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139 lines
4.3 KiB
C
139 lines
4.3 KiB
C
/* Bug 20116: Test rapid creation of detached threads.
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Copyright (C) 2017-2025 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; see the file COPYING.LIB. If
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not, see <https://www.gnu.org/licenses/>. */
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/* The goal of the test is to trigger a failure if the parent touches
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any part of the thread descriptor after the detached thread has
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exited. We test this by creating many detached threads with large
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stacks. The stacks quickly fill the the stack cache and subsequent
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threads will start to cause the thread stacks to be immediately
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unmapped to satisfy the stack cache max. With the stacks being
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unmapped the parent's read of any part of the thread descriptor will
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trigger a segfault. That segfault is what we are trying to cause,
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since any segfault is a defect in the implementation. */
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#include <pthread.h>
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#include <stdio.h>
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#include <errno.h>
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#include <unistd.h>
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#include <stdbool.h>
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#include <sys/resource.h>
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#include <support/xthread.h>
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/* Number of threads to create. */
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enum { threads_to_create = 100000 };
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/* Number of threads which should spawn other threads. */
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enum { creator_threads = 2 };
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/* Counter of threads created so far. This is incremented by all the
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running creator threads. */
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static unsigned threads_created;
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/* Thread callback which does nothing, so that the thread exits
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immediatedly. */
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static void *
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do_nothing (void *arg)
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{
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return NULL;
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}
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/* Attribute indicating that the thread should be created in a detached
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fashion. */
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static pthread_attr_t detached;
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/* Barrier to synchronize initialization. */
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static pthread_barrier_t barrier;
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static void *
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creator_thread (void *arg)
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{
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int ret;
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xpthread_barrier_wait (&barrier);
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while (true)
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{
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pthread_t thr;
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/* Thread creation will fail if the kernel does not free old
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threads quickly enough, so we do not report errors. */
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ret = pthread_create (&thr, &detached, do_nothing, NULL);
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if (ret == 0 && __atomic_add_fetch (&threads_created, 1, __ATOMIC_SEQ_CST)
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>= threads_to_create)
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break;
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}
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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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/* Limit the size of the process, so that memory allocation will
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fail without impacting the entire system. */
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{
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struct rlimit limit;
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if (getrlimit (RLIMIT_AS, &limit) != 0)
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{
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printf ("FAIL: getrlimit (RLIMIT_AS) failed: %m\n");
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return 1;
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}
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/* This limit, 800MB, is just a heuristic. Any value can be
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picked. */
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long target = 800 * 1024 * 1024;
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if (limit.rlim_cur == RLIM_INFINITY || limit.rlim_cur > target)
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{
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limit.rlim_cur = target;
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if (setrlimit (RLIMIT_AS, &limit) != 0)
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{
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printf ("FAIL: setrlimit (RLIMIT_AS) failed: %m\n");
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return 1;
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}
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}
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}
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xpthread_attr_init (&detached);
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xpthread_attr_setdetachstate (&detached, PTHREAD_CREATE_DETACHED);
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/* A large thread stack seems beneficial for reproducing a race
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condition in detached thread creation. The goal is to reach the
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limit of the runtime thread stack cache such that the detached
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thread's stack is unmapped after exit and causes a segfault when
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the parent reads the thread descriptor data stored on the the
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unmapped stack. */
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xpthread_attr_setstacksize (&detached, 16 * 1024 * 1024);
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xpthread_barrier_init (&barrier, NULL, creator_threads);
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pthread_t threads[creator_threads];
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for (int i = 0; i < creator_threads; ++i)
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threads[i] = xpthread_create (NULL, creator_thread, NULL);
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for (int i = 0; i < creator_threads; ++i)
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xpthread_join (threads[i]);
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xpthread_attr_destroy (&detached);
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xpthread_barrier_destroy (&barrier);
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return 0;
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}
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#define TIMEOUT 100
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#include <support/test-driver.c>
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