mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-08 14:20:07 +00:00
122 lines
3.6 KiB
C
122 lines
3.6 KiB
C
/* Copyright (C) 2002-2017 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 <futex-internal.h>
|
|
|
|
|
|
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)
|
|
futex_wait_simple (&deleted->handler->refcntr, val, FUTEX_PRIVATE);
|
|
|
|
deleted = deleted->next;
|
|
}
|
|
}
|