clock.c revision 38494 
1/*
2 * Copyright (c) 1997-1998 Erez Zadok
3 * Copyright (c) 1989 Jan-Simon Pendry
4 * Copyright (c) 1989 Imperial College of Science, Technology & Medicine
5 * Copyright (c) 1989 The Regents of the University of California.
6 * All rights reserved.
7 *
8 * This code is derived from software contributed to Berkeley by
9 * Jan-Simon Pendry at Imperial College, London.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 *    notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 *    notice, this list of conditions and the following disclaimer in the
18 *    documentation and/or other materials provided with the distribution.
19 * 3. All advertising materials mentioning features or use of this software
20 *    must display the following acknowledgement:
21 *      This product includes software developed by the University of
22 *      California, Berkeley and its contributors.
23 * 4. Neither the name of the University nor the names of its contributors
24 *    may be used to endorse or promote products derived from this software
25 *    without specific prior written permission.
26 *
27 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
28 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
29 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
30 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
31 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
32 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
33 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
34 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
35 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
36 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
37 * SUCH DAMAGE.
38 *
39 *      %W% (Berkeley) %G%
40 *
41 * $Id: clock.c,v 5.2.2.1 1992/02/09 15:08:20 jsp beta $
42 *
43 */
44
45/*
46 * Callouts.
47 *
48 * Modelled on kernel object of the same name.
49 * See usual references.
50 *
51 * Use of a heap-based mechanism was rejected:
52 * 1.  more complex implementation needed.
53 * 2.  not obvious that a list is too slow for Amd.
54 */
55
56#ifdef HAVE_CONFIG_H
57# include <config.h>
58#endif /* HAVE_CONFIG_H */
59#include <am_defs.h>
60#include <amd.h>
61
62int timeout(u_int secs, void (*fn) (voidp), voidp closure);
63void reschedule_timeouts(time_t now, time_t then);
64
65typedef struct callout callout;
66struct callout {
67  callout *c_next;		/* List of callouts */
68  void (*c_fn) (voidp);		/* Function to call */
69  voidp c_closure;		/* Closure to pass to call */
70  time_t c_time;		/* Time of call */
71  int c_id;			/* Unique identifier */
72};
73
74static callout callouts;	/* List of pending callouts */
75static callout *free_callouts;	/* Cache of free callouts */
76static int nfree_callouts;	/* Number on free list */
77static int callout_id;		/* Next free callout identifier */
78
79time_t next_softclock;		/* Time of next call to softclock() */
80
81
82/*
83 * Number of callout slots we keep on the free list
84 */
85#define	CALLOUT_FREE_SLOP	10
86
87/*
88 * Global assumption: valid id's are non-zero.
89 */
90#define	CID_ALLOC(struct )	(++callout_id)
91#define	CID_UNDEF		(0)
92
93
94static callout *
95alloc_callout(void)
96{
97  callout *cp = free_callouts;
98
99  if (cp) {
100    --nfree_callouts;
101    free_callouts = free_callouts->c_next;
102    return cp;
103  }
104  return ALLOC(struct callout);
105}
106
107
108static void
109free_callout(callout *cp)
110{
111  if (nfree_callouts > CALLOUT_FREE_SLOP) {
112    XFREE(cp);
113  } else {
114    cp->c_next = free_callouts;
115    free_callouts = cp;
116    nfree_callouts++;
117  }
118}
119
120
121/*
122 * Schedule a callout.
123 *
124 * (*fn)(closure) will be called at clocktime() + secs
125 */
126int
127timeout(u_int secs, void (*fn) (voidp), voidp closure)
128{
129  callout *cp, *cp2;
130  time_t t = clocktime() + secs;
131
132  /*
133   * Allocate and fill in a new callout structure
134   */
135  callout *cpnew = alloc_callout();
136  cpnew->c_closure = closure;
137  cpnew->c_fn = fn;
138  cpnew->c_time = t;
139  cpnew->c_id = CID_ALLOC(struct );
140
141  if (t < next_softclock)
142    next_softclock = t;
143
144  /*
145   * Find the correct place in the list
146   */
147  for (cp = &callouts; (cp2 = cp->c_next); cp = cp2)
148    if (cp2->c_time >= t)
149      break;
150
151  /*
152   * And link it in
153   */
154  cp->c_next = cpnew;
155  cpnew->c_next = cp2;
156
157  /*
158   * Return callout identifier
159   */
160  return cpnew->c_id;
161}
162
163
164/*
165 * De-schedule a callout
166 */
167void
168untimeout(int id)
169{
170  callout *cp, *cp2;
171  for (cp = &callouts; (cp2 = cp->c_next); cp = cp2) {
172    if (cp2->c_id == id) {
173      cp->c_next = cp2->c_next;
174      free_callout(cp2);
175      break;
176    }
177  }
178}
179
180
181/*
182 * Reschedule after clock changed
183 */
184void
185reschedule_timeouts(time_t now, time_t then)
186{
187  callout *cp;
188
189  for (cp = callouts.c_next; cp; cp = cp->c_next) {
190    if (cp->c_time >= now && cp->c_time <= then) {
191      plog(XLOG_WARNING, "job %d rescheduled to run immediately", cp->c_id);
192#ifdef DEBUG
193      dlog("rescheduling job %d back %d seconds", cp->c_id, cp->c_time - now);
194#endif /* DEBUG */
195      next_softclock = cp->c_time = now;
196    }
197  }
198}
199
200
201/*
202 * Clock handler
203 */
204int
205softclock(void)
206{
207  time_t now;
208  callout *cp;
209
210  do {
211    if (task_notify_todo)
212      do_task_notify();
213
214    now = clocktime();
215
216    /*
217     * While there are more callouts waiting...
218     */
219    while ((cp = callouts.c_next) && cp->c_time <= now) {
220      /*
221       * Extract first from list, save fn & closure and
222       * unlink callout from list and free.
223       * Finally call function.
224       *
225       * The free is done first because
226       * it is quite common that the
227       * function will call timeout()
228       * and try to allocate a callout
229       */
230      void (*fn) (voidp) = cp->c_fn;
231      voidp closure = cp->c_closure;
232
233      callouts.c_next = cp->c_next;
234      free_callout(cp);
235      (*fn) (closure);
236    }
237
238  } while (task_notify_todo);
239
240  /*
241   * Return number of seconds to next event,
242   * or 0 if there is no event.
243   */
244  if ((cp = callouts.c_next))
245    return cp->c_time - now;
246  return 0;
247}
248