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- /* Copyright (C) 2002, 2003, 2005, 2007 Free Software Foundation, Inc.
- This file is part of the GNU C Library.
- Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
- 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/>. */
- #include <errno.h>
- #include <stdlib.h>
- #include <fork.h>
- #include <atomic.h>
- #include <tls.h>
- #ifdef __ARCH_USE_MMU__
- void
- __unregister_atfork (
- void *dso_handle)
- {
- /* Check whether there is any entry in the list which we have to
- remove. It is likely that this is not the case so don't bother
- getting the lock.
- We do not worry about other threads adding entries for this DSO
- right this moment. If this happens this is a race and we can do
- whatever we please. The program will crash anyway seen. */
- struct fork_handler *runp = __fork_handlers;
- struct fork_handler *lastp = NULL;
- while (runp != NULL)
- if (runp->dso_handle == dso_handle)
- break;
- else
- {
- lastp = runp;
- runp = runp->next;
- }
- if (runp == NULL)
- /* Nothing to do. */
- return;
- /* Get the lock to not conflict with additions or deletions. Note
- that there couldn't have been another thread deleting something.
- The __unregister_atfork function is only called from the
- dlclose() code which itself serializes the operations. */
- lll_lock (__fork_lock, LLL_PRIVATE);
- /* We have to create a new list with all the entries we don't remove. */
- struct deleted_handler
- {
- struct fork_handler *handler;
- struct deleted_handler *next;
- } *deleted = NULL;
- /* Remove the entries for the DSO which is unloaded from the list.
- It's a single linked list so readers are. */
- do
- {
- again:
- if (runp->dso_handle == dso_handle)
- {
- if (lastp == NULL)
- {
- /* We have to use an atomic operation here because
- __linkin_atfork also uses one. */
- if (catomic_compare_and_exchange_bool_acq (&__fork_handlers,
- runp->next, runp)
- != 0)
- {
- runp = __fork_handlers;
- goto again;
- }
- }
- else
- lastp->next = runp->next;
- /* We cannot overwrite the ->next element now. Put the deleted
- entries in a separate list. */
- struct deleted_handler *newp = alloca (sizeof (*newp));
- newp->handler = runp;
- newp->next = deleted;
- deleted = newp;
- }
- else
- lastp = runp;
- runp = runp->next;
- }
- while (runp != NULL);
- /* Release the lock. */
- lll_unlock (__fork_lock, LLL_PRIVATE);
- /* Walk the list of all entries which have to be deleted. */
- while (deleted != NULL)
- {
- /* We need to be informed by possible current users. */
- deleted->handler->need_signal = 1;
- /* Make sure this gets written out first. */
- atomic_write_barrier ();
- /* Decrement the reference counter. If it does not reach zero
- wait for the last user. */
- atomic_decrement (&deleted->handler->refcntr);
- unsigned int val;
- while ((val = deleted->handler->refcntr) != 0)
- lll_futex_wait (&deleted->handler->refcntr, val, LLL_PRIVATE);
- deleted = deleted->next;
- }
- }
- #else
- void
- __unregister_atfork (
- void *dso_handle)
- {
- /* Nothing to do. */
- }
- #endif
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