Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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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/8.3/sys/kern/kern_timeout.c 225288 2011-08-31 09:14:56Z attilio $"); 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 #ifdef SMP 60 #include <machine/cpu.h> 61 #endif 62 63 SDT_PROVIDER_DEFINE(callout_execute); 64 SDT_PROBE_DEFINE(callout_execute, kernel, , callout_start, callout-start); 65 SDT_PROBE_ARGTYPE(callout_execute, kernel, , callout_start, 0, 66 "struct callout *"); 67 SDT_PROBE_DEFINE(callout_execute, kernel, , callout_end, callout-end); 68 SDT_PROBE_ARGTYPE(callout_execute, kernel, , callout_end, 0, 69 "struct callout *"); 70 71 static int avg_depth; 72 SYSCTL_INT(_debug, OID_AUTO, to_avg_depth, CTLFLAG_RD, &avg_depth, 0, 73 "Average number of items examined per softclock call. Units = 1/1000"); 74 static int avg_gcalls; 75 SYSCTL_INT(_debug, OID_AUTO, to_avg_gcalls, CTLFLAG_RD, &avg_gcalls, 0, 76 "Average number of Giant callouts made per softclock call. Units = 1/1000"); 77 static int avg_lockcalls; 78 SYSCTL_INT(_debug, OID_AUTO, to_avg_lockcalls, CTLFLAG_RD, &avg_lockcalls, 0, 79 "Average number of lock callouts made per softclock call. Units = 1/1000"); 80 static int avg_mpcalls; 81 SYSCTL_INT(_debug, OID_AUTO, to_avg_mpcalls, CTLFLAG_RD, &avg_mpcalls, 0, 82 "Average number of MP callouts made per softclock call. Units = 1/1000"); 83 /* 84 * TODO: 85 * allocate more timeout table slots when table overflows. 86 */ 87 int callwheelsize, callwheelbits, callwheelmask; 88 89 /* 90 * The callout cpu migration entity represents informations necessary for 91 * describing the migrating callout to the new callout cpu. 92 * The cached informations are very important for deferring migration when 93 * the migrating callout is already running. 94 */ 95 struct cc_mig_ent { 96 #ifdef SMP 97 void (*ce_migration_func)(void *); 98 void *ce_migration_arg; 99 int ce_migration_cpu; 100 int ce_migration_ticks; 101 #endif 102 }; 103 104 /* 105 * There is one struct callout_cpu per cpu, holding all relevant 106 * state for the callout processing thread on the individual CPU. 107 * In particular: 108 * cc_ticks is incremented once per tick in callout_cpu(). 109 * It tracks the global 'ticks' but in a way that the individual 110 * threads should not worry about races in the order in which 111 * hardclock() and hardclock_cpu() run on the various CPUs. 112 * cc_softclock is advanced in callout_cpu() to point to the 113 * first entry in cc_callwheel that may need handling. In turn, 114 * a softclock() is scheduled so it can serve the various entries i 115 * such that cc_softclock <= i <= cc_ticks . 116 * XXX maybe cc_softclock and cc_ticks should be volatile ? 117 * 118 * cc_ticks is also used in callout_reset_cpu() to determine 119 * when the callout should be served. 120 */ 121 struct callout_cpu { 122 struct cc_mig_ent cc_migrating_entity; 123 struct mtx cc_lock; 124 struct callout *cc_callout; 125 struct callout_tailq *cc_callwheel; 126 struct callout_list cc_callfree; 127 struct callout *cc_next; 128 struct callout *cc_curr; 129 void *cc_cookie; 130 int cc_ticks; 131 int cc_softticks; 132 int cc_cancel; 133 int cc_waiting; 134 }; 135 136 #ifdef SMP 137 #define cc_migration_func cc_migrating_entity.ce_migration_func 138 #define cc_migration_arg cc_migrating_entity.ce_migration_arg 139 #define cc_migration_cpu cc_migrating_entity.ce_migration_cpu 140 #define cc_migration_ticks cc_migrating_entity.ce_migration_ticks 141 142 struct callout_cpu cc_cpu[MAXCPU]; 143 #define CPUBLOCK MAXCPU 144 #define CC_CPU(cpu) (&cc_cpu[(cpu)]) 145 #define CC_SELF() CC_CPU(PCPU_GET(cpuid)) 146 #else 147 struct callout_cpu cc_cpu; 148 #define CC_CPU(cpu) &cc_cpu 149 #define CC_SELF() &cc_cpu 150 #endif 151 #define CC_LOCK(cc) mtx_lock_spin(&(cc)->cc_lock) 152 #define CC_UNLOCK(cc) mtx_unlock_spin(&(cc)->cc_lock) 153 #define CC_LOCK_ASSERT(cc) mtx_assert(&(cc)->cc_lock, MA_OWNED) 154 155 static int timeout_cpu; 156 157 MALLOC_DEFINE(M_CALLOUT, "callout", "Callout datastructures"); 158 159 /** 160 * Locked by cc_lock: 161 * cc_curr - If a callout is in progress, it is curr_callout. 162 * If curr_callout is non-NULL, threads waiting in 163 * callout_drain() will be woken up as soon as the 164 * relevant callout completes. 165 * cc_cancel - Changing to 1 with both callout_lock and c_lock held 166 * guarantees that the current callout will not run. 167 * The softclock() function sets this to 0 before it 168 * drops callout_lock to acquire c_lock, and it calls 169 * the handler only if curr_cancelled is still 0 after 170 * c_lock is successfully acquired. 171 * cc_waiting - If a thread is waiting in callout_drain(), then 172 * callout_wait is nonzero. Set only when 173 * curr_callout is non-NULL. 174 */ 175 176 /* 177 * Resets the migration entity tied to a specific callout cpu. 178 */ 179 static void 180 cc_cme_cleanup(struct callout_cpu *cc) 181 { 182 183 #ifdef SMP 184 cc->cc_migration_cpu = CPUBLOCK; 185 cc->cc_migration_ticks = 0; 186 cc->cc_migration_func = NULL; 187 cc->cc_migration_arg = NULL; 188 #endif 189 } 190 191 /* 192 * Checks if migration is requested by a specific callout cpu. 193 */ 194 static int 195 cc_cme_migrating(struct callout_cpu *cc) 196 { 197 198 #ifdef SMP 199 return (cc->cc_migration_cpu != CPUBLOCK); 200 #else 201 return (0); 202 #endif 203 } 204 205 /* 206 * kern_timeout_callwheel_alloc() - kernel low level callwheel initialization 207 * 208 * This code is called very early in the kernel initialization sequence, 209 * and may be called more then once. 210 */ 211 caddr_t 212 kern_timeout_callwheel_alloc(caddr_t v) 213 { 214 struct callout_cpu *cc; 215 216 timeout_cpu = PCPU_GET(cpuid); 217 cc = CC_CPU(timeout_cpu); 218 /* 219 * Calculate callout wheel size 220 */ 221 for (callwheelsize = 1, callwheelbits = 0; 222 callwheelsize < ncallout; 223 callwheelsize <<= 1, ++callwheelbits) 224 ; 225 callwheelmask = callwheelsize - 1; 226 227 cc->cc_callout = (struct callout *)v; 228 v = (caddr_t)(cc->cc_callout + ncallout); 229 cc->cc_callwheel = (struct callout_tailq *)v; 230 v = (caddr_t)(cc->cc_callwheel + callwheelsize); 231 return(v); 232 } 233 234 static void 235 callout_cpu_init(struct callout_cpu *cc) 236 { 237 struct callout *c; 238 int i; 239 240 mtx_init(&cc->cc_lock, "callout", NULL, MTX_SPIN | MTX_RECURSE); 241 SLIST_INIT(&cc->cc_callfree); 242 for (i = 0; i < callwheelsize; i++) { 243 TAILQ_INIT(&cc->cc_callwheel[i]); 244 } 245 cc_cme_cleanup(cc); 246 if (cc->cc_callout == NULL) 247 return; 248 for (i = 0; i < ncallout; i++) { 249 c = &cc->cc_callout[i]; 250 callout_init(c, 0); 251 c->c_flags = CALLOUT_LOCAL_ALLOC; 252 SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle); 253 } 254 } 255 256 #ifdef SMP 257 /* 258 * Switches the cpu tied to a specific callout. 259 * The function expects a locked incoming callout cpu and returns with 260 * locked outcoming callout cpu. 261 */ 262 static struct callout_cpu * 263 callout_cpu_switch(struct callout *c, struct callout_cpu *cc, int new_cpu) 264 { 265 struct callout_cpu *new_cc; 266 267 MPASS(c != NULL && cc != NULL); 268 CC_LOCK_ASSERT(cc); 269 270 /* 271 * Avoid interrupts and preemption firing after the callout cpu 272 * is blocked in order to avoid deadlocks as the new thread 273 * may be willing to acquire the callout cpu lock. 274 */ 275 c->c_cpu = CPUBLOCK; 276 spinlock_enter(); 277 CC_UNLOCK(cc); 278 new_cc = CC_CPU(new_cpu); 279 CC_LOCK(new_cc); 280 spinlock_exit(); 281 c->c_cpu = new_cpu; 282 return (new_cc); 283 } 284 #endif 285 286 /* 287 * kern_timeout_callwheel_init() - initialize previously reserved callwheel 288 * space. 289 * 290 * This code is called just once, after the space reserved for the 291 * callout wheel has been finalized. 292 */ 293 void 294 kern_timeout_callwheel_init(void) 295 { 296 callout_cpu_init(CC_CPU(timeout_cpu)); 297 } 298 299 /* 300 * Start standard softclock thread. 301 */ 302 void *softclock_ih; 303 304 static void 305 start_softclock(void *dummy) 306 { 307 struct callout_cpu *cc; 308 #ifdef SMP 309 int cpu; 310 #endif 311 312 cc = CC_CPU(timeout_cpu); 313 if (swi_add(&clk_intr_event, "clock", softclock, cc, SWI_CLOCK, 314 INTR_MPSAFE, &softclock_ih)) 315 panic("died while creating standard software ithreads"); 316 cc->cc_cookie = softclock_ih; 317 #ifdef SMP 318 CPU_FOREACH(cpu) { 319 if (cpu == timeout_cpu) 320 continue; 321 cc = CC_CPU(cpu); 322 if (swi_add(NULL, "clock", softclock, cc, SWI_CLOCK, 323 INTR_MPSAFE, &cc->cc_cookie)) 324 panic("died while creating standard software ithreads"); 325 cc->cc_callout = NULL; /* Only cpu0 handles timeout(). */ 326 cc->cc_callwheel = malloc( 327 sizeof(struct callout_tailq) * callwheelsize, M_CALLOUT, 328 M_WAITOK); 329 callout_cpu_init(cc); 330 } 331 #endif 332 } 333 334 SYSINIT(start_softclock, SI_SUB_SOFTINTR, SI_ORDER_FIRST, start_softclock, NULL); 335 336 void 337 callout_tick(void) 338 { 339 struct callout_cpu *cc; 340 int need_softclock; 341 int bucket; 342 343 /* 344 * Process callouts at a very low cpu priority, so we don't keep the 345 * relatively high clock interrupt priority any longer than necessary. 346 */ 347 need_softclock = 0; 348 cc = CC_SELF(); 349 mtx_lock_spin_flags(&cc->cc_lock, MTX_QUIET); 350 cc->cc_ticks++; 351 for (; (cc->cc_softticks - cc->cc_ticks) <= 0; cc->cc_softticks++) { 352 bucket = cc->cc_softticks & callwheelmask; 353 if (!TAILQ_EMPTY(&cc->cc_callwheel[bucket])) { 354 need_softclock = 1; 355 break; 356 } 357 } 358 mtx_unlock_spin_flags(&cc->cc_lock, MTX_QUIET); 359 /* 360 * swi_sched acquires the thread lock, so we don't want to call it 361 * with cc_lock held; incorrect locking order. 362 */ 363 if (need_softclock) 364 swi_sched(cc->cc_cookie, 0); 365 } 366 367 static struct callout_cpu * 368 callout_lock(struct callout *c) 369 { 370 struct callout_cpu *cc; 371 int cpu; 372 373 for (;;) { 374 cpu = c->c_cpu; 375 #ifdef SMP 376 if (cpu == CPUBLOCK) { 377 while (c->c_cpu == CPUBLOCK) 378 cpu_spinwait(); 379 continue; 380 } 381 #endif 382 cc = CC_CPU(cpu); 383 CC_LOCK(cc); 384 if (cpu == c->c_cpu) 385 break; 386 CC_UNLOCK(cc); 387 } 388 return (cc); 389 } 390 391 static void 392 callout_cc_add(struct callout *c, struct callout_cpu *cc, int to_ticks, 393 void (*func)(void *), void *arg, int cpu) 394 { 395 396 CC_LOCK_ASSERT(cc); 397 398 if (to_ticks <= 0) 399 to_ticks = 1; 400 c->c_arg = arg; 401 c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING); 402 c->c_func = func; 403 c->c_time = cc->cc_ticks + to_ticks; 404 TAILQ_INSERT_TAIL(&cc->cc_callwheel[c->c_time & callwheelmask], 405 c, c_links.tqe); 406 } 407 408 /* 409 * The callout mechanism is based on the work of Adam M. Costello and 410 * George Varghese, published in a technical report entitled "Redesigning 411 * the BSD Callout and Timer Facilities" and modified slightly for inclusion 412 * in FreeBSD by Justin T. Gibbs. The original work on the data structures 413 * used in this implementation was published by G. Varghese and T. Lauck in 414 * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for 415 * the Efficient Implementation of a Timer Facility" in the Proceedings of 416 * the 11th ACM Annual Symposium on Operating Systems Principles, 417 * Austin, Texas Nov 1987. 418 */ 419 420 /* 421 * Software (low priority) clock interrupt. 422 * Run periodic events from timeout queue. 423 */ 424 void 425 softclock(void *arg) 426 { 427 struct callout_cpu *cc; 428 struct callout *c; 429 struct callout_tailq *bucket; 430 int curticks; 431 int steps; /* #steps since we last allowed interrupts */ 432 int depth; 433 int mpcalls; 434 int lockcalls; 435 int gcalls; 436 #ifdef DIAGNOSTIC 437 struct bintime bt1, bt2; 438 struct timespec ts2; 439 static uint64_t maxdt = 36893488147419102LL; /* 2 msec */ 440 static timeout_t *lastfunc; 441 #endif 442 443 #ifndef MAX_SOFTCLOCK_STEPS 444 #define MAX_SOFTCLOCK_STEPS 100 /* Maximum allowed value of steps. */ 445 #endif /* MAX_SOFTCLOCK_STEPS */ 446 447 mpcalls = 0; 448 lockcalls = 0; 449 gcalls = 0; 450 depth = 0; 451 steps = 0; 452 cc = (struct callout_cpu *)arg; 453 CC_LOCK(cc); 454 while (cc->cc_softticks - 1 != cc->cc_ticks) { 455 /* 456 * cc_softticks may be modified by hard clock, so cache 457 * it while we work on a given bucket. 458 */ 459 curticks = cc->cc_softticks; 460 cc->cc_softticks++; 461 bucket = &cc->cc_callwheel[curticks & callwheelmask]; 462 c = TAILQ_FIRST(bucket); 463 while (c) { 464 depth++; 465 if (c->c_time != curticks) { 466 c = TAILQ_NEXT(c, c_links.tqe); 467 ++steps; 468 if (steps >= MAX_SOFTCLOCK_STEPS) { 469 cc->cc_next = c; 470 /* Give interrupts a chance. */ 471 CC_UNLOCK(cc); 472 ; /* nothing */ 473 CC_LOCK(cc); 474 c = cc->cc_next; 475 steps = 0; 476 } 477 } else { 478 void (*c_func)(void *); 479 void *c_arg; 480 struct lock_class *class; 481 struct lock_object *c_lock; 482 int c_flags, sharedlock; 483 484 cc->cc_next = TAILQ_NEXT(c, c_links.tqe); 485 TAILQ_REMOVE(bucket, c, c_links.tqe); 486 class = (c->c_lock != NULL) ? 487 LOCK_CLASS(c->c_lock) : NULL; 488 sharedlock = (c->c_flags & CALLOUT_SHAREDLOCK) ? 489 0 : 1; 490 c_lock = c->c_lock; 491 c_func = c->c_func; 492 c_arg = c->c_arg; 493 c_flags = c->c_flags; 494 if (c->c_flags & CALLOUT_LOCAL_ALLOC) { 495 c->c_flags = CALLOUT_LOCAL_ALLOC; 496 } else { 497 c->c_flags = 498 (c->c_flags & ~CALLOUT_PENDING); 499 } 500 cc->cc_curr = c; 501 cc->cc_cancel = 0; 502 CC_UNLOCK(cc); 503 if (c_lock != NULL) { 504 class->lc_lock(c_lock, sharedlock); 505 /* 506 * The callout may have been cancelled 507 * while we switched locks. 508 */ 509 if (cc->cc_cancel) { 510 class->lc_unlock(c_lock); 511 goto skip; 512 } 513 /* The callout cannot be stopped now. */ 514 cc->cc_cancel = 1; 515 516 if (c_lock == &Giant.lock_object) { 517 gcalls++; 518 CTR3(KTR_CALLOUT, 519 "callout %p func %p arg %p", 520 c, c_func, c_arg); 521 } else { 522 lockcalls++; 523 CTR3(KTR_CALLOUT, "callout lock" 524 " %p func %p arg %p", 525 c, c_func, c_arg); 526 } 527 } else { 528 mpcalls++; 529 CTR3(KTR_CALLOUT, 530 "callout mpsafe %p func %p arg %p", 531 c, c_func, c_arg); 532 } 533 #ifdef DIAGNOSTIC 534 binuptime(&bt1); 535 #endif 536 THREAD_NO_SLEEPING(); 537 SDT_PROBE(callout_execute, kernel, , 538 callout_start, c, 0, 0, 0, 0); 539 c_func(c_arg); 540 SDT_PROBE(callout_execute, kernel, , 541 callout_end, c, 0, 0, 0, 0); 542 THREAD_SLEEPING_OK(); 543 #ifdef DIAGNOSTIC 544 binuptime(&bt2); 545 bintime_sub(&bt2, &bt1); 546 if (bt2.frac > maxdt) { 547 if (lastfunc != c_func || 548 bt2.frac > maxdt * 2) { 549 bintime2timespec(&bt2, &ts2); 550 printf( 551 "Expensive timeout(9) function: %p(%p) %jd.%09ld s\n", 552 c_func, c_arg, 553 (intmax_t)ts2.tv_sec, 554 ts2.tv_nsec); 555 } 556 maxdt = bt2.frac; 557 lastfunc = c_func; 558 } 559 #endif 560 CTR1(KTR_CALLOUT, "callout %p finished", c); 561 if ((c_flags & CALLOUT_RETURNUNLOCKED) == 0) 562 class->lc_unlock(c_lock); 563 skip: 564 CC_LOCK(cc); 565 /* 566 * If the current callout is locally 567 * allocated (from timeout(9)) 568 * then put it on the freelist. 569 * 570 * Note: we need to check the cached 571 * copy of c_flags because if it was not 572 * local, then it's not safe to deref the 573 * callout pointer. 574 */ 575 if (c_flags & CALLOUT_LOCAL_ALLOC) { 576 KASSERT(c->c_flags == 577 CALLOUT_LOCAL_ALLOC, 578 ("corrupted callout")); 579 c->c_func = NULL; 580 SLIST_INSERT_HEAD(&cc->cc_callfree, c, 581 c_links.sle); 582 } 583 cc->cc_curr = NULL; 584 if (cc->cc_waiting) { 585 586 /* 587 * There is someone waiting for the 588 * callout to complete. 589 * If the callout was scheduled for 590 * migration just cancel it. 591 */ 592 if (cc_cme_migrating(cc)) 593 cc_cme_cleanup(cc); 594 cc->cc_waiting = 0; 595 CC_UNLOCK(cc); 596 wakeup(&cc->cc_waiting); 597 CC_LOCK(cc); 598 } else if (cc_cme_migrating(cc)) { 599 #ifdef SMP 600 struct callout_cpu *new_cc; 601 void (*new_func)(void *); 602 void *new_arg; 603 int new_cpu, new_ticks; 604 605 /* 606 * If the callout was scheduled for 607 * migration just perform it now. 608 */ 609 new_cpu = cc->cc_migration_cpu; 610 new_ticks = cc->cc_migration_ticks; 611 new_func = cc->cc_migration_func; 612 new_arg = cc->cc_migration_arg; 613 cc_cme_cleanup(cc); 614 615 /* 616 * It should be assert here that the 617 * callout is not destroyed but that 618 * is not easy. 619 */ 620 new_cc = callout_cpu_switch(c, cc, 621 new_cpu); 622 callout_cc_add(c, new_cc, new_ticks, 623 new_func, new_arg, new_cpu); 624 CC_UNLOCK(new_cc); 625 CC_LOCK(cc); 626 #else 627 panic("migration should not happen"); 628 #endif 629 } 630 steps = 0; 631 c = cc->cc_next; 632 } 633 } 634 } 635 avg_depth += (depth * 1000 - avg_depth) >> 8; 636 avg_mpcalls += (mpcalls * 1000 - avg_mpcalls) >> 8; 637 avg_lockcalls += (lockcalls * 1000 - avg_lockcalls) >> 8; 638 avg_gcalls += (gcalls * 1000 - avg_gcalls) >> 8; 639 cc->cc_next = NULL; 640 CC_UNLOCK(cc); 641 } 642 643 /* 644 * timeout -- 645 * Execute a function after a specified length of time. 646 * 647 * untimeout -- 648 * Cancel previous timeout function call. 649 * 650 * callout_handle_init -- 651 * Initialize a handle so that using it with untimeout is benign. 652 * 653 * See AT&T BCI Driver Reference Manual for specification. This 654 * implementation differs from that one in that although an 655 * identification value is returned from timeout, the original 656 * arguments to timeout as well as the identifier are used to 657 * identify entries for untimeout. 658 */ 659 struct callout_handle 660 timeout(ftn, arg, to_ticks) 661 timeout_t *ftn; 662 void *arg; 663 int to_ticks; 664 { 665 struct callout_cpu *cc; 666 struct callout *new; 667 struct callout_handle handle; 668 669 cc = CC_CPU(timeout_cpu); 670 CC_LOCK(cc); 671 /* Fill in the next free callout structure. */ 672 new = SLIST_FIRST(&cc->cc_callfree); 673 if (new == NULL) 674 /* XXX Attempt to malloc first */ 675 panic("timeout table full"); 676 SLIST_REMOVE_HEAD(&cc->cc_callfree, c_links.sle); 677 callout_reset(new, to_ticks, ftn, arg); 678 handle.callout = new; 679 CC_UNLOCK(cc); 680 681 return (handle); 682 } 683 684 void 685 untimeout(ftn, arg, handle) 686 timeout_t *ftn; 687 void *arg; 688 struct callout_handle handle; 689 { 690 struct callout_cpu *cc; 691 692 /* 693 * Check for a handle that was initialized 694 * by callout_handle_init, but never used 695 * for a real timeout. 696 */ 697 if (handle.callout == NULL) 698 return; 699 700 cc = callout_lock(handle.callout); 701 if (handle.callout->c_func == ftn && handle.callout->c_arg == arg) 702 callout_stop(handle.callout); 703 CC_UNLOCK(cc); 704 } 705 706 void 707 callout_handle_init(struct callout_handle *handle) 708 { 709 handle->callout = NULL; 710 } 711 712 /* 713 * New interface; clients allocate their own callout structures. 714 * 715 * callout_reset() - establish or change a timeout 716 * callout_stop() - disestablish a timeout 717 * callout_init() - initialize a callout structure so that it can 718 * safely be passed to callout_reset() and callout_stop() 719 * 720 * <sys/callout.h> defines three convenience macros: 721 * 722 * callout_active() - returns truth if callout has not been stopped, 723 * drained, or deactivated since the last time the callout was 724 * reset. 725 * callout_pending() - returns truth if callout is still waiting for timeout 726 * callout_deactivate() - marks the callout as having been serviced 727 */ 728 int 729 callout_reset_on(struct callout *c, int to_ticks, void (*ftn)(void *), 730 void *arg, int cpu) 731 { 732 struct callout_cpu *cc; 733 int cancelled = 0; 734 735 /* 736 * Don't allow migration of pre-allocated callouts lest they 737 * become unbalanced. 738 */ 739 if (c->c_flags & CALLOUT_LOCAL_ALLOC) 740 cpu = c->c_cpu; 741 cc = callout_lock(c); 742 if (cc->cc_curr == c) { 743 /* 744 * We're being asked to reschedule a callout which is 745 * currently in progress. If there is a lock then we 746 * can cancel the callout if it has not really started. 747 */ 748 if (c->c_lock != NULL && !cc->cc_cancel) 749 cancelled = cc->cc_cancel = 1; 750 if (cc->cc_waiting) { 751 /* 752 * Someone has called callout_drain to kill this 753 * callout. Don't reschedule. 754 */ 755 CTR4(KTR_CALLOUT, "%s %p func %p arg %p", 756 cancelled ? "cancelled" : "failed to cancel", 757 c, c->c_func, c->c_arg); 758 CC_UNLOCK(cc); 759 return (cancelled); 760 } 761 } 762 if (c->c_flags & CALLOUT_PENDING) { 763 if (cc->cc_next == c) { 764 cc->cc_next = TAILQ_NEXT(c, c_links.tqe); 765 } 766 TAILQ_REMOVE(&cc->cc_callwheel[c->c_time & callwheelmask], c, 767 c_links.tqe); 768 769 cancelled = 1; 770 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING); 771 } 772 773 #ifdef SMP 774 /* 775 * If the callout must migrate try to perform it immediately. 776 * If the callout is currently running, just defer the migration 777 * to a more appropriate moment. 778 */ 779 if (c->c_cpu != cpu) { 780 if (cc->cc_curr == c) { 781 cc->cc_migration_cpu = cpu; 782 cc->cc_migration_ticks = to_ticks; 783 cc->cc_migration_func = ftn; 784 cc->cc_migration_arg = arg; 785 CTR5(KTR_CALLOUT, 786 "migration of %p func %p arg %p in %d to %u deferred", 787 c, c->c_func, c->c_arg, to_ticks, cpu); 788 CC_UNLOCK(cc); 789 return (cancelled); 790 } 791 cc = callout_cpu_switch(c, cc, cpu); 792 } 793 #endif 794 795 callout_cc_add(c, cc, to_ticks, ftn, arg, cpu); 796 CTR5(KTR_CALLOUT, "%sscheduled %p func %p arg %p in %d", 797 cancelled ? "re" : "", c, c->c_func, c->c_arg, to_ticks); 798 CC_UNLOCK(cc); 799 800 return (cancelled); 801 } 802 803 /* 804 * Common idioms that can be optimized in the future. 805 */ 806 int 807 callout_schedule_on(struct callout *c, int to_ticks, int cpu) 808 { 809 return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, cpu); 810 } 811 812 int 813 callout_schedule(struct callout *c, int to_ticks) 814 { 815 return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, c->c_cpu); 816 } 817 818 int 819 _callout_stop_safe(c, safe) 820 struct callout *c; 821 int safe; 822 { 823 struct callout_cpu *cc, *old_cc; 824 struct lock_class *class; 825 int use_lock, sq_locked; 826 827 /* 828 * Some old subsystems don't hold Giant while running a callout_stop(), 829 * so just discard this check for the moment. 830 */ 831 if (!safe && c->c_lock != NULL) { 832 if (c->c_lock == &Giant.lock_object) 833 use_lock = mtx_owned(&Giant); 834 else { 835 use_lock = 1; 836 class = LOCK_CLASS(c->c_lock); 837 class->lc_assert(c->c_lock, LA_XLOCKED); 838 } 839 } else 840 use_lock = 0; 841 842 sq_locked = 0; 843 old_cc = NULL; 844 again: 845 cc = callout_lock(c); 846 847 /* 848 * If the callout was migrating while the callout cpu lock was 849 * dropped, just drop the sleepqueue lock and check the states 850 * again. 851 */ 852 if (sq_locked != 0 && cc != old_cc) { 853 #ifdef SMP 854 CC_UNLOCK(cc); 855 sleepq_release(&old_cc->cc_waiting); 856 sq_locked = 0; 857 old_cc = NULL; 858 goto again; 859 #else 860 panic("migration should not happen"); 861 #endif 862 } 863 864 /* 865 * If the callout isn't pending, it's not on the queue, so 866 * don't attempt to remove it from the queue. We can try to 867 * stop it by other means however. 868 */ 869 if (!(c->c_flags & CALLOUT_PENDING)) { 870 c->c_flags &= ~CALLOUT_ACTIVE; 871 872 /* 873 * If it wasn't on the queue and it isn't the current 874 * callout, then we can't stop it, so just bail. 875 */ 876 if (cc->cc_curr != c) { 877 CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p", 878 c, c->c_func, c->c_arg); 879 CC_UNLOCK(cc); 880 if (sq_locked) 881 sleepq_release(&cc->cc_waiting); 882 return (0); 883 } 884 885 if (safe) { 886 /* 887 * The current callout is running (or just 888 * about to run) and blocking is allowed, so 889 * just wait for the current invocation to 890 * finish. 891 */ 892 while (cc->cc_curr == c) { 893 894 /* 895 * Use direct calls to sleepqueue interface 896 * instead of cv/msleep in order to avoid 897 * a LOR between cc_lock and sleepqueue 898 * chain spinlocks. This piece of code 899 * emulates a msleep_spin() call actually. 900 * 901 * If we already have the sleepqueue chain 902 * locked, then we can safely block. If we 903 * don't already have it locked, however, 904 * we have to drop the cc_lock to lock 905 * it. This opens several races, so we 906 * restart at the beginning once we have 907 * both locks. If nothing has changed, then 908 * we will end up back here with sq_locked 909 * set. 910 */ 911 if (!sq_locked) { 912 CC_UNLOCK(cc); 913 sleepq_lock(&cc->cc_waiting); 914 sq_locked = 1; 915 old_cc = cc; 916 goto again; 917 } 918 919 /* 920 * Migration could be cancelled here, but 921 * as long as it is still not sure when it 922 * will be packed up, just let softclock() 923 * take care of it. 924 */ 925 cc->cc_waiting = 1; 926 DROP_GIANT(); 927 CC_UNLOCK(cc); 928 sleepq_add(&cc->cc_waiting, 929 &cc->cc_lock.lock_object, "codrain", 930 SLEEPQ_SLEEP, 0); 931 sleepq_wait(&cc->cc_waiting, 0); 932 sq_locked = 0; 933 old_cc = NULL; 934 935 /* Reacquire locks previously released. */ 936 PICKUP_GIANT(); 937 CC_LOCK(cc); 938 } 939 } else if (use_lock && !cc->cc_cancel) { 940 /* 941 * The current callout is waiting for its 942 * lock which we hold. Cancel the callout 943 * and return. After our caller drops the 944 * lock, the callout will be skipped in 945 * softclock(). 946 */ 947 cc->cc_cancel = 1; 948 CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p", 949 c, c->c_func, c->c_arg); 950 KASSERT(!cc_cme_migrating(cc), 951 ("callout wrongly scheduled for migration")); 952 CC_UNLOCK(cc); 953 KASSERT(!sq_locked, ("sleepqueue chain locked")); 954 return (1); 955 } 956 CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p", 957 c, c->c_func, c->c_arg); 958 CC_UNLOCK(cc); 959 KASSERT(!sq_locked, ("sleepqueue chain still locked")); 960 return (0); 961 } 962 if (sq_locked) 963 sleepq_release(&cc->cc_waiting); 964 965 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING); 966 967 if (cc->cc_next == c) { 968 cc->cc_next = TAILQ_NEXT(c, c_links.tqe); 969 } 970 TAILQ_REMOVE(&cc->cc_callwheel[c->c_time & callwheelmask], c, 971 c_links.tqe); 972 973 CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p", 974 c, c->c_func, c->c_arg); 975 976 if (c->c_flags & CALLOUT_LOCAL_ALLOC) { 977 c->c_func = NULL; 978 SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle); 979 } 980 CC_UNLOCK(cc); 981 return (1); 982 } 983 984 void 985 callout_init(c, mpsafe) 986 struct callout *c; 987 int mpsafe; 988 { 989 bzero(c, sizeof *c); 990 if (mpsafe) { 991 c->c_lock = NULL; 992 c->c_flags = CALLOUT_RETURNUNLOCKED; 993 } else { 994 c->c_lock = &Giant.lock_object; 995 c->c_flags = 0; 996 } 997 c->c_cpu = timeout_cpu; 998 } 999 1000 void 1001 _callout_init_lock(c, lock, flags) 1002 struct callout *c; 1003 struct lock_object *lock; 1004 int flags; 1005 { 1006 bzero(c, sizeof *c); 1007 c->c_lock = lock; 1008 KASSERT((flags & ~(CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK)) == 0, 1009 ("callout_init_lock: bad flags %d", flags)); 1010 KASSERT(lock != NULL || (flags & CALLOUT_RETURNUNLOCKED) == 0, 1011 ("callout_init_lock: CALLOUT_RETURNUNLOCKED with no lock")); 1012 KASSERT(lock == NULL || !(LOCK_CLASS(lock)->lc_flags & 1013 (LC_SPINLOCK | LC_SLEEPABLE)), ("%s: invalid lock class", 1014 __func__)); 1015 c->c_flags = flags & (CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK); 1016 c->c_cpu = timeout_cpu; 1017 } 1018 1019 #ifdef APM_FIXUP_CALLTODO 1020 /* 1021 * Adjust the kernel calltodo timeout list. This routine is used after 1022 * an APM resume to recalculate the calltodo timer list values with the 1023 * number of hz's we have been sleeping. The next hardclock() will detect 1024 * that there are fired timers and run softclock() to execute them. 1025 * 1026 * Please note, I have not done an exhaustive analysis of what code this 1027 * might break. I am motivated to have my select()'s and alarm()'s that 1028 * have expired during suspend firing upon resume so that the applications 1029 * which set the timer can do the maintanence the timer was for as close 1030 * as possible to the originally intended time. Testing this code for a 1031 * week showed that resuming from a suspend resulted in 22 to 25 timers 1032 * firing, which seemed independant on whether the suspend was 2 hours or 1033 * 2 days. Your milage may vary. - Ken Key <key@cs.utk.edu> 1034 */ 1035 void 1036 adjust_timeout_calltodo(time_change) 1037 struct timeval *time_change; 1038 { 1039 register struct callout *p; 1040 unsigned long delta_ticks; 1041 1042 /* 1043 * How many ticks were we asleep? 1044 * (stolen from tvtohz()). 1045 */ 1046 1047 /* Don't do anything */ 1048 if (time_change->tv_sec < 0) 1049 return; 1050 else if (time_change->tv_sec <= LONG_MAX / 1000000) 1051 delta_ticks = (time_change->tv_sec * 1000000 + 1052 time_change->tv_usec + (tick - 1)) / tick + 1; 1053 else if (time_change->tv_sec <= LONG_MAX / hz) 1054 delta_ticks = time_change->tv_sec * hz + 1055 (time_change->tv_usec + (tick - 1)) / tick + 1; 1056 else 1057 delta_ticks = LONG_MAX; 1058 1059 if (delta_ticks > INT_MAX) 1060 delta_ticks = INT_MAX; 1061 1062 /* 1063 * Now rip through the timer calltodo list looking for timers 1064 * to expire. 1065 */ 1066 1067 /* don't collide with softclock() */ 1068 CC_LOCK(cc); 1069 for (p = calltodo.c_next; p != NULL; p = p->c_next) { 1070 p->c_time -= delta_ticks; 1071 1072 /* Break if the timer had more time on it than delta_ticks */ 1073 if (p->c_time > 0) 1074 break; 1075 1076 /* take back the ticks the timer didn't use (p->c_time <= 0) */ 1077 delta_ticks = -p->c_time; 1078 } 1079 CC_UNLOCK(cc); 1080 1081 return; 1082 } 1083 #endif /* APM_FIXUP_CALLTODO */
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