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glibc/malloc/malloc-internal.h

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malloc: Run fork handler as late as possible [BZ #19431] Previously, a thread M invoking fork would acquire locks in this order: (M1) malloc arena locks (in the registered fork handler) (M2) libio list lock A thread F invoking flush (NULL) would acquire locks in this order: (F1) libio list lock (F2) individual _IO_FILE locks A thread G running getdelim would use this order: (G1) _IO_FILE lock (G2) malloc arena lock After executing (M1), (F1), (G1), none of the threads can make progress. This commit changes the fork lock order to: (M'1) libio list lock (M'2) malloc arena locks It explicitly encodes the lock order in the implementations of fork, and does not rely on the registration order, thus avoiding the deadlock.
2016-04-14 07:17:02 +00:00
/* Internal declarations for malloc, for use within libc.
Copyright (C) 2016 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; see the file COPYING.LIB. If
not, see <http://www.gnu.org/licenses/>. */
malloc: Adjust header file guard in malloc-internal.h
2016-05-04 13:25:39 +00:00
#ifndef _MALLOC_INTERNAL_H
#define _MALLOC_INTERNAL_H
malloc: Run fork handler as late as possible [BZ #19431] Previously, a thread M invoking fork would acquire locks in this order: (M1) malloc arena locks (in the registered fork handler) (M2) libio list lock A thread F invoking flush (NULL) would acquire locks in this order: (F1) libio list lock (F2) individual _IO_FILE locks A thread G running getdelim would use this order: (G1) _IO_FILE lock (G2) malloc arena lock After executing (M1), (F1), (G1), none of the threads can make progress. This commit changes the fork lock order to: (M'1) libio list lock (M'2) malloc arena locks It explicitly encodes the lock order in the implementations of fork, and does not rely on the registration order, thus avoiding the deadlock.
2016-04-14 07:17:02 +00:00
/* Called in the parent process before a fork. */
void __malloc_fork_lock_parent (void) internal_function attribute_hidden;
/* Called in the parent process after a fork. */
void __malloc_fork_unlock_parent (void) internal_function attribute_hidden;
/* Called in the child process after a fork. */
void __malloc_fork_unlock_child (void) internal_function attribute_hidden;
malloc: Adjust header file guard in malloc-internal.h
2016-05-04 13:25:39 +00:00
#endif /* _MALLOC_INTERNAL_H */
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