1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
|
#include <errno.h>
#include <error.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <ucontext.h>
#include "pt-machine.h"
#define N 4
#ifdef FLOATING_STACKS
static char stacks[N][8192];
static ucontext_t ctx[N][2];
static volatile int failures;
static void
fct (long int n)
{
/* Just to use the thread local descriptor. */
printf ("%ld: in %s now\n", n, __FUNCTION__);
errno = 0;
}
static void *
threadfct (void *arg)
{
int n = (int) (long int) arg;
if (getcontext (&ctx[n][1]) != 0)
{
printf ("%d: cannot get context: %m\n", n);
exit (1);
}
printf ("%d: %s: before makecontext\n", n, __FUNCTION__);
ctx[n][1].uc_stack.ss_sp = stacks[n];
ctx[n][1].uc_stack.ss_size = 8192;
ctx[n][1].uc_link = &ctx[n][0];
makecontext (&ctx[n][1], (void (*) (void)) fct, 1, (long int) n);
printf ("%d: %s: before swapcontext\n", n, __FUNCTION__);
if (swapcontext (&ctx[n][0], &ctx[n][1]) != 0)
{
++failures;
printf ("%d: %s: swapcontext failed\n", n, __FUNCTION__);
}
else
printf ("%d: back in %s\n", n, __FUNCTION__);
return NULL;
}
#endif
#ifdef FLOATING_STACKS
static volatile int global;
#endif
int
main (void)
{
#ifndef FLOATING_STACKS
puts ("not supported");
return 0;
#else
int n;
pthread_t th[N];
ucontext_t mctx;
puts ("making contexts");
if (getcontext (&mctx) != 0)
{
if (errno == ENOSYS)
{
puts ("context handling not supported");
exit (0);
}
printf ("%s: getcontext: %m\n", __FUNCTION__);
exit (1);
}
/* Play some tricks with this context. */
if (++global == 1)
if (setcontext (&mctx) != 0)
{
printf ("%s: setcontext: %m\n", __FUNCTION__);
exit (1);
}
if (global != 2)
{
printf ("%s: 'global' not incremented twice\n", __FUNCTION__);
exit (1);
}
for (n = 0; n < N; ++n)
if (pthread_create (&th[n], NULL, threadfct, (void *) (long int) n) != 0)
error (EXIT_FAILURE, errno, "cannot create all threads");
for (n = 0; n < N; ++n)
pthread_join (th[n], NULL);
return failures;
#endif
}
|
