1/* Copyright (C) 2002-2024 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18#include <errno.h>
19#include <semaphore.h>
20#include <stdint.h>
21#include <stdio.h>
22#include <stdlib.h>
23#include <string.h>
24#include <unistd.h>
25#include <sys/mman.h>
26#include <sys/wait.h>
27
28
29int
30do_test (void)
31{
32 size_t ps = sysconf (_SC_PAGESIZE);
33 char tmpfname[] = "/tmp/tst-sem3.XXXXXX";
34 char data[ps];
35 void *mem;
36 int fd;
37 sem_t *s;
38 pid_t pid;
39 char *p;
40
41 fd = mkstemp (template: tmpfname);
42 if (fd == -1)
43 {
44 printf (format: "cannot open temporary file: %m\n");
45 return 1;
46 }
47
48 /* Make sure it is always removed. */
49 unlink (name: tmpfname);
50
51 /* Create one page of data. */
52 memset (data, '\0', ps);
53
54 /* Write the data to the file. */
55 if (write (fd, data, ps) != (ssize_t) ps)
56 {
57 puts (s: "short write");
58 return 1;
59 }
60
61 mem = mmap (NULL, len: ps, PROT_READ | PROT_WRITE, MAP_SHARED, fd: fd, offset: 0);
62 if (mem == MAP_FAILED)
63 {
64 printf (format: "mmap failed: %m\n");
65 return 1;
66 }
67
68 s = (sem_t *) (((uintptr_t) mem + __alignof (sem_t))
69 & ~(__alignof (sem_t) - 1));
70 p = (char *) (s + 1);
71
72 if (sem_init (sem: s, pshared: 1, value: 1) == -1)
73 {
74 puts (s: "init failed");
75 return 1;
76 }
77
78 if (TEMP_FAILURE_RETRY (sem_wait (s)) == -1)
79 {
80 puts (s: "1st wait failed");
81 return 1;
82 }
83
84 errno = 0;
85 if (TEMP_FAILURE_RETRY (sem_trywait (s)) != -1)
86 {
87 puts (s: "trywait succeeded");
88 return 1;
89 }
90 else if (errno != EAGAIN)
91 {
92 puts (s: "trywait didn't return EAGAIN");
93 return 1;
94 }
95
96 *p = 0;
97
98 puts (s: "going to fork now");
99 pid = fork ();
100 if (pid == -1)
101 {
102 puts (s: "fork failed");
103 return 1;
104 }
105 else if (pid == 0)
106 {
107 /* Play some lock ping-pong. It's our turn to unlock first. */
108 if ((*p)++ != 0)
109 {
110 puts (s: "child: *p != 0");
111 return 1;
112 }
113
114 if (sem_post (sem: s) == -1)
115 {
116 puts (s: "child: 1st post failed");
117 return 1;
118 }
119
120 puts (s: "child done");
121 }
122 else
123 {
124 if (TEMP_FAILURE_RETRY (sem_wait (s)) == -1)
125 {
126 printf (format: "parent: 2nd wait failed: %m\n");
127 return 1;
128 }
129
130 if (*p != 1)
131 {
132 puts (s: "*p != 1");
133 return 1;
134 }
135
136 puts (s: "parent done");
137 }
138
139 return 0;
140}
141
142#define TEST_FUNCTION do_test ()
143#include "../test-skeleton.c"
144

source code of glibc/sysdeps/pthread/tst-sem3.c