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d614a753 | 1 | /* Copyright (C) 2015-2020 Free Software Foundation, Inc. |
b634486d TR |
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 | |
5a82c748 | 16 | <https://www.gnu.org/licenses/>. */ |
b634486d TR |
17 | |
18 | /* This tests that with a reader-preferring rwlock, all readers are woken if | |
19 | one reader "steals" lock ownership from a blocked writer. */ | |
20 | ||
21 | #include <errno.h> | |
22 | #include <pthread.h> | |
23 | #include <stdio.h> | |
24 | #include <stdlib.h> | |
25 | #include <semaphore.h> | |
26 | #include <unistd.h> | |
27 | ||
28 | /* If we strictly prefer writers over readers, a program must not expect | |
29 | that, in the presence of concurrent writers, one reader will also acquire | |
30 | the lock when another reader has already done so. Thus, use the | |
31 | default rwlock type that does not strictly prefer writers. */ | |
32 | static pthread_rwlock_t r = PTHREAD_RWLOCK_INITIALIZER; | |
33 | ||
34 | static pthread_mutex_t m = PTHREAD_MUTEX_INITIALIZER; | |
35 | static pthread_cond_t cv = PTHREAD_COND_INITIALIZER; | |
36 | ||
37 | /* Avoid using glibc-internal atomic operations. */ | |
38 | static sem_t stop; | |
39 | static int consumer_stop = 0; | |
40 | ||
41 | static void * | |
42 | writer (void *arg) | |
43 | { | |
44 | int s; | |
45 | ||
46 | do | |
47 | { | |
48 | if (pthread_rwlock_wrlock (&r) != 0) | |
49 | { | |
50 | puts ("wrlock failed"); | |
51 | exit (EXIT_FAILURE); | |
52 | } | |
53 | if (pthread_rwlock_unlock (&r) != 0) | |
54 | { | |
55 | puts ("unlock failed"); | |
56 | exit (EXIT_FAILURE); | |
57 | } | |
58 | sem_getvalue (&stop, &s); | |
59 | } | |
60 | while (s == 0); | |
61 | return NULL; | |
62 | } | |
63 | ||
64 | static void * | |
65 | reader_producer (void *arg) | |
66 | { | |
67 | int s; | |
68 | ||
69 | do | |
70 | { | |
71 | if (pthread_rwlock_rdlock (&r) != 0) | |
72 | { | |
73 | puts ("rdlock reader failed"); | |
74 | exit (EXIT_FAILURE); | |
75 | } | |
76 | ||
77 | sem_getvalue (&stop, &s); | |
78 | ||
79 | pthread_mutex_lock (&m); | |
80 | if (s != 0) | |
81 | consumer_stop = 1; | |
82 | pthread_cond_signal (&cv); | |
83 | pthread_mutex_unlock (&m); | |
84 | ||
85 | if (pthread_rwlock_unlock (&r) != 0) | |
86 | { | |
87 | puts ("unlock reader failed"); | |
88 | exit (EXIT_FAILURE); | |
89 | } | |
90 | } | |
91 | while (s == 0); | |
92 | puts ("producer finished"); | |
93 | return NULL; | |
94 | } | |
95 | ||
96 | static void * | |
97 | reader_consumer (void *arg) | |
98 | { | |
99 | int s; | |
100 | ||
101 | do | |
102 | { | |
103 | if (pthread_rwlock_rdlock (&r) != 0) | |
104 | { | |
105 | puts ("rdlock reader failed"); | |
106 | exit (EXIT_FAILURE); | |
107 | } | |
108 | ||
109 | pthread_mutex_lock (&m); | |
110 | s = consumer_stop; | |
111 | if (s == 0) | |
112 | pthread_cond_wait (&cv, &m); | |
113 | pthread_mutex_unlock (&m); | |
114 | ||
115 | if (pthread_rwlock_unlock (&r) != 0) | |
116 | { | |
117 | puts ("unlock reader failed"); | |
118 | exit (EXIT_FAILURE); | |
119 | } | |
120 | } | |
121 | while (s == 0); | |
122 | puts ("consumer finished"); | |
123 | return NULL; | |
124 | } | |
125 | ||
126 | ||
127 | static int | |
128 | do_test (void) | |
129 | { | |
130 | pthread_t w1, w2, rp, rc; | |
131 | ||
132 | if (pthread_create (&w1, NULL, writer, NULL) != 0) | |
133 | { | |
134 | puts ("create failed"); | |
135 | return 1; | |
136 | } | |
137 | if (pthread_create (&w2, NULL, writer, NULL) != 0) | |
138 | { | |
139 | puts ("create failed"); | |
140 | return 1; | |
141 | } | |
142 | if (pthread_create (&rc, NULL, reader_consumer, NULL) != 0) | |
143 | { | |
144 | puts ("create failed"); | |
145 | return 1; | |
146 | } | |
147 | if (pthread_create (&rp, NULL, reader_producer, NULL) != 0) | |
148 | { | |
149 | puts ("create failed"); | |
150 | return 1; | |
151 | } | |
152 | ||
153 | sleep (2); | |
154 | sem_post (&stop); | |
155 | ||
156 | if (pthread_join (w1, NULL) != 0) | |
157 | { | |
158 | puts ("w1 join failed"); | |
159 | return 1; | |
160 | } | |
161 | if (pthread_join (w2, NULL) != 0) | |
162 | { | |
163 | puts ("w2 join failed"); | |
164 | return 1; | |
165 | } | |
166 | if (pthread_join (rp, NULL) != 0) | |
167 | { | |
168 | puts ("reader_producer join failed"); | |
169 | return 1; | |
170 | } | |
171 | if (pthread_join (rc, NULL) != 0) | |
172 | { | |
173 | puts ("reader_consumer join failed"); | |
174 | return 1; | |
175 | } | |
176 | ||
177 | return 0; | |
178 | } | |
179 | ||
180 | ||
b634486d TR |
181 | #define TEST_FUNCTION do_test () |
182 | #include "../test-skeleton.c" |