mirror of
https://sourceware.org/git/glibc.git
synced 2024-12-01 01:00:10 +00:00
60f8062425
Commit27761a1042("Refactor atfork handlers") introduced a lock, atfork_lock, around fork handler list accesses. It turns out that this lock occasionally results in self-deadlocks in malloc/tst-mallocfork2: (gdb) bt #0 __lll_lock_wait_private () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:63 #1 0x00007f160c6f927a in __run_fork_handlers (who=(unknown: 209394016), who@entry=atfork_run_prepare) at register-atfork.c:116 #2 0x00007f160c6b7897 in __libc_fork () at ../sysdeps/nptl/fork.c:58 #3 0x00000000004027d6 in sigusr1_handler (signo=<optimized out>) at tst-mallocfork2.c:80 #4 sigusr1_handler (signo=<optimized out>) at tst-mallocfork2.c:64 #5 <signal handler called> #6 0x00007f160c6f92e4 in __run_fork_handlers (who=who@entry=atfork_run_parent) at register-atfork.c:136 #7 0x00007f160c6b79a2 in __libc_fork () at ../sysdeps/nptl/fork.c:152 #8 0x0000000000402567 in do_test () at tst-mallocfork2.c:156 #9 0x0000000000402dd2 in support_test_main (argc=1, argv=0x7ffc81ef1ab0, config=config@entry=0x7ffc81ef1970) at support_test_main.c:350 #10 0x0000000000402362 in main (argc=<optimized out>, argv=<optimized out>) at ../support/test-driver.c:168 If no locking happens in the single-threaded case (where fork is expected to be async-signal-safe), this deadlock is avoided. (pthread_atfork is not required to be async-signal-safe, so a fork call from a signal handler interrupting pthread_atfork is not a problem.) (cherry picked from commit669ff911e2)
67 lines
2.4 KiB
C
67 lines
2.4 KiB
C
/* 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 <lowlevellock.h>
|
|
|
|
/* The fork generation counter, defined in libpthread. */
|
|
extern unsigned long int __fork_generation attribute_hidden;
|
|
|
|
/* Pointer to the fork generation counter in the thread library. */
|
|
extern unsigned long int *__fork_generation_pointer attribute_hidden;
|
|
|
|
/* Elements of the fork handler lists. */
|
|
struct fork_handler
|
|
{
|
|
void (*prepare_handler) (void);
|
|
void (*parent_handler) (void);
|
|
void (*child_handler) (void);
|
|
void *dso_handle;
|
|
};
|
|
|
|
/* 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
|
|
};
|
|
|
|
/* Run the atfork handlers and lock/unlock the internal lock depending
|
|
of the WHO argument:
|
|
|
|
- atfork_run_prepare: run all the PREPARE_HANDLER in reverse order of
|
|
insertion and locks the internal lock.
|
|
- atfork_run_child: run all the CHILD_HANDLER and unlocks the internal
|
|
lock.
|
|
- atfork_run_parent: run all the PARENT_HANDLER and unlocks the internal
|
|
lock.
|
|
|
|
Perform locking only if DO_LOCKING. */
|
|
extern void __run_fork_handlers (enum __run_fork_handler_type who,
|
|
_Bool do_locking) 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)
|