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6d7e8eda | 1 | /* Copyright (C) 2015-2023 Free Software Foundation, Inc. |
3c9c61fe 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/>. */ |
3c9c61fe TR |
17 | |
18 | /* This tests that a writer that is preferred -- but times out due to a | |
19 | reader being present -- does not miss to wake other readers blocked on the | |
20 | writer's pending lock acquisition. */ | |
21 | ||
22 | #include <errno.h> | |
23 | #include <pthread.h> | |
24 | #include <stdio.h> | |
25 | #include <stdlib.h> | |
26 | #include <time.h> | |
27 | ||
28 | /* The bug existed in the code that strictly prefers writers over readers. */ | |
29 | static pthread_rwlock_t r = PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP; | |
30 | ||
31 | static void * | |
32 | writer (void *arg) | |
33 | { | |
34 | struct timespec ts; | |
35 | if (clock_gettime (CLOCK_REALTIME, &ts) != 0) | |
36 | { | |
37 | puts ("clock_gettime failed"); | |
38 | exit (EXIT_FAILURE); | |
39 | } | |
40 | ts.tv_sec += 1; | |
41 | int e = pthread_rwlock_timedwrlock (&r, &ts); | |
42 | if (e != ETIMEDOUT) | |
43 | { | |
44 | puts ("timedwrlock did not time out"); | |
45 | exit (EXIT_FAILURE); | |
46 | } | |
47 | return NULL; | |
48 | } | |
49 | ||
50 | static void * | |
51 | reader (void *arg) | |
52 | { | |
53 | /* This isn't a reliable way to get the interleaving we need (because a | |
54 | failed trylock doesn't synchronize with the writer, and because we could | |
55 | try to lock after the writer has already timed out). However, both will | |
56 | just lead to false positives. */ | |
57 | int e; | |
58 | while ((e = pthread_rwlock_tryrdlock (&r)) != EBUSY) | |
59 | { | |
60 | if (e != 0) | |
61 | exit (EXIT_FAILURE); | |
62 | pthread_rwlock_unlock (&r); | |
63 | } | |
64 | e = pthread_rwlock_rdlock (&r); | |
65 | if (e != 0) | |
66 | { | |
67 | puts ("reader rdlock failed"); | |
68 | exit (EXIT_FAILURE); | |
69 | } | |
70 | pthread_rwlock_unlock (&r); | |
71 | return NULL; | |
72 | } | |
73 | ||
74 | ||
75 | static int | |
76 | do_test (void) | |
77 | { | |
78 | /* Grab a rdlock, then create a writer and a reader, and wait until they | |
79 | finished. */ | |
80 | ||
81 | if (pthread_rwlock_rdlock (&r) != 0) | |
82 | { | |
83 | puts ("initial rdlock failed"); | |
84 | return 1; | |
85 | } | |
86 | ||
87 | pthread_t thw; | |
88 | if (pthread_create (&thw, NULL, writer, NULL) != 0) | |
89 | { | |
90 | puts ("create failed"); | |
91 | return 1; | |
92 | } | |
93 | pthread_t thr; | |
94 | if (pthread_create (&thr, NULL, reader, NULL) != 0) | |
95 | { | |
96 | puts ("create failed"); | |
97 | return 1; | |
98 | } | |
99 | ||
100 | if (pthread_join (thw, NULL) != 0) | |
101 | { | |
102 | puts ("writer join failed"); | |
103 | return 1; | |
104 | } | |
105 | if (pthread_join (thr, NULL) != 0) | |
106 | { | |
107 | puts ("reader join failed"); | |
108 | return 1; | |
109 | } | |
110 | ||
111 | return 0; | |
112 | } | |
113 | ||
114 | ||
115 | #define TEST_FUNCTION do_test () | |
116 | #include "../test-skeleton.c" |