subr_sleepqueue.c revision 145056
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 "opt_sleepqueue_profiling.h" 63 64#include <sys/cdefs.h> 65__FBSDID("$FreeBSD: head/sys/kern/subr_sleepqueue.c 145056 2005-04-14 06:30:32Z jhb $"); 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/malloc.h> 73#include <sys/mutex.h> 74#include <sys/proc.h> 75#include <sys/sched.h> 76#include <sys/signalvar.h> 77#include <sys/sleepqueue.h> 78#include <sys/sysctl.h> 79 80/* 81 * Constants for the hash table of sleep queue chains. These constants are 82 * the same ones that 4BSD (and possibly earlier versions of BSD) used. 83 * Basically, we ignore the lower 8 bits of the address since most wait 84 * channel pointers are aligned and only look at the next 7 bits for the 85 * hash. SC_TABLESIZE must be a power of two for SC_MASK to work properly. 86 */ 87#define SC_TABLESIZE 128 /* Must be power of 2. */ 88#define SC_MASK (SC_TABLESIZE - 1) 89#define SC_SHIFT 8 90#define SC_HASH(wc) (((uintptr_t)(wc) >> SC_SHIFT) & SC_MASK) 91#define SC_LOOKUP(wc) &sleepq_chains[SC_HASH(wc)] 92 93/* 94 * There two different lists of sleep queues. Both lists are connected 95 * via the sq_hash entries. The first list is the sleep queue chain list 96 * that a sleep queue is on when it is attached to a wait channel. The 97 * second list is the free list hung off of a sleep queue that is attached 98 * to a wait channel. 99 * 100 * Each sleep queue also contains the wait channel it is attached to, the 101 * list of threads blocked on that wait channel, flags specific to the 102 * wait channel, and the lock used to synchronize with a wait channel. 103 * The flags are used to catch mismatches between the various consumers 104 * of the sleep queue API (e.g. sleep/wakeup and condition variables). 105 * The lock pointer is only used when invariants are enabled for various 106 * debugging checks. 107 * 108 * Locking key: 109 * c - sleep queue chain lock 110 */ 111struct sleepqueue { 112 TAILQ_HEAD(, thread) sq_blocked; /* (c) Blocked threads. */ 113 LIST_ENTRY(sleepqueue) sq_hash; /* (c) Chain and free list. */ 114 LIST_HEAD(, sleepqueue) sq_free; /* (c) Free queues. */ 115 void *sq_wchan; /* (c) Wait channel. */ 116#ifdef INVARIANTS 117 int sq_type; /* (c) Queue type. */ 118 struct mtx *sq_lock; /* (c) Associated lock. */ 119#endif 120}; 121 122struct sleepqueue_chain { 123 LIST_HEAD(, sleepqueue) sc_queues; /* List of sleep queues. */ 124 struct mtx sc_lock; /* Spin lock for this chain. */ 125#ifdef SLEEPQUEUE_PROFILING 126 u_int sc_depth; /* Length of sc_queues. */ 127 u_int sc_max_depth; /* Max length of sc_queues. */ 128#endif 129}; 130 131#ifdef SLEEPQUEUE_PROFILING 132u_int sleepq_max_depth; 133SYSCTL_NODE(_debug, OID_AUTO, sleepq, CTLFLAG_RD, 0, "sleepq profiling"); 134SYSCTL_NODE(_debug_sleepq, OID_AUTO, chains, CTLFLAG_RD, 0, 135 "sleepq chain stats"); 136SYSCTL_UINT(_debug_sleepq, OID_AUTO, max_depth, CTLFLAG_RD, &sleepq_max_depth, 137 0, "maxmimum depth achieved of a single chain"); 138#endif 139static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE]; 140 141static MALLOC_DEFINE(M_SLEEPQUEUE, "sleep queues", "sleep queues"); 142 143/* 144 * Prototypes for non-exported routines. 145 */ 146static int sleepq_check_timeout(void); 147static void sleepq_switch(void *wchan); 148static void sleepq_timeout(void *arg); 149static void sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, int pri); 150 151/* 152 * Early initialization of sleep queues that is called from the sleepinit() 153 * SYSINIT. 154 */ 155void 156init_sleepqueues(void) 157{ 158#ifdef SLEEPQUEUE_PROFILING 159 struct sysctl_oid *chain_oid; 160 char chain_name[10]; 161#endif 162 int i; 163 164 for (i = 0; i < SC_TABLESIZE; i++) { 165 LIST_INIT(&sleepq_chains[i].sc_queues); 166 mtx_init(&sleepq_chains[i].sc_lock, "sleepq chain", NULL, 167 MTX_SPIN); 168#ifdef SLEEPQUEUE_PROFILING 169 snprintf(chain_name, sizeof(chain_name), "%d", i); 170 chain_oid = SYSCTL_ADD_NODE(NULL, 171 SYSCTL_STATIC_CHILDREN(_debug_sleepq_chains), OID_AUTO, 172 chain_name, CTLFLAG_RD, NULL, "sleepq chain stats"); 173 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO, 174 "depth", CTLFLAG_RD, &sleepq_chains[i].sc_depth, 0, NULL); 175 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO, 176 "max_depth", CTLFLAG_RD, &sleepq_chains[i].sc_max_depth, 0, 177 NULL); 178#endif 179 } 180 thread0.td_sleepqueue = sleepq_alloc(); 181} 182 183/* 184 * Malloc and initialize a new sleep queue for a new thread. 185 */ 186struct sleepqueue * 187sleepq_alloc(void) 188{ 189 struct sleepqueue *sq; 190 191 sq = malloc(sizeof(struct sleepqueue), M_SLEEPQUEUE, M_WAITOK | M_ZERO); 192 TAILQ_INIT(&sq->sq_blocked); 193 LIST_INIT(&sq->sq_free); 194 return (sq); 195} 196 197/* 198 * Free a sleep queue when a thread is destroyed. 199 */ 200void 201sleepq_free(struct sleepqueue *sq) 202{ 203 204 MPASS(sq != NULL); 205 MPASS(TAILQ_EMPTY(&sq->sq_blocked)); 206 free(sq, M_SLEEPQUEUE); 207} 208 209/* 210 * Lock the sleep queue chain associated with the specified wait channel. 211 */ 212void 213sleepq_lock(void *wchan) 214{ 215 struct sleepqueue_chain *sc; 216 217 sc = SC_LOOKUP(wchan); 218 mtx_lock_spin(&sc->sc_lock); 219} 220 221/* 222 * Look up the sleep queue associated with a given wait channel in the hash 223 * table locking the associated sleep queue chain. If no queue is found in 224 * the table, NULL is returned. 225 */ 226struct sleepqueue * 227sleepq_lookup(void *wchan) 228{ 229 struct sleepqueue_chain *sc; 230 struct sleepqueue *sq; 231 232 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__)); 233 sc = SC_LOOKUP(wchan); 234 mtx_assert(&sc->sc_lock, MA_OWNED); 235 LIST_FOREACH(sq, &sc->sc_queues, sq_hash) 236 if (sq->sq_wchan == wchan) 237 return (sq); 238 return (NULL); 239} 240 241/* 242 * Unlock the sleep queue chain associated with a given wait channel. 243 */ 244void 245sleepq_release(void *wchan) 246{ 247 struct sleepqueue_chain *sc; 248 249 sc = SC_LOOKUP(wchan); 250 mtx_unlock_spin(&sc->sc_lock); 251} 252 253/* 254 * Places the current thread on the sleep queue for the specified wait 255 * channel. If INVARIANTS is enabled, then it associates the passed in 256 * lock with the sleepq to make sure it is held when that sleep queue is 257 * woken up. 258 */ 259void 260sleepq_add(void *wchan, struct mtx *lock, const char *wmesg, int flags) 261{ 262 struct sleepqueue_chain *sc; 263 struct sleepqueue *sq; 264 struct thread *td; 265 266 td = curthread; 267 sc = SC_LOOKUP(wchan); 268 mtx_assert(&sc->sc_lock, MA_OWNED); 269 MPASS(td->td_sleepqueue != NULL); 270 MPASS(wchan != NULL); 271 272 /* Look up the sleep queue associated with the wait channel 'wchan'. */ 273 sq = sleepq_lookup(wchan); 274 275 /* 276 * If the wait channel does not already have a sleep queue, use 277 * this thread's sleep queue. Otherwise, insert the current thread 278 * into the sleep queue already in use by this wait channel. 279 */ 280 if (sq == NULL) { 281#ifdef SLEEPQUEUE_PROFILING 282 sc->sc_depth++; 283 if (sc->sc_depth > sc->sc_max_depth) { 284 sc->sc_max_depth = sc->sc_depth; 285 if (sc->sc_max_depth > sleepq_max_depth) 286 sleepq_max_depth = sc->sc_max_depth; 287 } 288#endif 289 sq = td->td_sleepqueue; 290 LIST_INSERT_HEAD(&sc->sc_queues, sq, sq_hash); 291 KASSERT(TAILQ_EMPTY(&sq->sq_blocked), 292 ("thread's sleep queue has a non-empty queue")); 293 KASSERT(LIST_EMPTY(&sq->sq_free), 294 ("thread's sleep queue has a non-empty free list")); 295 KASSERT(sq->sq_wchan == NULL, ("stale sq_wchan pointer")); 296 sq->sq_wchan = wchan; 297#ifdef INVARIANTS 298 sq->sq_lock = lock; 299 sq->sq_type = flags & SLEEPQ_TYPE; 300#endif 301 } else { 302 MPASS(wchan == sq->sq_wchan); 303 MPASS(lock == sq->sq_lock); 304 MPASS((flags & SLEEPQ_TYPE) == sq->sq_type); 305 LIST_INSERT_HEAD(&sq->sq_free, td->td_sleepqueue, sq_hash); 306 } 307 TAILQ_INSERT_TAIL(&sq->sq_blocked, td, td_slpq); 308 td->td_sleepqueue = NULL; 309 mtx_lock_spin(&sched_lock); 310 td->td_wchan = wchan; 311 td->td_wmesg = wmesg; 312 if (flags & SLEEPQ_INTERRUPTIBLE) 313 td->td_flags |= TDF_SINTR; 314 mtx_unlock_spin(&sched_lock); 315} 316 317/* 318 * Sets a timeout that will remove the current thread from the specified 319 * sleep queue after timo ticks if the thread has not already been awakened. 320 */ 321void 322sleepq_set_timeout(void *wchan, int timo) 323{ 324 struct sleepqueue_chain *sc; 325 struct thread *td; 326 327 td = curthread; 328 sc = SC_LOOKUP(wchan); 329 mtx_assert(&sc->sc_lock, MA_OWNED); 330 MPASS(TD_ON_SLEEPQ(td)); 331 MPASS(td->td_sleepqueue == NULL); 332 MPASS(wchan != NULL); 333 callout_reset(&td->td_slpcallout, timo, sleepq_timeout, td); 334} 335 336/* 337 * Marks the pending sleep of the current thread as interruptible and 338 * makes an initial check for pending signals before putting a thread 339 * to sleep. 340 */ 341int 342sleepq_catch_signals(void *wchan) 343{ 344 struct sleepqueue_chain *sc; 345 struct sleepqueue *sq; 346 struct thread *td; 347 struct proc *p; 348 int do_upcall; 349 int sig; 350 351 do_upcall = 0; 352 td = curthread; 353 p = td->td_proc; 354 sc = SC_LOOKUP(wchan); 355 mtx_assert(&sc->sc_lock, MA_OWNED); 356 MPASS(td->td_sleepqueue == NULL); 357 MPASS(wchan != NULL); 358 CTR3(KTR_PROC, "sleepq catching signals: thread %p (pid %ld, %s)", 359 (void *)td, (long)p->p_pid, p->p_comm); 360 361 /* Mark thread as being in an interruptible sleep. */ 362 MPASS(td->td_flags & TDF_SINTR); 363 MPASS(TD_ON_SLEEPQ(td)); 364 sleepq_release(wchan); 365 366 /* See if there are any pending signals for this thread. */ 367 PROC_LOCK(p); 368 mtx_lock(&p->p_sigacts->ps_mtx); 369 sig = cursig(td); 370 mtx_unlock(&p->p_sigacts->ps_mtx); 371 if (sig == 0 && thread_suspend_check(1)) 372 sig = SIGSTOP; 373 else 374 do_upcall = thread_upcall_check(td); 375 PROC_UNLOCK(p); 376 377 /* 378 * If there were pending signals and this thread is still on 379 * the sleep queue, remove it from the sleep queue. If the 380 * thread was removed from the sleep queue while we were blocked 381 * above, then clear TDF_SINTR before returning. 382 */ 383 sleepq_lock(wchan); 384 sq = sleepq_lookup(wchan); 385 mtx_lock_spin(&sched_lock); 386 if (TD_ON_SLEEPQ(td) && (sig != 0 || do_upcall != 0)) 387 sleepq_resume_thread(sq, td, -1); 388 else if (!TD_ON_SLEEPQ(td) && sig == 0) 389 td->td_flags &= ~TDF_SINTR; 390 mtx_unlock_spin(&sched_lock); 391 return (sig); 392} 393 394/* 395 * Switches to another thread if we are still asleep on a sleep queue and 396 * drop the lock on the sleep queue chain. Returns with sched_lock held. 397 */ 398static void 399sleepq_switch(void *wchan) 400{ 401 struct sleepqueue_chain *sc; 402 struct thread *td; 403 404 td = curthread; 405 sc = SC_LOOKUP(wchan); 406 mtx_assert(&sc->sc_lock, MA_OWNED); 407 408 /* 409 * If we have a sleep queue, then we've already been woken up, so 410 * just return. 411 */ 412 if (td->td_sleepqueue != NULL) { 413 MPASS(!TD_ON_SLEEPQ(td)); 414 mtx_unlock_spin(&sc->sc_lock); 415 mtx_lock_spin(&sched_lock); 416 return; 417 } 418 419 /* 420 * Otherwise, actually go to sleep. 421 */ 422 mtx_lock_spin(&sched_lock); 423 mtx_unlock_spin(&sc->sc_lock); 424 425 sched_sleep(td); 426 TD_SET_SLEEPING(td); 427 mi_switch(SW_VOL, NULL); 428 KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING")); 429 CTR3(KTR_PROC, "sleepq resume: thread %p (pid %ld, %s)", 430 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm); 431} 432 433/* 434 * Check to see if we timed out. 435 */ 436static int 437sleepq_check_timeout(void) 438{ 439 struct thread *td; 440 441 mtx_assert(&sched_lock, MA_OWNED); 442 td = curthread; 443 444 /* 445 * If TDF_TIMEOUT is set, we timed out. 446 */ 447 if (td->td_flags & TDF_TIMEOUT) { 448 td->td_flags &= ~TDF_TIMEOUT; 449 return (EWOULDBLOCK); 450 } 451 452 /* 453 * If TDF_TIMOFAIL is set, the timeout ran after we had 454 * already been woken up. 455 */ 456 if (td->td_flags & TDF_TIMOFAIL) 457 td->td_flags &= ~TDF_TIMOFAIL; 458 459 /* 460 * If callout_stop() fails, then the timeout is running on 461 * another CPU, so synchronize with it to avoid having it 462 * accidentally wake up a subsequent sleep. 463 */ 464 else if (callout_stop(&td->td_slpcallout) == 0) { 465 td->td_flags |= TDF_TIMEOUT; 466 TD_SET_SLEEPING(td); 467 mi_switch(SW_INVOL, NULL); 468 } 469 return (0); 470} 471 472/* 473 * Check to see if we were awoken by a signal. 474 */ 475static int 476sleepq_check_signals(void) 477{ 478 struct thread *td; 479 480 mtx_assert(&sched_lock, MA_OWNED); 481 td = curthread; 482 483 /* 484 * If TDF_SINTR is clear, then we were awakened while executing 485 * sleepq_catch_signals(). 486 */ 487 if (!(td->td_flags & TDF_SINTR)) 488 return (0); 489 490 /* We are no longer in an interruptible sleep. */ 491 td->td_flags &= ~TDF_SINTR; 492 493 if (td->td_flags & TDF_INTERRUPT) 494 return (td->td_intrval); 495 return (0); 496} 497 498/* 499 * If we were in an interruptible sleep and we weren't interrupted and 500 * didn't timeout, check to see if there are any pending signals and 501 * which return value we should use if so. The return value from an 502 * earlier call to sleepq_catch_signals() should be passed in as the 503 * argument. 504 */ 505int 506sleepq_calc_signal_retval(int sig) 507{ 508 struct thread *td; 509 struct proc *p; 510 int rval; 511 512 td = curthread; 513 p = td->td_proc; 514 PROC_LOCK(p); 515 mtx_lock(&p->p_sigacts->ps_mtx); 516 /* XXX: Should we always be calling cursig()? */ 517 if (sig == 0) 518 sig = cursig(td); 519 if (sig != 0) { 520 if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig)) 521 rval = EINTR; 522 else 523 rval = ERESTART; 524 } else 525 rval = 0; 526 mtx_unlock(&p->p_sigacts->ps_mtx); 527 PROC_UNLOCK(p); 528 return (rval); 529} 530 531/* 532 * Block the current thread until it is awakened from its sleep queue. 533 */ 534void 535sleepq_wait(void *wchan) 536{ 537 538 MPASS(!(curthread->td_flags & TDF_SINTR)); 539 sleepq_switch(wchan); 540 mtx_unlock_spin(&sched_lock); 541} 542 543/* 544 * Block the current thread until it is awakened from its sleep queue 545 * or it is interrupted by a signal. 546 */ 547int 548sleepq_wait_sig(void *wchan) 549{ 550 int rval; 551 552 sleepq_switch(wchan); 553 rval = sleepq_check_signals(); 554 mtx_unlock_spin(&sched_lock); 555 return (rval); 556} 557 558/* 559 * Block the current thread until it is awakened from its sleep queue 560 * or it times out while waiting. 561 */ 562int 563sleepq_timedwait(void *wchan) 564{ 565 int rval; 566 567 MPASS(!(curthread->td_flags & TDF_SINTR)); 568 sleepq_switch(wchan); 569 rval = sleepq_check_timeout(); 570 mtx_unlock_spin(&sched_lock); 571 return (rval); 572} 573 574/* 575 * Block the current thread until it is awakened from its sleep queue, 576 * it is interrupted by a signal, or it times out waiting to be awakened. 577 */ 578int 579sleepq_timedwait_sig(void *wchan, int signal_caught) 580{ 581 int rvalt, rvals; 582 583 sleepq_switch(wchan); 584 rvalt = sleepq_check_timeout(); 585 rvals = sleepq_check_signals(); 586 mtx_unlock_spin(&sched_lock); 587 if (signal_caught || rvalt == 0) 588 return (rvals); 589 else 590 return (rvalt); 591} 592 593/* 594 * Removes a thread from a sleep queue and makes it 595 * runnable. 596 */ 597static void 598sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, int pri) 599{ 600 struct sleepqueue_chain *sc; 601 602 MPASS(td != NULL); 603 MPASS(sq->sq_wchan != NULL); 604 MPASS(td->td_wchan == sq->sq_wchan); 605 sc = SC_LOOKUP(sq->sq_wchan); 606 mtx_assert(&sc->sc_lock, MA_OWNED); 607 mtx_assert(&sched_lock, MA_OWNED); 608 609 /* Remove the thread from the queue. */ 610 TAILQ_REMOVE(&sq->sq_blocked, td, td_slpq); 611 612 /* 613 * Get a sleep queue for this thread. If this is the last waiter, 614 * use the queue itself and take it out of the chain, otherwise, 615 * remove a queue from the free list. 616 */ 617 if (LIST_EMPTY(&sq->sq_free)) { 618 td->td_sleepqueue = sq; 619#ifdef INVARIANTS 620 sq->sq_wchan = NULL; 621#endif 622#ifdef SLEEPQUEUE_PROFILING 623 sc->sc_depth--; 624#endif 625 } else 626 td->td_sleepqueue = LIST_FIRST(&sq->sq_free); 627 LIST_REMOVE(td->td_sleepqueue, sq_hash); 628 629 td->td_wmesg = NULL; 630 td->td_wchan = NULL; 631 632 /* 633 * Note that thread td might not be sleeping if it is running 634 * sleepq_catch_signals() on another CPU or is blocked on 635 * its proc lock to check signals. It doesn't hurt to clear 636 * the sleeping flag if it isn't set though, so we just always 637 * do it. However, we can't assert that it is set. 638 */ 639 CTR3(KTR_PROC, "sleepq_wakeup: thread %p (pid %ld, %s)", 640 (void *)td, (long)td->td_proc->p_pid, td->td_proc->p_comm); 641 TD_CLR_SLEEPING(td); 642 643 /* Adjust priority if requested. */ 644 MPASS(pri == -1 || (pri >= PRI_MIN && pri <= PRI_MAX)); 645 if (pri != -1 && td->td_priority > pri) 646 sched_prio(td, pri); 647 setrunnable(td); 648} 649 650/* 651 * Find the highest priority thread sleeping on a wait channel and resume it. 652 */ 653void 654sleepq_signal(void *wchan, int flags, int pri) 655{ 656 struct sleepqueue *sq; 657 struct thread *td, *besttd; 658 659 CTR2(KTR_PROC, "sleepq_signal(%p, %d)", wchan, flags); 660 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__)); 661 sq = sleepq_lookup(wchan); 662 if (sq == NULL) { 663 sleepq_release(wchan); 664 return; 665 } 666 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE), 667 ("%s: mismatch between sleep/wakeup and cv_*", __func__)); 668 669 /* 670 * Find the highest priority thread on the queue. If there is a 671 * tie, use the thread that first appears in the queue as it has 672 * been sleeping the longest since threads are always added to 673 * the tail of sleep queues. 674 */ 675 besttd = NULL; 676 TAILQ_FOREACH(td, &sq->sq_blocked, td_slpq) { 677 if (besttd == NULL || td->td_priority < besttd->td_priority) 678 besttd = td; 679 } 680 MPASS(besttd != NULL); 681 mtx_lock_spin(&sched_lock); 682 sleepq_resume_thread(sq, besttd, pri); 683 mtx_unlock_spin(&sched_lock); 684 sleepq_release(wchan); 685} 686 687/* 688 * Resume all threads sleeping on a specified wait channel. 689 */ 690void 691sleepq_broadcast(void *wchan, int flags, int pri) 692{ 693 struct sleepqueue *sq; 694 695 CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags); 696 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__)); 697 sq = sleepq_lookup(wchan); 698 if (sq == NULL) { 699 sleepq_release(wchan); 700 return; 701 } 702 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE), 703 ("%s: mismatch between sleep/wakeup and cv_*", __func__)); 704 705 /* Resume all blocked threads on the sleep queue. */ 706 mtx_lock_spin(&sched_lock); 707 while (!TAILQ_EMPTY(&sq->sq_blocked)) 708 sleepq_resume_thread(sq, TAILQ_FIRST(&sq->sq_blocked), pri); 709 mtx_unlock_spin(&sched_lock); 710 sleepq_release(wchan); 711} 712 713/* 714 * Time sleeping threads out. When the timeout expires, the thread is 715 * removed from the sleep queue and made runnable if it is still asleep. 716 */ 717static void 718sleepq_timeout(void *arg) 719{ 720 struct sleepqueue *sq; 721 struct thread *td; 722 void *wchan; 723 724 td = arg; 725 CTR3(KTR_PROC, "sleepq_timeout: thread %p (pid %ld, %s)", 726 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm); 727 728 /* 729 * First, see if the thread is asleep and get the wait channel if 730 * it is. 731 */ 732 mtx_lock_spin(&sched_lock); 733 if (TD_ON_SLEEPQ(td)) { 734 wchan = td->td_wchan; 735 mtx_unlock_spin(&sched_lock); 736 sleepq_lock(wchan); 737 sq = sleepq_lookup(wchan); 738 mtx_lock_spin(&sched_lock); 739 } else { 740 wchan = NULL; 741 sq = NULL; 742 } 743 744 /* 745 * At this point, if the thread is still on the sleep queue, 746 * we have that sleep queue locked as it cannot migrate sleep 747 * queues while we dropped sched_lock. If it had resumed and 748 * was on another CPU while the lock was dropped, it would have 749 * seen that TDF_TIMEOUT and TDF_TIMOFAIL are clear and the 750 * call to callout_stop() to stop this routine would have failed 751 * meaning that it would have already set TDF_TIMEOUT to 752 * synchronize with this function. 753 */ 754 if (TD_ON_SLEEPQ(td)) { 755 MPASS(td->td_wchan == wchan); 756 MPASS(sq != NULL); 757 td->td_flags |= TDF_TIMEOUT; 758 sleepq_resume_thread(sq, td, -1); 759 mtx_unlock_spin(&sched_lock); 760 sleepq_release(wchan); 761 return; 762 } else if (wchan != NULL) 763 sleepq_release(wchan); 764 765 /* 766 * Now check for the edge cases. First, if TDF_TIMEOUT is set, 767 * then the other thread has already yielded to us, so clear 768 * the flag and resume it. If TDF_TIMEOUT is not set, then the 769 * we know that the other thread is not on a sleep queue, but it 770 * hasn't resumed execution yet. In that case, set TDF_TIMOFAIL 771 * to let it know that the timeout has already run and doesn't 772 * need to be canceled. 773 */ 774 if (td->td_flags & TDF_TIMEOUT) { 775 MPASS(TD_IS_SLEEPING(td)); 776 td->td_flags &= ~TDF_TIMEOUT; 777 TD_CLR_SLEEPING(td); 778 setrunnable(td); 779 } else 780 td->td_flags |= TDF_TIMOFAIL; 781 mtx_unlock_spin(&sched_lock); 782} 783 784/* 785 * Resumes a specific thread from the sleep queue associated with a specific 786 * wait channel if it is on that queue. 787 */ 788void 789sleepq_remove(struct thread *td, void *wchan) 790{ 791 struct sleepqueue *sq; 792 793 /* 794 * Look up the sleep queue for this wait channel, then re-check 795 * that the thread is asleep on that channel, if it is not, then 796 * bail. 797 */ 798 MPASS(wchan != NULL); 799 sleepq_lock(wchan); 800 sq = sleepq_lookup(wchan); 801 mtx_lock_spin(&sched_lock); 802 if (!TD_ON_SLEEPQ(td) || td->td_wchan != wchan) { 803 mtx_unlock_spin(&sched_lock); 804 sleepq_release(wchan); 805 return; 806 } 807 MPASS(sq != NULL); 808 809 /* Thread is asleep on sleep queue sq, so wake it up. */ 810 sleepq_resume_thread(sq, td, -1); 811 sleepq_release(wchan); 812 mtx_unlock_spin(&sched_lock); 813} 814 815/* 816 * Abort a thread as if an interrupt had occurred. Only abort 817 * interruptible waits (unfortunately it isn't safe to abort others). 818 * 819 * XXX: What in the world does the comment below mean? 820 * Also, whatever the signal code does... 821 */ 822void 823sleepq_abort(struct thread *td) 824{ 825 void *wchan; 826 827 mtx_assert(&sched_lock, MA_OWNED); 828 MPASS(TD_ON_SLEEPQ(td)); 829 MPASS(td->td_flags & TDF_SINTR); 830 831 /* 832 * If the TDF_TIMEOUT flag is set, just leave. A 833 * timeout is scheduled anyhow. 834 */ 835 if (td->td_flags & TDF_TIMEOUT) 836 return; 837 838 CTR3(KTR_PROC, "sleepq_abort: thread %p (pid %ld, %s)", 839 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm); 840 wchan = td->td_wchan; 841 mtx_unlock_spin(&sched_lock); 842 sleepq_remove(td, wchan); 843 mtx_lock_spin(&sched_lock); 844} 845