glibc/include/register-atfork.h

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/* Internal pthread_atfork definitions.
Copyright (C) 2021-2023 Free Software Foundation, Inc.
This file is part of the GNU C Library.
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
Prefer https to http for gnu.org and fsf.org URLs Also, change sources.redhat.com to sourceware.org. This patch was automatically generated by running the following shell script, which uses GNU sed, and which avoids modifying files imported from upstream: sed -ri ' s,(http|ftp)(://(.*\.)?(gnu|fsf|sourceware)\.org($|[^.]|\.[^a-z])),https\2,g s,(http|ftp)(://(.*\.)?)sources\.redhat\.com($|[^.]|\.[^a-z]),https\2sourceware.org\4,g ' \ $(find $(git ls-files) -prune -type f \ ! -name '*.po' \ ! -name 'ChangeLog*' \ ! -path COPYING ! -path COPYING.LIB \ ! -path manual/fdl-1.3.texi ! -path manual/lgpl-2.1.texi \ ! -path manual/texinfo.tex ! -path scripts/config.guess \ ! -path scripts/config.sub ! -path scripts/install-sh \ ! -path scripts/mkinstalldirs ! -path scripts/move-if-change \ ! -path INSTALL ! -path locale/programs/charmap-kw.h \ ! -path po/libc.pot ! -path sysdeps/gnu/errlist.c \ ! '(' -name configure \ -execdir test -f configure.ac -o -f configure.in ';' ')' \ ! '(' -name preconfigure \ -execdir test -f preconfigure.ac ';' ')' \ -print) and then by running 'make dist-prepare' to regenerate files built from the altered files, and then executing the following to cleanup: chmod a+x sysdeps/unix/sysv/linux/riscv/configure # Omit irrelevant whitespace and comment-only changes, # perhaps from a slightly-different Autoconf version. git checkout -f \ sysdeps/csky/configure \ sysdeps/hppa/configure \ sysdeps/riscv/configure \ sysdeps/unix/sysv/linux/csky/configure # Omit changes that caused a pre-commit check to fail like this: # remote: *** error: sysdeps/powerpc/powerpc64/ppc-mcount.S: trailing lines git checkout -f \ sysdeps/powerpc/powerpc64/ppc-mcount.S \ sysdeps/unix/sysv/linux/s390/s390-64/syscall.S # Omit change that caused a pre-commit check to fail like this: # remote: *** error: sysdeps/sparc/sparc64/multiarch/memcpy-ultra3.S: last line does not end in newline git checkout -f sysdeps/sparc/sparc64/multiarch/memcpy-ultra3.S
2019-09-07 05:40:42 +00:00
<https://www.gnu.org/licenses/>. */
#ifndef _REGISTER_ATFORK_H
#define _REGISTER_ATFORK_H
/* Elements of the fork handler lists. */
struct fork_handler
{
void (*prepare_handler) (void);
void (*parent_handler) (void);
void (*child_handler) (void);
void *dso_handle;
Fix deadlock when pthread_atfork handler calls pthread_atfork or dlclose In multi-threaded programs, registering via pthread_atfork, de-registering implicitly via dlclose, or running pthread_atfork handlers during fork was protected by an internal lock. This meant that a pthread_atfork handler attempting to register another handler or dlclose a dynamically loaded library would lead to a deadlock. This commit fixes the deadlock in the following way: During the execution of handlers at fork time, the atfork lock is released prior to the execution of each handler and taken again upon its return. Any handler registrations or de-registrations that occurred during the execution of the handler are accounted for before proceeding with further handler execution. If a handler that hasn't been executed yet gets de-registered by another handler during fork, it will not be executed. If a handler gets registered by another handler during fork, it will not be executed during that particular fork. The possibility that handlers may now be registered or deregistered during handler execution means that identifying the next handler to be run after a given handler may register/de-register others requires some bookkeeping. The fork_handler struct has an additional field, 'id', which is assigned sequentially during registration. Thus, handlers are executed in ascending order of 'id' during 'prepare', and descending order of 'id' during parent/child handler execution after the fork. Two tests are included: * tst-atfork3: Adhemerval Zanella <adhemerval.zanella@linaro.org> This test exercises calling dlclose from prepare, parent, and child handlers. * tst-atfork4: This test exercises calling pthread_atfork and dlclose from the prepare handler. [BZ #24595, BZ #27054] Co-authored-by: Adhemerval Zanella <adhemerval.zanella@linaro.org> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2022-05-24 15:57:36 +00:00
uint64_t id;
};
/* Function to call to unregister fork handlers. */
extern void __unregister_atfork (void *dso_handle) attribute_hidden;
#define UNREGISTER_ATFORK(dso_handle) __unregister_atfork (dso_handle)
enum __run_fork_handler_type
{
atfork_run_prepare,
atfork_run_child,
atfork_run_parent
};
Fix deadlock when pthread_atfork handler calls pthread_atfork or dlclose In multi-threaded programs, registering via pthread_atfork, de-registering implicitly via dlclose, or running pthread_atfork handlers during fork was protected by an internal lock. This meant that a pthread_atfork handler attempting to register another handler or dlclose a dynamically loaded library would lead to a deadlock. This commit fixes the deadlock in the following way: During the execution of handlers at fork time, the atfork lock is released prior to the execution of each handler and taken again upon its return. Any handler registrations or de-registrations that occurred during the execution of the handler are accounted for before proceeding with further handler execution. If a handler that hasn't been executed yet gets de-registered by another handler during fork, it will not be executed. If a handler gets registered by another handler during fork, it will not be executed during that particular fork. The possibility that handlers may now be registered or deregistered during handler execution means that identifying the next handler to be run after a given handler may register/de-register others requires some bookkeeping. The fork_handler struct has an additional field, 'id', which is assigned sequentially during registration. Thus, handlers are executed in ascending order of 'id' during 'prepare', and descending order of 'id' during parent/child handler execution after the fork. Two tests are included: * tst-atfork3: Adhemerval Zanella <adhemerval.zanella@linaro.org> This test exercises calling dlclose from prepare, parent, and child handlers. * tst-atfork4: This test exercises calling pthread_atfork and dlclose from the prepare handler. [BZ #24595, BZ #27054] Co-authored-by: Adhemerval Zanella <adhemerval.zanella@linaro.org> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2022-05-24 15:57:36 +00:00
/* Run the atfork prepare handlers in the reverse order of registration and
return the ID of the last registered handler. If DO_LOCKING is true, the
internal lock is held locked upon return. */
extern uint64_t __run_prefork_handlers (_Bool do_locking) attribute_hidden;
/* Given a handler type (parent or child), run all the atfork handlers in
the order of registration up to and including the handler with id equal
to LASTRUN. If DO_LOCKING is true, the internal lock is unlocked prior
to return. */
extern void __run_postfork_handlers (enum __run_fork_handler_type who,
_Bool do_locking,
uint64_t lastrun) attribute_hidden;
/* C library side function to register new fork handlers. */
extern int __register_atfork (void (*__prepare) (void),
void (*__parent) (void),
void (*__child) (void),
void *dso_handle);
libc_hidden_proto (__register_atfork)
#endif