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 #include "opt_sched.h" 68 69 #include <sys/param.h> 70 #include <sys/systm.h> 71 #include <sys/lock.h> 72 #include <sys/kernel.h> 73 #include <sys/ktr.h> 74 #include <sys/mutex.h> 75 #include <sys/proc.h> 76 #include <sys/sbuf.h> 77 #include <sys/sched.h> 78 #include <sys/signalvar.h> 79 #include <sys/sleepqueue.h> 80 #include <sys/sysctl.h> 81 82 #include <vm/uma.h> 83 84 #ifdef DDB 85 #include <ddb/ddb.h> 86 #endif 87 88 /* 89 * Constants for the hash table of sleep queue chains. These constants are 90 * the same ones that 4BSD (and possibly earlier versions of BSD) used. 91 * Basically, we ignore the lower 8 bits of the address since most wait 92 * channel pointers are aligned and only look at the next 7 bits for the 93 * hash. SC_TABLESIZE must be a power of two for SC_MASK to work properly. 94 */ 95 #define SC_TABLESIZE 128 /* Must be power of 2. */ 96 #define SC_MASK (SC_TABLESIZE - 1) 97 #define SC_SHIFT 8 98 #define SC_HASH(wc) (((uintptr_t)(wc) >> SC_SHIFT) & SC_MASK) 99 #define SC_LOOKUP(wc) &sleepq_chains[SC_HASH(wc)] 100 #define NR_SLEEPQS 2 101 /* 102 * There two different lists of sleep queues. Both lists are connected 103 * via the sq_hash entries. The first list is the sleep queue chain list 104 * that a sleep queue is on when it is attached to a wait channel. The 105 * second list is the free list hung off of a sleep queue that is attached 106 * to a wait channel. 107 * 108 * Each sleep queue also contains the wait channel it is attached to, the 109 * list of threads blocked on that wait channel, flags specific to the 110 * wait channel, and the lock used to synchronize with a wait channel. 111 * The flags are used to catch mismatches between the various consumers 112 * of the sleep queue API (e.g. sleep/wakeup and condition variables). 113 * The lock pointer is only used when invariants are enabled for various 114 * debugging checks. 115 * 116 * Locking key: 117 * c - sleep queue chain lock 118 */ 119 struct sleepqueue { 120 TAILQ_HEAD(, thread) sq_blocked[NR_SLEEPQS]; /* (c) Blocked threads. */ 121 u_int sq_blockedcnt[NR_SLEEPQS]; /* (c) N. of blocked threads. */ 122 LIST_ENTRY(sleepqueue) sq_hash; /* (c) Chain and free list. */ 123 LIST_HEAD(, sleepqueue) sq_free; /* (c) Free queues. */ 124 void *sq_wchan; /* (c) Wait channel. */ 125 #ifdef INVARIANTS 126 int sq_type; /* (c) Queue type. */ 127 struct lock_object *sq_lock; /* (c) Associated lock. */ 128 #endif 129 }; 130 131 struct sleepqueue_chain { 132 LIST_HEAD(, sleepqueue) sc_queues; /* List of sleep queues. */ 133 struct mtx sc_lock; /* Spin lock for this chain. */ 134 #ifdef SLEEPQUEUE_PROFILING 135 u_int sc_depth; /* Length of sc_queues. */ 136 u_int sc_max_depth; /* Max length of sc_queues. */ 137 #endif 138 }; 139 140 #ifdef SLEEPQUEUE_PROFILING 141 u_int sleepq_max_depth; 142 SYSCTL_NODE(_debug, OID_AUTO, sleepq, CTLFLAG_RD, 0, "sleepq profiling"); 143 SYSCTL_NODE(_debug_sleepq, OID_AUTO, chains, CTLFLAG_RD, 0, 144 "sleepq chain stats"); 145 SYSCTL_UINT(_debug_sleepq, OID_AUTO, max_depth, CTLFLAG_RD, &sleepq_max_depth, 146 0, "maxmimum depth achieved of a single chain"); 147 148 static void sleepq_profile(const char *wmesg); 149 static int prof_enabled; 150 #endif 151 static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE]; 152 static uma_zone_t sleepq_zone; 153 154 /* 155 * Prototypes for non-exported routines. 156 */ 157 static int sleepq_catch_signals(void *wchan, int pri); 158 static int sleepq_check_signals(void); 159 static int sleepq_check_timeout(void); 160 #ifdef INVARIANTS 161 static void sleepq_dtor(void *mem, int size, void *arg); 162 #endif 163 static int sleepq_init(void *mem, int size, int flags); 164 static int sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, 165 int pri); 166 static void sleepq_switch(void *wchan, int pri); 167 static void sleepq_timeout(void *arg); 168 169 /* 170 * Early initialization of sleep queues that is called from the sleepinit() 171 * SYSINIT. 172 */ 173 void 174 init_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 */ 211 struct sleepqueue * 212 sleepq_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 */ 221 void 222 sleepq_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 */ 231 void 232 sleepq_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 */ 245 struct sleepqueue * 246 sleepq_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 */ 263 void 264 sleepq_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 */ 278 void 279 sleepq_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_pflags & TDP_NOSLEEPING), 295 ("Trying sleep, but thread marked as sleeping prohibited")); 296 297 /* Look up the sleep queue associated with the wait channel 'wchan'. */ 298 sq = sleepq_lookup(wchan); 299 300 /* 301 * If the wait channel does not already have a sleep queue, use 302 * this thread's sleep queue. Otherwise, insert the current thread 303 * into the sleep queue already in use by this wait channel. 304 */ 305 if (sq == NULL) { 306 #ifdef INVARIANTS 307 int i; 308 309 sq = td->td_sleepqueue; 310 for (i = 0; i < NR_SLEEPQS; i++) { 311 KASSERT(TAILQ_EMPTY(&sq->sq_blocked[i]), 312 ("thread's sleep queue %d is not empty", i)); 313 KASSERT(sq->sq_blockedcnt[i] == 0, 314 ("thread's sleep queue %d count mismatches", i)); 315 } 316 KASSERT(LIST_EMPTY(&sq->sq_free), 317 ("thread's sleep queue has a non-empty free list")); 318 KASSERT(sq->sq_wchan == NULL, ("stale sq_wchan pointer")); 319 sq->sq_lock = lock; 320 sq->sq_type = flags & SLEEPQ_TYPE; 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 } else { 334 MPASS(wchan == sq->sq_wchan); 335 MPASS(lock == sq->sq_lock); 336 MPASS((flags & SLEEPQ_TYPE) == sq->sq_type); 337 LIST_INSERT_HEAD(&sq->sq_free, td->td_sleepqueue, sq_hash); 338 } 339 thread_lock(td); 340 TAILQ_INSERT_TAIL(&sq->sq_blocked[queue], td, td_slpq); 341 sq->sq_blockedcnt[queue]++; 342 td->td_sleepqueue = NULL; 343 td->td_sqqueue = queue; 344 td->td_wchan = wchan; 345 td->td_wmesg = wmesg; 346 if (flags & SLEEPQ_INTERRUPTIBLE) { 347 td->td_flags |= TDF_SINTR; 348 td->td_flags &= ~TDF_SLEEPABORT; 349 if (flags & SLEEPQ_STOP_ON_BDRY) 350 td->td_flags |= TDF_SBDRY; 351 } 352 thread_unlock(td); 353 } 354 355 /* 356 * Sets a timeout that will remove the current thread from the specified 357 * sleep queue after timo ticks if the thread has not already been awakened. 358 */ 359 void 360 sleepq_set_timeout(void *wchan, int timo) 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_curcpu(&td->td_slpcallout, timo, sleepq_timeout, td); 372 } 373 374 /* 375 * Return the number of actual sleepers for the specified queue. 376 */ 377 u_int 378 sleepq_sleepcnt(void *wchan, int queue) 379 { 380 struct sleepqueue *sq; 381 382 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__)); 383 MPASS((queue >= 0) && (queue < NR_SLEEPQS)); 384 sq = sleepq_lookup(wchan); 385 if (sq == NULL) 386 return (0); 387 return (sq->sq_blockedcnt[queue]); 388 } 389 390 /* 391 * Marks the pending sleep of the current thread as interruptible and 392 * makes an initial check for pending signals before putting a thread 393 * to sleep. Enters and exits with the thread lock held. Thread lock 394 * may have transitioned from the sleepq lock to a run lock. 395 */ 396 static int 397 sleepq_catch_signals(void *wchan, int pri) 398 { 399 struct sleepqueue_chain *sc; 400 struct sleepqueue *sq; 401 struct thread *td; 402 struct proc *p; 403 struct sigacts *ps; 404 int sig, ret, stop_allowed; 405 406 td = curthread; 407 p = curproc; 408 sc = SC_LOOKUP(wchan); 409 mtx_assert(&sc->sc_lock, MA_OWNED); 410 MPASS(wchan != NULL); 411 /* 412 * See if there are any pending signals for this thread. If not 413 * we can switch immediately. Otherwise do the signal processing 414 * directly. 415 */ 416 thread_lock(td); 417 if ((td->td_flags & (TDF_NEEDSIGCHK | TDF_NEEDSUSPCHK)) == 0) { 418 sleepq_switch(wchan, pri); 419 return (0); 420 } 421 stop_allowed = (td->td_flags & TDF_SBDRY) ? SIG_STOP_NOT_ALLOWED : 422 SIG_STOP_ALLOWED; 423 thread_unlock(td); 424 mtx_unlock_spin(&sc->sc_lock); 425 CTR3(KTR_PROC, "sleepq catching signals: thread %p (pid %ld, %s)", 426 (void *)td, (long)p->p_pid, td->td_name); 427 PROC_LOCK(p); 428 ps = p->p_sigacts; 429 mtx_lock(&ps->ps_mtx); 430 sig = cursig(td, stop_allowed); 431 if (sig == 0) { 432 mtx_unlock(&ps->ps_mtx); 433 ret = thread_suspend_check(1); 434 MPASS(ret == 0 || ret == EINTR || ret == ERESTART); 435 } else { 436 if (SIGISMEMBER(ps->ps_sigintr, sig)) 437 ret = EINTR; 438 else 439 ret = ERESTART; 440 mtx_unlock(&ps->ps_mtx); 441 } 442 /* 443 * Lock the per-process spinlock prior to dropping the PROC_LOCK 444 * to avoid a signal delivery race. PROC_LOCK, PROC_SLOCK, and 445 * thread_lock() are currently held in tdsignal(). 446 */ 447 PROC_SLOCK(p); 448 mtx_lock_spin(&sc->sc_lock); 449 PROC_UNLOCK(p); 450 thread_lock(td); 451 PROC_SUNLOCK(p); 452 if (ret == 0) { 453 sleepq_switch(wchan, pri); 454 return (0); 455 } 456 /* 457 * There were pending signals and this thread is still 458 * on the sleep queue, remove it from the sleep queue. 459 */ 460 if (TD_ON_SLEEPQ(td)) { 461 sq = sleepq_lookup(wchan); 462 if (sleepq_resume_thread(sq, td, 0)) { 463 #ifdef INVARIANTS 464 /* 465 * This thread hasn't gone to sleep yet, so it 466 * should not be swapped out. 467 */ 468 panic("not waking up swapper"); 469 #endif 470 } 471 } 472 mtx_unlock_spin(&sc->sc_lock); 473 MPASS(td->td_lock != &sc->sc_lock); 474 return (ret); 475 } 476 477 /* 478 * Switches to another thread if we are still asleep on a sleep queue. 479 * Returns with thread lock. 480 */ 481 static void 482 sleepq_switch(void *wchan, int pri) 483 { 484 struct sleepqueue_chain *sc; 485 struct sleepqueue *sq; 486 struct thread *td; 487 488 td = curthread; 489 sc = SC_LOOKUP(wchan); 490 mtx_assert(&sc->sc_lock, MA_OWNED); 491 THREAD_LOCK_ASSERT(td, MA_OWNED); 492 493 /* 494 * If we have a sleep queue, then we've already been woken up, so 495 * just return. 496 */ 497 if (td->td_sleepqueue != NULL) { 498 mtx_unlock_spin(&sc->sc_lock); 499 return; 500 } 501 502 /* 503 * If TDF_TIMEOUT is set, then our sleep has been timed out 504 * already but we are still on the sleep queue, so dequeue the 505 * thread and return. 506 */ 507 if (td->td_flags & TDF_TIMEOUT) { 508 MPASS(TD_ON_SLEEPQ(td)); 509 sq = sleepq_lookup(wchan); 510 if (sleepq_resume_thread(sq, td, 0)) { 511 #ifdef INVARIANTS 512 /* 513 * This thread hasn't gone to sleep yet, so it 514 * should not be swapped out. 515 */ 516 panic("not waking up swapper"); 517 #endif 518 } 519 mtx_unlock_spin(&sc->sc_lock); 520 return; 521 } 522 #ifdef SLEEPQUEUE_PROFILING 523 if (prof_enabled) 524 sleepq_profile(td->td_wmesg); 525 #endif 526 MPASS(td->td_sleepqueue == NULL); 527 sched_sleep(td, pri); 528 thread_lock_set(td, &sc->sc_lock); 529 TD_SET_SLEEPING(td); 530 mi_switch(SW_VOL | SWT_SLEEPQ, NULL); 531 KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING")); 532 CTR3(KTR_PROC, "sleepq resume: thread %p (pid %ld, %s)", 533 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name); 534 } 535 536 /* 537 * Check to see if we timed out. 538 */ 539 static int 540 sleepq_check_timeout(void) 541 { 542 struct thread *td; 543 544 td = curthread; 545 THREAD_LOCK_ASSERT(td, MA_OWNED); 546 547 /* 548 * If TDF_TIMEOUT is set, we timed out. 549 */ 550 if (td->td_flags & TDF_TIMEOUT) { 551 td->td_flags &= ~TDF_TIMEOUT; 552 return (EWOULDBLOCK); 553 } 554 555 /* 556 * If TDF_TIMOFAIL is set, the timeout ran after we had 557 * already been woken up. 558 */ 559 if (td->td_flags & TDF_TIMOFAIL) 560 td->td_flags &= ~TDF_TIMOFAIL; 561 562 /* 563 * If callout_stop() fails, then the timeout is running on 564 * another CPU, so synchronize with it to avoid having it 565 * accidentally wake up a subsequent sleep. 566 */ 567 else if (callout_stop(&td->td_slpcallout) == 0) { 568 td->td_flags |= TDF_TIMEOUT; 569 TD_SET_SLEEPING(td); 570 mi_switch(SW_INVOL | SWT_SLEEPQTIMO, NULL); 571 } 572 return (0); 573 } 574 575 /* 576 * Check to see if we were awoken by a signal. 577 */ 578 static int 579 sleepq_check_signals(void) 580 { 581 struct thread *td; 582 583 td = curthread; 584 THREAD_LOCK_ASSERT(td, MA_OWNED); 585 586 /* We are no longer in an interruptible sleep. */ 587 if (td->td_flags & TDF_SINTR) 588 td->td_flags &= ~(TDF_SINTR | TDF_SBDRY); 589 590 if (td->td_flags & TDF_SLEEPABORT) { 591 td->td_flags &= ~TDF_SLEEPABORT; 592 return (td->td_intrval); 593 } 594 595 return (0); 596 } 597 598 /* 599 * Block the current thread until it is awakened from its sleep queue. 600 */ 601 void 602 sleepq_wait(void *wchan, int pri) 603 { 604 struct thread *td; 605 606 td = curthread; 607 MPASS(!(td->td_flags & TDF_SINTR)); 608 thread_lock(td); 609 sleepq_switch(wchan, pri); 610 thread_unlock(td); 611 } 612 613 /* 614 * Block the current thread until it is awakened from its sleep queue 615 * or it is interrupted by a signal. 616 */ 617 int 618 sleepq_wait_sig(void *wchan, int pri) 619 { 620 int rcatch; 621 int rval; 622 623 rcatch = sleepq_catch_signals(wchan, pri); 624 rval = sleepq_check_signals(); 625 thread_unlock(curthread); 626 if (rcatch) 627 return (rcatch); 628 return (rval); 629 } 630 631 /* 632 * Block the current thread until it is awakened from its sleep queue 633 * or it times out while waiting. 634 */ 635 int 636 sleepq_timedwait(void *wchan, int pri) 637 { 638 struct thread *td; 639 int rval; 640 641 td = curthread; 642 MPASS(!(td->td_flags & TDF_SINTR)); 643 thread_lock(td); 644 sleepq_switch(wchan, pri); 645 rval = sleepq_check_timeout(); 646 thread_unlock(td); 647 648 return (rval); 649 } 650 651 /* 652 * Block the current thread until it is awakened from its sleep queue, 653 * it is interrupted by a signal, or it times out waiting to be awakened. 654 */ 655 int 656 sleepq_timedwait_sig(void *wchan, int pri) 657 { 658 int rcatch, rvalt, rvals; 659 660 rcatch = sleepq_catch_signals(wchan, pri); 661 rvalt = sleepq_check_timeout(); 662 rvals = sleepq_check_signals(); 663 thread_unlock(curthread); 664 if (rcatch) 665 return (rcatch); 666 if (rvals) 667 return (rvals); 668 return (rvalt); 669 } 670 671 /* 672 * Removes a thread from a sleep queue and makes it 673 * runnable. 674 */ 675 static int 676 sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, int pri) 677 { 678 struct sleepqueue_chain *sc; 679 680 MPASS(td != NULL); 681 MPASS(sq->sq_wchan != NULL); 682 MPASS(td->td_wchan == sq->sq_wchan); 683 MPASS(td->td_sqqueue < NR_SLEEPQS && td->td_sqqueue >= 0); 684 THREAD_LOCK_ASSERT(td, MA_OWNED); 685 sc = SC_LOOKUP(sq->sq_wchan); 686 mtx_assert(&sc->sc_lock, MA_OWNED); 687 688 /* Remove the thread from the queue. */ 689 sq->sq_blockedcnt[td->td_sqqueue]--; 690 TAILQ_REMOVE(&sq->sq_blocked[td->td_sqqueue], td, td_slpq); 691 692 /* 693 * Get a sleep queue for this thread. If this is the last waiter, 694 * use the queue itself and take it out of the chain, otherwise, 695 * remove a queue from the free list. 696 */ 697 if (LIST_EMPTY(&sq->sq_free)) { 698 td->td_sleepqueue = sq; 699 #ifdef INVARIANTS 700 sq->sq_wchan = NULL; 701 #endif 702 #ifdef SLEEPQUEUE_PROFILING 703 sc->sc_depth--; 704 #endif 705 } else 706 td->td_sleepqueue = LIST_FIRST(&sq->sq_free); 707 LIST_REMOVE(td->td_sleepqueue, sq_hash); 708 709 td->td_wmesg = NULL; 710 td->td_wchan = NULL; 711 td->td_flags &= ~(TDF_SINTR | TDF_SBDRY); 712 713 CTR3(KTR_PROC, "sleepq_wakeup: thread %p (pid %ld, %s)", 714 (void *)td, (long)td->td_proc->p_pid, td->td_name); 715 716 /* Adjust priority if requested. */ 717 MPASS(pri == 0 || (pri >= PRI_MIN && pri <= PRI_MAX)); 718 if (pri != 0 && td->td_priority > pri) 719 sched_prio(td, pri); 720 721 /* 722 * Note that thread td might not be sleeping if it is running 723 * sleepq_catch_signals() on another CPU or is blocked on its 724 * proc lock to check signals. There's no need to mark the 725 * thread runnable in that case. 726 */ 727 if (TD_IS_SLEEPING(td)) { 728 TD_CLR_SLEEPING(td); 729 return (setrunnable(td)); 730 } 731 return (0); 732 } 733 734 #ifdef INVARIANTS 735 /* 736 * UMA zone item deallocator. 737 */ 738 static void 739 sleepq_dtor(void *mem, int size, void *arg) 740 { 741 struct sleepqueue *sq; 742 int i; 743 744 sq = mem; 745 for (i = 0; i < NR_SLEEPQS; i++) { 746 MPASS(TAILQ_EMPTY(&sq->sq_blocked[i])); 747 MPASS(sq->sq_blockedcnt[i] == 0); 748 } 749 } 750 #endif 751 752 /* 753 * UMA zone item initializer. 754 */ 755 static int 756 sleepq_init(void *mem, int size, int flags) 757 { 758 struct sleepqueue *sq; 759 int i; 760 761 bzero(mem, size); 762 sq = mem; 763 for (i = 0; i < NR_SLEEPQS; i++) { 764 TAILQ_INIT(&sq->sq_blocked[i]); 765 sq->sq_blockedcnt[i] = 0; 766 } 767 LIST_INIT(&sq->sq_free); 768 return (0); 769 } 770 771 /* 772 * Find the highest priority thread sleeping on a wait channel and resume it. 773 */ 774 int 775 sleepq_signal(void *wchan, int flags, int pri, int queue) 776 { 777 struct sleepqueue *sq; 778 struct thread *td, *besttd; 779 int wakeup_swapper; 780 781 CTR2(KTR_PROC, "sleepq_signal(%p, %d)", wchan, flags); 782 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__)); 783 MPASS((queue >= 0) && (queue < NR_SLEEPQS)); 784 sq = sleepq_lookup(wchan); 785 if (sq == NULL) 786 return (0); 787 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE), 788 ("%s: mismatch between sleep/wakeup and cv_*", __func__)); 789 790 /* 791 * Find the highest priority thread on the queue. If there is a 792 * tie, use the thread that first appears in the queue as it has 793 * been sleeping the longest since threads are always added to 794 * the tail of sleep queues. 795 */ 796 besttd = NULL; 797 TAILQ_FOREACH(td, &sq->sq_blocked[queue], td_slpq) { 798 if (besttd == NULL || td->td_priority < besttd->td_priority) 799 besttd = td; 800 } 801 MPASS(besttd != NULL); 802 thread_lock(besttd); 803 wakeup_swapper = sleepq_resume_thread(sq, besttd, pri); 804 thread_unlock(besttd); 805 return (wakeup_swapper); 806 } 807 808 /* 809 * Resume all threads sleeping on a specified wait channel. 810 */ 811 int 812 sleepq_broadcast(void *wchan, int flags, int pri, int queue) 813 { 814 struct sleepqueue *sq; 815 struct thread *td, *tdn; 816 int wakeup_swapper; 817 818 CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags); 819 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__)); 820 MPASS((queue >= 0) && (queue < NR_SLEEPQS)); 821 sq = sleepq_lookup(wchan); 822 if (sq == NULL) 823 return (0); 824 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE), 825 ("%s: mismatch between sleep/wakeup and cv_*", __func__)); 826 827 /* Resume all blocked threads on the sleep queue. */ 828 wakeup_swapper = 0; 829 TAILQ_FOREACH_SAFE(td, &sq->sq_blocked[queue], td_slpq, tdn) { 830 thread_lock(td); 831 if (sleepq_resume_thread(sq, td, pri)) 832 wakeup_swapper = 1; 833 thread_unlock(td); 834 } 835 return (wakeup_swapper); 836 } 837 838 /* 839 * Time sleeping threads out. When the timeout expires, the thread is 840 * removed from the sleep queue and made runnable if it is still asleep. 841 */ 842 static void 843 sleepq_timeout(void *arg) 844 { 845 struct sleepqueue_chain *sc; 846 struct sleepqueue *sq; 847 struct thread *td; 848 void *wchan; 849 int wakeup_swapper; 850 851 td = arg; 852 wakeup_swapper = 0; 853 CTR3(KTR_PROC, "sleepq_timeout: thread %p (pid %ld, %s)", 854 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name); 855 856 /* 857 * First, see if the thread is asleep and get the wait channel if 858 * it is. 859 */ 860 thread_lock(td); 861 if (TD_IS_SLEEPING(td) && TD_ON_SLEEPQ(td)) { 862 wchan = td->td_wchan; 863 sc = SC_LOOKUP(wchan); 864 THREAD_LOCKPTR_ASSERT(td, &sc->sc_lock); 865 sq = sleepq_lookup(wchan); 866 MPASS(sq != NULL); 867 td->td_flags |= TDF_TIMEOUT; 868 wakeup_swapper = sleepq_resume_thread(sq, td, 0); 869 thread_unlock(td); 870 if (wakeup_swapper) 871 kick_proc0(); 872 return; 873 } 874 875 /* 876 * If the thread is on the SLEEPQ but isn't sleeping yet, it 877 * can either be on another CPU in between sleepq_add() and 878 * one of the sleepq_*wait*() routines or it can be in 879 * sleepq_catch_signals(). 880 */ 881 if (TD_ON_SLEEPQ(td)) { 882 td->td_flags |= TDF_TIMEOUT; 883 thread_unlock(td); 884 return; 885 } 886 887 /* 888 * Now check for the edge cases. First, if TDF_TIMEOUT is set, 889 * then the other thread has already yielded to us, so clear 890 * the flag and resume it. If TDF_TIMEOUT is not set, then the 891 * we know that the other thread is not on a sleep queue, but it 892 * hasn't resumed execution yet. In that case, set TDF_TIMOFAIL 893 * to let it know that the timeout has already run and doesn't 894 * need to be canceled. 895 */ 896 if (td->td_flags & TDF_TIMEOUT) { 897 MPASS(TD_IS_SLEEPING(td)); 898 td->td_flags &= ~TDF_TIMEOUT; 899 TD_CLR_SLEEPING(td); 900 wakeup_swapper = setrunnable(td); 901 } else 902 td->td_flags |= TDF_TIMOFAIL; 903 thread_unlock(td); 904 if (wakeup_swapper) 905 kick_proc0(); 906 } 907 908 /* 909 * Resumes a specific thread from the sleep queue associated with a specific 910 * wait channel if it is on that queue. 911 */ 912 void 913 sleepq_remove(struct thread *td, void *wchan) 914 { 915 struct sleepqueue *sq; 916 int wakeup_swapper; 917 918 /* 919 * Look up the sleep queue for this wait channel, then re-check 920 * that the thread is asleep on that channel, if it is not, then 921 * bail. 922 */ 923 MPASS(wchan != NULL); 924 sleepq_lock(wchan); 925 sq = sleepq_lookup(wchan); 926 /* 927 * We can not lock the thread here as it may be sleeping on a 928 * different sleepq. However, holding the sleepq lock for this 929 * wchan can guarantee that we do not miss a wakeup for this 930 * channel. The asserts below will catch any false positives. 931 */ 932 if (!TD_ON_SLEEPQ(td) || td->td_wchan != wchan) { 933 sleepq_release(wchan); 934 return; 935 } 936 /* Thread is asleep on sleep queue sq, so wake it up. */ 937 thread_lock(td); 938 MPASS(sq != NULL); 939 MPASS(td->td_wchan == wchan); 940 wakeup_swapper = sleepq_resume_thread(sq, td, 0); 941 thread_unlock(td); 942 sleepq_release(wchan); 943 if (wakeup_swapper) 944 kick_proc0(); 945 } 946 947 /* 948 * Abort a thread as if an interrupt had occurred. Only abort 949 * interruptible waits (unfortunately it isn't safe to abort others). 950 */ 951 int 952 sleepq_abort(struct thread *td, int intrval) 953 { 954 struct sleepqueue *sq; 955 void *wchan; 956 957 THREAD_LOCK_ASSERT(td, MA_OWNED); 958 MPASS(TD_ON_SLEEPQ(td)); 959 MPASS(td->td_flags & TDF_SINTR); 960 MPASS(intrval == EINTR || intrval == ERESTART); 961 962 /* 963 * If the TDF_TIMEOUT flag is set, just leave. A 964 * timeout is scheduled anyhow. 965 */ 966 if (td->td_flags & TDF_TIMEOUT) 967 return (0); 968 969 CTR3(KTR_PROC, "sleepq_abort: thread %p (pid %ld, %s)", 970 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name); 971 td->td_intrval = intrval; 972 td->td_flags |= TDF_SLEEPABORT; 973 /* 974 * If the thread has not slept yet it will find the signal in 975 * sleepq_catch_signals() and call sleepq_resume_thread. Otherwise 976 * we have to do it here. 977 */ 978 if (!TD_IS_SLEEPING(td)) 979 return (0); 980 wchan = td->td_wchan; 981 MPASS(wchan != NULL); 982 sq = sleepq_lookup(wchan); 983 MPASS(sq != NULL); 984 985 /* Thread is asleep on sleep queue sq, so wake it up. */ 986 return (sleepq_resume_thread(sq, td, 0)); 987 } 988 989 #ifdef SLEEPQUEUE_PROFILING 990 #define SLEEPQ_PROF_LOCATIONS 1024 991 #define SLEEPQ_SBUFSIZE (40 * 512) 992 struct sleepq_prof { 993 LIST_ENTRY(sleepq_prof) sp_link; 994 const char *sp_wmesg; 995 long sp_count; 996 }; 997 998 LIST_HEAD(sqphead, sleepq_prof); 999 1000 struct sqphead sleepq_prof_free; 1001 struct sqphead sleepq_hash[SC_TABLESIZE]; 1002 static struct sleepq_prof sleepq_profent[SLEEPQ_PROF_LOCATIONS]; 1003 static struct mtx sleepq_prof_lock; 1004 MTX_SYSINIT(sleepq_prof_lock, &sleepq_prof_lock, "sleepq_prof", MTX_SPIN); 1005 1006 static void 1007 sleepq_profile(const char *wmesg) 1008 { 1009 struct sleepq_prof *sp; 1010 1011 mtx_lock_spin(&sleepq_prof_lock); 1012 if (prof_enabled == 0) 1013 goto unlock; 1014 LIST_FOREACH(sp, &sleepq_hash[SC_HASH(wmesg)], sp_link) 1015 if (sp->sp_wmesg == wmesg) 1016 goto done; 1017 sp = LIST_FIRST(&sleepq_prof_free); 1018 if (sp == NULL) 1019 goto unlock; 1020 sp->sp_wmesg = wmesg; 1021 LIST_REMOVE(sp, sp_link); 1022 LIST_INSERT_HEAD(&sleepq_hash[SC_HASH(wmesg)], sp, sp_link); 1023 done: 1024 sp->sp_count++; 1025 unlock: 1026 mtx_unlock_spin(&sleepq_prof_lock); 1027 return; 1028 } 1029 1030 static void 1031 sleepq_prof_reset(void) 1032 { 1033 struct sleepq_prof *sp; 1034 int enabled; 1035 int i; 1036 1037 mtx_lock_spin(&sleepq_prof_lock); 1038 enabled = prof_enabled; 1039 prof_enabled = 0; 1040 for (i = 0; i < SC_TABLESIZE; i++) 1041 LIST_INIT(&sleepq_hash[i]); 1042 LIST_INIT(&sleepq_prof_free); 1043 for (i = 0; i < SLEEPQ_PROF_LOCATIONS; i++) { 1044 sp = &sleepq_profent[i]; 1045 sp->sp_wmesg = NULL; 1046 sp->sp_count = 0; 1047 LIST_INSERT_HEAD(&sleepq_prof_free, sp, sp_link); 1048 } 1049 prof_enabled = enabled; 1050 mtx_unlock_spin(&sleepq_prof_lock); 1051 } 1052 1053 static int 1054 enable_sleepq_prof(SYSCTL_HANDLER_ARGS) 1055 { 1056 int error, v; 1057 1058 v = prof_enabled; 1059 error = sysctl_handle_int(oidp, &v, v, req); 1060 if (error) 1061 return (error); 1062 if (req->newptr == NULL) 1063 return (error); 1064 if (v == prof_enabled) 1065 return (0); 1066 if (v == 1) 1067 sleepq_prof_reset(); 1068 mtx_lock_spin(&sleepq_prof_lock); 1069 prof_enabled = !!v; 1070 mtx_unlock_spin(&sleepq_prof_lock); 1071 1072 return (0); 1073 } 1074 1075 static int 1076 reset_sleepq_prof_stats(SYSCTL_HANDLER_ARGS) 1077 { 1078 int error, v; 1079 1080 v = 0; 1081 error = sysctl_handle_int(oidp, &v, 0, req); 1082 if (error) 1083 return (error); 1084 if (req->newptr == NULL) 1085 return (error); 1086 if (v == 0) 1087 return (0); 1088 sleepq_prof_reset(); 1089 1090 return (0); 1091 } 1092 1093 static int 1094 dump_sleepq_prof_stats(SYSCTL_HANDLER_ARGS) 1095 { 1096 static int multiplier = 1; 1097 struct sleepq_prof *sp; 1098 struct sbuf *sb; 1099 int enabled; 1100 int error; 1101 int i; 1102 1103 retry_sbufops: 1104 sb = sbuf_new(NULL, NULL, SLEEPQ_SBUFSIZE * multiplier, SBUF_FIXEDLEN); 1105 sbuf_printf(sb, "\nwmesg\tcount\n"); 1106 enabled = prof_enabled; 1107 mtx_lock_spin(&sleepq_prof_lock); 1108 prof_enabled = 0; 1109 mtx_unlock_spin(&sleepq_prof_lock); 1110 for (i = 0; i < SC_TABLESIZE; i++) { 1111 LIST_FOREACH(sp, &sleepq_hash[i], sp_link) { 1112 sbuf_printf(sb, "%s\t%ld\n", 1113 sp->sp_wmesg, sp->sp_count); 1114 if (sbuf_overflowed(sb)) { 1115 sbuf_delete(sb); 1116 multiplier++; 1117 goto retry_sbufops; 1118 } 1119 } 1120 } 1121 mtx_lock_spin(&sleepq_prof_lock); 1122 prof_enabled = enabled; 1123 mtx_unlock_spin(&sleepq_prof_lock); 1124 1125 sbuf_finish(sb); 1126 error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1); 1127 sbuf_delete(sb); 1128 return (error); 1129 } 1130 1131 SYSCTL_PROC(_debug_sleepq, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD, 1132 NULL, 0, dump_sleepq_prof_stats, "A", "Sleepqueue profiling statistics"); 1133 SYSCTL_PROC(_debug_sleepq, OID_AUTO, reset, CTLTYPE_INT | CTLFLAG_RW, 1134 NULL, 0, reset_sleepq_prof_stats, "I", 1135 "Reset sleepqueue profiling statistics"); 1136 SYSCTL_PROC(_debug_sleepq, OID_AUTO, enable, CTLTYPE_INT | CTLFLAG_RW, 1137 NULL, 0, enable_sleepq_prof, "I", "Enable sleepqueue profiling"); 1138 #endif 1139 1140 #ifdef DDB 1141 DB_SHOW_COMMAND(sleepq, db_show_sleepqueue) 1142 { 1143 struct sleepqueue_chain *sc; 1144 struct sleepqueue *sq; 1145 #ifdef INVARIANTS 1146 struct lock_object *lock; 1147 #endif 1148 struct thread *td; 1149 void *wchan; 1150 int i; 1151 1152 if (!have_addr) 1153 return; 1154 1155 /* 1156 * First, see if there is an active sleep queue for the wait channel 1157 * indicated by the address. 1158 */ 1159 wchan = (void *)addr; 1160 sc = SC_LOOKUP(wchan); 1161 LIST_FOREACH(sq, &sc->sc_queues, sq_hash) 1162 if (sq->sq_wchan == wchan) 1163 goto found; 1164 1165 /* 1166 * Second, see if there is an active sleep queue at the address 1167 * indicated. 1168 */ 1169 for (i = 0; i < SC_TABLESIZE; i++) 1170 LIST_FOREACH(sq, &sleepq_chains[i].sc_queues, sq_hash) { 1171 if (sq == (struct sleepqueue *)addr) 1172 goto found; 1173 } 1174 1175 db_printf("Unable to locate a sleep queue via %p\n", (void *)addr); 1176 return; 1177 found: 1178 db_printf("Wait channel: %p\n", sq->sq_wchan); 1179 #ifdef INVARIANTS 1180 db_printf("Queue type: %d\n", sq->sq_type); 1181 if (sq->sq_lock) { 1182 lock = sq->sq_lock; 1183 db_printf("Associated Interlock: %p - (%s) %s\n", lock, 1184 LOCK_CLASS(lock)->lc_name, lock->lo_name); 1185 } 1186 #endif 1187 db_printf("Blocked threads:\n"); 1188 for (i = 0; i < NR_SLEEPQS; i++) { 1189 db_printf("\nQueue[%d]:\n", i); 1190 if (TAILQ_EMPTY(&sq->sq_blocked[i])) 1191 db_printf("\tempty\n"); 1192 else 1193 TAILQ_FOREACH(td, &sq->sq_blocked[0], 1194 td_slpq) { 1195 db_printf("\t%p (tid %d, pid %d, \"%s\")\n", td, 1196 td->td_tid, td->td_proc->p_pid, 1197 td->td_name); 1198 } 1199 db_printf("(expected: %u)\n", sq->sq_blockedcnt[i]); 1200 } 1201 } 1202 1203 /* Alias 'show sleepqueue' to 'show sleepq'. */ 1204 DB_SHOW_ALIAS(sleepqueue, db_show_sleepqueue); 1205 #endif 1206