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faf8c066 | 1 | /* Test program for a read-phase / write-phase explicit hand-over. |
dff8da6b | 2 | Copyright (C) 2017-2024 Free Software Foundation, Inc. |
faf8c066 CD |
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 License as | |
6 | published by the Free Software Foundation; either version 2.1 of the | |
7 | 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; see the file COPYING.LIB. If | |
5a82c748 | 16 | not, see <https://www.gnu.org/licenses/>. */ |
faf8c066 CD |
17 | |
18 | #include <errno.h> | |
19 | #include <error.h> | |
20 | #include <pthread.h> | |
21 | #include <stdio.h> | |
22 | #include <stdlib.h> | |
23 | #include <unistd.h> | |
24 | #include <stdint.h> | |
25 | #include <time.h> | |
26 | #include <atomic.h> | |
27 | #include <support/xthread.h> | |
28 | ||
7f0d9e61 | 29 | /* We really want to set threads to 2 to reproduce this issue. The goal |
faf8c066 CD |
30 | is to have one primary writer and a single reader, and to hit the |
31 | bug that happens in the interleaving of those two phase transitions. | |
32 | However, on most hardware, adding a second writer seems to help the | |
33 | interleaving happen slightly more often, say 20% of the time. On a | |
34 | 16 core ppc64 machine this fails 100% of the time with an unpatched | |
35 | glibc. On a 8 core x86_64 machine this fails ~93% of the time, but | |
36 | it doesn't fail at all on a 4 core system, so having available | |
37 | unloaded cores makes a big difference in reproducibility. On an 8 | |
38 | core qemu/kvm guest the reproducer reliability drops to ~10%. */ | |
39 | #define THREADS 3 | |
40 | ||
41 | #define KIND PTHREAD_RWLOCK_PREFER_READER_NP | |
42 | ||
43 | static pthread_rwlock_t lock; | |
44 | static int done = 0; | |
45 | ||
46 | static void* | |
47 | tf (void* arg) | |
48 | { | |
49 | while (atomic_load_relaxed (&done) == 0) | |
50 | { | |
51 | int rcnt = 0; | |
52 | int wcnt = 100; | |
53 | if ((uintptr_t) arg == 0) | |
54 | { | |
55 | rcnt = 1; | |
56 | wcnt = 1; | |
57 | } | |
58 | ||
59 | do | |
60 | { | |
61 | if (wcnt) | |
62 | { | |
63 | xpthread_rwlock_wrlock (&lock); | |
64 | xpthread_rwlock_unlock (&lock); | |
65 | wcnt--; | |
66 | } | |
67 | if (rcnt) | |
68 | { | |
69 | xpthread_rwlock_rdlock (&lock); | |
70 | xpthread_rwlock_unlock (&lock); | |
71 | rcnt--; | |
72 | } | |
73 | } | |
74 | while ((atomic_load_relaxed (&done) == 0) && (rcnt + wcnt > 0)); | |
75 | ||
76 | } | |
77 | return NULL; | |
78 | } | |
79 | ||
80 | ||
81 | ||
82 | static int | |
83 | do_test (void) | |
84 | { | |
85 | pthread_t thr[THREADS]; | |
86 | int n; | |
87 | pthread_rwlockattr_t attr; | |
88 | ||
89 | xpthread_rwlockattr_init (&attr); | |
90 | xpthread_rwlockattr_setkind_np (&attr, KIND); | |
91 | ||
92 | xpthread_rwlock_init (&lock, &attr); | |
93 | ||
94 | /* Make standard error the same as standard output. */ | |
95 | dup2 (1, 2); | |
96 | ||
97 | /* Make sure we see all message, even those on stdout. */ | |
98 | setvbuf (stdout, NULL, _IONBF, 0); | |
99 | ||
100 | for (n = 0; n < THREADS; ++n) | |
101 | thr[n] = xpthread_create (NULL, tf, (void *) (uintptr_t) n); | |
102 | ||
103 | struct timespec delay; | |
104 | delay.tv_sec = 10; | |
105 | delay.tv_nsec = 0; | |
106 | nanosleep (&delay, NULL); | |
107 | atomic_store_relaxed (&done, 1); | |
108 | ||
109 | /* Wait for all the threads. */ | |
110 | for (n = 0; n < THREADS; ++n) | |
111 | xpthread_join (thr[n]); | |
112 | ||
113 | return 0; | |
114 | } | |
115 | ||
116 | #include <support/test-driver.c> |