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