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Diffstat (limited to 'nptl/tst-create-detached.c')
| -rw-r--r-- | nptl/tst-create-detached.c | 137 |
1 files changed, 137 insertions, 0 deletions
diff --git a/nptl/tst-create-detached.c b/nptl/tst-create-detached.c new file mode 100644 index 0000000000..ea93e441c7 --- /dev/null +++ b/nptl/tst-create-detached.c @@ -0,0 +1,137 @@ +/* Bug 20116: Test rapid creation of detached threads. + Copyright (C) 2017 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; see the file COPYING.LIB. If + not, see <http://www.gnu.org/licenses/>. */ + +/* The goal of the test is to trigger a failure if the parent touches + any part of the thread descriptor after the detached thread has + exited. We test this by creating many detached threads with large + stacks. The stacks quickly fill the the stack cache and subsequent + threads will start to cause the thread stacks to be immediately + unmapped to satisfy the stack cache max. With the stacks being + unmapped the parent's read of any part of the thread descriptor will + trigger a segfault. That segfault is what we are trying to cause, + since any segfault is a defect in the implementation. */ + +#include <pthread.h> +#include <stdio.h> +#include <errno.h> +#include <unistd.h> +#include <stdbool.h> +#include <sys/resource.h> +#include <support/xthread.h> + +/* Number of threads to create. */ +enum { threads_to_create = 100000 }; + +/* Number of threads which should spawn other threads. */ +enum { creator_threads = 2 }; + +/* Counter of threads created so far. This is incremented by all the + running creator threads. */ +static unsigned threads_created; + +/* Thread callback which does nothing, so that the thread exits + immediatedly. */ +static void * +do_nothing (void *arg) +{ + return NULL; +} + +/* Attribute indicating that the thread should be created in a detached + fashion. */ +static pthread_attr_t detached; + +/* Barrier to synchronize initialization. */ +static pthread_barrier_t barrier; + +static void * +creator_thread (void *arg) +{ + int ret; + xpthread_barrier_wait (&barrier); + + while (true) + { + pthread_t thr; + /* Thread creation will fail if the kernel does not free old + threads quickly enough, so we do not report errors. */ + ret = pthread_create (&thr, &detached, do_nothing, NULL); + if (ret == 0 && __atomic_add_fetch (&threads_created, 1, __ATOMIC_SEQ_CST) + >= threads_to_create) + break; + } + + return NULL; +} + +static int +do_test (void) +{ + /* Limit the size of the process, so that memory allocation will + fail without impacting the entire system. */ + { + struct rlimit limit; + if (getrlimit (RLIMIT_AS, &limit) != 0) + { + printf ("FAIL: getrlimit (RLIMIT_AS) failed: %m\n"); + return 1; + } + /* This limit, 800MB, is just a heuristic. Any value can be + picked. */ + long target = 800 * 1024 * 1024; + if (limit.rlim_cur == RLIM_INFINITY || limit.rlim_cur > target) + { + limit.rlim_cur = target; + if (setrlimit (RLIMIT_AS, &limit) != 0) + { + printf ("FAIL: setrlimit (RLIMIT_AS) failed: %m\n"); + return 1; + } + } + } + + xpthread_attr_init (&detached); + + xpthread_attr_setdetachstate (&detached, PTHREAD_CREATE_DETACHED); + + /* A large thread stack seems beneficial for reproducing a race + condition in detached thread creation. The goal is to reach the + limit of the runtime thread stack cache such that the detached + thread's stack is unmapped after exit and causes a segfault when + the parent reads the thread descriptor data stored on the the + unmapped stack. */ + xpthread_attr_setstacksize (&detached, 16 * 1024 * 1024); + + xpthread_barrier_init (&barrier, NULL, creator_threads); + + pthread_t threads[creator_threads]; + + for (int i = 0; i < creator_threads; ++i) + threads[i] = xpthread_create (NULL, creator_thread, NULL); + + for (int i = 0; i < creator_threads; ++i) + xpthread_join (threads[i]); + + xpthread_attr_destroy (&detached); + + xpthread_barrier_destroy (&barrier); + + return 0; +} + +#include <support/test-driver.c> |