| /* Spin locks for communication between threads and signal handlers. |
| Copyright (C) 2020-2021 Free Software Foundation, Inc. |
| |
| This program is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 3, or (at your option) |
| any later version. |
| |
| This program 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 General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with this program; if not, see <https://www.gnu.org/licenses/>. */ |
| |
| /* Written by Bruno Haible <bruno@clisp.org>, 2020. */ |
| |
| #ifndef _ASYNCSAFE_SPIN_H |
| #define _ASYNCSAFE_SPIN_H |
| |
| /* Usual spin locks are not allowed for communication between threads and signal |
| handlers, because the pthread_spin_* functions are not async-safe; see |
| <https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html> |
| section 2.4.3 Signal Actions. |
| |
| This module provides spin locks with a similar API. It can be used like this, |
| both in regular multithreaded code and in signal handlers: |
| |
| sigset_t saved_mask; |
| asyncsafe_spin_lock (&lock, &mask, &saved_mask); |
| do_something_contentious (); |
| asyncsafe_spin_unlock (&lock, &saved_mask); |
| |
| The mask you specify here is the set of signals whose handlers might want to |
| take the same lock. |
| |
| asyncsafe_spin_lock/unlock use pthread_sigmask, to ensure that while a thread |
| is executing such code, no signal handler will start such code for the same |
| lock *in the same thread* (because if this happened, the signal handler would |
| hang!). */ |
| |
| #include <signal.h> |
| |
| #if defined _WIN32 && ! defined __CYGWIN__ |
| # include "windows-spin.h" |
| typedef glwthread_spinlock_t asyncsafe_spinlock_t; |
| # define ASYNCSAFE_SPIN_INIT GLWTHREAD_SPIN_INIT |
| #else |
| typedef unsigned int asyncsafe_spinlock_t; |
| # define ASYNCSAFE_SPIN_INIT 0 |
| #endif |
| |
| #ifdef __cplusplus |
| extern "C" { |
| #endif |
| |
| extern void asyncsafe_spin_init (asyncsafe_spinlock_t *lock); |
| extern void asyncsafe_spin_lock (asyncsafe_spinlock_t *lock, |
| const sigset_t *mask, sigset_t *saved_mask); |
| extern void asyncsafe_spin_unlock (asyncsafe_spinlock_t *lock, |
| const sigset_t *saved_mask); |
| extern void asyncsafe_spin_destroy (asyncsafe_spinlock_t *lock); |
| |
| #ifdef __cplusplus |
| } |
| #endif |
| |
| #endif /* _ASYNCSAFE_SPIN_H */ |