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view src/timer.c @ 73:b4b7198986a6

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fixed a potential null dereference when deleting a bug in the redblack tree
author John Tsiombikas <nuclear@member.fsf.org>
date Sat, 15 Oct 2011 08:06:10 +0300
parents f44bec97a0ec
children
line source
1 #include <stdio.h>
2 #include <time.h>
3 #include "intr.h"
4 #include "asmops.h"
5 #include "timer.h"
6 #include "proc.h"
7 #include "sched.h"
8 #include "config.h"
9
10 /* frequency of the oscillator driving the 8254 timer */
11 #define OSC_FREQ_HZ 1193182
12
13 /* macro to divide and round to the nearest integer */
14 #define DIV_ROUND(a, b) ((a) / (b) + ((a) % (b)) / ((b) / 2))
15
16 /* I/O ports connected to the 8254 */
17 #define PORT_DATA0 0x40
18 #define PORT_DATA1 0x41
19 #define PORT_DATA2 0x42
20 #define PORT_CMD 0x43
21
22 /* command bits */
23 #define CMD_CHAN0 0
24 #define CMD_CHAN1 (1 << 6)
25 #define CMD_CHAN2 (2 << 6)
26 #define CMD_RDBACK (3 << 6)
27
28 #define CMD_LATCH 0
29 #define CMD_ACCESS_LOW (1 << 4)
30 #define CMD_ACCESS_HIGH (2 << 4)
31 #define CMD_ACCESS_BOTH (3 << 4)
32
33 #define CMD_OP_INT_TERM 0
34 #define CMD_OP_ONESHOT (1 << 1)
35 #define CMD_OP_RATE (2 << 1)
36 #define CMD_OP_SQWAVE (3 << 1)
37 #define CMD_OP_SOFT_STROBE (4 << 1)
38 #define CMD_OP_HW_STROBE (5 << 1)
39
40 #define CMD_MODE_BIN 0
41 #define CMD_MODE_BCD 1
42
43
44 #define MSEC_TO_TICKS(ms) ((ms) * TICK_FREQ_HZ / 1000)
45
46 struct timer_event {
47 int dt; /* remaining ticks delta from the previous event */
48 struct timer_event *next;
49 };
50
51
52 static void timer_handler();
53
54
55 static struct timer_event *evlist;
56
57
58 void init_timer(void)
59 {
60 /* calculate the reload count: round(osc / freq) */
61 int reload_count = DIV_ROUND(OSC_FREQ_HZ, TICK_FREQ_HZ);
62
63 /* set the mode to square wave for channel 0, both low
64 * and high reload count bytes will follow...
65 */
66 outb(CMD_CHAN0 | CMD_ACCESS_BOTH | CMD_OP_SQWAVE, PORT_CMD);
67
68 /* write the low and high bytes of the reload count to the
69 * port for channel 0
70 */
71 outb(reload_count & 0xff, PORT_DATA0);
72 outb((reload_count >> 8) & 0xff, PORT_DATA0);
73
74 /* set the timer interrupt handler */
75 interrupt(IRQ_TO_INTR(0), timer_handler);
76 }
77
78 int sys_sleep(int sec)
79 {
80 printf("process %d will sleep for %d seconds\n", get_current_pid(), sec);
81 sleep(sec * 1000); /* timer.c */
82
83 /* TODO if interrupted, return the remaining seconds */
84 return 0;
85 }
86
87 void sleep(unsigned long msec)
88 {
89 int ticks, tsum, istate;
90 struct timer_event *ev, *node;
91
92 if((ticks = MSEC_TO_TICKS(msec)) <= 0) {
93 return;
94 }
95
96 if(!(ev = malloc(sizeof *ev))) {
97 printf("sleep: failed to allocate timer_event structure\n");
98 return;
99 }
100
101 istate = get_intr_state();
102 disable_intr();
103
104 /* insert at the beginning */
105 if(!evlist || ticks <= evlist->dt) {
106 ev->next = evlist;
107 evlist = ev;
108
109 ev->dt = ticks;
110 if(ev->next) {
111 ev->next->dt -= ticks;
112 }
113 } else {
114
115 tsum = evlist->dt;
116 node = evlist;
117
118 while(node->next && ticks > tsum + node->next->dt) {
119 tsum += node->next->dt;
120 node = node->next;
121 }
122
123 ev->next = node->next;
124 node->next = ev;
125
126 /* fix the relative times */
127 ev->dt = ticks - tsum;
128 if(ev->next) {
129 ev->next->dt -= ev->dt;
130 }
131 }
132
133 set_intr_state(istate);
134
135 /* wait on the address of this timer event */
136 wait(ev);
137 }
138
139 /* This will be called by the interrupt dispatcher approximately
140 * every 1/250th of a second, so it must be extremely fast.
141 * For now, just increasing a tick counter will suffice.
142 */
143 static void timer_handler(int inum)
144 {
145 int istate;
146 struct process *p;
147
148 nticks++;
149
150 /*printf("TICKS: %d\n", nticks);*/
151
152 istate = get_intr_state();
153 disable_intr();
154
155 /* find out if there are any timers that have to go off */
156 if(evlist) {
157 evlist->dt--;
158
159 while(evlist && evlist->dt <= 0) {
160 struct timer_event *ev = evlist;
161 evlist = evlist->next;
162
163 printf("timer going off!!!\n");
164 /* wake up all processes waiting on this address */
165 wakeup(ev);
166 free(ev);
167 }
168 }
169
170 /* decrement the process' ticks_left and call the scheduler to decide if
171 * it's time to switch processes
172 */
173 if((p = get_current_proc())) {
174 p->ticks_left--;
175 }
176 schedule();
177
178 set_intr_state(istate);
179 }