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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 $
40 * $DragonFly: src/sys/kern/kern_timeout.c,v 1.8 2004/03/15 20:23:48 dillon Exp $
43 #include <sys/param.h>
44 #include <sys/systm.h>
45 #include <sys/callout.h>
46 #include <sys/kernel.h>
47 #include <sys/interrupt.h>
48 #include <sys/thread.h>
49 #include <sys/thread2.h>
50 #include <machine/ipl.h>
54 * allocate more timeout table slots when table overflows.
57 /* Exported to machdep.c and/or kern_clock.c. */
58 struct callout *callout;
59 struct callout_list callfree;
60 int callwheelsize, callwheelbits, callwheelmask;
61 struct callout_tailq *callwheel;
62 int softticks; /* Like ticks, but for softclock(). */
64 static volatile struct callout *nextsoftcheck; /* Next callout to checked. */
67 * The callout mechanism is based on the work of Adam M. Costello and
68 * George Varghese, published in a technical report entitled "Redesigning
69 * the BSD Callout and Timer Facilities" and modified slightly for inclusion
70 * in FreeBSD by Justin T. Gibbs. The original work on the data structures
71 * used in this implementation was published by G.Varghese and A. Lauck in
72 * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for
73 * the Efficient Implementation of a Timer Facility" in the Proceedings of
74 * the 11th ACM Annual Symposium on Operating Systems Principles,
75 * Austin, Texas Nov 1987.
79 * Software (low priority) clock interrupt.
80 * Run periodic events from timeout queue.
83 swi_softclock(void *dummy)
86 struct callout_tailq *bucket;
88 int steps; /* #steps since we last allowed interrupts */
90 #ifndef MAX_SOFTCLOCK_STEPS
91 #define MAX_SOFTCLOCK_STEPS 100 /* Maximum allowed value of steps. */
92 #endif /* MAX_SOFTCLOCK_STEPS */
96 while (softticks != ticks) {
99 * softticks may be modified by hard clock, so cache
100 * it while we work on a given bucket.
102 curticks = softticks;
103 bucket = &callwheel[curticks & callwheelmask];
104 c = TAILQ_FIRST(bucket);
106 if (c->c_time != curticks) {
107 c = TAILQ_NEXT(c, c_links.tqe);
109 if (steps >= MAX_SOFTCLOCK_STEPS) {
111 /* Give interrupts a chance. */
118 void (*c_func)(void *);
121 nextsoftcheck = TAILQ_NEXT(c, c_links.tqe);
122 TAILQ_REMOVE(bucket, c, c_links.tqe);
126 if (c->c_flags & CALLOUT_LOCAL_ALLOC) {
127 c->c_flags = CALLOUT_LOCAL_ALLOC;
128 SLIST_INSERT_HEAD(&callfree, c,
132 (c->c_flags & ~CALLOUT_PENDING);
142 nextsoftcheck = NULL;
148 * Execute a function after a specified length of time.
151 * Cancel previous timeout function call.
153 * callout_handle_init --
154 * Initialize a handle so that using it with untimeout is benign.
156 * See AT&T BCI Driver Reference Manual for specification. This
157 * implementation differs from that one in that although an
158 * identification value is returned from timeout, the original
159 * arguments to timeout as well as the identifier are used to
160 * identify entries for untimeout.
162 struct callout_handle
163 timeout(ftn, arg, to_ticks)
170 struct callout_handle handle;
174 /* Fill in the next free callout structure. */
175 new = SLIST_FIRST(&callfree);
177 /* XXX Attempt to malloc first */
178 panic("timeout table full");
179 SLIST_REMOVE_HEAD(&callfree, c_links.sle);
181 callout_reset(new, to_ticks, ftn, arg);
183 handle.callout = new;
189 untimeout(ftn, arg, handle)
192 struct callout_handle handle;
197 * Check for a handle that was initialized
198 * by callout_handle_init, but never used
199 * for a real timeout.
201 if (handle.callout == NULL)
205 if (handle.callout->c_func == ftn && handle.callout->c_arg == arg)
206 callout_stop(handle.callout);
211 callout_handle_init(struct callout_handle *handle)
213 handle->callout = NULL;
217 * New interface; clients allocate their own callout structures.
219 * callout_reset() - establish or change a timeout
220 * callout_stop() - disestablish a timeout
221 * callout_init() - initialize a callout structure so that it can
222 * safely be passed to callout_reset() and callout_stop()
224 * <sys/callout.h> defines three convenience macros:
226 * callout_active() - returns truth if callout has not been serviced
227 * callout_pending() - returns truth if callout is still waiting for timeout
228 * callout_deactivate() - marks the callout as having been serviced
231 callout_reset(c, to_ticks, ftn, arg)
234 void (*ftn) (void *);
240 if (c->c_flags & CALLOUT_PENDING)
244 * We could spl down here and back up at the TAILQ_INSERT_TAIL,
245 * but there's no point since doing this setup doesn't take much
252 c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING);
254 c->c_time = ticks + to_ticks;
255 TAILQ_INSERT_TAIL(&callwheel[c->c_time & callwheelmask],
269 * Don't attempt to delete a callout that's not on the queue.
271 if (!(c->c_flags & CALLOUT_PENDING)) {
272 c->c_flags &= ~CALLOUT_ACTIVE;
276 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
278 if (nextsoftcheck == c) {
279 nextsoftcheck = TAILQ_NEXT(c, c_links.tqe);
281 TAILQ_REMOVE(&callwheel[c->c_time & callwheelmask], c, c_links.tqe);
284 if (c->c_flags & CALLOUT_LOCAL_ALLOC) {
285 SLIST_INSERT_HEAD(&callfree, c, c_links.sle);
299 swi_softclock_setup(void *arg)
301 register_swi(SWI_CLOCK, swi_softclock, NULL, "swi_sftclk");
302 swi_setpriority(SWI_CLOCK, TDPRI_SOFT_TIMER);
305 SYSINIT(vm_setup, SI_SUB_CPU, SI_ORDER_ANY, swi_softclock_setup, NULL);
307 #ifdef APM_FIXUP_CALLTODO
309 * Adjust the kernel calltodo timeout list. This routine is used after
310 * an APM resume to recalculate the calltodo timer list values with the
311 * number of hz's we have been sleeping. The next hardclock() will detect
312 * that there are fired timers and run softclock() to execute them.
314 * Please note, I have not done an exhaustive analysis of what code this
315 * might break. I am motivated to have my select()'s and alarm()'s that
316 * have expired during suspend firing upon resume so that the applications
317 * which set the timer can do the maintanence the timer was for as close
318 * as possible to the originally intended time. Testing this code for a
319 * week showed that resuming from a suspend resulted in 22 to 25 timers
320 * firing, which seemed independant on whether the suspend was 2 hours or
321 * 2 days. Your milage may vary. - Ken Key <key@cs.utk.edu>
324 adjust_timeout_calltodo(time_change)
325 struct timeval *time_change;
328 unsigned long delta_ticks;
332 * How many ticks were we asleep?
333 * (stolen from tvtohz()).
336 /* Don't do anything */
337 if (time_change->tv_sec < 0)
339 else if (time_change->tv_sec <= LONG_MAX / 1000000)
340 delta_ticks = (time_change->tv_sec * 1000000 +
341 time_change->tv_usec + (tick - 1)) / tick + 1;
342 else if (time_change->tv_sec <= LONG_MAX / hz)
343 delta_ticks = time_change->tv_sec * hz +
344 (time_change->tv_usec + (tick - 1)) / tick + 1;
346 delta_ticks = LONG_MAX;
348 if (delta_ticks > INT_MAX)
349 delta_ticks = INT_MAX;
352 * Now rip through the timer calltodo list looking for timers
356 /* don't collide with softclock() */
358 for (p = calltodo.c_next; p != NULL; p = p->c_next) {
359 p->c_time -= delta_ticks;
361 /* Break if the timer had more time on it than delta_ticks */
365 /* take back the ticks the timer didn't use (p->c_time <= 0) */
366 delta_ticks = -p->c_time;
372 #endif /* APM_FIXUP_CALLTODO */