Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_timeout.c
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1 /*- 2 * Copyright (c) 1982, 1986, 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * (c) UNIX System Laboratories, Inc. 5 * All or some portions of this file are derived from material licensed 6 * to the University of California by American Telephone and Telegraph 7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 8 * the permission of UNIX System Laboratories, Inc. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 4. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * From: @(#)kern_clock.c 8.5 (Berkeley) 1/21/94 35 */ 36 37 #include <sys/cdefs.h> 38 __FBSDID("$FreeBSD: releng/8.0/sys/kern/kern_timeout.c 187664 2009-01-24 10:22:49Z rwatson $"); 39 40 #include "opt_kdtrace.h" 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/bus.h> 45 #include <sys/callout.h> 46 #include <sys/condvar.h> 47 #include <sys/interrupt.h> 48 #include <sys/kernel.h> 49 #include <sys/ktr.h> 50 #include <sys/lock.h> 51 #include <sys/malloc.h> 52 #include <sys/mutex.h> 53 #include <sys/proc.h> 54 #include <sys/sdt.h> 55 #include <sys/sleepqueue.h> 56 #include <sys/sysctl.h> 57 #include <sys/smp.h> 58 59 SDT_PROVIDER_DEFINE(callout_execute); 60 SDT_PROBE_DEFINE(callout_execute, kernel, , callout_start); 61 SDT_PROBE_ARGTYPE(callout_execute, kernel, , callout_start, 0, 62 "struct callout *"); 63 SDT_PROBE_DEFINE(callout_execute, kernel, , callout_end); 64 SDT_PROBE_ARGTYPE(callout_execute, kernel, , callout_end, 0, 65 "struct callout *"); 66 67 static int avg_depth; 68 SYSCTL_INT(_debug, OID_AUTO, to_avg_depth, CTLFLAG_RD, &avg_depth, 0, 69 "Average number of items examined per softclock call. Units = 1/1000"); 70 static int avg_gcalls; 71 SYSCTL_INT(_debug, OID_AUTO, to_avg_gcalls, CTLFLAG_RD, &avg_gcalls, 0, 72 "Average number of Giant callouts made per softclock call. Units = 1/1000"); 73 static int avg_lockcalls; 74 SYSCTL_INT(_debug, OID_AUTO, to_avg_lockcalls, CTLFLAG_RD, &avg_lockcalls, 0, 75 "Average number of lock callouts made per softclock call. Units = 1/1000"); 76 static int avg_mpcalls; 77 SYSCTL_INT(_debug, OID_AUTO, to_avg_mpcalls, CTLFLAG_RD, &avg_mpcalls, 0, 78 "Average number of MP callouts made per softclock call. Units = 1/1000"); 79 /* 80 * TODO: 81 * allocate more timeout table slots when table overflows. 82 */ 83 int callwheelsize, callwheelbits, callwheelmask; 84 85 struct callout_cpu { 86 struct mtx cc_lock; 87 struct callout *cc_callout; 88 struct callout_tailq *cc_callwheel; 89 struct callout_list cc_callfree; 90 struct callout *cc_next; 91 struct callout *cc_curr; 92 void *cc_cookie; 93 int cc_softticks; 94 int cc_cancel; 95 int cc_waiting; 96 }; 97 98 #ifdef SMP 99 struct callout_cpu cc_cpu[MAXCPU]; 100 #define CC_CPU(cpu) (&cc_cpu[(cpu)]) 101 #define CC_SELF() CC_CPU(PCPU_GET(cpuid)) 102 #else 103 struct callout_cpu cc_cpu; 104 #define CC_CPU(cpu) &cc_cpu 105 #define CC_SELF() &cc_cpu 106 #endif 107 #define CC_LOCK(cc) mtx_lock_spin(&(cc)->cc_lock) 108 #define CC_UNLOCK(cc) mtx_unlock_spin(&(cc)->cc_lock) 109 110 static int timeout_cpu; 111 112 MALLOC_DEFINE(M_CALLOUT, "callout", "Callout datastructures"); 113 114 /** 115 * Locked by cc_lock: 116 * cc_curr - If a callout is in progress, it is curr_callout. 117 * If curr_callout is non-NULL, threads waiting in 118 * callout_drain() will be woken up as soon as the 119 * relevant callout completes. 120 * cc_cancel - Changing to 1 with both callout_lock and c_lock held 121 * guarantees that the current callout will not run. 122 * The softclock() function sets this to 0 before it 123 * drops callout_lock to acquire c_lock, and it calls 124 * the handler only if curr_cancelled is still 0 after 125 * c_lock is successfully acquired. 126 * cc_waiting - If a thread is waiting in callout_drain(), then 127 * callout_wait is nonzero. Set only when 128 * curr_callout is non-NULL. 129 */ 130 131 /* 132 * kern_timeout_callwheel_alloc() - kernel low level callwheel initialization 133 * 134 * This code is called very early in the kernel initialization sequence, 135 * and may be called more then once. 136 */ 137 caddr_t 138 kern_timeout_callwheel_alloc(caddr_t v) 139 { 140 struct callout_cpu *cc; 141 142 timeout_cpu = PCPU_GET(cpuid); 143 cc = CC_CPU(timeout_cpu); 144 /* 145 * Calculate callout wheel size 146 */ 147 for (callwheelsize = 1, callwheelbits = 0; 148 callwheelsize < ncallout; 149 callwheelsize <<= 1, ++callwheelbits) 150 ; 151 callwheelmask = callwheelsize - 1; 152 153 cc->cc_callout = (struct callout *)v; 154 v = (caddr_t)(cc->cc_callout + ncallout); 155 cc->cc_callwheel = (struct callout_tailq *)v; 156 v = (caddr_t)(cc->cc_callwheel + callwheelsize); 157 return(v); 158 } 159 160 static void 161 callout_cpu_init(struct callout_cpu *cc) 162 { 163 struct callout *c; 164 int i; 165 166 mtx_init(&cc->cc_lock, "callout", NULL, MTX_SPIN | MTX_RECURSE); 167 SLIST_INIT(&cc->cc_callfree); 168 for (i = 0; i < callwheelsize; i++) { 169 TAILQ_INIT(&cc->cc_callwheel[i]); 170 } 171 if (cc->cc_callout == NULL) 172 return; 173 for (i = 0; i < ncallout; i++) { 174 c = &cc->cc_callout[i]; 175 callout_init(c, 0); 176 c->c_flags = CALLOUT_LOCAL_ALLOC; 177 SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle); 178 } 179 } 180 181 /* 182 * kern_timeout_callwheel_init() - initialize previously reserved callwheel 183 * space. 184 * 185 * This code is called just once, after the space reserved for the 186 * callout wheel has been finalized. 187 */ 188 void 189 kern_timeout_callwheel_init(void) 190 { 191 callout_cpu_init(CC_CPU(timeout_cpu)); 192 } 193 194 /* 195 * Start standard softclock thread. 196 */ 197 void *softclock_ih; 198 199 static void 200 start_softclock(void *dummy) 201 { 202 struct callout_cpu *cc; 203 #ifdef SMP 204 int cpu; 205 #endif 206 207 cc = CC_CPU(timeout_cpu); 208 if (swi_add(&clk_intr_event, "clock", softclock, cc, SWI_CLOCK, 209 INTR_MPSAFE, &softclock_ih)) 210 panic("died while creating standard software ithreads"); 211 cc->cc_cookie = softclock_ih; 212 #ifdef SMP 213 for (cpu = 0; cpu <= mp_maxid; cpu++) { 214 if (cpu == timeout_cpu) 215 continue; 216 if (CPU_ABSENT(cpu)) 217 continue; 218 cc = CC_CPU(cpu); 219 if (swi_add(NULL, "clock", softclock, cc, SWI_CLOCK, 220 INTR_MPSAFE, &cc->cc_cookie)) 221 panic("died while creating standard software ithreads"); 222 cc->cc_callout = NULL; /* Only cpu0 handles timeout(). */ 223 cc->cc_callwheel = malloc( 224 sizeof(struct callout_tailq) * callwheelsize, M_CALLOUT, 225 M_WAITOK); 226 callout_cpu_init(cc); 227 } 228 #endif 229 } 230 231 SYSINIT(start_softclock, SI_SUB_SOFTINTR, SI_ORDER_FIRST, start_softclock, NULL); 232 233 void 234 callout_tick(void) 235 { 236 struct callout_cpu *cc; 237 int need_softclock; 238 int bucket; 239 240 /* 241 * Process callouts at a very low cpu priority, so we don't keep the 242 * relatively high clock interrupt priority any longer than necessary. 243 */ 244 need_softclock = 0; 245 cc = CC_SELF(); 246 mtx_lock_spin_flags(&cc->cc_lock, MTX_QUIET); 247 for (; (cc->cc_softticks - ticks) < 0; cc->cc_softticks++) { 248 bucket = cc->cc_softticks & callwheelmask; 249 if (!TAILQ_EMPTY(&cc->cc_callwheel[bucket])) { 250 need_softclock = 1; 251 break; 252 } 253 } 254 mtx_unlock_spin_flags(&cc->cc_lock, MTX_QUIET); 255 /* 256 * swi_sched acquires the thread lock, so we don't want to call it 257 * with cc_lock held; incorrect locking order. 258 */ 259 if (need_softclock) 260 swi_sched(cc->cc_cookie, 0); 261 } 262 263 static struct callout_cpu * 264 callout_lock(struct callout *c) 265 { 266 struct callout_cpu *cc; 267 int cpu; 268 269 for (;;) { 270 cpu = c->c_cpu; 271 cc = CC_CPU(cpu); 272 CC_LOCK(cc); 273 if (cpu == c->c_cpu) 274 break; 275 CC_UNLOCK(cc); 276 } 277 return (cc); 278 } 279 280 /* 281 * The callout mechanism is based on the work of Adam M. Costello and 282 * George Varghese, published in a technical report entitled "Redesigning 283 * the BSD Callout and Timer Facilities" and modified slightly for inclusion 284 * in FreeBSD by Justin T. Gibbs. The original work on the data structures 285 * used in this implementation was published by G. Varghese and T. Lauck in 286 * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for 287 * the Efficient Implementation of a Timer Facility" in the Proceedings of 288 * the 11th ACM Annual Symposium on Operating Systems Principles, 289 * Austin, Texas Nov 1987. 290 */ 291 292 /* 293 * Software (low priority) clock interrupt. 294 * Run periodic events from timeout queue. 295 */ 296 void 297 softclock(void *arg) 298 { 299 struct callout_cpu *cc; 300 struct callout *c; 301 struct callout_tailq *bucket; 302 int curticks; 303 int steps; /* #steps since we last allowed interrupts */ 304 int depth; 305 int mpcalls; 306 int lockcalls; 307 int gcalls; 308 #ifdef DIAGNOSTIC 309 struct bintime bt1, bt2; 310 struct timespec ts2; 311 static uint64_t maxdt = 36893488147419102LL; /* 2 msec */ 312 static timeout_t *lastfunc; 313 #endif 314 315 #ifndef MAX_SOFTCLOCK_STEPS 316 #define MAX_SOFTCLOCK_STEPS 100 /* Maximum allowed value of steps. */ 317 #endif /* MAX_SOFTCLOCK_STEPS */ 318 319 mpcalls = 0; 320 lockcalls = 0; 321 gcalls = 0; 322 depth = 0; 323 steps = 0; 324 cc = (struct callout_cpu *)arg; 325 CC_LOCK(cc); 326 while (cc->cc_softticks != ticks) { 327 /* 328 * cc_softticks may be modified by hard clock, so cache 329 * it while we work on a given bucket. 330 */ 331 curticks = cc->cc_softticks; 332 cc->cc_softticks++; 333 bucket = &cc->cc_callwheel[curticks & callwheelmask]; 334 c = TAILQ_FIRST(bucket); 335 while (c) { 336 depth++; 337 if (c->c_time != curticks) { 338 c = TAILQ_NEXT(c, c_links.tqe); 339 ++steps; 340 if (steps >= MAX_SOFTCLOCK_STEPS) { 341 cc->cc_next = c; 342 /* Give interrupts a chance. */ 343 CC_UNLOCK(cc); 344 ; /* nothing */ 345 CC_LOCK(cc); 346 c = cc->cc_next; 347 steps = 0; 348 } 349 } else { 350 void (*c_func)(void *); 351 void *c_arg; 352 struct lock_class *class; 353 struct lock_object *c_lock; 354 int c_flags, sharedlock; 355 356 cc->cc_next = TAILQ_NEXT(c, c_links.tqe); 357 TAILQ_REMOVE(bucket, c, c_links.tqe); 358 class = (c->c_lock != NULL) ? 359 LOCK_CLASS(c->c_lock) : NULL; 360 sharedlock = (c->c_flags & CALLOUT_SHAREDLOCK) ? 361 0 : 1; 362 c_lock = c->c_lock; 363 c_func = c->c_func; 364 c_arg = c->c_arg; 365 c_flags = c->c_flags; 366 if (c->c_flags & CALLOUT_LOCAL_ALLOC) { 367 c->c_flags = CALLOUT_LOCAL_ALLOC; 368 } else { 369 c->c_flags = 370 (c->c_flags & ~CALLOUT_PENDING); 371 } 372 cc->cc_curr = c; 373 cc->cc_cancel = 0; 374 CC_UNLOCK(cc); 375 if (c_lock != NULL) { 376 class->lc_lock(c_lock, sharedlock); 377 /* 378 * The callout may have been cancelled 379 * while we switched locks. 380 */ 381 if (cc->cc_cancel) { 382 class->lc_unlock(c_lock); 383 goto skip; 384 } 385 /* The callout cannot be stopped now. */ 386 cc->cc_cancel = 1; 387 388 if (c_lock == &Giant.lock_object) { 389 gcalls++; 390 CTR3(KTR_CALLOUT, 391 "callout %p func %p arg %p", 392 c, c_func, c_arg); 393 } else { 394 lockcalls++; 395 CTR3(KTR_CALLOUT, "callout lock" 396 " %p func %p arg %p", 397 c, c_func, c_arg); 398 } 399 } else { 400 mpcalls++; 401 CTR3(KTR_CALLOUT, 402 "callout mpsafe %p func %p arg %p", 403 c, c_func, c_arg); 404 } 405 #ifdef DIAGNOSTIC 406 binuptime(&bt1); 407 #endif 408 THREAD_NO_SLEEPING(); 409 SDT_PROBE(callout_execute, kernel, , 410 callout_start, c, 0, 0, 0, 0); 411 c_func(c_arg); 412 SDT_PROBE(callout_execute, kernel, , 413 callout_end, c, 0, 0, 0, 0); 414 THREAD_SLEEPING_OK(); 415 #ifdef DIAGNOSTIC 416 binuptime(&bt2); 417 bintime_sub(&bt2, &bt1); 418 if (bt2.frac > maxdt) { 419 if (lastfunc != c_func || 420 bt2.frac > maxdt * 2) { 421 bintime2timespec(&bt2, &ts2); 422 printf( 423 "Expensive timeout(9) function: %p(%p) %jd.%09ld s\n", 424 c_func, c_arg, 425 (intmax_t)ts2.tv_sec, 426 ts2.tv_nsec); 427 } 428 maxdt = bt2.frac; 429 lastfunc = c_func; 430 } 431 #endif 432 CTR1(KTR_CALLOUT, "callout %p finished", c); 433 if ((c_flags & CALLOUT_RETURNUNLOCKED) == 0) 434 class->lc_unlock(c_lock); 435 skip: 436 CC_LOCK(cc); 437 /* 438 * If the current callout is locally 439 * allocated (from timeout(9)) 440 * then put it on the freelist. 441 * 442 * Note: we need to check the cached 443 * copy of c_flags because if it was not 444 * local, then it's not safe to deref the 445 * callout pointer. 446 */ 447 if (c_flags & CALLOUT_LOCAL_ALLOC) { 448 KASSERT(c->c_flags == 449 CALLOUT_LOCAL_ALLOC, 450 ("corrupted callout")); 451 c->c_func = NULL; 452 SLIST_INSERT_HEAD(&cc->cc_callfree, c, 453 c_links.sle); 454 } 455 cc->cc_curr = NULL; 456 if (cc->cc_waiting) { 457 /* 458 * There is someone waiting 459 * for the callout to complete. 460 */ 461 cc->cc_waiting = 0; 462 CC_UNLOCK(cc); 463 wakeup(&cc->cc_waiting); 464 CC_LOCK(cc); 465 } 466 steps = 0; 467 c = cc->cc_next; 468 } 469 } 470 } 471 avg_depth += (depth * 1000 - avg_depth) >> 8; 472 avg_mpcalls += (mpcalls * 1000 - avg_mpcalls) >> 8; 473 avg_lockcalls += (lockcalls * 1000 - avg_lockcalls) >> 8; 474 avg_gcalls += (gcalls * 1000 - avg_gcalls) >> 8; 475 cc->cc_next = NULL; 476 CC_UNLOCK(cc); 477 } 478 479 /* 480 * timeout -- 481 * Execute a function after a specified length of time. 482 * 483 * untimeout -- 484 * Cancel previous timeout function call. 485 * 486 * callout_handle_init -- 487 * Initialize a handle so that using it with untimeout is benign. 488 * 489 * See AT&T BCI Driver Reference Manual for specification. This 490 * implementation differs from that one in that although an 491 * identification value is returned from timeout, the original 492 * arguments to timeout as well as the identifier are used to 493 * identify entries for untimeout. 494 */ 495 struct callout_handle 496 timeout(ftn, arg, to_ticks) 497 timeout_t *ftn; 498 void *arg; 499 int to_ticks; 500 { 501 struct callout_cpu *cc; 502 struct callout *new; 503 struct callout_handle handle; 504 505 cc = CC_CPU(timeout_cpu); 506 CC_LOCK(cc); 507 /* Fill in the next free callout structure. */ 508 new = SLIST_FIRST(&cc->cc_callfree); 509 if (new == NULL) 510 /* XXX Attempt to malloc first */ 511 panic("timeout table full"); 512 SLIST_REMOVE_HEAD(&cc->cc_callfree, c_links.sle); 513 callout_reset(new, to_ticks, ftn, arg); 514 handle.callout = new; 515 CC_UNLOCK(cc); 516 517 return (handle); 518 } 519 520 void 521 untimeout(ftn, arg, handle) 522 timeout_t *ftn; 523 void *arg; 524 struct callout_handle handle; 525 { 526 struct callout_cpu *cc; 527 528 /* 529 * Check for a handle that was initialized 530 * by callout_handle_init, but never used 531 * for a real timeout. 532 */ 533 if (handle.callout == NULL) 534 return; 535 536 cc = callout_lock(handle.callout); 537 if (handle.callout->c_func == ftn && handle.callout->c_arg == arg) 538 callout_stop(handle.callout); 539 CC_UNLOCK(cc); 540 } 541 542 void 543 callout_handle_init(struct callout_handle *handle) 544 { 545 handle->callout = NULL; 546 } 547 548 /* 549 * New interface; clients allocate their own callout structures. 550 * 551 * callout_reset() - establish or change a timeout 552 * callout_stop() - disestablish a timeout 553 * callout_init() - initialize a callout structure so that it can 554 * safely be passed to callout_reset() and callout_stop() 555 * 556 * <sys/callout.h> defines three convenience macros: 557 * 558 * callout_active() - returns truth if callout has not been stopped, 559 * drained, or deactivated since the last time the callout was 560 * reset. 561 * callout_pending() - returns truth if callout is still waiting for timeout 562 * callout_deactivate() - marks the callout as having been serviced 563 */ 564 int 565 callout_reset_on(struct callout *c, int to_ticks, void (*ftn)(void *), 566 void *arg, int cpu) 567 { 568 struct callout_cpu *cc; 569 int cancelled = 0; 570 571 /* 572 * Don't allow migration of pre-allocated callouts lest they 573 * become unbalanced. 574 */ 575 if (c->c_flags & CALLOUT_LOCAL_ALLOC) 576 cpu = c->c_cpu; 577 retry: 578 cc = callout_lock(c); 579 if (cc->cc_curr == c) { 580 /* 581 * We're being asked to reschedule a callout which is 582 * currently in progress. If there is a lock then we 583 * can cancel the callout if it has not really started. 584 */ 585 if (c->c_lock != NULL && !cc->cc_cancel) 586 cancelled = cc->cc_cancel = 1; 587 if (cc->cc_waiting) { 588 /* 589 * Someone has called callout_drain to kill this 590 * callout. Don't reschedule. 591 */ 592 CTR4(KTR_CALLOUT, "%s %p func %p arg %p", 593 cancelled ? "cancelled" : "failed to cancel", 594 c, c->c_func, c->c_arg); 595 CC_UNLOCK(cc); 596 return (cancelled); 597 } 598 } 599 if (c->c_flags & CALLOUT_PENDING) { 600 if (cc->cc_next == c) { 601 cc->cc_next = TAILQ_NEXT(c, c_links.tqe); 602 } 603 TAILQ_REMOVE(&cc->cc_callwheel[c->c_time & callwheelmask], c, 604 c_links.tqe); 605 606 cancelled = 1; 607 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING); 608 } 609 /* 610 * If the lock must migrate we have to check the state again as 611 * we can't hold both the new and old locks simultaneously. 612 */ 613 if (c->c_cpu != cpu) { 614 c->c_cpu = cpu; 615 CC_UNLOCK(cc); 616 goto retry; 617 } 618 619 if (to_ticks <= 0) 620 to_ticks = 1; 621 622 c->c_arg = arg; 623 c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING); 624 c->c_func = ftn; 625 c->c_time = ticks + to_ticks; 626 TAILQ_INSERT_TAIL(&cc->cc_callwheel[c->c_time & callwheelmask], 627 c, c_links.tqe); 628 CTR5(KTR_CALLOUT, "%sscheduled %p func %p arg %p in %d", 629 cancelled ? "re" : "", c, c->c_func, c->c_arg, to_ticks); 630 CC_UNLOCK(cc); 631 632 return (cancelled); 633 } 634 635 /* 636 * Common idioms that can be optimized in the future. 637 */ 638 int 639 callout_schedule_on(struct callout *c, int to_ticks, int cpu) 640 { 641 return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, cpu); 642 } 643 644 int 645 callout_schedule(struct callout *c, int to_ticks) 646 { 647 return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, c->c_cpu); 648 } 649 650 int 651 _callout_stop_safe(c, safe) 652 struct callout *c; 653 int safe; 654 { 655 struct callout_cpu *cc; 656 struct lock_class *class; 657 int use_lock, sq_locked; 658 659 /* 660 * Some old subsystems don't hold Giant while running a callout_stop(), 661 * so just discard this check for the moment. 662 */ 663 if (!safe && c->c_lock != NULL) { 664 if (c->c_lock == &Giant.lock_object) 665 use_lock = mtx_owned(&Giant); 666 else { 667 use_lock = 1; 668 class = LOCK_CLASS(c->c_lock); 669 class->lc_assert(c->c_lock, LA_XLOCKED); 670 } 671 } else 672 use_lock = 0; 673 674 sq_locked = 0; 675 again: 676 cc = callout_lock(c); 677 /* 678 * If the callout isn't pending, it's not on the queue, so 679 * don't attempt to remove it from the queue. We can try to 680 * stop it by other means however. 681 */ 682 if (!(c->c_flags & CALLOUT_PENDING)) { 683 c->c_flags &= ~CALLOUT_ACTIVE; 684 685 /* 686 * If it wasn't on the queue and it isn't the current 687 * callout, then we can't stop it, so just bail. 688 */ 689 if (cc->cc_curr != c) { 690 CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p", 691 c, c->c_func, c->c_arg); 692 CC_UNLOCK(cc); 693 if (sq_locked) 694 sleepq_release(&cc->cc_waiting); 695 return (0); 696 } 697 698 if (safe) { 699 /* 700 * The current callout is running (or just 701 * about to run) and blocking is allowed, so 702 * just wait for the current invocation to 703 * finish. 704 */ 705 while (cc->cc_curr == c) { 706 707 /* 708 * Use direct calls to sleepqueue interface 709 * instead of cv/msleep in order to avoid 710 * a LOR between cc_lock and sleepqueue 711 * chain spinlocks. This piece of code 712 * emulates a msleep_spin() call actually. 713 * 714 * If we already have the sleepqueue chain 715 * locked, then we can safely block. If we 716 * don't already have it locked, however, 717 * we have to drop the cc_lock to lock 718 * it. This opens several races, so we 719 * restart at the beginning once we have 720 * both locks. If nothing has changed, then 721 * we will end up back here with sq_locked 722 * set. 723 */ 724 if (!sq_locked) { 725 CC_UNLOCK(cc); 726 sleepq_lock(&cc->cc_waiting); 727 sq_locked = 1; 728 goto again; 729 } 730 cc->cc_waiting = 1; 731 DROP_GIANT(); 732 CC_UNLOCK(cc); 733 sleepq_add(&cc->cc_waiting, 734 &cc->cc_lock.lock_object, "codrain", 735 SLEEPQ_SLEEP, 0); 736 sleepq_wait(&cc->cc_waiting, 0); 737 sq_locked = 0; 738 739 /* Reacquire locks previously released. */ 740 PICKUP_GIANT(); 741 CC_LOCK(cc); 742 } 743 } else if (use_lock && !cc->cc_cancel) { 744 /* 745 * The current callout is waiting for its 746 * lock which we hold. Cancel the callout 747 * and return. After our caller drops the 748 * lock, the callout will be skipped in 749 * softclock(). 750 */ 751 cc->cc_cancel = 1; 752 CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p", 753 c, c->c_func, c->c_arg); 754 CC_UNLOCK(cc); 755 KASSERT(!sq_locked, ("sleepqueue chain locked")); 756 return (1); 757 } 758 CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p", 759 c, c->c_func, c->c_arg); 760 CC_UNLOCK(cc); 761 KASSERT(!sq_locked, ("sleepqueue chain still locked")); 762 return (0); 763 } 764 if (sq_locked) 765 sleepq_release(&cc->cc_waiting); 766 767 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING); 768 769 if (cc->cc_next == c) { 770 cc->cc_next = TAILQ_NEXT(c, c_links.tqe); 771 } 772 TAILQ_REMOVE(&cc->cc_callwheel[c->c_time & callwheelmask], c, 773 c_links.tqe); 774 775 CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p", 776 c, c->c_func, c->c_arg); 777 778 if (c->c_flags & CALLOUT_LOCAL_ALLOC) { 779 c->c_func = NULL; 780 SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle); 781 } 782 CC_UNLOCK(cc); 783 return (1); 784 } 785 786 void 787 callout_init(c, mpsafe) 788 struct callout *c; 789 int mpsafe; 790 { 791 bzero(c, sizeof *c); 792 if (mpsafe) { 793 c->c_lock = NULL; 794 c->c_flags = CALLOUT_RETURNUNLOCKED; 795 } else { 796 c->c_lock = &Giant.lock_object; 797 c->c_flags = 0; 798 } 799 c->c_cpu = timeout_cpu; 800 } 801 802 void 803 _callout_init_lock(c, lock, flags) 804 struct callout *c; 805 struct lock_object *lock; 806 int flags; 807 { 808 bzero(c, sizeof *c); 809 c->c_lock = lock; 810 KASSERT((flags & ~(CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK)) == 0, 811 ("callout_init_lock: bad flags %d", flags)); 812 KASSERT(lock != NULL || (flags & CALLOUT_RETURNUNLOCKED) == 0, 813 ("callout_init_lock: CALLOUT_RETURNUNLOCKED with no lock")); 814 KASSERT(lock == NULL || !(LOCK_CLASS(lock)->lc_flags & 815 (LC_SPINLOCK | LC_SLEEPABLE)), ("%s: invalid lock class", 816 __func__)); 817 c->c_flags = flags & (CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK); 818 c->c_cpu = timeout_cpu; 819 } 820 821 #ifdef APM_FIXUP_CALLTODO 822 /* 823 * Adjust the kernel calltodo timeout list. This routine is used after 824 * an APM resume to recalculate the calltodo timer list values with the 825 * number of hz's we have been sleeping. The next hardclock() will detect 826 * that there are fired timers and run softclock() to execute them. 827 * 828 * Please note, I have not done an exhaustive analysis of what code this 829 * might break. I am motivated to have my select()'s and alarm()'s that 830 * have expired during suspend firing upon resume so that the applications 831 * which set the timer can do the maintanence the timer was for as close 832 * as possible to the originally intended time. Testing this code for a 833 * week showed that resuming from a suspend resulted in 22 to 25 timers 834 * firing, which seemed independant on whether the suspend was 2 hours or 835 * 2 days. Your milage may vary. - Ken Key <key@cs.utk.edu> 836 */ 837 void 838 adjust_timeout_calltodo(time_change) 839 struct timeval *time_change; 840 { 841 register struct callout *p; 842 unsigned long delta_ticks; 843 844 /* 845 * How many ticks were we asleep? 846 * (stolen from tvtohz()). 847 */ 848 849 /* Don't do anything */ 850 if (time_change->tv_sec < 0) 851 return; 852 else if (time_change->tv_sec <= LONG_MAX / 1000000) 853 delta_ticks = (time_change->tv_sec * 1000000 + 854 time_change->tv_usec + (tick - 1)) / tick + 1; 855 else if (time_change->tv_sec <= LONG_MAX / hz) 856 delta_ticks = time_change->tv_sec * hz + 857 (time_change->tv_usec + (tick - 1)) / tick + 1; 858 else 859 delta_ticks = LONG_MAX; 860 861 if (delta_ticks > INT_MAX) 862 delta_ticks = INT_MAX; 863 864 /* 865 * Now rip through the timer calltodo list looking for timers 866 * to expire. 867 */ 868 869 /* don't collide with softclock() */ 870 CC_LOCK(cc); 871 for (p = calltodo.c_next; p != NULL; p = p->c_next) { 872 p->c_time -= delta_ticks; 873 874 /* Break if the timer had more time on it than delta_ticks */ 875 if (p->c_time > 0) 876 break; 877 878 /* take back the ticks the timer didn't use (p->c_time <= 0) */ 879 delta_ticks = -p->c_time; 880 } 881 CC_UNLOCK(cc); 882 883 return; 884 } 885 #endif /* APM_FIXUP_CALLTODO */
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