); 920 return; 921 } 922 923 /* 924 * If the thread is on the SLEEPQ but isn't sleeping yet, it 925 * can either be on another CPU in between sleepq_add() and 926 * one of the sleepq_*wait*() routines or it can be in 927 * sleepq_catch_signals(). 928 */ 929 if (TD_ON_SLEEPQ(td)) { 930 td->td_flags |= TDF_TIMEOUT; 931 thread_unlock(td); 932 return; 933 } 934 935 /* 936 * Now check for the edge cases. First, if TDF_TIMEOUT is set, 937 * then the other thread has already yielded to us, so clear 938 * the flag and resume it. If TDF_TIMEOUT is not set, then the 939 * we know that the other thread is not on a sleep queue, but it 940 * hasn't resumed execution yet. In that case, set TDF_TIMOFAIL 941 * to let it know that the timeout has already run and doesn't 942 * need to be canceled. 943 */ 944 if (td->td_flags & TDF_TIMEOUT) { 945 MPASS(TD_IS_SLEEPING(td)); 946 td->td_flags &= ~TDF_TIMEOUT; 947 TD_CLR_SLEEPING(td); 948 wakeup_swapper = setrunnable(td); 949 } else 950 td->td_flags |= TDF_TIMOFAIL; 951 thread_unlock(td); 952 if (wakeup_swapper) 953 kick_proc0(); 954 } 955 956 /* 957 * Resumes a specific thread from the sleep queue associated with a specific 958 * wait channel if it is on that queue. 959 */ 960 void 961 sleepq_remove(struct thread *td, void *wchan) 962 { 963 struct sleepqueue *sq; 964 int wakeup_swapper; 965 966 /* 967 * Look up the sleep queue for this wait channel, then re-check 968 * that the thread is asleep on that channel, if it is not, then 969 * bail. 970 */ 971 MPASS(wchan != NULL); 972 sleepq_lock(wchan); 973 sq = sleepq_lookup(wchan); 974 /* 975 * We can not lock the thread here as it may be sleeping on a 976 * different sleepq. However, holding the sleepq lock for this 977 * wchan can guarantee that we do not miss a wakeup for this 978 * channel. The asserts below will catch any false positives. 979 */ 980 if (!TD_ON_SLEEPQ(td) || td->td_wchan != wchan) { 981 sleepq_release(wchan); 982 return; 983 } 984 /* Thread is asleep on sleep queue sq, so wake it up. */ 985 thread_lock(td); 986 MPASS(sq != NULL); 987 MPASS(td->td_wchan == wchan); 988 wakeup_swapper = sleepq_resume_thread(sq, td, 0); 989 thread_unlock(td); 990 sleepq_release(wchan); 991 if (wakeup_swapper) 992 kick_proc0(); 993 } 994 995 /* 996 * Abort a thread as if an interrupt had occurred. Only abort 997 * interruptible waits (unfortunately it isn't safe to abort others). 998 */ 999 int 1000 sleepq_abort(struct thread *td, int intrval) 1001 { 1002 struct sleepqueue *sq; 1003 void *wchan; 1004 1005 THREAD_LOCK_ASSERT(td, MA_OWNED); 1006 MPASS(TD_ON_SLEEPQ(td)); 1007 MPASS(td->td_flags & TDF_SINTR); 1008 MPASS(intrval == EINTR || intrval == ERESTART); 1009 1010 /* 1011 * If the TDF_TIMEOUT flag is set, just leave. A 1012 * timeout is scheduled anyhow. 1013 */ 1014 if (td->td_flags & TDF_TIMEOUT) 1015 return (0); 1016 1017 CTR3(KTR_PROC, "sleepq_abort: thread %p (pid %ld, %s)", 1018 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name); 1019 td->td_intrval = intrval; 1020 td->td_flags |= TDF_SLEEPABORT; 1021 /* 1022 * If the thread has not slept yet it will find the signal in 1023 * sleepq_catch_signals() and call sleepq_resume_thread. Otherwise 1024 * we have to do it here. 1025 */ 1026 if (!TD_IS_SLEEPING(td)) 1027 return (0); 1028 wchan = td->td_wchan; 1029 MPASS(wchan != NULL); 1030 sq = sleepq_lookup(wchan); 1031 MPASS(sq != NULL); 1032 1033 /* Thread is asleep on sleep queue sq, so wake it up. */ 1034 return (sleepq_resume_thread(sq, td, 0)); 1035 } 1036 1037 #ifdef SLEEPQUEUE_PROFILING 1038 #define SLEEPQ_PROF_LOCATIONS 1024 1039 #define SLEEPQ_SBUFSIZE 512 1040 struct sleepq_prof { 1041 LIST_ENTRY(sleepq_prof) sp_link; 1042 const char *sp_wmesg; 1043 long sp_count; 1044 }; 1045 1046 LIST_HEAD(sqphead, sleepq_prof); 1047 1048 struct sqphead sleepq_prof_free; 1049 struct sqphead sleepq_hash[SC_TABLESIZE]; 1050 static struct sleepq_prof sleepq_profent[SLEEPQ_PROF_LOCATIONS]; 1051 static struct mtx sleepq_prof_lock; 1052 MTX_SYSINIT(sleepq_prof_lock, &sleepq_prof_lock, "sleepq_prof", MTX_SPIN); 1053 1054 static void 1055 sleepq_profile(const char *wmesg) 1056 { 1057 struct sleepq_prof *sp; 1058 1059 mtx_lock_spin(&sleepq_prof_lock); 1060 if (prof_enabled == 0) 1061 goto unlock; 1062 LIST_FOREACH(sp, &sleepq_hash[SC_HASH(wmesg)], sp_link) 1063 if (sp->sp_wmesg == wmesg) 1064 goto done; 1065 sp = LIST_FIRST(&sleepq_prof_free); 1066 if (sp == NULL) 1067 goto unlock; 1068 sp->sp_wmesg = wmesg; 1069 LIST_REMOVE(sp, sp_link); 1070 LIST_INSERT_HEAD(&sleepq_hash[SC_HASH(wmesg)], sp, sp_link); 1071 done: 1072 sp->sp_count++; 1073 unlock: 1074 mtx_unlock_spin(&sleepq_prof_lock); 1075 return; 1076 } 1077 1078 static void 1079 sleepq_prof_reset(void) 1080 { 1081 struct sleepq_prof *sp; 1082 int enabled; 1083 int i; 1084 1085 mtx_lock_spin(&sleepq_prof_lock); 1086 enabled = prof_enabled; 1087 prof_enabled = 0; 1088 for (i = 0; i < SC_TABLESIZE; i++) 1089 LIST_INIT(&sleepq_hash[i]); 1090 LIST_INIT(&sleepq_prof_free); 1091 for (i = 0; i < SLEEPQ_PROF_LOCATIONS; i++) { 1092 sp = &sleepq_profent[i]; 1093 sp->sp_wmesg = NULL; 1094 sp->sp_count = 0; 1095 LIST_INSERT_HEAD(&sleepq_prof_free, sp, sp_link); 1096 } 1097 prof_enabled = enabled; 1098 mtx_unlock_spin(&sleepq_prof_lock); 1099 } 1100 1101 static int 1102 enable_sleepq_prof(SYSCTL_HANDLER_ARGS) 1103 { 1104 int error, v; 1105 1106 v = prof_enabled; 1107 error = sysctl_handle_int(oidp, &v, v, req); 1108 if (error) 1109 return (error); 1110 if (req->newptr == NULL) 1111 return (error); 1112 if (v == prof_enabled) 1113 return (0); 1114 if (v == 1) 1115 sleepq_prof_reset(); 1116 mtx_lock_spin(&sleepq_prof_lock); 1117 prof_enabled = !!v; 1118 mtx_unlock_spin(&sleepq_prof_lock); 1119 1120 return (0); 1121 } 1122 1123 static int 1124 reset_sleepq_prof_stats(SYSCTL_HANDLER_ARGS) 1125 { 1126 int error, v; 1127 1128 v = 0; 1129 error = sysctl_handle_int(oidp, &v, 0, req); 1130 if (error) 1131 return (error); 1132 if (req->newptr == NULL) 1133 return (error); 1134 if (v == 0) 1135 return (0); 1136 sleepq_prof_reset(); 1137 1138 return (0); 1139 } 1140 1141 static int 1142 dump_sleepq_prof_stats(SYSCTL_HANDLER_ARGS) 1143 { 1144 struct sleepq_prof *sp; 1145 struct sbuf *sb; 1146 int enabled; 1147 int error; 1148 int i; 1149 1150 error = sysctl_wire_old_buffer(req, 0); 1151 if (error != 0) 1152 return (error); 1153 sb = sbuf_new_for_sysctl(NULL, NULL, SLEEPQ_SBUFSIZE, req); 1154 sbuf_printf(sb, "\nwmesg\tcount\n"); 1155 enabled = prof_enabled; 1156 mtx_lock_spin(&sleepq_prof_lock); 1157 prof_enabled = 0; 1158 mtx_unlock_spin(&sleepq_prof_lock); 1159 for (i = 0; i < SC_TABLESIZE; i++) { 1160 LIST_FOREACH(sp, &sleepq_hash[i], sp_link) { 1161 sbuf_printf(sb, "%s\t%ld\n", 1162 sp->sp_wmesg, sp->sp_count); 1163 } 1164 } 1165 mtx_lock_spin(&sleepq_prof_lock); 1166 prof_enabled = enabled; 1167 mtx_unlock_spin(&sleepq_prof_lock); 1168 1169 error = sbuf_finish(sb); 1170 sbuf_delete(sb); 1171 return (error); 1172 } 1173 1174 SYSCTL_PROC(_debug_sleepq, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD, 1175 NULL, 0, dump_sleepq_prof_stats, "A", "Sleepqueue profiling statistics"); 1176 SYSCTL_PROC(_debug_sleepq, OID_AUTO, reset, CTLTYPE_INT | CTLFLAG_RW, 1177 NULL, 0, reset_sleepq_prof_stats, "I", 1178 "Reset sleepqueue profiling statistics"); 1179 SYSCTL_PROC(_debug_sleepq, OID_AUTO, enable, CTLTYPE_INT | CTLFLAG_RW, 1180 NULL, 0, enable_sleepq_prof, "I", "Enable sleepqueue profiling"); 1181 #endif 1182 1183 #ifdef DDB 1184 DB_SHOW_COMMAND(sleepq, db_show_sleepqueue) 1185 { 1186 struct sleepqueue_chain *sc; 1187 struct sleepqueue *sq; 1188 #ifdef INVARIANTS 1189 struct lock_object *lock; 1190 #endif 1191 struct thread *td; 1192 void *wchan; 1193 int i; 1194 1195 if (!have_addr) 1196 return; 1197 1198 /* 1199 * First, see if there is an active sleep queue for the wait channel 1200 * indicated by the address. 1201 */ 1202 wchan = (void *)addr; 1203 sc = SC_LOOKUP(wchan); 1204 LIST_FOREACH(sq, &sc->sc_queues, sq_hash) 1205 if (sq->sq_wchan == wchan) 1206 goto found; 1207 1208 /* 1209 * Second, see if there is an active sleep queue at the address 1210 * indicated. 1211 */ 1212 for (i = 0; i < SC_TABLESIZE; i++) 1213 LIST_FOREACH(sq, &sleepq_chains[i].sc_queues, sq_hash) { 1214 if (sq == (struct sleepqueue *)addr) 1215 goto found; 1216 } 1217 1218 db_printf("Unable to locate a sleep queue via %p\n", (void *)addr); 1219 return; 1220 found: 1221 db_printf("Wait channel: %p\n", sq->sq_wchan); 1222 db_printf("Queue type: %d\n", sq->sq_type); 1223 #ifdef INVARIANTS 1224 if (sq->sq_lock) { 1225 lock = sq->sq_lock; 1226 db_printf("Associated Interlock: %p - (%s) %s\n", lock, 1227 LOCK_CLASS(lock)->lc_name, lock->lo_name); 1228 } 1229 #endif 1230 db_printf("Blocked threads:\n"); 1231 for (i = 0; i < NR_SLEEPQS; i++) { 1232 db_printf("\nQueue[%d]:\n", i); 1233 if (TAILQ_EMPTY(&sq->sq_blocked[i])) 1234 db_printf("\tempty\n"); 1235 else 1236 TAILQ_FOREACH(td, &sq->sq_blocked[0], 1237 td_slpq) { 1238 db_printf("\t%p (tid %d, pid %d, \"%s\")\n", td, 1239 td->td_tid, td->td_proc->p_pid, 1240 td->td_name); 1241 } 1242 db_printf("(expected: %u)\n", sq->sq_blockedcnt[i]); 1243 } 1244 } 1245 1246 /* Alias 'show sleepqueue' to 'show sleepq'. */ 1247 DB_SHOW_ALIAS(sleepqueue, db_show_sleepqueue); 1248 #endif 1249