kc3-lang/gnulib/lib/asyncsafe-spin.h

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• Hash : 4b948321
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  Date : 2021-01-01T07:28:52
  

  maint: run 'make update-copyright'
  

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• lib/asyncsafe-spin.h

• /* 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 2, 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 */
  

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