+2016-04-14 Florian Weimer <fweimer@redhat.com>
+
+ [BZ #19431]
+ Run the malloc fork handler as late as possible to avoid deadlocks.
+ * malloc/malloc-internal.h: New file.
+ * malloc/malloc.c: Include it.
+ * malloc/arena.c (ATFORK_MEM): Remove.
+ (__malloc_fork_lock_parent): Rename from ptmalloc_lock_all.
+ Update comment.
+ (__malloc_fork_unlock_parent): Rename from ptmalloc_unlock_all.
+ (__malloc_fork_unlock_child): Rename from ptmalloc_unlock_all2.
+ Remove outdated comment.
+ (ptmalloc_init): Do not call thread_atfork. Remove
+ thread_atfork_static.
+ * malloc/tst-malloc-fork-deadlock.c: New file.
+ * Makefile (tests): Add tst-malloc-fork-deadlock.
+ (tst-malloc-fork-deadlock): Link against libpthread.
+ * manual/memory.texi (Aligned Memory Blocks): Update safety
+ annotation comments.
+ * sysdeps/nptl/fork.c (__libc_fork): Call
+ __malloc_fork_lock_parent, __malloc_fork_unlock_parent,
+ __malloc_fork_unlock_child.
+ * sysdeps/mach/hurd/fork.c (__fork): Likewise.
+
2015-12-21 Florian Weimer <fweimer@redhat.com>
[BZ #19182]
tests := mallocbug tst-malloc tst-valloc tst-calloc tst-obstack \
tst-mallocstate tst-mcheck tst-mallocfork tst-trim1 \
tst-malloc-usable tst-realloc tst-posix_memalign \
- tst-pvalloc tst-memalign tst-mallopt
+ tst-pvalloc tst-memalign tst-mallopt tst-malloc-fork-deadlock
test-srcs = tst-mtrace
routines = malloc morecore mcheck mtrace obstack
libmemusage-routines = memusage
libmemusage-inhibit-o = $(filter-out .os,$(object-suffixes))
+$(objpfx)tst-malloc-fork-deadlock: $(shared-thread-library)
+
# These should be removed by `make clean'.
extra-objs = mcheck-init.o libmcheck.a
static void (*save_free_hook) (void *__ptr, const void *);
static void *save_arena;
-# ifdef ATFORK_MEM
-ATFORK_MEM;
-# endif
-
/* Magic value for the thread-specific arena pointer when
malloc_atfork() is in use. */
/* Counter for number of times the list is locked by the same thread. */
static unsigned int atfork_recursive_cntr;
-/* The following two functions are registered via thread_atfork() to
- make sure that the mutexes remain in a consistent state in the
- fork()ed version of a thread. Also adapt the malloc and free hooks
- temporarily, because the `atfork' handler mechanism may use
- malloc/free internally (e.g. in LinuxThreads). */
+/* The following three functions are called around fork from a
+ multi-threaded process. We do not use the general fork handler
+ mechanism to make sure that our handlers are the last ones being
+ called, so that other fork handlers can use the malloc
+ subsystem. */
-static void
-ptmalloc_lock_all (void)
+void
+__malloc_fork_lock_parent (void)
{
mstate ar_ptr;
return;
/* We do not acquire free_list_lock here because we completely
- reconstruct free_list in ptmalloc_unlock_all2. */
+ reconstruct free_list in __malloc_fork_unlock_child. */
if (mutex_trylock (&list_lock))
{
__free_hook = free_atfork;
/* Only the current thread may perform malloc/free calls now.
save_arena will be reattached to the current thread, in
- ptmalloc_lock_all, so save_arena->attached_threads is not
+ __malloc_fork_lock_parent, so save_arena->attached_threads is not
updated. */
save_arena = thread_arena;
thread_arena = ATFORK_ARENA_PTR;
++atfork_recursive_cntr;
}
-static void
-ptmalloc_unlock_all (void)
+void
+__malloc_fork_unlock_parent (void)
{
mstate ar_ptr;
return;
/* Replace ATFORK_ARENA_PTR with save_arena.
- save_arena->attached_threads was not changed in ptmalloc_lock_all
- and is still correct. */
+ save_arena->attached_threads was not changed in
+ __malloc_fork_lock_parent and is still correct. */
thread_arena = save_arena;
__malloc_hook = save_malloc_hook;
__free_hook = save_free_hook;
(void) mutex_unlock (&list_lock);
}
-# ifdef __linux__
-
-/* In NPTL, unlocking a mutex in the child process after a
- fork() is currently unsafe, whereas re-initializing it is safe and
- does not leak resources. Therefore, a special atfork handler is
- installed for the child. */
-
-static void
-ptmalloc_unlock_all2 (void)
+void
+__malloc_fork_unlock_child (void)
{
mstate ar_ptr;
# else
# define ptmalloc_unlock_all2 ptmalloc_unlock_all
-# endif
-#endif /* !NO_THREADS */
+#endif
+
/* Initialization routine. */
#include <string.h>
#endif
thread_arena = &main_arena;
- thread_atfork (ptmalloc_lock_all, ptmalloc_unlock_all, ptmalloc_unlock_all2);
const char *s = NULL;
if (__glibc_likely (_environ != NULL))
{
__malloc_initialized = 1;
}
-/* There are platforms (e.g. Hurd) with a link-time hook mechanism. */
-#ifdef thread_atfork_static
-thread_atfork_static (ptmalloc_lock_all, ptmalloc_unlock_all, \
- ptmalloc_unlock_all2)
-#endif
-
-
-
/* Managing heaps and arenas (for concurrent threads) */
#if MALLOC_DEBUG > 1
limit is reached). At this point, some arena has to be attached
to two threads. We could acquire the arena lock before list_lock
to make it less likely that reused_arena picks this new arena,
- but this could result in a deadlock with ptmalloc_lock_all. */
+ but this could result in a deadlock with
+ __malloc_fork_lock_parent. */
(void) mutex_lock (&a->mutex);
--- /dev/null
+/* Internal declarations for malloc, for use within libc.
+ Copyright (C) 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; see the file COPYING.LIB. If
+ not, see <http://www.gnu.org/licenses/>. */
+
+#ifndef _MALLOC_PRIVATE_H
+#define _MALLOC_PRIVATE_H
+
+/* Called in the parent process before a fork. */
+void __malloc_fork_lock_parent (void) internal_function attribute_hidden;
+
+/* Called in the parent process after a fork. */
+void __malloc_fork_unlock_parent (void) internal_function attribute_hidden;
+
+/* Called in the child process after a fork. */
+void __malloc_fork_unlock_child (void) internal_function attribute_hidden;
+
+
+#endif /* _MALLOC_PRIVATE_H */
/* For MIN, MAX, powerof2. */
#include <sys/param.h>
+/* For ALIGN_UP et. al. */
+#include <libc-internal.h>
+
+#include <malloc/malloc-internal.h>
/*
Debugging:
--- /dev/null
+/* Test concurrent fork, getline, and fflush (NULL).
+ Copyright (C) 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; see the file COPYING.LIB. If
+ not, see <http://www.gnu.org/licenses/>. */
+
+#include <sys/wait.h>
+#include <unistd.h>
+#include <errno.h>
+#include <stdio.h>
+#include <pthread.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <malloc.h>
+#include <time.h>
+#include <string.h>
+#include <signal.h>
+
+static int do_test (void);
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
+
+enum {
+ /* Number of threads which call fork. */
+ fork_thread_count = 4,
+ /* Number of threads which call getline (and, indirectly,
+ malloc). */
+ read_thread_count = 8,
+};
+
+static bool termination_requested;
+
+static void *
+fork_thread_function (void *closure)
+{
+ while (!__atomic_load_n (&termination_requested, __ATOMIC_RELAXED))
+ {
+ pid_t pid = fork ();
+ if (pid < 0)
+ {
+ printf ("error: fork: %m\n");
+ abort ();
+ }
+ else if (pid == 0)
+ _exit (17);
+
+ int status;
+ if (waitpid (pid, &status, 0) < 0)
+ {
+ printf ("error: waitpid: %m\n");
+ abort ();
+ }
+ if (!WIFEXITED (status) || WEXITSTATUS (status) != 17)
+ {
+ printf ("error: waitpid returned invalid status: %d\n", status);
+ abort ();
+ }
+ }
+ return NULL;
+}
+
+static char *file_to_read;
+
+static void *
+read_thread_function (void *closure)
+{
+ FILE *f = fopen (file_to_read, "r");
+ if (f == NULL)
+ {
+ printf ("error: fopen (%s): %m\n", file_to_read);
+ abort ();
+ }
+
+ while (!__atomic_load_n (&termination_requested, __ATOMIC_RELAXED))
+ {
+ rewind (f);
+ char *line = NULL;
+ size_t line_allocated = 0;
+ ssize_t ret = getline (&line, &line_allocated, f);
+ if (ret < 0)
+ {
+ printf ("error: getline: %m\n");
+ abort ();
+ }
+ free (line);
+ }
+ fclose (f);
+
+ return NULL;
+}
+
+static void *
+flushall_thread_function (void *closure)
+{
+ while (!__atomic_load_n (&termination_requested, __ATOMIC_RELAXED))
+ if (fflush (NULL) != 0)
+ {
+ printf ("error: fflush (NULL): %m\n");
+ abort ();
+ }
+ return NULL;
+}
+
+static void
+create_threads (pthread_t *threads, size_t count, void *(*func) (void *))
+{
+ for (size_t i = 0; i < count; ++i)
+ {
+ int ret = pthread_create (threads + i, NULL, func, NULL);
+ if (ret != 0)
+ {
+ errno = ret;
+ printf ("error: pthread_create: %m\n");
+ abort ();
+ }
+ }
+}
+
+static void
+join_threads (pthread_t *threads, size_t count)
+{
+ for (size_t i = 0; i < count; ++i)
+ {
+ int ret = pthread_join (threads[i], NULL);
+ if (ret != 0)
+ {
+ errno = ret;
+ printf ("error: pthread_join: %m\n");
+ abort ();
+ }
+ }
+}
+
+/* Create a file which consists of a single long line, and assigns
+ file_to_read. The hope is that this triggers an allocation in
+ getline which needs a lock. */
+static void
+create_file_with_large_line (void)
+{
+ int fd = create_temp_file ("bug19431-large-line", &file_to_read);
+ if (fd < 0)
+ {
+ printf ("error: create_temp_file: %m\n");
+ abort ();
+ }
+ FILE *f = fdopen (fd, "w+");
+ if (f == NULL)
+ {
+ printf ("error: fdopen: %m\n");
+ abort ();
+ }
+ for (int i = 0; i < 50000; ++i)
+ fputc ('x', f);
+ fputc ('\n', f);
+ if (ferror (f))
+ {
+ printf ("error: fputc: %m\n");
+ abort ();
+ }
+ if (fclose (f) != 0)
+ {
+ printf ("error: fclose: %m\n");
+ abort ();
+ }
+}
+
+static int
+do_test (void)
+{
+ /* Make sure that we do not exceed the arena limit with the number
+ of threads we configured. */
+ if (mallopt (M_ARENA_MAX, 400) == 0)
+ {
+ printf ("error: mallopt (M_ARENA_MAX) failed\n");
+ return 1;
+ }
+
+ /* Leave some room for shutting down all threads gracefully. */
+ int timeout = 3;
+ if (timeout > TIMEOUT)
+ timeout = TIMEOUT - 1;
+
+ create_file_with_large_line ();
+
+ pthread_t fork_threads[fork_thread_count];
+ create_threads (fork_threads, fork_thread_count, fork_thread_function);
+ pthread_t read_threads[read_thread_count];
+ create_threads (read_threads, read_thread_count, read_thread_function);
+ pthread_t flushall_threads[1];
+ create_threads (flushall_threads, 1, flushall_thread_function);
+
+ struct timespec ts = {timeout, 0};
+ if (nanosleep (&ts, NULL))
+ {
+ printf ("error: error: nanosleep: %m\n");
+ abort ();
+ }
+
+ __atomic_store_n (&termination_requested, true, __ATOMIC_RELAXED);
+
+ join_threads (flushall_threads, 1);
+ join_threads (read_threads, read_thread_count);
+ join_threads (fork_threads, fork_thread_count);
+
+ free (file_to_read);
+
+ return 0;
+}
@c _dl_addr_inside_object ok
@c determine_info ok
@c __rtld_lock_unlock_recursive (dl_load_lock) @aculock
-@c thread_atfork @asulock @aculock @acsfd @acsmem
-@c __register_atfork @asulock @aculock @acsfd @acsmem
-@c lll_lock (__fork_lock) @asulock @aculock
-@c fork_handler_alloc @asulock @aculock @acsfd @acsmem
-@c calloc dup @asulock @aculock @acsfd @acsmem
-@c __linkin_atfork ok
-@c catomic_compare_and_exchange_bool_acq ok
-@c lll_unlock (__fork_lock) @aculock
@c *_environ @mtsenv
@c next_env_entry ok
@c strcspn dup ok
#include <assert.h>
#include "hurdmalloc.h" /* XXX */
#include <tls.h>
+#include <malloc/malloc-internal.h>
#undef __fork
/* Run things that prepare for forking before we create the task. */
RUN_HOOK (_hurd_fork_prepare_hook, ());
+ /* Acquire malloc locks. This needs to come last because fork
+ handlers may use malloc, and the libio list lock has an
+ indirect malloc dependency as well (via the getdelim
+ function). */
+ __malloc_fork_lock_parent ();
+
/* Lock things that want to be locked before we fork. */
{
void *const *p;
nthreads * sizeof (*threads));
}
+ /* Release malloc locks. */
+ __malloc_fork_unlock_parent ();
+
/* Run things that want to run in the parent to restore it to
normality. Usually prepare hooks and parent hooks are
symmetrical: the prepare hook arrests state in some way for the
/* Forking clears the trace flag. */
__sigemptyset (&_hurdsig_traced);
+ /* Release malloc locks. */
+ __malloc_fork_unlock_child ();
+
/* Run things that want to run in the child task to set up. */
RUN_HOOK (_hurd_fork_child_hook, ());
#include <nptl/pthreadP.h>
#include <fork.h>
#include <arch-fork.h>
-
+#include <malloc/malloc-internal.h>
static void
fresetlockfiles (void)
_IO_list_lock ();
+ /* Acquire malloc locks. This needs to come last because fork
+ handlers may use malloc, and the libio list lock has an indirect
+ malloc dependency as well (via the getdelim function). */
+ __malloc_fork_lock_parent ();
+
#ifndef NDEBUG
pid_t ppid = THREAD_GETMEM (THREAD_SELF, tid);
#endif
# endif
#endif
+ /* Release malloc locks. */
+ __malloc_fork_unlock_child ();
+
/* Reset the file list. These are recursive mutexes. */
fresetlockfiles ();
/* Restore the PID value. */
THREAD_SETMEM (THREAD_SELF, pid, parentpid);
+ /* Release malloc locks, parent process variant. */
+ __malloc_fork_unlock_parent ();
+
/* We execute this even if the 'fork' call failed. */
_IO_list_unlock ();
projects / thirdparty / glibc.git / commitdiff
