kern_timeout.c revision 81481
1/*- 2 * Copyright (c) 1982, 1986, 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * (c) UNIX System Laboratories, Inc. 5 * All or some portions of this file are derived from material licensed 6 * to the University of California by American Telephone and Telegraph 7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 8 * the permission of UNIX System Laboratories, Inc. 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 University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 * 38 * From: @(#)kern_clock.c 8.5 (Berkeley) 1/21/94 39 * $FreeBSD: head/sys/kern/kern_timeout.c 81481 2001-08-10 21:06:59Z jhb $ 40 */ 41 42#include <sys/param.h> 43#include <sys/systm.h> 44#include <sys/callout.h> 45#include <sys/kernel.h> 46#include <sys/lock.h> 47#include <sys/mutex.h> 48 49/* 50 * TODO: 51 * allocate more timeout table slots when table overflows. 52 */ 53 54/* Exported to machdep.c and/or kern_clock.c. */ 55struct callout *callout; 56struct callout_list callfree; 57int callwheelsize, callwheelbits, callwheelmask; 58struct callout_tailq *callwheel; 59int softticks; /* Like ticks, but for softclock(). */ 60struct mtx callout_lock; 61 62static struct callout *nextsoftcheck; /* Next callout to be checked. */ 63 64/* 65 * The callout mechanism is based on the work of Adam M. Costello and 66 * George Varghese, published in a technical report entitled "Redesigning 67 * the BSD Callout and Timer Facilities" and modified slightly for inclusion 68 * in FreeBSD by Justin T. Gibbs. The original work on the data structures 69 * used in this implementation was published by G.Varghese and A. Lauck in 70 * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for 71 * the Efficient Implementation of a Timer Facility" in the Proceedings of 72 * the 11th ACM Annual Symposium on Operating Systems Principles, 73 * Austin, Texas Nov 1987. 74 */ 75 76/* 77 * Software (low priority) clock interrupt. 78 * Run periodic events from timeout queue. 79 */ 80void 81softclock(void *dummy) 82{ 83 register struct callout *c; 84 register struct callout_tailq *bucket; 85 register int curticks; 86 register int steps; /* #steps since we last allowed interrupts */ 87 88#ifndef MAX_SOFTCLOCK_STEPS 89#define MAX_SOFTCLOCK_STEPS 100 /* Maximum allowed value of steps. */ 90#endif /* MAX_SOFTCLOCK_STEPS */ 91 92 steps = 0; 93 mtx_lock_spin(&callout_lock); 94 while (softticks != ticks) { 95 softticks++; 96 /* 97 * softticks may be modified by hard clock, so cache 98 * it while we work on a given bucket. 99 */ 100 curticks = softticks; 101 bucket = &callwheel[curticks & callwheelmask]; 102 c = TAILQ_FIRST(bucket); 103 while (c) { 104 if (c->c_time != curticks) { 105 c = TAILQ_NEXT(c, c_links.tqe); 106 ++steps; 107 if (steps >= MAX_SOFTCLOCK_STEPS) { 108 nextsoftcheck = c; 109 /* Give interrupts a chance. */ 110 mtx_unlock_spin(&callout_lock); 111 ; /* nothing */ 112 mtx_lock_spin(&callout_lock); 113 c = nextsoftcheck; 114 steps = 0; 115 } 116 } else { 117 void (*c_func)(void *); 118 void *c_arg; 119 int c_flags; 120 121 nextsoftcheck = TAILQ_NEXT(c, c_links.tqe); 122 TAILQ_REMOVE(bucket, c, c_links.tqe); 123 c_func = c->c_func; 124 c_arg = c->c_arg; 125 c_flags = c->c_flags; 126 c->c_func = NULL; 127 if (c->c_flags & CALLOUT_LOCAL_ALLOC) { 128 c->c_flags = CALLOUT_LOCAL_ALLOC; 129 SLIST_INSERT_HEAD(&callfree, c, 130 c_links.sle); 131 } else { 132 c->c_flags = 133 (c->c_flags & ~CALLOUT_PENDING); 134 } 135 mtx_unlock_spin(&callout_lock); 136 if (!(c_flags & CALLOUT_MPSAFE)) 137 mtx_lock(&Giant); 138 c_func(c_arg); 139 if (!(c_flags & CALLOUT_MPSAFE)) 140 mtx_unlock(&Giant); 141 mtx_lock_spin(&callout_lock); 142 steps = 0; 143 c = nextsoftcheck; 144 } 145 } 146 } 147 nextsoftcheck = NULL; 148 mtx_unlock_spin(&callout_lock); 149} 150 151/* 152 * timeout -- 153 * Execute a function after a specified length of time. 154 * 155 * untimeout -- 156 * Cancel previous timeout function call. 157 * 158 * callout_handle_init -- 159 * Initialize a handle so that using it with untimeout is benign. 160 * 161 * See AT&T BCI Driver Reference Manual for specification. This 162 * implementation differs from that one in that although an 163 * identification value is returned from timeout, the original 164 * arguments to timeout as well as the identifier are used to 165 * identify entries for untimeout. 166 */ 167struct callout_handle 168timeout(ftn, arg, to_ticks) 169 timeout_t *ftn; 170 void *arg; 171 int to_ticks; 172{ 173 struct callout *new; 174 struct callout_handle handle; 175 176 mtx_lock_spin(&callout_lock); 177 178 /* Fill in the next free callout structure. */ 179 new = SLIST_FIRST(&callfree); 180 if (new == NULL) 181 /* XXX Attempt to malloc first */ 182 panic("timeout table full"); 183 SLIST_REMOVE_HEAD(&callfree, c_links.sle); 184 185 callout_reset(new, to_ticks, ftn, arg); 186 187 handle.callout = new; 188 mtx_unlock_spin(&callout_lock); 189 return (handle); 190} 191 192void 193untimeout(ftn, arg, handle) 194 timeout_t *ftn; 195 void *arg; 196 struct callout_handle handle; 197{ 198 199 /* 200 * Check for a handle that was initialized 201 * by callout_handle_init, but never used 202 * for a real timeout. 203 */ 204 if (handle.callout == NULL) 205 return; 206 207 mtx_lock_spin(&callout_lock); 208 if (handle.callout->c_func == ftn && handle.callout->c_arg == arg) 209 callout_stop(handle.callout); 210 mtx_unlock_spin(&callout_lock); 211} 212 213void 214callout_handle_init(struct callout_handle *handle) 215{ 216 handle->callout = NULL; 217} 218 219/* 220 * New interface; clients allocate their own callout structures. 221 * 222 * callout_reset() - establish or change a timeout 223 * callout_stop() - disestablish a timeout 224 * callout_init() - initialize a callout structure so that it can 225 * safely be passed to callout_reset() and callout_stop() 226 * 227 * <sys/callout.h> defines three convenience macros: 228 * 229 * callout_active() - returns truth if callout has not been serviced 230 * callout_pending() - returns truth if callout is still waiting for timeout 231 * callout_deactivate() - marks the callout as having been serviced 232 */ 233void 234callout_reset(c, to_ticks, ftn, arg) 235 struct callout *c; 236 int to_ticks; 237 void (*ftn) __P((void *)); 238 void *arg; 239{ 240 241 mtx_lock_spin(&callout_lock); 242 if (c->c_flags & CALLOUT_PENDING) 243 callout_stop(c); 244 245 /* 246 * We could unlock callout_lock here and lock it again before the 247 * TAILQ_INSERT_TAIL, but there's no point since doing this setup 248 * doesn't take much time. 249 */ 250 if (to_ticks <= 0) 251 to_ticks = 1; 252 253 c->c_arg = arg; 254 c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING); 255 c->c_func = ftn; 256 c->c_time = ticks + to_ticks; 257 TAILQ_INSERT_TAIL(&callwheel[c->c_time & callwheelmask], 258 c, c_links.tqe); 259 mtx_unlock_spin(&callout_lock); 260} 261 262int 263callout_stop(c) 264 struct callout *c; 265{ 266 267 mtx_lock_spin(&callout_lock); 268 /* 269 * Don't attempt to delete a callout that's not on the queue. 270 */ 271 if (!(c->c_flags & CALLOUT_PENDING)) { 272 c->c_flags &= ~CALLOUT_ACTIVE; 273 mtx_unlock_spin(&callout_lock); 274 return (0); 275 } 276 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING); 277 278 if (nextsoftcheck == c) { 279 nextsoftcheck = TAILQ_NEXT(c, c_links.tqe); 280 } 281 TAILQ_REMOVE(&callwheel[c->c_time & callwheelmask], c, c_links.tqe); 282 c->c_func = NULL; 283 284 if (c->c_flags & CALLOUT_LOCAL_ALLOC) { 285 SLIST_INSERT_HEAD(&callfree, c, c_links.sle); 286 } 287 mtx_unlock_spin(&callout_lock); 288 return (1); 289} 290 291void 292callout_init(c, mpsafe) 293 struct callout *c; 294 int mpsafe; 295{ 296 bzero(c, sizeof *c); 297 if (mpsafe) 298 c->c_flags |= CALLOUT_MPSAFE; 299} 300 301#ifdef APM_FIXUP_CALLTODO 302/* 303 * Adjust the kernel calltodo timeout list. This routine is used after 304 * an APM resume to recalculate the calltodo timer list values with the 305 * number of hz's we have been sleeping. The next hardclock() will detect 306 * that there are fired timers and run softclock() to execute them. 307 * 308 * Please note, I have not done an exhaustive analysis of what code this 309 * might break. I am motivated to have my select()'s and alarm()'s that 310 * have expired during suspend firing upon resume so that the applications 311 * which set the timer can do the maintanence the timer was for as close 312 * as possible to the originally intended time. Testing this code for a 313 * week showed that resuming from a suspend resulted in 22 to 25 timers 314 * firing, which seemed independant on whether the suspend was 2 hours or 315 * 2 days. Your milage may vary. - Ken Key <key@cs.utk.edu> 316 */ 317void 318adjust_timeout_calltodo(time_change) 319 struct timeval *time_change; 320{ 321 register struct callout *p; 322 unsigned long delta_ticks; 323 324 /* 325 * How many ticks were we asleep? 326 * (stolen from tvtohz()). 327 */ 328 329 /* Don't do anything */ 330 if (time_change->tv_sec < 0) 331 return; 332 else if (time_change->tv_sec <= LONG_MAX / 1000000) 333 delta_ticks = (time_change->tv_sec * 1000000 + 334 time_change->tv_usec + (tick - 1)) / tick + 1; 335 else if (time_change->tv_sec <= LONG_MAX / hz) 336 delta_ticks = time_change->tv_sec * hz + 337 (time_change->tv_usec + (tick - 1)) / tick + 1; 338 else 339 delta_ticks = LONG_MAX; 340 341 if (delta_ticks > INT_MAX) 342 delta_ticks = INT_MAX; 343 344 /* 345 * Now rip through the timer calltodo list looking for timers 346 * to expire. 347 */ 348 349 /* don't collide with softclock() */ 350 mtx_lock_spin(&callout_lock); 351 for (p = calltodo.c_next; p != NULL; p = p->c_next) { 352 p->c_time -= delta_ticks; 353 354 /* Break if the timer had more time on it than delta_ticks */ 355 if (p->c_time > 0) 356 break; 357 358 /* take back the ticks the timer didn't use (p->c_time <= 0) */ 359 delta_ticks = -p->c_time; 360 } 361 mtx_unlock_spin(&callout_lock); 362 363 return; 364} 365#endif /* APM_FIXUP_CALLTODO */ 366