diff options
Diffstat (limited to 'REORG.TODO/nptl/unregister-atfork.c')
| -rw-r--r-- | REORG.TODO/nptl/unregister-atfork.c | 121 |
1 files changed, 121 insertions, 0 deletions
diff --git a/REORG.TODO/nptl/unregister-atfork.c b/REORG.TODO/nptl/unregister-atfork.c new file mode 100644 index 0000000000..1eb11d60c6 --- /dev/null +++ b/REORG.TODO/nptl/unregister-atfork.c @@ -0,0 +1,121 @@ +/* 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; + } +} |