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1/* Test rwlock with PREFER_WRITER_NONRECURSIVE_NP (bug 23861).
2 Copyright (C) 2018-2019 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <http://www.gnu.org/licenses/>. */
18
19#include <stdio.h>
20#include <stdlib.h>
21#include <unistd.h>
22#include <pthread.h>
23#include <support/xthread.h>
24
25/* We choose 10 iterations because this happens to be able to trigger the
26 stall on contemporary hardware. */
27#define LOOPS 10
28/* We need 3 threads to trigger bug 23861. One thread as a writer, and
29 two reader threads. The test verifies that the second-to-last reader
30 is able to notify the *last* reader that it should be done waiting.
31 If the second-to-last reader fails to notify the last reader or does
32 so incorrectly then the last reader may stall indefinitely. */
33#define NTHREADS 3
34
35_Atomic int do_exit;
36pthread_rwlockattr_t mylock_attr;
37pthread_rwlock_t mylock;
38
39void *
40run_loop (void *a)
41{
42 while (!do_exit)
43 {
44 if (random () & 1)
45 {
46 xpthread_rwlock_wrlock (&mylock);
47 xpthread_rwlock_unlock (&mylock);
48 }
49 else
50 {
51 xpthread_rwlock_rdlock (&mylock);
52 xpthread_rwlock_unlock (&mylock);
53 }
54 }
55 return NULL;
56}
57
58int
59do_test (void)
60{
61 xpthread_rwlockattr_init (&mylock_attr);
62 xpthread_rwlockattr_setkind_np (&mylock_attr,
63 PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP);
64 xpthread_rwlock_init (&mylock, &mylock_attr);
65
66 for (int n = 0; n < LOOPS; n++)
67 {
68 pthread_t tids[NTHREADS];
69 do_exit = 0;
70 for (int i = 0; i < NTHREADS; i++)
71 tids[i] = xpthread_create (NULL, run_loop, NULL);
72 /* Let the threads run for some time. */
73 sleep (1);
74 printf ("Exiting...");
75 fflush (stdout);
76 do_exit = 1;
77 for (int i = 0; i < NTHREADS; i++)
78 xpthread_join (tids[i]);
79 printf ("done.\n");
80 }
81 pthread_rwlock_destroy (&mylock);
82 pthread_rwlockattr_destroy (&mylock_attr);
83 return 0;
84}
85
86#define TIMEOUT (DEFAULT_TIMEOUT + 3 * LOOPS)
87#include <support/test-driver.c>
88

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