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145 lines
3.7 KiB
C
145 lines
3.7 KiB
C
/* Copyright (C) 2002-2017 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
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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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<http://www.gnu.org/licenses/>. */
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#include <errno.h>
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#include <stdlib.h>
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#include <string.h>
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#include <fork.h>
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#include <atomic.h>
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struct fork_handler *__fork_handlers;
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/* Lock to protect allocation and deallocation of fork handlers. */
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int __fork_lock = LLL_LOCK_INITIALIZER;
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/* Number of pre-allocated handler entries. */
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#define NHANDLER 48
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/* Memory pool for fork handler structures. */
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static struct fork_handler_pool
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{
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struct fork_handler_pool *next;
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struct fork_handler mem[NHANDLER];
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} fork_handler_pool;
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static struct fork_handler *
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fork_handler_alloc (void)
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{
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struct fork_handler_pool *runp = &fork_handler_pool;
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struct fork_handler *result = NULL;
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unsigned int i;
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do
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{
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/* Search for an empty entry. */
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for (i = 0; i < NHANDLER; ++i)
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if (runp->mem[i].refcntr == 0)
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goto found;
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}
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while ((runp = runp->next) != NULL);
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/* We have to allocate a new entry. */
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runp = (struct fork_handler_pool *) calloc (1, sizeof (*runp));
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if (runp != NULL)
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{
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/* Enqueue the new memory pool into the list. */
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runp->next = fork_handler_pool.next;
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fork_handler_pool.next = runp;
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/* We use the last entry on the page. This means when we start
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searching from the front the next time we will find the first
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entry unused. */
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i = NHANDLER - 1;
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found:
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result = &runp->mem[i];
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result->refcntr = 1;
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result->need_signal = 0;
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}
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return result;
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}
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int
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__register_atfork (void (*prepare) (void), void (*parent) (void),
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void (*child) (void), void *dso_handle)
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{
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/* Get the lock to not conflict with other allocations. */
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lll_lock (__fork_lock, LLL_PRIVATE);
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struct fork_handler *newp = fork_handler_alloc ();
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if (newp != NULL)
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{
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/* Initialize the new record. */
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newp->prepare_handler = prepare;
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newp->parent_handler = parent;
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newp->child_handler = child;
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newp->dso_handle = dso_handle;
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__linkin_atfork (newp);
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}
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/* Release the lock. */
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lll_unlock (__fork_lock, LLL_PRIVATE);
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return newp == NULL ? ENOMEM : 0;
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}
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libc_hidden_def (__register_atfork)
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void
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attribute_hidden
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__linkin_atfork (struct fork_handler *newp)
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{
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do
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newp->next = __fork_handlers;
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while (catomic_compare_and_exchange_bool_acq (&__fork_handlers,
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newp, newp->next) != 0);
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}
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libc_freeres_fn (free_mem)
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{
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/* Get the lock to not conflict with running forks. */
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lll_lock (__fork_lock, LLL_PRIVATE);
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/* No more fork handlers. */
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__fork_handlers = NULL;
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/* Free eventually allocated memory blocks for the object pool. */
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struct fork_handler_pool *runp = fork_handler_pool.next;
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memset (&fork_handler_pool, '\0', sizeof (fork_handler_pool));
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/* Release the lock. */
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lll_unlock (__fork_lock, LLL_PRIVATE);
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/* We can free the memory after releasing the lock. */
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while (runp != NULL)
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{
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struct fork_handler_pool *oldp = runp;
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runp = runp->next;
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free (oldp);
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}
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}
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