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glibc/nptl/tst-rwlock15.c
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/* Copyright (C) 2015-2016 Free Software Foundation, Inc. | |
This file is part of the GNU C Library. | |
The GNU C Library is free software; you can redistribute it and/or | |
modify it under the terms of the GNU Lesser General Public | |
License as published by the Free Software Foundation; either | |
version 2.1 of the License, or (at your option) any later version. | |
The GNU C Library is distributed in the hope that it will be useful, | |
but WITHOUT ANY WARRANTY; without even the implied warranty of | |
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
Lesser General Public License for more details. | |
You should have received a copy of the GNU Lesser General Public | |
License along with the GNU C Library; if not, see | |
<http://www.gnu.org/licenses/>. */ | |
/* This tests that a writer that is preferred -- but times out due to a | |
reader being present -- does not miss to wake other readers blocked on the | |
writer's pending lock acquisition. */ | |
#include <errno.h> | |
#include <pthread.h> | |
#include <stdio.h> | |
#include <stdlib.h> | |
#include <time.h> | |
/* The bug existed in the code that strictly prefers writers over readers. */ | |
static pthread_rwlock_t r = PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP; | |
static void * | |
writer (void *arg) | |
{ | |
struct timespec ts; | |
if (clock_gettime (CLOCK_REALTIME, &ts) != 0) | |
{ | |
puts ("clock_gettime failed"); | |
exit (EXIT_FAILURE); | |
} | |
ts.tv_sec += 1; | |
int e = pthread_rwlock_timedwrlock (&r, &ts); | |
if (e != ETIMEDOUT) | |
{ | |
puts ("timedwrlock did not time out"); | |
exit (EXIT_FAILURE); | |
} | |
return NULL; | |
} | |
static void * | |
reader (void *arg) | |
{ | |
/* This isn't a reliable way to get the interleaving we need (because a | |
failed trylock doesn't synchronize with the writer, and because we could | |
try to lock after the writer has already timed out). However, both will | |
just lead to false positives. */ | |
int e; | |
while ((e = pthread_rwlock_tryrdlock (&r)) != EBUSY) | |
{ | |
if (e != 0) | |
exit (EXIT_FAILURE); | |
pthread_rwlock_unlock (&r); | |
} | |
e = pthread_rwlock_rdlock (&r); | |
if (e != 0) | |
{ | |
puts ("reader rdlock failed"); | |
exit (EXIT_FAILURE); | |
} | |
pthread_rwlock_unlock (&r); | |
return NULL; | |
} | |
static int | |
do_test (void) | |
{ | |
/* Grab a rdlock, then create a writer and a reader, and wait until they | |
finished. */ | |
if (pthread_rwlock_rdlock (&r) != 0) | |
{ | |
puts ("initial rdlock failed"); | |
return 1; | |
} | |
pthread_t thw; | |
if (pthread_create (&thw, NULL, writer, NULL) != 0) | |
{ | |
puts ("create failed"); | |
return 1; | |
} | |
pthread_t thr; | |
if (pthread_create (&thr, NULL, reader, NULL) != 0) | |
{ | |
puts ("create failed"); | |
return 1; | |
} | |
if (pthread_join (thw, NULL) != 0) | |
{ | |
puts ("writer join failed"); | |
return 1; | |
} | |
if (pthread_join (thr, NULL) != 0) | |
{ | |
puts ("reader join failed"); | |
return 1; | |
} | |
return 0; | |
} | |
#define TEST_FUNCTION do_test () | |
#include "../test-skeleton.c" |