diff options
Diffstat (limited to 'nptl')
| -rw-r--r-- | nptl/Makefile | 2 | ||||
| -rw-r--r-- | nptl/register-atfork.c | 174 | ||||
| -rw-r--r-- | nptl/unregister-atfork.c | 121 |
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; - } -} |