1 /* $OpenBSD: kern_timeout.c,v 1.25 2006/07/19 20:25:08 miod Exp $ */ 2 /* 3 * Copyright (c) 2001 Thomas Nordin <nordin@openbsd.org> 4 * Copyright (c) 2000-2001 Artur Grabowski <art@openbsd.org> 5 * All rights reserved. 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. The name of the author may not be used to endorse or promote products 14 * derived from this software without specific prior written permission. 15 * 16 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, 17 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY 18 * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL 19 * THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 20 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 21 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; 22 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 23 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR 24 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 25 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 */ 27 28 #include <sys/param.h> 29 #include <sys/systm.h> 30 #include <sys/lock.h> 31 #include <sys/timeout.h> 32 #include <sys/mutex.h> 33 #include <sys/queue.h> 34 35 #ifdef DDB 36 #include <machine/db_machdep.h> 37 #include <ddb/db_interface.h> 38 #include <ddb/db_access.h> 39 #include <ddb/db_sym.h> 40 #include <ddb/db_output.h> 41 #endif 42 43 /* 44 * Timeouts are kept in a hierarchical timing wheel. The to_time is the value 45 * of the global variable "ticks" when the timeout should be called. There are 46 * four levels with 256 buckets each. See 'Scheme 7' in 47 * "Hashed and Hierarchical Timing Wheels: Efficient Data Structures for 48 * Implementing a Timer Facility" by George Varghese and Tony Lauck. 49 */ 50 #define BUCKETS 1024 51 #define WHEELSIZE 256 52 #define WHEELMASK 255 53 #define WHEELBITS 8 54 55 struct circq timeout_wheel[BUCKETS]; /* Queues of timeouts */ 56 struct circq timeout_todo; /* Worklist */ 57 58 #define MASKWHEEL(wheel, time) (((time) >> ((wheel)*WHEELBITS)) & WHEELMASK) 59 60 #define BUCKET(rel, abs) \ 61 (timeout_wheel[ \ 62 ((rel) <= (1 << (2*WHEELBITS))) \ 63 ? ((rel) <= (1 << WHEELBITS)) \ 64 ? MASKWHEEL(0, (abs)) \ 65 : MASKWHEEL(1, (abs)) + WHEELSIZE \ 66 : ((rel) <= (1 << (3*WHEELBITS))) \ 67 ? MASKWHEEL(2, (abs)) + 2*WHEELSIZE \ 68 : MASKWHEEL(3, (abs)) + 3*WHEELSIZE]) 69 70 #define MOVEBUCKET(wheel, time) \ 71 CIRCQ_APPEND(&timeout_todo, \ 72 &timeout_wheel[MASKWHEEL((wheel), (time)) + (wheel)*WHEELSIZE]) 73 74 /* 75 * All wheels are locked with the same mutex. 76 * 77 * We need locking since the timeouts are manipulated from hardclock that's 78 * not behind the big lock. 79 */ 80 struct mutex timeout_mutex = MUTEX_INITIALIZER(IPL_HIGH); 81 82 /* 83 * Circular queue definitions. 84 */ 85 86 #define CIRCQ_INIT(elem) do { \ 87 (elem)->next = (elem); \ 88 (elem)->prev = (elem); \ 89 } while (0) 90 91 #define CIRCQ_INSERT(elem, list) do { \ 92 (elem)->prev = (list)->prev; \ 93 (elem)->next = (list); \ 94 (list)->prev->next = (elem); \ 95 (list)->prev = (elem); \ 96 } while (0) 97 98 #define CIRCQ_APPEND(fst, snd) do { \ 99 if (!CIRCQ_EMPTY(snd)) { \ 100 (fst)->prev->next = (snd)->next;\ 101 (snd)->next->prev = (fst)->prev;\ 102 (snd)->prev->next = (fst); \ 103 (fst)->prev = (snd)->prev; \ 104 CIRCQ_INIT(snd); \ 105 } \ 106 } while (0) 107 108 #define CIRCQ_REMOVE(elem) do { \ 109 (elem)->next->prev = (elem)->prev; \ 110 (elem)->prev->next = (elem)->next; \ 111 _Q_INVALIDATE((elem)->prev); \ 112 _Q_INVALIDATE((elem)->next); \ 113 } while (0) 114 115 #define CIRCQ_FIRST(elem) ((elem)->next) 116 117 #define CIRCQ_EMPTY(elem) (CIRCQ_FIRST(elem) == (elem)) 118 119 /* 120 * Some of the "math" in here is a bit tricky. 121 * 122 * We have to beware of wrapping ints. 123 * We use the fact that any element added to the queue must be added with a 124 * positive time. That means that any element `to' on the queue cannot be 125 * scheduled to timeout further in time than INT_MAX, but to->to_time can 126 * be positive or negative so comparing it with anything is dangerous. 127 * The only way we can use the to->to_time value in any predictable way 128 * is when we calculate how far in the future `to' will timeout - 129 * "to->to_time - ticks". The result will always be positive for future 130 * timeouts and 0 or negative for due timeouts. 131 */ 132 extern int ticks; /* XXX - move to sys/X.h */ 133 134 void 135 timeout_startup(void) 136 { 137 int b; 138 139 CIRCQ_INIT(&timeout_todo); 140 for (b = 0; b < BUCKETS; b++) 141 CIRCQ_INIT(&timeout_wheel[b]); 142 } 143 144 void 145 timeout_set(struct timeout *new, void (*fn)(void *), void *arg) 146 { 147 new->to_func = fn; 148 new->to_arg = arg; 149 new->to_flags = TIMEOUT_INITIALIZED; 150 } 151 152 153 void 154 timeout_add(struct timeout *new, int to_ticks) 155 { 156 int old_time; 157 158 #ifdef DIAGNOSTIC 159 if (!(new->to_flags & TIMEOUT_INITIALIZED)) 160 panic("timeout_add: not initialized"); 161 if (to_ticks < 0) 162 panic("timeout_add: to_ticks (%d) < 0", to_ticks); 163 #endif 164 165 mtx_enter(&timeout_mutex); 166 /* Initialize the time here, it won't change. */ 167 old_time = new->to_time; 168 new->to_time = to_ticks + ticks; 169 new->to_flags &= ~TIMEOUT_TRIGGERED; 170 171 /* 172 * If this timeout already is scheduled and now is moved 173 * earlier, reschedule it now. Otherwise leave it in place 174 * and let it be rescheduled later. 175 */ 176 if (new->to_flags & TIMEOUT_ONQUEUE) { 177 if (new->to_time - ticks < old_time - ticks) { 178 CIRCQ_REMOVE(&new->to_list); 179 CIRCQ_INSERT(&new->to_list, &timeout_todo); 180 } 181 } else { 182 new->to_flags |= TIMEOUT_ONQUEUE; 183 CIRCQ_INSERT(&new->to_list, &timeout_todo); 184 } 185 mtx_leave(&timeout_mutex); 186 } 187 188 void 189 timeout_del(struct timeout *to) 190 { 191 mtx_enter(&timeout_mutex); 192 if (to->to_flags & TIMEOUT_ONQUEUE) { 193 CIRCQ_REMOVE(&to->to_list); 194 to->to_flags &= ~TIMEOUT_ONQUEUE; 195 } 196 to->to_flags &= ~TIMEOUT_TRIGGERED; 197 mtx_leave(&timeout_mutex); 198 } 199 200 /* 201 * This is called from hardclock() once every tick. 202 * We return !0 if we need to schedule a softclock. 203 */ 204 int 205 timeout_hardclock_update(void) 206 { 207 int ret; 208 209 mtx_enter(&timeout_mutex); 210 211 ticks++; 212 213 MOVEBUCKET(0, ticks); 214 if (MASKWHEEL(0, ticks) == 0) { 215 MOVEBUCKET(1, ticks); 216 if (MASKWHEEL(1, ticks) == 0) { 217 MOVEBUCKET(2, ticks); 218 if (MASKWHEEL(2, ticks) == 0) 219 MOVEBUCKET(3, ticks); 220 } 221 } 222 ret = !CIRCQ_EMPTY(&timeout_todo); 223 mtx_leave(&timeout_mutex); 224 225 return (ret); 226 } 227 228 void 229 softclock(void) 230 { 231 struct timeout *to; 232 void (*fn)(void *); 233 void *arg; 234 235 mtx_enter(&timeout_mutex); 236 while (!CIRCQ_EMPTY(&timeout_todo)) { 237 238 to = (struct timeout *)CIRCQ_FIRST(&timeout_todo); /* XXX */ 239 CIRCQ_REMOVE(&to->to_list); 240 241 /* If due run it, otherwise insert it into the right bucket. */ 242 if (to->to_time - ticks > 0) { 243 CIRCQ_INSERT(&to->to_list, 244 &BUCKET((to->to_time - ticks), to->to_time)); 245 } else { 246 #ifdef DEBUG 247 if (to->to_time - ticks < 0) 248 printf("timeout delayed %d\n", to->to_time - 249 ticks); 250 #endif 251 to->to_flags &= ~TIMEOUT_ONQUEUE; 252 to->to_flags |= TIMEOUT_TRIGGERED; 253 254 fn = to->to_func; 255 arg = to->to_arg; 256 257 mtx_leave(&timeout_mutex); 258 fn(arg); 259 mtx_enter(&timeout_mutex); 260 } 261 } 262 mtx_leave(&timeout_mutex); 263 } 264 265 #ifdef DDB 266 void db_show_callout_bucket(struct circq *); 267 268 void 269 db_show_callout_bucket(struct circq *bucket) 270 { 271 struct timeout *to; 272 struct circq *p; 273 db_expr_t offset; 274 char *name; 275 276 for (p = CIRCQ_FIRST(bucket); p != bucket; p = CIRCQ_FIRST(p)) { 277 to = (struct timeout *)p; /* XXX */ 278 db_find_sym_and_offset((db_addr_t)to->to_func, &name, &offset); 279 name = name ? name : "?"; 280 db_printf("%9d %2d/%-4d %8x %s\n", to->to_time - ticks, 281 (bucket - timeout_wheel) / WHEELSIZE, 282 bucket - timeout_wheel, to->to_arg, name); 283 } 284 } 285 286 void 287 db_show_callout(db_expr_t addr, int haddr, db_expr_t count, char *modif) 288 { 289 int b; 290 291 db_printf("ticks now: %d\n", ticks); 292 db_printf(" ticks wheel arg func\n"); 293 294 mtx_enter(&timeout_mutex); 295 db_show_callout_bucket(&timeout_todo); 296 for (b = 0; b < BUCKETS; b++) 297 db_show_callout_bucket(&timeout_wheel[b]); 298 mtx_leave(&timeout_mutex); 299 } 300 #endif 301