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024a7640ab
The fix for bug 19329 caused a regression such that pthread_create can
deadlock when concurrent ctors from dlopen are waiting for it to finish.
Use a new GL(dl_load_tls_lock) in pthread_create that is not taken
around ctors in dlopen.
The new lock is also used in __tls_get_addr instead of GL(dl_load_lock).
The new lock is held in _dl_open_worker and _dl_close_worker around
most of the logic before/after the init/fini routines. When init/fini
routines are running then TLS is in a consistent, usable state.
In _dl_open_worker the new lock requires catching and reraising dlopen
failures that happen in the critical section.
The new lock is reinitialized in a fork child, to keep the existing
behaviour and it is kept recursive in case malloc interposition or TLS
access from signal handlers can retake it. It is not obvious if this
is necessary or helps, but avoids changing the preexisting behaviour.
The new lock may be more appropriate for dl_iterate_phdr too than
GL(dl_load_write_lock), since TLS state of an incompletely loaded
module may be accessed. If the new lock can replace the old one,
that can be a separate change.
Fixes bug 28357.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
(cherry picked from commit 83b5323261)
137 lines
4.2 KiB
C
137 lines
4.2 KiB
C
/* fork - create a child process.
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Copyright (C) 1991-2021 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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#include <fork.h>
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#include <libio/libioP.h>
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#include <ldsodefs.h>
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#include <malloc/malloc-internal.h>
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#include <nss/nss_database.h>
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#include <register-atfork.h>
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#include <stdio-lock.h>
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#include <sys/single_threaded.h>
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#include <unwind-link.h>
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static void
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fresetlockfiles (void)
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{
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_IO_ITER i;
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for (i = _IO_iter_begin(); i != _IO_iter_end(); i = _IO_iter_next(i))
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if ((_IO_iter_file (i)->_flags & _IO_USER_LOCK) == 0)
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_IO_lock_init (*((_IO_lock_t *) _IO_iter_file(i)->_lock));
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}
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pid_t
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__libc_fork (void)
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{
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/* Determine if we are running multiple threads. We skip some fork
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handlers in the single-thread case, to make fork safer to use in
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signal handlers. Although POSIX has dropped async-signal-safe
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requirement for fork (Austin Group tracker issue #62) this is
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best effort to make is async-signal-safe at least for single-thread
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case. */
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bool multiple_threads = __libc_single_threaded == 0;
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__run_fork_handlers (atfork_run_prepare, multiple_threads);
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struct nss_database_data nss_database_data;
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/* If we are not running multiple threads, we do not have to
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preserve lock state. If fork runs from a signal handler, only
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async-signal-safe functions can be used in the child. These data
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structures are only used by unsafe functions, so their state does
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not matter if fork was called from a signal handler. */
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if (multiple_threads)
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{
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call_function_static_weak (__nss_database_fork_prepare_parent,
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&nss_database_data);
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_IO_list_lock ();
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/* Acquire malloc locks. This needs to come last because fork
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handlers may use malloc, and the libio list lock has an
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indirect malloc dependency as well (via the getdelim
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function). */
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call_function_static_weak (__malloc_fork_lock_parent);
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}
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pid_t pid = _Fork ();
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if (pid == 0)
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{
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fork_system_setup ();
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/* Reset the lock state in the multi-threaded case. */
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if (multiple_threads)
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{
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__libc_unwind_link_after_fork ();
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fork_system_setup_after_fork ();
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/* Release malloc locks. */
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call_function_static_weak (__malloc_fork_unlock_child);
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/* Reset the file list. These are recursive mutexes. */
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fresetlockfiles ();
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/* Reset locks in the I/O code. */
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_IO_list_resetlock ();
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call_function_static_weak (__nss_database_fork_subprocess,
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&nss_database_data);
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}
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/* Reset the lock the dynamic loader uses to protect its data. */
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__rtld_lock_initialize (GL(dl_load_lock));
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/* Reset the lock protecting dynamic TLS related data. */
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__rtld_lock_initialize (GL(dl_load_tls_lock));
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reclaim_stacks ();
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/* Run the handlers registered for the child. */
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__run_fork_handlers (atfork_run_child, multiple_threads);
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}
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else
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{
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/* If _Fork failed, preserve its errno value. */
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int save_errno = errno;
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/* Release acquired locks in the multi-threaded case. */
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if (multiple_threads)
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{
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/* Release malloc locks, parent process variant. */
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call_function_static_weak (__malloc_fork_unlock_parent);
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/* We execute this even if the 'fork' call failed. */
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_IO_list_unlock ();
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}
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/* Run the handlers registered for the parent. */
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__run_fork_handlers (atfork_run_parent, multiple_threads);
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if (pid < 0)
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__set_errno (save_errno);
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}
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return pid;
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}
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weak_alias (__libc_fork, __fork)
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libc_hidden_def (__fork)
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weak_alias (__libc_fork, fork)
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