70 lines
2.6 KiB
C
Executable File
70 lines
2.6 KiB
C
Executable File
/* Spin locks for communication between threads and signal handlers.
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Copyright (C) 2020-2024 Free Software Foundation, Inc.
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This file is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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This file is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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/* Written by Bruno Haible <bruno@clisp.org>, 2020. */
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#ifndef _ASYNCSAFE_SPIN_H
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#define _ASYNCSAFE_SPIN_H
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/* Usual spin locks are not allowed for communication between threads and signal
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handlers, because the pthread_spin_* functions are not async-safe; see
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<https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html>
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section 2.4.3 Signal Actions.
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This module provides spin locks with a similar API. It can be used like this,
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both in regular multithreaded code and in signal handlers:
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sigset_t saved_mask;
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asyncsafe_spin_lock (&lock, &mask, &saved_mask);
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do_something_contentious ();
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asyncsafe_spin_unlock (&lock, &saved_mask);
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The mask you specify here is the set of signals whose handlers might want to
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take the same lock.
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asyncsafe_spin_lock/unlock use pthread_sigmask, to ensure that while a thread
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is executing such code, no signal handler will start such code for the same
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lock *in the same thread* (because if this happened, the signal handler would
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hang!). */
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#include <signal.h>
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#if defined _WIN32 && ! defined __CYGWIN__
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# include "windows-spin.h"
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typedef glwthread_spinlock_t asyncsafe_spinlock_t;
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# define ASYNCSAFE_SPIN_INIT GLWTHREAD_SPIN_INIT
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#else
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typedef unsigned int asyncsafe_spinlock_t;
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# define ASYNCSAFE_SPIN_INIT 0
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#endif
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#ifdef __cplusplus
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extern "C" {
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#endif
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extern void asyncsafe_spin_init (asyncsafe_spinlock_t *lock);
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extern void asyncsafe_spin_lock (asyncsafe_spinlock_t *lock,
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const sigset_t *mask, sigset_t *saved_mask);
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extern void asyncsafe_spin_unlock (asyncsafe_spinlock_t *lock,
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const sigset_t *saved_mask);
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extern void asyncsafe_spin_destroy (asyncsafe_spinlock_t *lock);
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#ifdef __cplusplus
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}
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#endif
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#endif /* _ASYNCSAFE_SPIN_H */
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