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 struct callout *running;/* currently running callout */ 121 int softticks; /* softticks index */ 122 int curticks; /* per-cpu ticks counter */ 123 int isrunning; 124 struct thread thread; 125 126 }; 127 128 typedef struct softclock_pcpu *softclock_pcpu_t; 129 130 /* 131 * TODO: 132 * allocate more timeout table slots when table overflows. 133 */ 134 static MALLOC_DEFINE(M_CALLOUT, "callout", "callout structures"); 135 static int callwheelsize; 136 static int callwheelbits; 137 static int callwheelmask; 138 static struct softclock_pcpu softclock_pcpu_ary[MAXCPU]; 139 140 static void softclock_handler(void *arg); 141 142 static void 143 swi_softclock_setup(void *arg) 144 { 145 int cpu; 146 int i; 147 148 /* 149 * Figure out how large a callwheel we need. It must be a power of 2. 150 */ 151 callwheelsize = 1; 152 callwheelbits = 0; 153 while (callwheelsize < ncallout) { 154 callwheelsize <<= 1; 155 ++callwheelbits; 156 } 157 callwheelmask = callwheelsize - 1; 158 159 /* 160 * Initialize per-cpu data structures. 161 */ 162 for (cpu = 0; cpu < ncpus; ++cpu) { 163 softclock_pcpu_t sc; 164 165 sc = &softclock_pcpu_ary[cpu]; 166 167 sc->callwheel = kmalloc(sizeof(*sc->callwheel) * callwheelsize, 168 M_CALLOUT, M_WAITOK|M_ZERO); 169 for (i = 0; i < callwheelsize; ++i) 170 TAILQ_INIT(&sc->callwheel[i]); 171 172 /* 173 * Mark the softclock handler as being an interrupt thread 174 * even though it really isn't, but do not allow it to 175 * preempt other threads (do not assign td_preemptable). 176 * 177 * Kernel code now assumes that callouts do not preempt 178 * the cpu they were scheduled on. 179 */ 180 lwkt_create(softclock_handler, sc, NULL, 181 &sc->thread, TDF_STOPREQ | TDF_INTTHREAD, 182 cpu, "softclock %d", cpu); 183 } 184 } 185 186 /* 187 * Must occur after ncpus has been initialized. 188 */ 189 SYSINIT(softclock_setup, SI_BOOT2_SOFTCLOCK, SI_ORDER_SECOND, 190 swi_softclock_setup, NULL); 191 192 /* 193 * This routine is called from the hardclock() (basically a FASTint/IPI) on 194 * each cpu in the system. sc->curticks is this cpu's notion of the timebase. 195 * It IS NOT NECESSARILY SYNCHRONIZED WITH 'ticks'! sc->softticks is where 196 * the callwheel is currently indexed. 197 * 198 * WARNING! The MP lock is not necessarily held on call, nor can it be 199 * safely obtained. 200 * 201 * sc->softticks is adjusted by either this routine or our helper thread 202 * depending on whether the helper thread is running or not. 203 */ 204 void 205 hardclock_softtick(globaldata_t gd) 206 { 207 softclock_pcpu_t sc; 208 209 sc = &softclock_pcpu_ary[gd->gd_cpuid]; 210 ++sc->curticks; 211 if (sc->isrunning) 212 return; 213 if (sc->softticks == sc->curticks) { 214 /* 215 * in sync, only wakeup the thread if there is something to 216 * do. 217 */ 218 if (TAILQ_FIRST(&sc->callwheel[sc->softticks & callwheelmask])) 219 { 220 sc->isrunning = 1; 221 lwkt_schedule(&sc->thread); 222 } else { 223 ++sc->softticks; 224 } 225 } else { 226 /* 227 * out of sync, wakeup the thread unconditionally so it can 228 * catch up. 229 */ 230 sc->isrunning = 1; 231 lwkt_schedule(&sc->thread); 232 } 233 } 234 235 /* 236 * This procedure is the main loop of our per-cpu helper thread. The 237 * sc->isrunning flag prevents us from racing hardclock_softtick() and 238 * a critical section is sufficient to interlock sc->curticks and protect 239 * us from remote IPI's / list removal. 240 * 241 * The thread starts with the MP lock released and not in a critical 242 * section. The loop itself is MP safe while individual callbacks 243 * may or may not be, so we obtain or release the MP lock as appropriate. 244 */ 245 static void 246 softclock_handler(void *arg) 247 { 248 softclock_pcpu_t sc; 249 struct callout *c; 250 struct callout_tailq *bucket; 251 void (*c_func)(void *); 252 void *c_arg; 253 #ifdef SMP 254 int mpsafe = 1; 255 #endif 256 257 lwkt_setpri_self(TDPRI_SOFT_NORM); 258 259 sc = arg; 260 crit_enter(); 261 loop: 262 while (sc->softticks != (int)(sc->curticks + 1)) { 263 bucket = &sc->callwheel[sc->softticks & callwheelmask]; 264 265 for (c = TAILQ_FIRST(bucket); c; c = sc->next) { 266 if (c->c_time != sc->softticks) { 267 sc->next = TAILQ_NEXT(c, c_links.tqe); 268 continue; 269 } 270 #ifdef SMP 271 if (c->c_flags & CALLOUT_MPSAFE) { 272 if (mpsafe == 0) { 273 mpsafe = 1; 274 rel_mplock(); 275 } 276 } else { 277 /* 278 * The request might be removed while we 279 * are waiting to get the MP lock. If it 280 * was removed sc->next will point to the 281 * next valid request or NULL, loop up. 282 */ 283 if (mpsafe) { 284 mpsafe = 0; 285 sc->next = c; 286 get_mplock(); 287 if (c != sc->next) 288 continue; 289 } 290 } 291 #endif 292 sc->next = TAILQ_NEXT(c, c_links.tqe); 293 TAILQ_REMOVE(bucket, c, c_links.tqe); 294 295 sc->running = c; 296 c_func = c->c_func; 297 c_arg = c->c_arg; 298 c->c_func = NULL; 299 KKASSERT(c->c_flags & CALLOUT_DID_INIT); 300 c->c_flags &= ~CALLOUT_PENDING; 301 crit_exit(); 302 c_func(c_arg); 303 crit_enter(); 304 sc->running = NULL; 305 /* NOTE: list may have changed */ 306 } 307 ++sc->softticks; 308 } 309 sc->isrunning = 0; 310 lwkt_deschedule_self(&sc->thread); /* == curthread */ 311 lwkt_switch(); 312 goto loop; 313 /* NOT REACHED */ 314 } 315 316 /* 317 * New interface; clients allocate their own callout structures. 318 * 319 * callout_reset() - establish or change a timeout 320 * callout_stop() - disestablish a timeout 321 * callout_init() - initialize a callout structure so that it can 322 * safely be passed to callout_reset() and callout_stop() 323 * callout_init_mp() - same but any installed functions must be MP safe. 324 * 325 * <sys/callout.h> defines three convenience macros: 326 * 327 * callout_active() - returns truth if callout has not been serviced 328 * callout_pending() - returns truth if callout is still waiting for timeout 329 * callout_deactivate() - marks the callout as having been serviced 330 */ 331 332 /* 333 * Start or restart a timeout. Install the callout structure in the 334 * callwheel. Callers may legally pass any value, even if 0 or negative, 335 * but since the sc->curticks index may have already been processed a 336 * minimum timeout of 1 tick will be enforced. 337 * 338 * The callout is installed on and will be processed on the current cpu's 339 * callout wheel. 340 * 341 * WARNING! This function may be called from any cpu but the caller must 342 * serialize callout_stop() and callout_reset() calls on the passed 343 * structure regardless of cpu. 344 */ 345 void 346 callout_reset(struct callout *c, int to_ticks, void (*ftn)(void *), 347 void *arg) 348 { 349 softclock_pcpu_t sc; 350 globaldata_t gd; 351 352 #ifdef INVARIANTS 353 if ((c->c_flags & CALLOUT_DID_INIT) == 0) { 354 callout_init(c); 355 kprintf( 356 "callout_reset(%p) from %p: callout was not initialized\n", 357 c, ((int **)&c)[-1]); 358 print_backtrace(-1); 359 } 360 #endif 361 gd = mycpu; 362 sc = &softclock_pcpu_ary[gd->gd_cpuid]; 363 crit_enter_gd(gd); 364 365 if (c->c_flags & CALLOUT_ACTIVE) 366 callout_stop(c); 367 368 if (to_ticks <= 0) 369 to_ticks = 1; 370 371 c->c_arg = arg; 372 c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING); 373 c->c_func = ftn; 374 c->c_time = sc->curticks + to_ticks; 375 #ifdef SMP 376 c->c_gd = gd; 377 #endif 378 379 TAILQ_INSERT_TAIL(&sc->callwheel[c->c_time & callwheelmask], 380 c, c_links.tqe); 381 crit_exit_gd(gd); 382 } 383 384 /* 385 * Stop a running timer. WARNING! If called on a cpu other then the one 386 * the callout was started on this function will liveloop on its IPI to 387 * the target cpu to process the request. It is possible for the callout 388 * to execute in that case. 389 * 390 * WARNING! This function may be called from any cpu but the caller must 391 * serialize callout_stop() and callout_reset() calls on the passed 392 * structure regardless of cpu. 393 * 394 * WARNING! This routine may be called from an IPI 395 * 396 * WARNING! This function can return while it's c_func is still running 397 * in the callout thread, a secondary check may be needed. 398 */ 399 int 400 callout_stop(struct callout *c) 401 { 402 globaldata_t gd = mycpu; 403 #ifdef SMP 404 globaldata_t tgd; 405 #endif 406 softclock_pcpu_t sc; 407 408 #ifdef INVARIANTS 409 if ((c->c_flags & CALLOUT_DID_INIT) == 0) { 410 callout_init(c); 411 kprintf( 412 "callout_stop(%p) from %p: callout was not initialized\n", 413 c, ((int **)&c)[-1]); 414 print_backtrace(-1); 415 } 416 #endif 417 crit_enter_gd(gd); 418 419 /* 420 * Don't attempt to delete a callout that's not on the queue. The 421 * callout may not have a cpu assigned to it. Callers do not have 422 * to be on the issuing cpu but must still serialize access to the 423 * callout structure. 424 * 425 * We are not cpu-localized here and cannot safely modify the 426 * flags field in the callout structure. Note that most of the 427 * time CALLOUT_ACTIVE will be 0 if CALLOUT_PENDING is also 0. 428 * 429 * If we race another cpu's dispatch of this callout it is possible 430 * for CALLOUT_ACTIVE to be set with CALLOUT_PENDING unset. This 431 * will cause us to fall through and synchronize with the other 432 * cpu. 433 */ 434 if ((c->c_flags & CALLOUT_PENDING) == 0) { 435 #ifdef SMP 436 if ((c->c_flags & CALLOUT_ACTIVE) == 0) { 437 crit_exit_gd(gd); 438 return (0); 439 } 440 if (c->c_gd == NULL || c->c_gd == gd) { 441 c->c_flags &= ~CALLOUT_ACTIVE; 442 crit_exit_gd(gd); 443 return (0); 444 } 445 /* fall-through to the cpu-localization code. */ 446 #else 447 c->c_flags &= ~CALLOUT_ACTIVE; 448 crit_exit_gd(gd); 449 return (0); 450 #endif 451 } 452 #ifdef SMP 453 if ((tgd = c->c_gd) != gd) { 454 /* 455 * If the callout is owned by a different CPU we have to 456 * execute the function synchronously on the target cpu. 457 */ 458 int seq; 459 460 cpu_ccfence(); /* don't let tgd alias c_gd */ 461 seq = lwkt_send_ipiq(tgd, (void *)callout_stop, c); 462 lwkt_wait_ipiq(tgd, seq); 463 } else 464 #endif 465 { 466 /* 467 * If the callout is owned by the same CPU we can 468 * process it directly, but if we are racing our helper 469 * thread (sc->next), we have to adjust sc->next. The 470 * race is interlocked by a critical section. 471 */ 472 sc = &softclock_pcpu_ary[gd->gd_cpuid]; 473 474 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING); 475 if (sc->next == c) 476 sc->next = TAILQ_NEXT(c, c_links.tqe); 477 478 TAILQ_REMOVE(&sc->callwheel[c->c_time & callwheelmask], 479 c, c_links.tqe); 480 c->c_func = NULL; 481 } 482 crit_exit_gd(gd); 483 return (1); 484 } 485 486 /* 487 * Terminate a callout 488 * 489 * This function will stop any pending callout and also block while the 490 * callout's function is running. It should only be used in cases where 491 * no deadlock is possible (due to the callout function acquiring locks 492 * that the current caller of callout_terminate() already holds), when 493 * the caller is ready to destroy the callout structure. 494 * 495 * This function clears the CALLOUT_DID_INIT flag. 496 * 497 * lwkt_token locks are ok. 498 */ 499 void 500 callout_terminate(struct callout *c) 501 { 502 softclock_pcpu_t sc; 503 504 if (c->c_flags & CALLOUT_DID_INIT) { 505 callout_stop(c); 506 #ifdef SMP 507 sc = &softclock_pcpu_ary[c->c_gd->gd_cpuid]; 508 #else 509 sc = &softclock_pcpu_ary[0]; 510 #endif 511 if (sc->running == c) { 512 while (sc->running == c) 513 tsleep(&sc->running, 0, "crace", 1); 514 } 515 KKASSERT((c->c_flags & (CALLOUT_PENDING|CALLOUT_ACTIVE)) == 0); 516 c->c_flags &= ~CALLOUT_DID_INIT; 517 } 518 } 519 520 /* 521 * Prepare a callout structure for use by callout_reset() and/or 522 * callout_stop(). The MP version of this routine requires that the callback 523 * function installed by callout_reset() be MP safe. 524 * 525 * The init functions can be called from any cpu and do not have to be 526 * called from the cpu that the timer will eventually run on. 527 */ 528 void 529 callout_init(struct callout *c) 530 { 531 bzero(c, sizeof *c); 532 c->c_flags = CALLOUT_DID_INIT; 533 } 534 535 void 536 callout_init_mp(struct callout *c) 537 { 538 callout_init(c); 539 c->c_flags |= CALLOUT_MPSAFE; 540 } 541 542 /* What, are you joking? This is nuts! -Matt */ 543 #if 0 544 #ifdef APM_FIXUP_CALLTODO 545 /* 546 * Adjust the kernel calltodo timeout list. This routine is used after 547 * an APM resume to recalculate the calltodo timer list values with the 548 * number of hz's we have been sleeping. The next hardclock() will detect 549 * that there are fired timers and run softclock() to execute them. 550 * 551 * Please note, I have not done an exhaustive analysis of what code this 552 * might break. I am motivated to have my select()'s and alarm()'s that 553 * have expired during suspend firing upon resume so that the applications 554 * which set the timer can do the maintanence the timer was for as close 555 * as possible to the originally intended time. Testing this code for a 556 * week showed that resuming from a suspend resulted in 22 to 25 timers 557 * firing, which seemed independant on whether the suspend was 2 hours or 558 * 2 days. Your milage may vary. - Ken Key <key@cs.utk.edu> 559 */ 560 void 561 adjust_timeout_calltodo(struct timeval *time_change) 562 { 563 struct callout *p; 564 unsigned long delta_ticks; 565 566 /* 567 * How many ticks were we asleep? 568 * (stolen from tvtohz()). 569 */ 570 571 /* Don't do anything */ 572 if (time_change->tv_sec < 0) 573 return; 574 else if (time_change->tv_sec <= LONG_MAX / 1000000) 575 delta_ticks = (time_change->tv_sec * 1000000 + 576 time_change->tv_usec + (tick - 1)) / tick + 1; 577 else if (time_change->tv_sec <= LONG_MAX / hz) 578 delta_ticks = time_change->tv_sec * hz + 579 (time_change->tv_usec + (tick - 1)) / tick + 1; 580 else 581 delta_ticks = LONG_MAX; 582 583 if (delta_ticks > INT_MAX) 584 delta_ticks = INT_MAX; 585 586 /* 587 * Now rip through the timer calltodo list looking for timers 588 * to expire. 589 */ 590 591 /* don't collide with softclock() */ 592 crit_enter(); 593 for (p = calltodo.c_next; p != NULL; p = p->c_next) { 594 p->c_time -= delta_ticks; 595 596 /* Break if the timer had more time on it than delta_ticks */ 597 if (p->c_time > 0) 598 break; 599 600 /* take back the ticks the timer didn't use (p->c_time <= 0) */ 601 delta_ticks = -p->c_time; 602 } 603 crit_exit(); 604 605 return; 606 } 607 #endif /* APM_FIXUP_CALLTODO */ 608 #endif 609 610