pmt: initial 3.0.2 update

include/libgnulib/asyncsafe-spin.h

@@ -0,0 +1,69 @@
+/* Spin locks for communication between threads and signal handlers.
+   Copyright (C) 2020-2024 Free Software Foundation, Inc.
+
+   This file 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.
+
+   This file 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 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 */