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-rw-r--r--nptl/Makefile2
-rw-r--r--nptl/register-atfork.c174
-rw-r--r--nptl/unregister-atfork.c121
3 files changed, 90 insertions, 207 deletions
diff --git a/nptl/Makefile b/nptl/Makefile
index 9340f9f699..de37fb4680 100644
--- a/nptl/Makefile
+++ b/nptl/Makefile
@@ -30,7 +30,7 @@ install-lib-ldscripts := libpthread.so
routines = alloca_cutoff forward libc-lowlevellock libc-cancellation \
libc-cleanup libc_pthread_init libc_multiple_threads \
- register-atfork unregister-atfork pthread_self
+ register-atfork pthread_self
shared-only-routines = forward
# We need to provide certain routines for compatibility with existing
diff --git a/nptl/register-atfork.c b/nptl/register-atfork.c
index f309cec945..5ff1c1be8c 100644
--- a/nptl/register-atfork.c
+++ b/nptl/register-atfork.c
@@ -22,123 +22,127 @@
#include <fork.h>
#include <atomic.h>
+#define DYNARRAY_ELEMENT struct fork_handler
+#define DYNARRAY_STRUCT fork_handler_list
+#define DYNARRAY_PREFIX fork_handler_list_
+#define DYNARRAY_INITIAL_SIZE 48
+#include <malloc/dynarray-skeleton.c>
-struct fork_handler *__fork_handlers;
-
-/* Lock to protect allocation and deallocation of fork handlers. */
-int __fork_lock = LLL_LOCK_INITIALIZER;
-
-
-/* Number of pre-allocated handler entries. */
-#define NHANDLER 48
-
-/* Memory pool for fork handler structures. */
-static struct fork_handler_pool
-{
- struct fork_handler_pool *next;
- struct fork_handler mem[NHANDLER];
-} fork_handler_pool;
-
-
-static struct fork_handler *
-fork_handler_alloc (void)
-{
- struct fork_handler_pool *runp = &fork_handler_pool;
- struct fork_handler *result = NULL;
- unsigned int i;
-
- do
- {
- /* Search for an empty entry. */
- for (i = 0; i < NHANDLER; ++i)
- if (runp->mem[i].refcntr == 0)
- goto found;
- }
- while ((runp = runp->next) != NULL);
-
- /* We have to allocate a new entry. */
- runp = (struct fork_handler_pool *) calloc (1, sizeof (*runp));
- if (runp != NULL)
- {
- /* Enqueue the new memory pool into the list. */
- runp->next = fork_handler_pool.next;
- fork_handler_pool.next = runp;
-
- /* We use the last entry on the page. This means when we start
- searching from the front the next time we will find the first
- entry unused. */
- i = NHANDLER - 1;
-
- found:
- result = &runp->mem[i];
- result->refcntr = 1;
- result->need_signal = 0;
- }
-
- return result;
-}
+static struct fork_handler_list fork_handlers;
+static bool fork_handler_init = false;
+static int atfork_lock = LLL_LOCK_INITIALIZER;
int
__register_atfork (void (*prepare) (void), void (*parent) (void),
void (*child) (void), void *dso_handle)
{
- /* Get the lock to not conflict with other allocations. */
- lll_lock (__fork_lock, LLL_PRIVATE);
+ lll_lock (atfork_lock, LLL_PRIVATE);
- struct fork_handler *newp = fork_handler_alloc ();
+ if (!fork_handler_init)
+ {
+ fork_handler_list_init (&fork_handlers);
+ fork_handler_init = true;
+ }
+ struct fork_handler *newp = fork_handler_list_emplace (&fork_handlers);
if (newp != NULL)
{
- /* Initialize the new record. */
newp->prepare_handler = prepare;
newp->parent_handler = parent;
newp->child_handler = child;
newp->dso_handle = dso_handle;
-
- __linkin_atfork (newp);
}
/* Release the lock. */
- lll_unlock (__fork_lock, LLL_PRIVATE);
+ lll_unlock (atfork_lock, LLL_PRIVATE);
return newp == NULL ? ENOMEM : 0;
}
libc_hidden_def (__register_atfork)
+static struct fork_handler *
+fork_handler_list_find (struct fork_handler_list *fork_handlers,
+ void *dso_handle)
+{
+ for (size_t i = 0; i < fork_handler_list_size (fork_handlers); i++)
+ {
+ struct fork_handler *elem = fork_handler_list_at (fork_handlers, i);
+ if (elem->dso_handle == dso_handle)
+ return elem;
+ }
+ return NULL;
+}
void
-attribute_hidden
-__linkin_atfork (struct fork_handler *newp)
+__unregister_atfork (void *dso_handle)
{
- do
- newp->next = __fork_handlers;
- while (catomic_compare_and_exchange_bool_acq (&__fork_handlers,
- newp, newp->next) != 0);
-}
+ lll_lock (atfork_lock, LLL_PRIVATE);
+
+ struct fork_handler *first = fork_handler_list_find (&fork_handlers,
+ dso_handle);
+ /* Removing is done by shifting the elements in the way the elements
+ that are not to be removed appear in the beginning in dynarray.
+ This avoid the quadradic run-time if a naive strategy to remove and
+ shift one element at time. */
+ if (first != NULL)
+ {
+ struct fork_handler *new_end = first;
+ first++;
+ for (; first != fork_handler_list_end (&fork_handlers); ++first)
+ {
+ if (first->dso_handle != dso_handle)
+ {
+ *new_end = *first;
+ ++new_end;
+ }
+ }
+
+ ptrdiff_t removed = first - new_end;
+ for (size_t i = 0; i < removed; i++)
+ fork_handler_list_remove_last (&fork_handlers);
+ }
+ lll_unlock (atfork_lock, LLL_PRIVATE);
+}
-libc_freeres_fn (free_mem)
+void
+__run_fork_handlers (enum __run_fork_handler_type who)
{
- /* Get the lock to not conflict with running forks. */
- lll_lock (__fork_lock, LLL_PRIVATE);
+ struct fork_handler *runp;
- /* No more fork handlers. */
- __fork_handlers = NULL;
+ if (who == atfork_run_prepare)
+ {
+ lll_lock (atfork_lock, LLL_PRIVATE);
+ size_t sl = fork_handler_list_size (&fork_handlers);
+ for (size_t i = sl; i > 0; i--)
+ {
+ runp = fork_handler_list_at (&fork_handlers, i - 1);
+ if (runp->prepare_handler != NULL)
+ runp->prepare_handler ();
+ }
+ }
+ else
+ {
+ size_t sl = fork_handler_list_size (&fork_handlers);
+ for (size_t i = 0; i < sl; i++)
+ {
+ runp = fork_handler_list_at (&fork_handlers, i);
+ if (who == atfork_run_child && runp->child_handler)
+ runp->child_handler ();
+ else if (who == atfork_run_parent && runp->parent_handler)
+ runp->parent_handler ();
+ }
+ lll_unlock (atfork_lock, LLL_PRIVATE);
+ }
+}
- /* Free eventually allocated memory blocks for the object pool. */
- struct fork_handler_pool *runp = fork_handler_pool.next;
- memset (&fork_handler_pool, '\0', sizeof (fork_handler_pool));
+libc_freeres_fn (free_mem)
+{
+ lll_lock (atfork_lock, LLL_PRIVATE);
- /* Release the lock. */
- lll_unlock (__fork_lock, LLL_PRIVATE);
+ fork_handler_list_free (&fork_handlers);
- /* We can free the memory after releasing the lock. */
- while (runp != NULL)
- {
- struct fork_handler_pool *oldp = runp;
- runp = runp->next;
- free (oldp);
- }
+ lll_unlock (atfork_lock, LLL_PRIVATE);
}
diff --git a/nptl/unregister-atfork.c b/nptl/unregister-atfork.c
deleted file mode 100644
index 20411ed14c..0000000000
--- a/nptl/unregister-atfork.c
+++ /dev/null
@@ -1,121 +0,0 @@
-/* Copyright (C) 2002-2018 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;
- }
-}
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