117 lines
2.9 KiB
C
117 lines
2.9 KiB
C
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/* Copyright (C) 2015-2022 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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/* This tests that a writer that is preferred -- but times out due to a
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reader being present -- does not miss to wake other readers blocked on the
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writer's pending lock acquisition. */
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#include <errno.h>
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#include <pthread.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <time.h>
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/* The bug existed in the code that strictly prefers writers over readers. */
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static pthread_rwlock_t r = PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP;
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static void *
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writer (void *arg)
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{
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struct timespec ts;
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if (clock_gettime (CLOCK_REALTIME, &ts) != 0)
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{
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puts ("clock_gettime failed");
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exit (EXIT_FAILURE);
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}
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ts.tv_sec += 1;
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int e = pthread_rwlock_timedwrlock (&r, &ts);
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if (e != ETIMEDOUT)
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{
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puts ("timedwrlock did not time out");
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exit (EXIT_FAILURE);
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}
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return NULL;
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}
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static void *
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reader (void *arg)
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{
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/* This isn't a reliable way to get the interleaving we need (because a
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failed trylock doesn't synchronize with the writer, and because we could
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try to lock after the writer has already timed out). However, both will
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just lead to false positives. */
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int e;
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while ((e = pthread_rwlock_tryrdlock (&r)) != EBUSY)
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{
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if (e != 0)
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exit (EXIT_FAILURE);
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pthread_rwlock_unlock (&r);
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}
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e = pthread_rwlock_rdlock (&r);
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if (e != 0)
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{
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puts ("reader rdlock failed");
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exit (EXIT_FAILURE);
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}
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pthread_rwlock_unlock (&r);
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return NULL;
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}
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static int
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do_test (void)
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{
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/* Grab a rdlock, then create a writer and a reader, and wait until they
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finished. */
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if (pthread_rwlock_rdlock (&r) != 0)
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{
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puts ("initial rdlock failed");
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return 1;
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}
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pthread_t thw;
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if (pthread_create (&thw, NULL, writer, NULL) != 0)
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{
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puts ("create failed");
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return 1;
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}
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pthread_t thr;
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if (pthread_create (&thr, NULL, reader, NULL) != 0)
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{
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puts ("create failed");
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return 1;
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}
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if (pthread_join (thw, NULL) != 0)
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{
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puts ("writer join failed");
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return 1;
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}
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if (pthread_join (thr, NULL) != 0)
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{
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puts ("reader join failed");
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return 1;
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}
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return 0;
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}
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#define TEST_FUNCTION do_test ()
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#include "../test-skeleton.c"
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