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 #include <sys/thread2.h> 109 110 #ifndef MAX_SOFTCLOCK_STEPS 111 #define MAX_SOFTCLOCK_STEPS 100 /* Maximum allowed value of steps. */ 112 #endif 113 114 115 struct softclock_pcpu { 116 struct callout_tailq *callwheel; 117 struct callout * volatile next; 118 int softticks; /* softticks index */ 119 int curticks; /* per-cpu ticks counter */ 120 int isrunning; 121 struct thread thread; 122 123 }; 124 125 typedef struct softclock_pcpu *softclock_pcpu_t; 126 127 /* 128 * TODO: 129 * allocate more timeout table slots when table overflows. 130 */ 131 static MALLOC_DEFINE(M_CALLOUT, "callout", "callout structures"); 132 static int callwheelsize; 133 static int callwheelbits; 134 static int callwheelmask; 135 static struct softclock_pcpu softclock_pcpu_ary[MAXCPU]; 136 137 static void softclock_handler(void *arg); 138 139 static void 140 swi_softclock_setup(void *arg) 141 { 142 int cpu; 143 int i; 144 145 /* 146 * Figure out how large a callwheel we need. It must be a power of 2. 147 */ 148 callwheelsize = 1; 149 callwheelbits = 0; 150 while (callwheelsize < ncallout) { 151 callwheelsize <<= 1; 152 ++callwheelbits; 153 } 154 callwheelmask = callwheelsize - 1; 155 156 /* 157 * Initialize per-cpu data structures. 158 */ 159 for (cpu = 0; cpu < ncpus; ++cpu) { 160 softclock_pcpu_t sc; 161 162 sc = &softclock_pcpu_ary[cpu]; 163 164 sc->callwheel = kmalloc(sizeof(*sc->callwheel) * callwheelsize, 165 M_CALLOUT, M_WAITOK|M_ZERO); 166 for (i = 0; i < callwheelsize; ++i) 167 TAILQ_INIT(&sc->callwheel[i]); 168 169 /* 170 * Create a preemption-capable thread for each cpu to handle 171 * softclock timeouts on that cpu. The preemption can only 172 * be blocked by a critical section. The thread can itself 173 * be preempted by normal interrupts. 174 */ 175 lwkt_create(softclock_handler, sc, NULL, 176 &sc->thread, TDF_STOPREQ|TDF_INTTHREAD, cpu, 177 "softclock %d", cpu); 178 #if 0 179 /* 180 * Do not make the thread preemptable until we clean up all 181 * the splsoftclock() calls in the system. Since the threads 182 * are no longer operated as a software interrupt, the 183 * splsoftclock() calls will not have any effect on them. 184 */ 185 sc->thread.td_preemptable = lwkt_preempt; 186 #endif 187 } 188 } 189 190 /* 191 * Must occur after ncpus has been initialized. 192 */ 193 SYSINIT(softclock_setup, SI_BOOT2_SOFTCLOCK, SI_ORDER_SECOND, 194 swi_softclock_setup, NULL); 195 196 /* 197 * This routine is called from the hardclock() (basically a FASTint/IPI) on 198 * each cpu in the system. sc->curticks is this cpu's notion of the timebase. 199 * It IS NOT NECESSARILY SYNCHRONIZED WITH 'ticks'! sc->softticks is where 200 * the callwheel is currently indexed. 201 * 202 * WARNING! The MP lock is not necessarily held on call, nor can it be 203 * safely obtained. 204 * 205 * sc->softticks is adjusted by either this routine or our helper thread 206 * depending on whether the helper thread is running or not. 207 */ 208 void 209 hardclock_softtick(globaldata_t gd) 210 { 211 softclock_pcpu_t sc; 212 213 sc = &softclock_pcpu_ary[gd->gd_cpuid]; 214 ++sc->curticks; 215 if (sc->isrunning) 216 return; 217 if (sc->softticks == sc->curticks) { 218 /* 219 * in sync, only wakeup the thread if there is something to 220 * do. 221 */ 222 if (TAILQ_FIRST(&sc->callwheel[sc->softticks & callwheelmask])) 223 { 224 sc->isrunning = 1; 225 lwkt_schedule(&sc->thread); 226 } else { 227 ++sc->softticks; 228 } 229 } else { 230 /* 231 * out of sync, wakeup the thread unconditionally so it can 232 * catch up. 233 */ 234 sc->isrunning = 1; 235 lwkt_schedule(&sc->thread); 236 } 237 } 238 239 /* 240 * This procedure is the main loop of our per-cpu helper thread. The 241 * sc->isrunning flag prevents us from racing hardclock_softtick() and 242 * a critical section is sufficient to interlock sc->curticks and protect 243 * us from remote IPI's / list removal. 244 * 245 * The thread starts with the MP lock held and not in a critical section. 246 * The loop itself is MP safe while individual callbacks may or may not 247 * be, so we obtain or release the MP lock as appropriate. 248 */ 249 static void 250 softclock_handler(void *arg) 251 { 252 softclock_pcpu_t sc; 253 struct callout *c; 254 struct callout_tailq *bucket; 255 void (*c_func)(void *); 256 void *c_arg; 257 #ifdef SMP 258 int mpsafe = 0; 259 #endif 260 261 lwkt_setpri_self(TDPRI_SOFT_NORM); 262 263 sc = arg; 264 crit_enter(); 265 loop: 266 while (sc->softticks != (int)(sc->curticks + 1)) { 267 bucket = &sc->callwheel[sc->softticks & callwheelmask]; 268 269 for (c = TAILQ_FIRST(bucket); c; c = sc->next) { 270 if (c->c_time != sc->softticks) { 271 sc->next = TAILQ_NEXT(c, c_links.tqe); 272 continue; 273 } 274 #ifdef SMP 275 if (c->c_flags & CALLOUT_MPSAFE) { 276 if (mpsafe == 0) { 277 mpsafe = 1; 278 rel_mplock(); 279 } 280 } else { 281 /* 282 * The request might be removed while we 283 * are waiting to get the MP lock. If it 284 * was removed sc->next will point to the 285 * next valid request or NULL, loop up. 286 */ 287 if (mpsafe) { 288 mpsafe = 0; 289 sc->next = c; 290 get_mplock(); 291 if (c != sc->next) 292 continue; 293 } 294 } 295 #endif 296 sc->next = TAILQ_NEXT(c, c_links.tqe); 297 TAILQ_REMOVE(bucket, c, c_links.tqe); 298 299 c_func = c->c_func; 300 c_arg = c->c_arg; 301 c->c_func = NULL; 302 KKASSERT(c->c_flags & CALLOUT_DID_INIT); 303 c->c_flags &= ~CALLOUT_PENDING; 304 crit_exit(); 305 c_func(c_arg); 306 crit_enter(); 307 /* NOTE: list may have changed */ 308 } 309 ++sc->softticks; 310 } 311 sc->isrunning = 0; 312 lwkt_deschedule_self(&sc->thread); /* == curthread */ 313 lwkt_switch(); 314 goto loop; 315 /* NOT REACHED */ 316 } 317 318 /* 319 * New interface; clients allocate their own callout structures. 320 * 321 * callout_reset() - establish or change a timeout 322 * callout_stop() - disestablish a timeout 323 * callout_init() - initialize a callout structure so that it can 324 * safely be passed to callout_reset() and callout_stop() 325 * callout_init_mp() - same but any installed functions must be MP safe. 326 * 327 * <sys/callout.h> defines three convenience macros: 328 * 329 * callout_active() - returns truth if callout has not been serviced 330 * callout_pending() - returns truth if callout is still waiting for timeout 331 * callout_deactivate() - marks the callout as having been serviced 332 */ 333 334 /* 335 * Start or restart a timeout. Install the callout structure in the 336 * callwheel. Callers may legally pass any value, even if 0 or negative, 337 * but since the sc->curticks index may have already been processed a 338 * minimum timeout of 1 tick will be enforced. 339 * 340 * The callout is installed on and will be processed on the current cpu's 341 * callout wheel. 342 * 343 * WARNING! This function may be called from any cpu but the caller must 344 * serialize callout_stop() and callout_reset() calls on the passed 345 * structure regardless of cpu. 346 */ 347 void 348 callout_reset(struct callout *c, int to_ticks, void (*ftn)(void *), 349 void *arg) 350 { 351 softclock_pcpu_t sc; 352 globaldata_t gd; 353 354 #ifdef INVARIANTS 355 if ((c->c_flags & CALLOUT_DID_INIT) == 0) { 356 callout_init(c); 357 kprintf( 358 "callout_reset(%p) from %p: callout was not initialized\n", 359 c, ((int **)&c)[-1]); 360 print_backtrace(); 361 } 362 #endif 363 gd = mycpu; 364 sc = &softclock_pcpu_ary[gd->gd_cpuid]; 365 crit_enter_gd(gd); 366 367 if (c->c_flags & CALLOUT_PENDING) 368 callout_stop(c); 369 370 if (to_ticks <= 0) 371 to_ticks = 1; 372 373 c->c_arg = arg; 374 c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING); 375 c->c_func = ftn; 376 c->c_time = sc->curticks + to_ticks; 377 #ifdef SMP 378 c->c_gd = gd; 379 #endif 380 381 TAILQ_INSERT_TAIL(&sc->callwheel[c->c_time & callwheelmask], 382 c, c_links.tqe); 383 crit_exit_gd(gd); 384 } 385 386 /* 387 * Stop a running timer. WARNING! If called on a cpu other then the one 388 * the callout was started on this function will liveloop on its IPI to 389 * the target cpu to process the request. It is possible for the callout 390 * to execute in that case. 391 * 392 * WARNING! This function may be called from any cpu but the caller must 393 * serialize callout_stop() and callout_reset() calls on the passed 394 * structure regardless of cpu. 395 * 396 * WARNING! This routine may be called from an IPI 397 */ 398 int 399 callout_stop(struct callout *c) 400 { 401 globaldata_t gd = mycpu; 402 #ifdef SMP 403 globaldata_t tgd; 404 #endif 405 softclock_pcpu_t sc; 406 407 #ifdef INVARIANTS 408 if ((c->c_flags & CALLOUT_DID_INIT) == 0) { 409 callout_init(c); 410 kprintf( 411 "callout_stop(%p) from %p: callout was not initialized\n", 412 c, ((int **)&c)[-1]); 413 print_backtrace(); 414 } 415 #endif 416 crit_enter_gd(gd); 417 418 /* 419 * Don't attempt to delete a callout that's not on the queue. The 420 * callout may not have a cpu assigned to it. Callers do not have 421 * to be on the issuing cpu but must still serialize access to the 422 * callout structure. 423 * 424 * We are not cpu-localized here and cannot safely modify the 425 * flags field in the callout structure. Note that most of the 426 * time CALLOUT_ACTIVE will be 0 if CALLOUT_PENDING is also 0. 427 * 428 * If we race another cpu's dispatch of this callout it is possible 429 * for CALLOUT_ACTIVE to be set with CALLOUT_PENDING unset. This 430 * will cause us to fall through and synchronize with the other 431 * cpu. 432 */ 433 if ((c->c_flags & CALLOUT_PENDING) == 0) { 434 #ifdef SMP 435 if ((c->c_flags & CALLOUT_ACTIVE) == 0) { 436 crit_exit_gd(gd); 437 return (0); 438 } 439 if (c->c_gd == NULL || c->c_gd == gd) { 440 c->c_flags &= ~CALLOUT_ACTIVE; 441 crit_exit_gd(gd); 442 return (0); 443 } 444 /* fall-through to the cpu-localization code. */ 445 #else 446 c->c_flags &= ~CALLOUT_ACTIVE; 447 crit_exit_gd(gd); 448 return (0); 449 #endif 450 } 451 #ifdef SMP 452 if ((tgd = c->c_gd) != gd) { 453 /* 454 * If the callout is owned by a different CPU we have to 455 * execute the function synchronously on the target cpu. 456 */ 457 int seq; 458 459 cpu_ccfence(); /* don't let tgd alias c_gd */ 460 seq = lwkt_send_ipiq(tgd, (void *)callout_stop, c); 461 lwkt_wait_ipiq(tgd, seq); 462 } else 463 #endif 464 { 465 /* 466 * If the callout is owned by the same CPU we can 467 * process it directly, but if we are racing our helper 468 * thread (sc->next), we have to adjust sc->next. The 469 * race is interlocked by a critical section. 470 */ 471 sc = &softclock_pcpu_ary[gd->gd_cpuid]; 472 473 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING); 474 if (sc->next == c) 475 sc->next = TAILQ_NEXT(c, c_links.tqe); 476 477 TAILQ_REMOVE(&sc->callwheel[c->c_time & callwheelmask], 478 c, c_links.tqe); 479 c->c_func = NULL; 480 } 481 crit_exit_gd(gd); 482 return (1); 483 } 484 485 /* 486 * Prepare a callout structure for use by callout_reset() and/or 487 * callout_stop(). The MP version of this routine requires that the callback 488 * function installed by callout_reset() be MP safe. 489 */ 490 void 491 callout_init(struct callout *c) 492 { 493 bzero(c, sizeof *c); 494 c->c_flags = CALLOUT_DID_INIT; 495 } 496 497 void 498 callout_init_mp(struct callout *c) 499 { 500 callout_init(c); 501 c->c_flags |= CALLOUT_MPSAFE; 502 } 503 504 /* What, are you joking? This is nuts! -Matt */ 505 #if 0 506 #ifdef APM_FIXUP_CALLTODO 507 /* 508 * Adjust the kernel calltodo timeout list. This routine is used after 509 * an APM resume to recalculate the calltodo timer list values with the 510 * number of hz's we have been sleeping. The next hardclock() will detect 511 * that there are fired timers and run softclock() to execute them. 512 * 513 * Please note, I have not done an exhaustive analysis of what code this 514 * might break. I am motivated to have my select()'s and alarm()'s that 515 * have expired during suspend firing upon resume so that the applications 516 * which set the timer can do the maintanence the timer was for as close 517 * as possible to the originally intended time. Testing this code for a 518 * week showed that resuming from a suspend resulted in 22 to 25 timers 519 * firing, which seemed independant on whether the suspend was 2 hours or 520 * 2 days. Your milage may vary. - Ken Key <key@cs.utk.edu> 521 */ 522 void 523 adjust_timeout_calltodo(struct timeval *time_change) 524 { 525 struct callout *p; 526 unsigned long delta_ticks; 527 528 /* 529 * How many ticks were we asleep? 530 * (stolen from tvtohz()). 531 */ 532 533 /* Don't do anything */ 534 if (time_change->tv_sec < 0) 535 return; 536 else if (time_change->tv_sec <= LONG_MAX / 1000000) 537 delta_ticks = (time_change->tv_sec * 1000000 + 538 time_change->tv_usec + (tick - 1)) / tick + 1; 539 else if (time_change->tv_sec <= LONG_MAX / hz) 540 delta_ticks = time_change->tv_sec * hz + 541 (time_change->tv_usec + (tick - 1)) / tick + 1; 542 else 543 delta_ticks = LONG_MAX; 544 545 if (delta_ticks > INT_MAX) 546 delta_ticks = INT_MAX; 547 548 /* 549 * Now rip through the timer calltodo list looking for timers 550 * to expire. 551 */ 552 553 /* don't collide with softclock() */ 554 crit_enter(); 555 for (p = calltodo.c_next; p != NULL; p = p->c_next) { 556 p->c_time -= delta_ticks; 557 558 /* Break if the timer had more time on it than delta_ticks */ 559 if (p->c_time > 0) 560 break; 561 562 /* take back the ticks the timer didn't use (p->c_time <= 0) */ 563 delta_ticks = -p->c_time; 564 } 565 crit_exit(); 566 567 return; 568 } 569 #endif /* APM_FIXUP_CALLTODO */ 570 #endif 571 572