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DEFINITIONS
This source file includes following definitions.
- hardclock_bootstrap
- timerclock
- hardclock
- clocksleep
1 /*
2 * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
3 * The President and Fellows of Harvard College.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. Neither the name of the University nor the names of its contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30 #include <types.h>
31 #include <lib.h>
32 #include <cpu.h>
33 #include <wchan.h>
34 #include <clock.h>
35 #include <thread.h>
36 #include <current.h>
37
38 /*
39 * Time handling.
40 *
41 * This is pretty primitive. A real kernel will typically have some
42 * kind of support for scheduling callbacks to happen at specific
43 * points in the future, usually with more resolution that one second.
44 *
45 * A real kernel also has to maintain the time of day; in OS/161 we
46 * skimp on that because we have a known-good hardware clock.
47 */
48
49 /*
50 * Timing constants. These should be tuned along with any work done on
51 * the scheduler.
52 */
53 #define SCHEDULE_HARDCLOCKS 4 /* Reschedule every 4 hardclocks. */
54 #define MIGRATE_HARDCLOCKS 16 /* Migrate every 16 hardclocks. */
55
56 /*
57 * Once a second, everything waiting on lbolt is awakened by CPU 0.
58 */
59 static struct wchan *lbolt;
60
61 /*
62 * Setup.
63 */
64 void
65 hardclock_bootstrap(void)
66 {
67 lbolt = wchan_create("lbolt");
68 if (lbolt == NULL) {
69 panic("Couldn't create lbolt\n");
70 }
71 }
72
73 /*
74 * This is called once per second, on one processor, by the timer
75 * code.
76 */
77 void
78 timerclock(void)
79 {
80 /* Just broadcast on lbolt */
81 wchan_wakeall(lbolt);
82 }
83
84 /*
85 * This is called HZ times a second (on each processor) by the timer
86 * code.
87 */
88 void
89 hardclock(void)
90 {
91 /*
92 * Collect statistics here as desired.
93 */
94
95 curcpu->c_hardclocks++;
96 if ((curcpu->c_hardclocks % SCHEDULE_HARDCLOCKS) == 0) {
97 schedule();
98 }
99 if ((curcpu->c_hardclocks % MIGRATE_HARDCLOCKS) == 0) {
100 thread_consider_migration();
101 }
102 thread_yield();
103 }
104
105 /*
106 * Suspend execution for n seconds.
107 */
108 void
109 clocksleep(int num_secs)
110 {
111 while (num_secs > 0) {
112 wchan_lock(lbolt);
113 wchan_sleep(lbolt);
114 num_secs--;
115 }
116 }