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38 * From: @(#)kern_clock.c 8.5 (Berkeley) 1/21/94
39 * $FreeBSD: src/sys/kern/kern_timeout.c,v 1.59.2.1 2001/11/13 18:24:52 archie Exp $
42 #include <sys/param.h>
43 #include <sys/systm.h>
44 #include <sys/callout.h>
45 #include <sys/kernel.h>
49 * allocate more timeout table slots when table overflows.
52 /* Exported to machdep.c and/or kern_clock.c. */
53 struct callout *callout;
54 struct callout_list callfree;
55 int callwheelsize, callwheelbits, callwheelmask;
56 struct callout_tailq *callwheel;
57 int softticks; /* Like ticks, but for softclock(). */
59 static struct callout *nextsoftcheck; /* Next callout to be checked. */
62 * The callout mechanism is based on the work of Adam M. Costello and
63 * George Varghese, published in a technical report entitled "Redesigning
64 * the BSD Callout and Timer Facilities" and modified slightly for inclusion
65 * in FreeBSD by Justin T. Gibbs. The original work on the data structures
66 * used in this implementation was published by G.Varghese and A. Lauck in
67 * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for
68 * the Efficient Implementation of a Timer Facility" in the Proceedings of
69 * the 11th ACM Annual Symposium on Operating Systems Principles,
70 * Austin, Texas Nov 1987.
74 * Software (low priority) clock interrupt.
75 * Run periodic events from timeout queue.
80 register struct callout *c;
81 register struct callout_tailq *bucket;
83 register int curticks;
84 register int steps; /* #steps since we last allowed interrupts */
86 #ifndef MAX_SOFTCLOCK_STEPS
87 #define MAX_SOFTCLOCK_STEPS 100 /* Maximum allowed value of steps. */
88 #endif /* MAX_SOFTCLOCK_STEPS */
92 while (softticks != ticks) {
95 * softticks may be modified by hard clock, so cache
96 * it while we work on a given bucket.
99 bucket = &callwheel[curticks & callwheelmask];
100 c = TAILQ_FIRST(bucket);
102 if (c->c_time != curticks) {
103 c = TAILQ_NEXT(c, c_links.tqe);
105 if (steps >= MAX_SOFTCLOCK_STEPS) {
107 /* Give interrupts a chance. */
114 void (*c_func)(void *);
117 nextsoftcheck = TAILQ_NEXT(c, c_links.tqe);
118 TAILQ_REMOVE(bucket, c, c_links.tqe);
122 if (c->c_flags & CALLOUT_LOCAL_ALLOC) {
123 c->c_flags = CALLOUT_LOCAL_ALLOC;
124 SLIST_INSERT_HEAD(&callfree, c,
128 (c->c_flags & ~CALLOUT_PENDING);
138 nextsoftcheck = NULL;
144 * Execute a function after a specified length of time.
147 * Cancel previous timeout function call.
149 * callout_handle_init --
150 * Initialize a handle so that using it with untimeout is benign.
152 * See AT&T BCI Driver Reference Manual for specification. This
153 * implementation differs from that one in that although an
154 * identification value is returned from timeout, the original
155 * arguments to timeout as well as the identifier are used to
156 * identify entries for untimeout.
158 struct callout_handle
159 timeout(ftn, arg, to_ticks)
162 register int to_ticks;
166 struct callout_handle handle;
170 /* Fill in the next free callout structure. */
171 new = SLIST_FIRST(&callfree);
173 /* XXX Attempt to malloc first */
174 panic("timeout table full");
175 SLIST_REMOVE_HEAD(&callfree, c_links.sle);
177 callout_reset(new, to_ticks, ftn, arg);
179 handle.callout = new;
185 untimeout(ftn, arg, handle)
188 struct callout_handle handle;
193 * Check for a handle that was initialized
194 * by callout_handle_init, but never used
195 * for a real timeout.
197 if (handle.callout == NULL)
201 if (handle.callout->c_func == ftn && handle.callout->c_arg == arg)
202 callout_stop(handle.callout);
207 callout_handle_init(struct callout_handle *handle)
209 handle->callout = NULL;
213 * New interface; clients allocate their own callout structures.
215 * callout_reset() - establish or change a timeout
216 * callout_stop() - disestablish a timeout
217 * callout_init() - initialize a callout structure so that it can
218 * safely be passed to callout_reset() and callout_stop()
220 * <sys/callout.h> defines three convenience macros:
222 * callout_active() - returns truth if callout has not been serviced
223 * callout_pending() - returns truth if callout is still waiting for timeout
224 * callout_deactivate() - marks the callout as having been serviced
227 callout_reset(c, to_ticks, ftn, arg)
230 void (*ftn) __P((void *));
236 if (c->c_flags & CALLOUT_PENDING)
240 * We could spl down here and back up at the TAILQ_INSERT_TAIL,
241 * but there's no point since doing this setup doesn't take much
248 c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING);
250 c->c_time = ticks + to_ticks;
251 TAILQ_INSERT_TAIL(&callwheel[c->c_time & callwheelmask],
265 * Don't attempt to delete a callout that's not on the queue.
267 if (!(c->c_flags & CALLOUT_PENDING)) {
268 c->c_flags &= ~CALLOUT_ACTIVE;
272 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
274 if (nextsoftcheck == c) {
275 nextsoftcheck = TAILQ_NEXT(c, c_links.tqe);
277 TAILQ_REMOVE(&callwheel[c->c_time & callwheelmask], c, c_links.tqe);
280 if (c->c_flags & CALLOUT_LOCAL_ALLOC) {
281 SLIST_INSERT_HEAD(&callfree, c, c_links.sle);
294 #ifdef APM_FIXUP_CALLTODO
296 * Adjust the kernel calltodo timeout list. This routine is used after
297 * an APM resume to recalculate the calltodo timer list values with the
298 * number of hz's we have been sleeping. The next hardclock() will detect
299 * that there are fired timers and run softclock() to execute them.
301 * Please note, I have not done an exhaustive analysis of what code this
302 * might break. I am motivated to have my select()'s and alarm()'s that
303 * have expired during suspend firing upon resume so that the applications
304 * which set the timer can do the maintanence the timer was for as close
305 * as possible to the originally intended time. Testing this code for a
306 * week showed that resuming from a suspend resulted in 22 to 25 timers
307 * firing, which seemed independant on whether the suspend was 2 hours or
308 * 2 days. Your milage may vary. - Ken Key <key@cs.utk.edu>
311 adjust_timeout_calltodo(time_change)
312 struct timeval *time_change;
314 register struct callout *p;
315 unsigned long delta_ticks;
319 * How many ticks were we asleep?
320 * (stolen from tvtohz()).
323 /* Don't do anything */
324 if (time_change->tv_sec < 0)
326 else if (time_change->tv_sec <= LONG_MAX / 1000000)
327 delta_ticks = (time_change->tv_sec * 1000000 +
328 time_change->tv_usec + (tick - 1)) / tick + 1;
329 else if (time_change->tv_sec <= LONG_MAX / hz)
330 delta_ticks = time_change->tv_sec * hz +
331 (time_change->tv_usec + (tick - 1)) / tick + 1;
333 delta_ticks = LONG_MAX;
335 if (delta_ticks > INT_MAX)
336 delta_ticks = INT_MAX;
339 * Now rip through the timer calltodo list looking for timers
343 /* don't collide with softclock() */
345 for (p = calltodo.c_next; p != NULL; p = p->c_next) {
346 p->c_time -= delta_ticks;
348 /* Break if the timer had more time on it than delta_ticks */
352 /* take back the ticks the timer didn't use (p->c_time <= 0) */
353 delta_ticks = -p->c_time;
359 #endif /* APM_FIXUP_CALLTODO */