1 /* 2 * Copyright (c) 2004 The DragonFly Project. All rights reserved. 3 * 4 * This code is derived from software contributed to The DragonFly Project 5 * by Matthew Dillon <dillon@backplane.com> 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in 15 * the documentation and/or other materials provided with the 16 * distribution. 17 * 3. Neither the name of The DragonFly Project nor the names of its 18 * contributors may be used to endorse or promote products derived 19 * from this software without specific, prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 /* 35 * Copyright (c) 1982, 1986, 1991, 1993 36 * The Regents of the University of California. All rights reserved. 37 * (c) UNIX System Laboratories, Inc. 38 * All or some portions of this file are derived from material licensed 39 * to the University of California by American Telephone and Telegraph 40 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 41 * the permission of UNIX System Laboratories, Inc. 42 * 43 * Redistribution and use in source and binary forms, with or without 44 * modification, are permitted provided that the following conditions 45 * are met: 46 * 1. Redistributions of source code must retain the above copyright 47 * notice, this list of conditions and the following disclaimer. 48 * 2. Redistributions in binary form must reproduce the above copyright 49 * notice, this list of conditions and the following disclaimer in the 50 * documentation and/or other materials provided with the distribution. 51 * 3. All advertising materials mentioning features or use of this software 52 * must display the following acknowledgement: 53 * This product includes software developed by the University of 54 * California, Berkeley and its contributors. 55 * 4. Neither the name of the University nor the names of its contributors 56 * may be used to endorse or promote products derived from this software 57 * without specific prior written permission. 58 * 59 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 60 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 61 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 62 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 63 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 64 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 65 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 66 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 67 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 68 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 69 * SUCH DAMAGE. 70 * 71 * From: @(#)kern_clock.c 8.5 (Berkeley) 1/21/94 72 * $FreeBSD: src/sys/kern/kern_timeout.c,v 1.59.2.1 2001/11/13 18:24:52 archie Exp $ 73 * $DragonFly: src/sys/kern/kern_timeout.c,v 1.27 2007/11/14 18:27:52 swildner Exp $ 74 */ 75 /* 76 * DRAGONFLY BGL STATUS 77 * 78 * All the API functions should be MP safe. 79 * 80 * The callback functions will be flagged as being MP safe if the 81 * timeout structure is initialized with callout_init_mp() instead of 82 * callout_init(). 83 * 84 * The helper threads cannot be made preempt-capable until after we 85 * clean up all the uses of splsoftclock() and related interlocks (which 86 * require the related functions to be MP safe as well). 87 */ 88 /* 89 * The callout mechanism is based on the work of Adam M. Costello and 90 * George Varghese, published in a technical report entitled "Redesigning 91 * the BSD Callout and Timer Facilities" and modified slightly for inclusion 92 * in FreeBSD by Justin T. Gibbs. The original work on the data structures 93 * used in this implementation was published by G. Varghese and T. Lauck in 94 * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for 95 * the Efficient Implementation of a Timer Facility" in the Proceedings of 96 * the 11th ACM Annual Symposium on Operating Systems Principles, 97 * Austin, Texas Nov 1987. 98 * 99 * The per-cpu augmentation was done by Matthew Dillon. 100 */ 101 102 #include <sys/param.h> 103 #include <sys/systm.h> 104 #include <sys/callout.h> 105 #include <sys/kernel.h> 106 #include <sys/interrupt.h> 107 #include <sys/thread.h> 108 109 #include <sys/thread2.h> 110 #include <sys/mplock2.h> 111 112 #ifndef MAX_SOFTCLOCK_STEPS 113 #define MAX_SOFTCLOCK_STEPS 100 /* Maximum allowed value of steps. */ 114 #endif 115 116 117 struct softclock_pcpu { 118 struct callout_tailq *callwheel; 119 struct callout * volatile next; 120 int softticks; /* softticks index */ 121 int curticks; /* per-cpu ticks counter */ 122 int isrunning; 123 struct thread thread; 124 125 }; 126 127 typedef struct softclock_pcpu *softclock_pcpu_t; 128 129 /* 130 * TODO: 131 * allocate more timeout table slots when table overflows. 132 */ 133 static MALLOC_DEFINE(M_CALLOUT, "callout", "callout structures"); 134 static int callwheelsize; 135 static int callwheelbits; 136 static int callwheelmask; 137 static struct softclock_pcpu softclock_pcpu_ary[MAXCPU]; 138 139 static void softclock_handler(void *arg); 140 141 static void 142 swi_softclock_setup(void *arg) 143 { 144 int cpu; 145 int i; 146 147 /* 148 * Figure out how large a callwheel we need. It must be a power of 2. 149 */ 150 callwheelsize = 1; 151 callwheelbits = 0; 152 while (callwheelsize < ncallout) { 153 callwheelsize <<= 1; 154 ++callwheelbits; 155 } 156 callwheelmask = callwheelsize - 1; 157 158 /* 159 * Initialize per-cpu data structures. 160 */ 161 for (cpu = 0; cpu < ncpus; ++cpu) { 162 softclock_pcpu_t sc; 163 164 sc = &softclock_pcpu_ary[cpu]; 165 166 sc->callwheel = kmalloc(sizeof(*sc->callwheel) * callwheelsize, 167 M_CALLOUT, M_WAITOK|M_ZERO); 168 for (i = 0; i < callwheelsize; ++i) 169 TAILQ_INIT(&sc->callwheel[i]); 170 171 /* 172 * Create a preemption-capable thread for each cpu to handle 173 * softclock timeouts on that cpu. The preemption can only 174 * be blocked by a critical section. The thread can itself 175 * be preempted by normal interrupts. 176 */ 177 lwkt_create(softclock_handler, sc, NULL, 178 &sc->thread, TDF_STOPREQ|TDF_INTTHREAD, cpu, 179 "softclock %d", cpu); 180 #if 0 181 /* 182 * Do not make the thread preemptable until we clean up all 183 * the splsoftclock() calls in the system. Since the threads 184 * are no longer operated as a software interrupt, the 185 * splsoftclock() calls will not have any effect on them. 186 */ 187 sc->thread.td_preemptable = lwkt_preempt; 188 #endif 189 } 190 } 191 192 /* 193 * Must occur after ncpus has been initialized. 194 */ 195 SYSINIT(softclock_setup, SI_BOOT2_SOFTCLOCK, SI_ORDER_SECOND, 196 swi_softclock_setup, NULL); 197 198 /* 199 * This routine is called from the hardclock() (basically a FASTint/IPI) on 200 * each cpu in the system. sc->curticks is this cpu's notion of the timebase. 201 * It IS NOT NECESSARILY SYNCHRONIZED WITH 'ticks'! sc->softticks is where 202 * the callwheel is currently indexed. 203 * 204 * WARNING! The MP lock is not necessarily held on call, nor can it be 205 * safely obtained. 206 * 207 * sc->softticks is adjusted by either this routine or our helper thread 208 * depending on whether the helper thread is running or not. 209 */ 210 void 211 hardclock_softtick(globaldata_t gd) 212 { 213 softclock_pcpu_t sc; 214 215 sc = &softclock_pcpu_ary[gd->gd_cpuid]; 216 ++sc->curticks; 217 if (sc->isrunning) 218 return; 219 if (sc->softticks == sc->curticks) { 220 /* 221 * in sync, only wakeup the thread if there is something to 222 * do. 223 */ 224 if (TAILQ_FIRST(&sc->callwheel[sc->softticks & callwheelmask])) 225 { 226 sc->isrunning = 1; 227 lwkt_schedule(&sc->thread); 228 } else { 229 ++sc->softticks; 230 } 231 } else { 232 /* 233 * out of sync, wakeup the thread unconditionally so it can 234 * catch up. 235 */ 236 sc->isrunning = 1; 237 lwkt_schedule(&sc->thread); 238 } 239 } 240 241 /* 242 * This procedure is the main loop of our per-cpu helper thread. The 243 * sc->isrunning flag prevents us from racing hardclock_softtick() and 244 * a critical section is sufficient to interlock sc->curticks and protect 245 * us from remote IPI's / list removal. 246 * 247 * The thread starts with the MP lock held and not in a critical section. 248 * The loop itself is MP safe while individual callbacks may or may not 249 * be, so we obtain or release the MP lock as appropriate. 250 */ 251 static void 252 softclock_handler(void *arg) 253 { 254 softclock_pcpu_t sc; 255 struct callout *c; 256 struct callout_tailq *bucket; 257 void (*c_func)(void *); 258 void *c_arg; 259 #ifdef SMP 260 int mpsafe = 0; 261 #endif 262 263 lwkt_setpri_self(TDPRI_SOFT_NORM); 264 265 sc = arg; 266 crit_enter(); 267 loop: 268 while (sc->softticks != (int)(sc->curticks + 1)) { 269 bucket = &sc->callwheel[sc->softticks & callwheelmask]; 270 271 for (c = TAILQ_FIRST(bucket); c; c = sc->next) { 272 if (c->c_time != sc->softticks) { 273 sc->next = TAILQ_NEXT(c, c_links.tqe); 274 continue; 275 } 276 #ifdef SMP 277 if (c->c_flags & CALLOUT_MPSAFE) { 278 if (mpsafe == 0) { 279 mpsafe = 1; 280 rel_mplock(); 281 } 282 } else { 283 /* 284 * The request might be removed while we 285 * are waiting to get the MP lock. If it 286 * was removed sc->next will point to the 287 * next valid request or NULL, loop up. 288 */ 289 if (mpsafe) { 290 mpsafe = 0; 291 sc->next = c; 292 get_mplock(); 293 if (c != sc->next) 294 continue; 295 } 296 } 297 #endif 298 sc->next = TAILQ_NEXT(c, c_links.tqe); 299 TAILQ_REMOVE(bucket, c, c_links.tqe); 300 301 c_func = c->c_func; 302 c_arg = c->c_arg; 303 c->c_func = NULL; 304 KKASSERT(c->c_flags & CALLOUT_DID_INIT); 305 c->c_flags &= ~CALLOUT_PENDING; 306 crit_exit(); 307 c_func(c_arg); 308 crit_enter(); 309 /* NOTE: list may have changed */ 310 } 311 ++sc->softticks; 312 } 313 sc->isrunning = 0; 314 lwkt_deschedule_self(&sc->thread); /* == curthread */ 315 lwkt_switch(); 316 goto loop; 317 /* NOT REACHED */ 318 } 319 320 /* 321 * New interface; clients allocate their own callout structures. 322 * 323 * callout_reset() - establish or change a timeout 324 * callout_stop() - disestablish a timeout 325 * callout_init() - initialize a callout structure so that it can 326 * safely be passed to callout_reset() and callout_stop() 327 * callout_init_mp() - same but any installed functions must be MP safe. 328 * 329 * <sys/callout.h> defines three convenience macros: 330 * 331 * callout_active() - returns truth if callout has not been serviced 332 * callout_pending() - returns truth if callout is still waiting for timeout 333 * callout_deactivate() - marks the callout as having been serviced 334 */ 335 336 /* 337 * Start or restart a timeout. Install the callout structure in the 338 * callwheel. Callers may legally pass any value, even if 0 or negative, 339 * but since the sc->curticks index may have already been processed a 340 * minimum timeout of 1 tick will be enforced. 341 * 342 * The callout is installed on and will be processed on the current cpu's 343 * callout wheel. 344 * 345 * WARNING! This function may be called from any cpu but the caller must 346 * serialize callout_stop() and callout_reset() calls on the passed 347 * structure regardless of cpu. 348 */ 349 void 350 callout_reset(struct callout *c, int to_ticks, void (*ftn)(void *), 351 void *arg) 352 { 353 softclock_pcpu_t sc; 354 globaldata_t gd; 355 356 #ifdef INVARIANTS 357 if ((c->c_flags & CALLOUT_DID_INIT) == 0) { 358 callout_init(c); 359 kprintf( 360 "callout_reset(%p) from %p: callout was not initialized\n", 361 c, ((int **)&c)[-1]); 362 print_backtrace(-1); 363 } 364 #endif 365 gd = mycpu; 366 sc = &softclock_pcpu_ary[gd->gd_cpuid]; 367 crit_enter_gd(gd); 368 369 if (c->c_flags & CALLOUT_PENDING) 370 callout_stop(c); 371 372 if (to_ticks <= 0) 373 to_ticks = 1; 374 375 c->c_arg = arg; 376 c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING); 377 c->c_func = ftn; 378 c->c_time = sc->curticks + to_ticks; 379 #ifdef SMP 380 c->c_gd = gd; 381 #endif 382 383 TAILQ_INSERT_TAIL(&sc->callwheel[c->c_time & callwheelmask], 384 c, c_links.tqe); 385 crit_exit_gd(gd); 386 } 387 388 /* 389 * Stop a running timer. WARNING! If called on a cpu other then the one 390 * the callout was started on this function will liveloop on its IPI to 391 * the target cpu to process the request. It is possible for the callout 392 * to execute in that case. 393 * 394 * WARNING! This function may be called from any cpu but the caller must 395 * serialize callout_stop() and callout_reset() calls on the passed 396 * structure regardless of cpu. 397 * 398 * WARNING! This routine may be called from an IPI 399 */ 400 int 401 callout_stop(struct callout *c) 402 { 403 globaldata_t gd = mycpu; 404 #ifdef SMP 405 globaldata_t tgd; 406 #endif 407 softclock_pcpu_t sc; 408 409 #ifdef INVARIANTS 410 if ((c->c_flags & CALLOUT_DID_INIT) == 0) { 411 callout_init(c); 412 kprintf( 413 "callout_stop(%p) from %p: callout was not initialized\n", 414 c, ((int **)&c)[-1]); 415 print_backtrace(-1); 416 } 417 #endif 418 crit_enter_gd(gd); 419 420 /* 421 * Don't attempt to delete a callout that's not on the queue. The 422 * callout may not have a cpu assigned to it. Callers do not have 423 * to be on the issuing cpu but must still serialize access to the 424 * callout structure. 425 * 426 * We are not cpu-localized here and cannot safely modify the 427 * flags field in the callout structure. Note that most of the 428 * time CALLOUT_ACTIVE will be 0 if CALLOUT_PENDING is also 0. 429 * 430 * If we race another cpu's dispatch of this callout it is possible 431 * for CALLOUT_ACTIVE to be set with CALLOUT_PENDING unset. This 432 * will cause us to fall through and synchronize with the other 433 * cpu. 434 */ 435 if ((c->c_flags & CALLOUT_PENDING) == 0) { 436 #ifdef SMP 437 if ((c->c_flags & CALLOUT_ACTIVE) == 0) { 438 crit_exit_gd(gd); 439 return (0); 440 } 441 if (c->c_gd == NULL || c->c_gd == gd) { 442 c->c_flags &= ~CALLOUT_ACTIVE; 443 crit_exit_gd(gd); 444 return (0); 445 } 446 /* fall-through to the cpu-localization code. */ 447 #else 448 c->c_flags &= ~CALLOUT_ACTIVE; 449 crit_exit_gd(gd); 450 return (0); 451 #endif 452 } 453 #ifdef SMP 454 if ((tgd = c->c_gd) != gd) { 455 /* 456 * If the callout is owned by a different CPU we have to 457 * execute the function synchronously on the target cpu. 458 */ 459 int seq; 460 461 cpu_ccfence(); /* don't let tgd alias c_gd */ 462 seq = lwkt_send_ipiq(tgd, (void *)callout_stop, c); 463 lwkt_wait_ipiq(tgd, seq); 464 } else 465 #endif 466 { 467 /* 468 * If the callout is owned by the same CPU we can 469 * process it directly, but if we are racing our helper 470 * thread (sc->next), we have to adjust sc->next. The 471 * race is interlocked by a critical section. 472 */ 473 sc = &softclock_pcpu_ary[gd->gd_cpuid]; 474 475 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING); 476 if (sc->next == c) 477 sc->next = TAILQ_NEXT(c, c_links.tqe); 478 479 TAILQ_REMOVE(&sc->callwheel[c->c_time & callwheelmask], 480 c, c_links.tqe); 481 c->c_func = NULL; 482 } 483 crit_exit_gd(gd); 484 return (1); 485 } 486 487 /* 488 * Prepare a callout structure for use by callout_reset() and/or 489 * callout_stop(). The MP version of this routine requires that the callback 490 * function installed by callout_reset() be MP safe. 491 * 492 * The init functions can be called from any cpu and do not have to be 493 * called from the cpu that the timer will eventually run on. 494 */ 495 void 496 callout_init(struct callout *c) 497 { 498 bzero(c, sizeof *c); 499 c->c_flags = CALLOUT_DID_INIT; 500 } 501 502 void 503 callout_init_mp(struct callout *c) 504 { 505 callout_init(c); 506 c->c_flags |= CALLOUT_MPSAFE; 507 } 508 509 /* What, are you joking? This is nuts! -Matt */ 510 #if 0 511 #ifdef APM_FIXUP_CALLTODO 512 /* 513 * Adjust the kernel calltodo timeout list. This routine is used after 514 * an APM resume to recalculate the calltodo timer list values with the 515 * number of hz's we have been sleeping. The next hardclock() will detect 516 * that there are fired timers and run softclock() to execute them. 517 * 518 * Please note, I have not done an exhaustive analysis of what code this 519 * might break. I am motivated to have my select()'s and alarm()'s that 520 * have expired during suspend firing upon resume so that the applications 521 * which set the timer can do the maintanence the timer was for as close 522 * as possible to the originally intended time. Testing this code for a 523 * week showed that resuming from a suspend resulted in 22 to 25 timers 524 * firing, which seemed independant on whether the suspend was 2 hours or 525 * 2 days. Your milage may vary. - Ken Key <key@cs.utk.edu> 526 */ 527 void 528 adjust_timeout_calltodo(struct timeval *time_change) 529 { 530 struct callout *p; 531 unsigned long delta_ticks; 532 533 /* 534 * How many ticks were we asleep? 535 * (stolen from tvtohz()). 536 */ 537 538 /* Don't do anything */ 539 if (time_change->tv_sec < 0) 540 return; 541 else if (time_change->tv_sec <= LONG_MAX / 1000000) 542 delta_ticks = (time_change->tv_sec * 1000000 + 543 time_change->tv_usec + (tick - 1)) / tick + 1; 544 else if (time_change->tv_sec <= LONG_MAX / hz) 545 delta_ticks = time_change->tv_sec * hz + 546 (time_change->tv_usec + (tick - 1)) / tick + 1; 547 else 548 delta_ticks = LONG_MAX; 549 550 if (delta_ticks > INT_MAX) 551 delta_ticks = INT_MAX; 552 553 /* 554 * Now rip through the timer calltodo list looking for timers 555 * to expire. 556 */ 557 558 /* don't collide with softclock() */ 559 crit_enter(); 560 for (p = calltodo.c_next; p != NULL; p = p->c_next) { 561 p->c_time -= delta_ticks; 562 563 /* Break if the timer had more time on it than delta_ticks */ 564 if (p->c_time > 0) 565 break; 566 567 /* take back the ticks the timer didn't use (p->c_time <= 0) */ 568 delta_ticks = -p->c_time; 569 } 570 crit_exit(); 571 572 return; 573 } 574 #endif /* APM_FIXUP_CALLTODO */ 575 #endif 576 577