1 /* $OpenBSD: kern_timeout.c,v 1.19 2004/07/20 20:20:52 art 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 34 #ifdef DDB 35 #include <machine/db_machdep.h> 36 #include <ddb/db_interface.h> 37 #include <ddb/db_access.h> 38 #include <ddb/db_sym.h> 39 #include <ddb/db_output.h> 40 #endif 41 42 /* 43 * Timeouts are kept in a hierarchical timing wheel. The to_time is the value 44 * of the global variable "ticks" when the timeout should be called. There are 45 * four levels with 256 buckets each. See 'Scheme 7' in 46 * "Hashed and Hierarchical Timing Wheels: Efficient Data Structures for 47 * Implementing a Timer Facility" by George Varghese and Tony Lauck. 48 */ 49 #define BUCKETS 1024 50 #define WHEELSIZE 256 51 #define WHEELMASK 255 52 #define WHEELBITS 8 53 54 struct circq timeout_wheel[BUCKETS]; /* Queues of timeouts */ 55 struct circq timeout_todo; /* Worklist */ 56 57 #define MASKWHEEL(wheel, time) (((time) >> ((wheel)*WHEELBITS)) & WHEELMASK) 58 59 #define BUCKET(rel, abs) \ 60 (((rel) <= (1 << (2*WHEELBITS))) \ 61 ? ((rel) <= (1 << WHEELBITS)) \ 62 ? timeout_wheel[MASKWHEEL(0, (abs))] \ 63 : timeout_wheel[MASKWHEEL(1, (abs)) + WHEELSIZE] \ 64 : ((rel) <= (1 << (3*WHEELBITS))) \ 65 ? timeout_wheel[MASKWHEEL(2, (abs)) + 2*WHEELSIZE] \ 66 : timeout_wheel[MASKWHEEL(3, (abs)) + 3*WHEELSIZE]) 67 68 #define MOVEBUCKET(wheel, time) \ 69 CIRCQ_APPEND(&timeout_todo, \ 70 &timeout_wheel[MASKWHEEL((wheel), (time)) + (wheel)*WHEELSIZE]) 71 72 /* 73 * All wheels are locked with the same mutex. 74 * 75 * We need locking since the timeouts are manipulated from hardclock that's 76 * not behind the big lock. 77 */ 78 struct mutex timeout_mutex = MUTEX_INITIALIZER(IPL_HIGH); 79 80 /* 81 * Circular queue definitions. 82 */ 83 84 #define CIRCQ_INIT(elem) do { \ 85 (elem)->next = (elem); \ 86 (elem)->prev = (elem); \ 87 } while (0) 88 89 #define CIRCQ_INSERT(elem, list) do { \ 90 (elem)->prev = (list)->prev; \ 91 (elem)->next = (list); \ 92 (list)->prev->next = (elem); \ 93 (list)->prev = (elem); \ 94 } while (0) 95 96 #define CIRCQ_APPEND(fst, snd) do { \ 97 if (!CIRCQ_EMPTY(snd)) { \ 98 (fst)->prev->next = (snd)->next;\ 99 (snd)->next->prev = (fst)->prev;\ 100 (snd)->prev->next = (fst); \ 101 (fst)->prev = (snd)->prev; \ 102 CIRCQ_INIT(snd); \ 103 } \ 104 } while (0) 105 106 #define CIRCQ_REMOVE(elem) do { \ 107 (elem)->next->prev = (elem)->prev; \ 108 (elem)->prev->next = (elem)->next; \ 109 } while (0) 110 111 #define CIRCQ_FIRST(elem) ((elem)->next) 112 113 #define CIRCQ_EMPTY(elem) (CIRCQ_FIRST(elem) == (elem)) 114 115 /* 116 * Some of the "math" in here is a bit tricky. 117 * 118 * We have to beware of wrapping ints. 119 * We use the fact that any element added to the queue must be added with a 120 * positive time. That means that any element `to' on the queue cannot be 121 * scheduled to timeout further in time than INT_MAX, but to->to_time can 122 * be positive or negative so comparing it with anything is dangerous. 123 * The only way we can use the to->to_time value in any predictable way 124 * is when we calculate how far in the future `to' will timeout - 125 * "to->to_time - ticks". The result will always be positive for future 126 * timeouts and 0 or negative for due timeouts. 127 */ 128 extern int ticks; /* XXX - move to sys/X.h */ 129 130 void 131 timeout_startup(void) 132 { 133 int b; 134 135 CIRCQ_INIT(&timeout_todo); 136 for (b = 0; b < BUCKETS; b++) 137 CIRCQ_INIT(&timeout_wheel[b]); 138 } 139 140 void 141 timeout_set(struct timeout *new, void (*fn)(void *), void *arg) 142 { 143 new->to_func = fn; 144 new->to_arg = arg; 145 new->to_flags = TIMEOUT_INITIALIZED; 146 } 147 148 149 void 150 timeout_add(struct timeout *new, int to_ticks) 151 { 152 int old_time; 153 154 #ifdef DIAGNOSTIC 155 if (!(new->to_flags & TIMEOUT_INITIALIZED)) 156 panic("timeout_add: not initialized"); 157 if (to_ticks < 0) 158 panic("timeout_add: to_ticks < 0"); 159 #endif 160 161 mtx_enter(&timeout_mutex); 162 /* Initialize the time here, it won't change. */ 163 old_time = new->to_time; 164 new->to_time = to_ticks + ticks; 165 new->to_flags &= ~TIMEOUT_TRIGGERED; 166 167 /* 168 * If this timeout already is scheduled and now is moved 169 * earlier, reschedule it now. Otherwise leave it in place 170 * and let it be rescheduled later. 171 */ 172 if (new->to_flags & TIMEOUT_ONQUEUE) { 173 if (new->to_time - ticks < old_time - ticks) { 174 CIRCQ_REMOVE(&new->to_list); 175 CIRCQ_INSERT(&new->to_list, &timeout_todo); 176 } 177 } else { 178 new->to_flags |= TIMEOUT_ONQUEUE; 179 CIRCQ_INSERT(&new->to_list, &timeout_todo); 180 } 181 mtx_leave(&timeout_mutex); 182 } 183 184 void 185 timeout_del(struct timeout *to) 186 { 187 mtx_enter(&timeout_mutex); 188 if (to->to_flags & TIMEOUT_ONQUEUE) { 189 CIRCQ_REMOVE(&to->to_list); 190 to->to_flags &= ~TIMEOUT_ONQUEUE; 191 } 192 to->to_flags &= ~TIMEOUT_TRIGGERED; 193 mtx_leave(&timeout_mutex); 194 } 195 196 /* 197 * This is called from hardclock() once every tick. 198 * We return !0 if we need to schedule a softclock. 199 */ 200 int 201 timeout_hardclock_update(void) 202 { 203 mtx_enter(&timeout_mutex); 204 MOVEBUCKET(0, ticks); 205 if (MASKWHEEL(0, ticks) == 0) { 206 MOVEBUCKET(1, ticks); 207 if (MASKWHEEL(1, ticks) == 0) { 208 MOVEBUCKET(2, ticks); 209 if (MASKWHEEL(2, ticks) == 0) 210 MOVEBUCKET(3, ticks); 211 } 212 } 213 mtx_leave(&timeout_mutex); 214 return (!CIRCQ_EMPTY(&timeout_todo)); 215 } 216 217 void 218 softclock(void) 219 { 220 struct timeout *to; 221 void (*fn)(void *); 222 void *arg; 223 224 mtx_enter(&timeout_mutex); 225 while (!CIRCQ_EMPTY(&timeout_todo)) { 226 227 to = (struct timeout *)CIRCQ_FIRST(&timeout_todo); /* XXX */ 228 CIRCQ_REMOVE(&to->to_list); 229 230 /* If due run it, otherwise insert it into the right bucket. */ 231 if (to->to_time - ticks > 0) { 232 CIRCQ_INSERT(&to->to_list, 233 &BUCKET((to->to_time - ticks), to->to_time)); 234 } else { 235 #ifdef DEBUG 236 if (to->to_time - ticks < 0) 237 printf("timeout delayed %d\n", to->to_time - 238 ticks); 239 #endif 240 to->to_flags &= ~TIMEOUT_ONQUEUE; 241 to->to_flags |= TIMEOUT_TRIGGERED; 242 243 fn = to->to_func; 244 arg = to->to_arg; 245 246 mtx_leave(&timeout_mutex); 247 fn(arg); 248 mtx_enter(&timeout_mutex); 249 } 250 } 251 mtx_leave(&timeout_mutex); 252 } 253 254 #ifdef DDB 255 void db_show_callout_bucket(struct circq *); 256 257 void 258 db_show_callout_bucket(struct circq *bucket) 259 { 260 struct timeout *to; 261 struct circq *p; 262 db_expr_t offset; 263 char *name; 264 265 for (p = CIRCQ_FIRST(bucket); p != bucket; p = CIRCQ_FIRST(p)) { 266 to = (struct timeout *)p; /* XXX */ 267 db_find_sym_and_offset((db_addr_t)to->to_func, &name, &offset); 268 name = name ? name : "?"; 269 db_printf("%9d %2d/%-4d %8x %s\n", to->to_time - ticks, 270 (bucket - timeout_wheel) / WHEELSIZE, 271 bucket - timeout_wheel, to->to_arg, name); 272 } 273 } 274 275 void 276 db_show_callout(db_expr_t addr, int haddr, db_expr_t count, char *modif) 277 { 278 int b; 279 280 db_printf("ticks now: %d\n", ticks); 281 db_printf(" ticks wheel arg func\n"); 282 283 mtx_enter(&timeout_mutex); 284 db_show_callout_bucket(&timeout_todo); 285 for (b = 0; b < BUCKETS; b++) 286 db_show_callout_bucket(&timeout_wheel[b]); 287 mtx_leave(&timeout_mutex); 288 } 289 #endif 290