/* $OpenBSD: kern_timeout.c,v 1.22 2004/12/28 22:48:30 deraadt Exp $ */ /* * Copyright (c) 2001 Thomas Nordin * Copyright (c) 2000-2001 Artur Grabowski * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. The name of the author may not be used to endorse or promote products * derived from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL * THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #include #include #include #include #include #ifdef DDB #include #include #include #include #include #endif /* * Timeouts are kept in a hierarchical timing wheel. The to_time is the value * of the global variable "ticks" when the timeout should be called. There are * four levels with 256 buckets each. See 'Scheme 7' in * "Hashed and Hierarchical Timing Wheels: Efficient Data Structures for * Implementing a Timer Facility" by George Varghese and Tony Lauck. */ #define BUCKETS 1024 #define WHEELSIZE 256 #define WHEELMASK 255 #define WHEELBITS 8 struct circq timeout_wheel[BUCKETS]; /* Queues of timeouts */ struct circq timeout_todo; /* Worklist */ #define MASKWHEEL(wheel, time) (((time) >> ((wheel)*WHEELBITS)) & WHEELMASK) #define BUCKET(rel, abs) \ (timeout_wheel[ \ ((rel) <= (1 << (2*WHEELBITS))) \ ? ((rel) <= (1 << WHEELBITS)) \ ? MASKWHEEL(0, (abs)) \ : MASKWHEEL(1, (abs)) + WHEELSIZE \ : ((rel) <= (1 << (3*WHEELBITS))) \ ? MASKWHEEL(2, (abs)) + 2*WHEELSIZE \ : MASKWHEEL(3, (abs)) + 3*WHEELSIZE]) #define MOVEBUCKET(wheel, time) \ CIRCQ_APPEND(&timeout_todo, \ &timeout_wheel[MASKWHEEL((wheel), (time)) + (wheel)*WHEELSIZE]) /* * All wheels are locked with the same mutex. * * We need locking since the timeouts are manipulated from hardclock that's * not behind the big lock. */ struct mutex timeout_mutex = MUTEX_INITIALIZER(IPL_HIGH); /* * Circular queue definitions. */ #define CIRCQ_INIT(elem) do { \ (elem)->next = (elem); \ (elem)->prev = (elem); \ } while (0) #define CIRCQ_INSERT(elem, list) do { \ (elem)->prev = (list)->prev; \ (elem)->next = (list); \ (list)->prev->next = (elem); \ (list)->prev = (elem); \ } while (0) #define CIRCQ_APPEND(fst, snd) do { \ if (!CIRCQ_EMPTY(snd)) { \ (fst)->prev->next = (snd)->next;\ (snd)->next->prev = (fst)->prev;\ (snd)->prev->next = (fst); \ (fst)->prev = (snd)->prev; \ CIRCQ_INIT(snd); \ } \ } while (0) #define CIRCQ_REMOVE(elem) do { \ (elem)->next->prev = (elem)->prev; \ (elem)->prev->next = (elem)->next; \ } while (0) #define CIRCQ_FIRST(elem) ((elem)->next) #define CIRCQ_EMPTY(elem) (CIRCQ_FIRST(elem) == (elem)) /* * Some of the "math" in here is a bit tricky. * * We have to beware of wrapping ints. * We use the fact that any element added to the queue must be added with a * positive time. That means that any element `to' on the queue cannot be * scheduled to timeout further in time than INT_MAX, but to->to_time can * be positive or negative so comparing it with anything is dangerous. * The only way we can use the to->to_time value in any predictable way * is when we calculate how far in the future `to' will timeout - * "to->to_time - ticks". The result will always be positive for future * timeouts and 0 or negative for due timeouts. */ extern int ticks; /* XXX - move to sys/X.h */ void timeout_startup(void) { int b; CIRCQ_INIT(&timeout_todo); for (b = 0; b < BUCKETS; b++) CIRCQ_INIT(&timeout_wheel[b]); } void timeout_set(struct timeout *new, void (*fn)(void *), void *arg) { new->to_func = fn; new->to_arg = arg; new->to_flags = TIMEOUT_INITIALIZED; } void timeout_add(struct timeout *new, int to_ticks) { int old_time; #ifdef DIAGNOSTIC if (!(new->to_flags & TIMEOUT_INITIALIZED)) panic("timeout_add: not initialized"); if (to_ticks < 0) panic("timeout_add: to_ticks (%d) < 0", to_ticks); #endif mtx_enter(&timeout_mutex); /* Initialize the time here, it won't change. */ old_time = new->to_time; new->to_time = to_ticks + ticks; new->to_flags &= ~TIMEOUT_TRIGGERED; /* * If this timeout already is scheduled and now is moved * earlier, reschedule it now. Otherwise leave it in place * and let it be rescheduled later. */ if (new->to_flags & TIMEOUT_ONQUEUE) { if (new->to_time - ticks < old_time - ticks) { CIRCQ_REMOVE(&new->to_list); CIRCQ_INSERT(&new->to_list, &timeout_todo); } } else { new->to_flags |= TIMEOUT_ONQUEUE; CIRCQ_INSERT(&new->to_list, &timeout_todo); } mtx_leave(&timeout_mutex); } void timeout_del(struct timeout *to) { mtx_enter(&timeout_mutex); if (to->to_flags & TIMEOUT_ONQUEUE) { CIRCQ_REMOVE(&to->to_list); to->to_flags &= ~TIMEOUT_ONQUEUE; } to->to_flags &= ~TIMEOUT_TRIGGERED; mtx_leave(&timeout_mutex); } /* * This is called from hardclock() once every tick. * We return !0 if we need to schedule a softclock. */ int timeout_hardclock_update(void) { int ret; mtx_enter(&timeout_mutex); ticks++; MOVEBUCKET(0, ticks); if (MASKWHEEL(0, ticks) == 0) { MOVEBUCKET(1, ticks); if (MASKWHEEL(1, ticks) == 0) { MOVEBUCKET(2, ticks); if (MASKWHEEL(2, ticks) == 0) MOVEBUCKET(3, ticks); } } ret = !CIRCQ_EMPTY(&timeout_todo); mtx_leave(&timeout_mutex); return (ret); } void softclock(void) { struct timeout *to; void (*fn)(void *); void *arg; mtx_enter(&timeout_mutex); while (!CIRCQ_EMPTY(&timeout_todo)) { to = (struct timeout *)CIRCQ_FIRST(&timeout_todo); /* XXX */ CIRCQ_REMOVE(&to->to_list); /* If due run it, otherwise insert it into the right bucket. */ if (to->to_time - ticks > 0) { CIRCQ_INSERT(&to->to_list, &BUCKET((to->to_time - ticks), to->to_time)); } else { #ifdef DEBUG if (to->to_time - ticks < 0) printf("timeout delayed %d\n", to->to_time - ticks); #endif to->to_flags &= ~TIMEOUT_ONQUEUE; to->to_flags |= TIMEOUT_TRIGGERED; fn = to->to_func; arg = to->to_arg; mtx_leave(&timeout_mutex); fn(arg); mtx_enter(&timeout_mutex); } } mtx_leave(&timeout_mutex); } #ifdef DDB void db_show_callout_bucket(struct circq *); void db_show_callout_bucket(struct circq *bucket) { struct timeout *to; struct circq *p; db_expr_t offset; char *name; for (p = CIRCQ_FIRST(bucket); p != bucket; p = CIRCQ_FIRST(p)) { to = (struct timeout *)p; /* XXX */ db_find_sym_and_offset((db_addr_t)to->to_func, &name, &offset); name = name ? name : "?"; db_printf("%9d %2d/%-4d %8x %s\n", to->to_time - ticks, (bucket - timeout_wheel) / WHEELSIZE, bucket - timeout_wheel, to->to_arg, name); } } void db_show_callout(db_expr_t addr, int haddr, db_expr_t count, char *modif) { int b; db_printf("ticks now: %d\n", ticks); db_printf(" ticks wheel arg func\n"); mtx_enter(&timeout_mutex); db_show_callout_bucket(&timeout_todo); for (b = 0; b < BUCKETS; b++) db_show_callout_bucket(&timeout_wheel[b]); mtx_leave(&timeout_mutex); } #endif