kern_timeout.c revision 1.17.20.2
1 /* $NetBSD: kern_timeout.c,v 1.17.20.2 2006/10/20 19:24:29 ad Exp $ */ 2 3 /*- 4 * Copyright (c) 2003, 2006 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Jason R. Thorpe. 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 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the NetBSD 21 * Foundation, Inc. and its contributors. 22 * 4. Neither the name of The NetBSD Foundation nor the names of its 23 * contributors may be used to endorse or promote products derived 24 * from this software without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 27 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 29 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 30 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 32 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 33 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 34 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 35 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 36 * POSSIBILITY OF SUCH DAMAGE. 37 */ 38 39 /* 40 * Copyright (c) 2001 Thomas Nordin <nordin (at) openbsd.org> 41 * Copyright (c) 2000-2001 Artur Grabowski <art (at) openbsd.org> 42 * All rights reserved. 43 * 44 * Redistribution and use in source and binary forms, with or without 45 * modification, are permitted provided that the following conditions 46 * are met: 47 * 48 * 1. Redistributions of source code must retain the above copyright 49 * notice, this list of conditions and the following disclaimer. 50 * 2. Redistributions in binary form must reproduce the above copyright 51 * notice, this list of conditions and the following disclaimer in the 52 * documentation and/or other materials provided with the distribution. 53 * 3. The name of the author may not be used to endorse or promote products 54 * derived from this software without specific prior written permission. 55 * 56 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, 57 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY 58 * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL 59 * THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 60 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 61 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; 62 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 63 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR 64 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 65 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 66 */ 67 68 #include <sys/cdefs.h> 69 __KERNEL_RCSID(0, "$NetBSD: kern_timeout.c,v 1.17.20.2 2006/10/20 19:24:29 ad Exp $"); 70 71 /* 72 * Adapted from OpenBSD: kern_timeout.c,v 1.15 2002/12/08 04:21:07 art Exp, 73 * modified to match NetBSD's pre-existing callout API. 74 */ 75 76 #include <sys/param.h> 77 #include <sys/systm.h> 78 #include <sys/kernel.h> 79 #include <sys/lock.h> 80 #include <sys/callout.h> 81 #include <sys/mutex.h> 82 83 #ifdef DDB 84 #include <machine/db_machdep.h> 85 #include <ddb/db_interface.h> 86 #include <ddb/db_access.h> 87 #include <ddb/db_sym.h> 88 #include <ddb/db_output.h> 89 #endif 90 91 /* 92 * Timeouts are kept in a hierarchical timing wheel. The c_time is the value 93 * of the global variable "hardclock_ticks" when the timeout should be called. 94 * There are four levels with 256 buckets each. See 'Scheme 7' in 95 * "Hashed and Hierarchical Timing Wheels: Efficient Data Structures for 96 * Implementing a Timer Facility" by George Varghese and Tony Lauck. 97 */ 98 #define BUCKETS 1024 99 #define WHEELSIZE 256 100 #define WHEELMASK 255 101 #define WHEELBITS 8 102 103 static struct callout_circq timeout_wheel[BUCKETS]; /* Queues of timeouts */ 104 static struct callout_circq timeout_todo; /* Worklist */ 105 106 #define MASKWHEEL(wheel, time) (((time) >> ((wheel)*WHEELBITS)) & WHEELMASK) 107 108 #define BUCKET(rel, abs) \ 109 (((rel) <= (1 << (2*WHEELBITS))) \ 110 ? ((rel) <= (1 << WHEELBITS)) \ 111 ? &timeout_wheel[MASKWHEEL(0, (abs))] \ 112 : &timeout_wheel[MASKWHEEL(1, (abs)) + WHEELSIZE] \ 113 : ((rel) <= (1 << (3*WHEELBITS))) \ 114 ? &timeout_wheel[MASKWHEEL(2, (abs)) + 2*WHEELSIZE] \ 115 : &timeout_wheel[MASKWHEEL(3, (abs)) + 3*WHEELSIZE]) 116 117 #define MOVEBUCKET(wheel, time) \ 118 CIRCQ_APPEND(&timeout_todo, \ 119 &timeout_wheel[MASKWHEEL((wheel), (time)) + (wheel)*WHEELSIZE]) 120 121 /* 122 * All wheels are locked with the same lock (which must also block out all 123 * interrupts). 124 */ 125 kmutex_t callout_mutex; 126 127 /* 128 * Circular queue definitions. 129 */ 130 131 #define CIRCQ_INIT(list) \ 132 do { \ 133 (list)->cq_next_l = (list); \ 134 (list)->cq_prev_l = (list); \ 135 } while (/*CONSTCOND*/0) 136 137 #define CIRCQ_INSERT(elem, list) \ 138 do { \ 139 (elem)->cq_prev_e = (list)->cq_prev_e; \ 140 (elem)->cq_next_l = (list); \ 141 (list)->cq_prev_l->cq_next_l = (elem); \ 142 (list)->cq_prev_l = (elem); \ 143 } while (/*CONSTCOND*/0) 144 145 #define CIRCQ_APPEND(fst, snd) \ 146 do { \ 147 if (!CIRCQ_EMPTY(snd)) { \ 148 (fst)->cq_prev_l->cq_next_l = (snd)->cq_next_l; \ 149 (snd)->cq_next_l->cq_prev_l = (fst)->cq_prev_l; \ 150 (snd)->cq_prev_l->cq_next_l = (fst); \ 151 (fst)->cq_prev_l = (snd)->cq_prev_l; \ 152 CIRCQ_INIT(snd); \ 153 } \ 154 } while (/*CONSTCOND*/0) 155 156 #define CIRCQ_REMOVE(elem) \ 157 do { \ 158 (elem)->cq_next_l->cq_prev_e = (elem)->cq_prev_e; \ 159 (elem)->cq_prev_l->cq_next_e = (elem)->cq_next_e; \ 160 } while (/*CONSTCOND*/0) 161 162 #define CIRCQ_FIRST(list) ((list)->cq_next_e) 163 #define CIRCQ_NEXT(elem) ((elem)->cq_next_e) 164 #define CIRCQ_LAST(elem,list) ((elem)->cq_next_l == (list)) 165 #define CIRCQ_EMPTY(list) ((list)->cq_next_l == (list)) 166 167 /* 168 * Some of the "math" in here is a bit tricky. 169 * 170 * We have to beware of wrapping ints. 171 * We use the fact that any element added to the queue must be added with a 172 * positive time. That means that any element `to' on the queue cannot be 173 * scheduled to timeout further in time than INT_MAX, but c->c_time can 174 * be positive or negative so comparing it with anything is dangerous. 175 * The only way we can use the c->c_time value in any predictable way 176 * is when we calculate how far in the future `to' will timeout - 177 * "c->c_time - hardclock_ticks". The result will always be positive for 178 * future timeouts and 0 or negative for due timeouts. 179 */ 180 181 #ifdef CALLOUT_EVENT_COUNTERS 182 static struct evcnt callout_ev_late; 183 #endif 184 185 /* 186 * callout_barrier: 187 * 188 * If the callout is running on another CPU, busy wait until it 189 * completes. 190 */ 191 static inline void 192 callout_barrier(struct callout *c) 193 { 194 #ifdef MULTIPROCESSOR 195 void *oncpu; 196 197 LOCK_ASSERT(mutex_owned(&callout_mutex)); 198 199 /* 200 * The callout may have already been dispatched to run on the 201 * current CPU. It's possible for us to arrive here before it 202 * actually runs because the SPL is dropped from IPL_SCHED in 203 * softclock(), and IPL_SOFTCLOCK is low priority. We can't deal 204 * with that race easily, so for now the caller must deal with 205 * it. 206 */ 207 oncpu = c->c_oncpu; 208 if (oncpu != NULL && oncpu != curcpu()) { 209 mutex_exit(&callout_mutex); 210 while (c->c_oncpu != NULL) 211 ; 212 mutex_enter(&callout_mutex); 213 } 214 #endif 215 } 216 217 /* 218 * callout_startup: 219 * 220 * Initialize the callout facility, called at system startup time. 221 */ 222 void 223 callout_startup(void) 224 { 225 int b; 226 227 CIRCQ_INIT(&timeout_todo); 228 for (b = 0; b < BUCKETS; b++) 229 CIRCQ_INIT(&timeout_wheel[b]); 230 mutex_init(&callout_mutex, MUTEX_SPIN, IPL_SCHED); 231 232 #ifdef CALLOUT_EVENT_COUNTERS 233 evcnt_attach_dynamic(&callout_ev_late, EVCNT_TYPE_MISC, 234 NULL, "callout", "late"); 235 #endif 236 } 237 238 /* 239 * callout_init: 240 * 241 * Initialize a callout structure. 242 */ 243 void 244 callout_init(struct callout *c) 245 { 246 247 memset(c, 0, sizeof(*c)); 248 } 249 250 /* 251 * callout_reset: 252 * 253 * Reset a callout structure with a new function and argument, and 254 * schedule it to run. 255 */ 256 void 257 callout_reset(struct callout *c, int to_ticks, void (*func)(void *), void *arg) 258 { 259 int old_time; 260 261 KASSERT(to_ticks >= 0); 262 263 mutex_enter(&callout_mutex); 264 265 callout_barrier(c); 266 267 /* Initialize the time here, it won't change. */ 268 old_time = c->c_time; 269 c->c_time = to_ticks + hardclock_ticks; 270 c->c_flags &= ~(CALLOUT_FIRED|CALLOUT_INVOKING); 271 272 c->c_func = func; 273 c->c_arg = arg; 274 275 /* 276 * If this timeout is already scheduled and now is moved 277 * earlier, reschedule it now. Otherwise leave it in place 278 * and let it be rescheduled later. 279 */ 280 if (callout_pending(c)) { 281 if (c->c_time - old_time < 0) { 282 CIRCQ_REMOVE(&c->c_list); 283 CIRCQ_INSERT(&c->c_list, &timeout_todo); 284 } 285 } else { 286 c->c_flags |= CALLOUT_PENDING; 287 CIRCQ_INSERT(&c->c_list, &timeout_todo); 288 } 289 290 mutex_exit(&callout_mutex); 291 } 292 293 /* 294 * callout_schedule: 295 * 296 * Schedule a callout to run. The function and argument must 297 * already be set in the callout structure. 298 */ 299 void 300 callout_schedule(struct callout *c, int to_ticks) 301 { 302 int old_time; 303 304 KASSERT(to_ticks >= 0); 305 306 mutex_enter(&callout_mutex); 307 308 callout_barrier(c); 309 310 /* Initialize the time here, it won't change. */ 311 old_time = c->c_time; 312 c->c_time = to_ticks + hardclock_ticks; 313 c->c_flags &= ~(CALLOUT_FIRED|CALLOUT_INVOKING); 314 315 /* 316 * If this timeout is already scheduled and now is moved 317 * earlier, reschedule it now. Otherwise leave it in place 318 * and let it be rescheduled later. 319 */ 320 if (callout_pending(c)) { 321 if (c->c_time - old_time < 0) { 322 CIRCQ_REMOVE(&c->c_list); 323 CIRCQ_INSERT(&c->c_list, &timeout_todo); 324 } 325 } else { 326 c->c_flags |= CALLOUT_PENDING; 327 CIRCQ_INSERT(&c->c_list, &timeout_todo); 328 } 329 330 mutex_exit(&callout_mutex); 331 } 332 333 /* 334 * callout_stop: 335 * 336 * Cancel a pending callout. 337 */ 338 void 339 callout_stop(struct callout *c) 340 { 341 342 mutex_enter(&callout_mutex); 343 344 callout_barrier(c); 345 346 if (callout_pending(c)) 347 CIRCQ_REMOVE(&c->c_list); 348 349 c->c_flags &= ~(CALLOUT_PENDING|CALLOUT_FIRED); 350 351 mutex_exit(&callout_mutex); 352 } 353 354 /* 355 * This is called from hardclock() once every tick. 356 * We return !0 if we need to schedule a softclock. 357 */ 358 int 359 callout_hardclock(void) 360 { 361 int needsoftclock; 362 363 mutex_enter(&callout_mutex); 364 365 MOVEBUCKET(0, hardclock_ticks); 366 if (MASKWHEEL(0, hardclock_ticks) == 0) { 367 MOVEBUCKET(1, hardclock_ticks); 368 if (MASKWHEEL(1, hardclock_ticks) == 0) { 369 MOVEBUCKET(2, hardclock_ticks); 370 if (MASKWHEEL(2, hardclock_ticks) == 0) 371 MOVEBUCKET(3, hardclock_ticks); 372 } 373 } 374 375 needsoftclock = !CIRCQ_EMPTY(&timeout_todo); 376 mutex_exit(&callout_mutex); 377 378 return needsoftclock; 379 } 380 381 /* ARGSUSED */ 382 void 383 softclock(void *v) 384 { 385 struct cpu_info *ci; 386 struct callout *c; 387 void (*func)(void *); 388 void *arg; 389 390 ci = curcpu(); 391 392 mutex_enter(&callout_mutex); 393 394 while (!CIRCQ_EMPTY(&timeout_todo)) { 395 c = CIRCQ_FIRST(&timeout_todo); 396 CIRCQ_REMOVE(&c->c_list); 397 398 /* If due run it, otherwise insert it into the right bucket. */ 399 if (c->c_time - hardclock_ticks > 0) { 400 CIRCQ_INSERT(&c->c_list, 401 BUCKET((c->c_time - hardclock_ticks), c->c_time)); 402 } else { 403 #ifdef CALLOUT_EVENT_COUNTERS 404 if (c->c_time - hardclock_ticks < 0) 405 callout_ev_late.ev_count++; 406 #endif 407 c->c_flags = (c->c_flags & ~CALLOUT_PENDING) | 408 (CALLOUT_FIRED|CALLOUT_INVOKING); 409 410 func = c->c_func; 411 arg = c->c_arg; 412 413 #ifdef MULTIPROCESSOR 414 c->c_oncpu = ci; 415 #endif 416 mutex_exit(&callout_mutex); 417 (*func)(arg); 418 mutex_enter(&callout_mutex); 419 #ifdef MULTIPROCESSOR 420 c->c_oncpu = NULL; 421 #endif 422 } 423 } 424 425 mutex_exit(&callout_mutex); 426 } 427 428 #ifdef DDB 429 static void 430 db_show_callout_bucket(struct callout_circq *bucket) 431 { 432 struct callout *c; 433 db_expr_t offset; 434 const char *name; 435 static char question[] = "?"; 436 437 if (CIRCQ_EMPTY(bucket)) 438 return; 439 440 for (c = CIRCQ_FIRST(bucket); /*nothing*/; c = CIRCQ_NEXT(&c->c_list)) { 441 db_find_sym_and_offset((db_addr_t)(intptr_t)c->c_func, &name, 442 &offset); 443 name = name ? name : question; 444 #ifdef _LP64 445 #define POINTER_WIDTH "%16lx" 446 #else 447 #define POINTER_WIDTH "%8lx" 448 #endif 449 db_printf("%9d %2d/%-4d " POINTER_WIDTH " %s\n", 450 c->c_time - hardclock_ticks, 451 (int)((bucket - timeout_wheel) / WHEELSIZE), 452 (int)(bucket - timeout_wheel), (u_long) c->c_arg, name); 453 454 if (CIRCQ_LAST(&c->c_list, bucket)) 455 break; 456 } 457 } 458 459 void 460 db_show_callout(db_expr_t addr, int haddr, db_expr_t count, const char *modif) 461 { 462 int b; 463 464 db_printf("hardclock_ticks now: %d\n", hardclock_ticks); 465 #ifdef _LP64 466 db_printf(" ticks wheel arg func\n"); 467 #else 468 db_printf(" ticks wheel arg func\n"); 469 #endif 470 471 /* 472 * Don't lock the callwheel; all the other CPUs are paused 473 * anyhow, and we might be called in a circumstance where 474 * some other CPU was paused while holding the lock. 475 */ 476 477 db_show_callout_bucket(&timeout_todo); 478 for (b = 0; b < BUCKETS; b++) 479 db_show_callout_bucket(&timeout_wheel[b]); 480 } 481 #endif /* DDB */ 482
Indexes created Sat Sep 20 22:09:52 GMT 2025