// Support for atomic operations -*- C++ -*-
-// Copyright (C) 2004, 2005, 2006 Free Software Foundation, Inc.
+// Copyright (C) 2004-2024 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library 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)
+// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// 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 library; see the file COPYING. If not, write to the Free
-// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
-// USA.
-
-// As a special exception, you may use this file as part of a free software
-// library without restriction. Specifically, if other files instantiate
-// templates or use macros or inline functions from this file, or you compile
-// this file and link it with other files to produce an executable, this
-// file does not by itself cause the resulting executable to be covered by
-// the GNU General Public License. This exception does not however
-// invalidate any other reasons why the executable file might be covered by
-// the GNU General Public License.
-
-/** @file atomicity.h
- * This is an internal header file, included by other library headers.
- * You should not attempt to use it directly.
+// Under Section 7 of GPL version 3, you are granted additional
+// permissions described in the GCC Runtime Library Exception, version
+// 3.1, as published by the Free Software Foundation.
+
+// You should have received a copy of the GNU General Public License and
+// a copy of the GCC Runtime Library Exception along with this program;
+// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
+// <http://www.gnu.org/licenses/>.
+
+/** @file ext/atomicity.h
+ * This file is a GNU extension to the Standard C++ Library.
*/
#ifndef _GLIBCXX_ATOMICITY_H
#define _GLIBCXX_ATOMICITY_H 1
+#pragma GCC system_header
+
#include <bits/c++config.h>
#include <bits/gthr.h>
#include <bits/atomic_word.h>
+#if __has_include(<sys/single_threaded.h>)
+# include <sys/single_threaded.h>
+#endif
-_GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
+namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+
+ __attribute__((__always_inline__))
+ inline bool
+ __is_single_threaded() _GLIBCXX_NOTHROW
+ {
+#ifndef __GTHREADS
+ return true;
+#elif __has_include(<sys/single_threaded.h>)
+ return ::__libc_single_threaded;
+#else
+ return !__gthread_active_p();
+#endif
+ }
// Functions for portable atomic access.
- // To abstract locking primatives across all thread policies, use:
+ // To abstract locking primitives across all thread policies, use:
// __exchange_and_add_dispatch
// __atomic_add_dispatch
#ifdef _GLIBCXX_ATOMIC_BUILTINS
- static inline _Atomic_word
+ inline _Atomic_word
+ __attribute__((__always_inline__))
__exchange_and_add(volatile _Atomic_word* __mem, int __val)
- { return __sync_fetch_and_add(__mem, __val); }
+ { return __atomic_fetch_add(__mem, __val, __ATOMIC_ACQ_REL); }
- static inline void
+ inline void
+ __attribute__((__always_inline__))
__atomic_add(volatile _Atomic_word* __mem, int __val)
- { __sync_fetch_and_add(__mem, __val); }
+ { __atomic_fetch_add(__mem, __val, __ATOMIC_ACQ_REL); }
#else
_Atomic_word
- __attribute__ ((__unused__))
- __exchange_and_add(volatile _Atomic_word*, int);
+ __exchange_and_add(volatile _Atomic_word*, int) _GLIBCXX_NOTHROW;
void
- __attribute__ ((__unused__))
- __atomic_add(volatile _Atomic_word*, int);
+ __atomic_add(volatile _Atomic_word*, int) _GLIBCXX_NOTHROW;
#endif
- static inline _Atomic_word
+ inline _Atomic_word
+ __attribute__((__always_inline__))
__exchange_and_add_single(_Atomic_word* __mem, int __val)
{
_Atomic_word __result = *__mem;
return __result;
}
- static inline void
+ inline void
+ __attribute__((__always_inline__))
__atomic_add_single(_Atomic_word* __mem, int __val)
{ *__mem += __val; }
- static inline _Atomic_word
- __attribute__ ((__unused__))
+ inline _Atomic_word
+ __attribute__ ((__always_inline__))
__exchange_and_add_dispatch(_Atomic_word* __mem, int __val)
{
-#ifdef __GTHREADS
- if (__gthread_active_p())
- return __exchange_and_add(__mem, __val);
- else
+ if (__is_single_threaded())
return __exchange_and_add_single(__mem, __val);
-#else
- return __exchange_and_add_single(__mem, __val);
-#endif
+ else
+ return __exchange_and_add(__mem, __val);
}
- static inline void
- __attribute__ ((__unused__))
+ inline void
+ __attribute__ ((__always_inline__))
__atomic_add_dispatch(_Atomic_word* __mem, int __val)
{
-#ifdef __GTHREADS
- if (__gthread_active_p())
- __atomic_add(__mem, __val);
- else
+ if (__is_single_threaded())
__atomic_add_single(__mem, __val);
-#else
- __atomic_add_single(__mem, __val);
-#endif
+ else
+ __atomic_add(__mem, __val);
}
-_GLIBCXX_END_NAMESPACE
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace
// Even if the CPU doesn't need a memory barrier, we need to ensure
// that the compiler doesn't reorder memory accesses across the
// barriers.
#ifndef _GLIBCXX_READ_MEM_BARRIER
-#define _GLIBCXX_READ_MEM_BARRIER __asm __volatile ("":::"memory")
+#define _GLIBCXX_READ_MEM_BARRIER __atomic_thread_fence (__ATOMIC_ACQUIRE)
#endif
#ifndef _GLIBCXX_WRITE_MEM_BARRIER
-#define _GLIBCXX_WRITE_MEM_BARRIER __asm __volatile ("":::"memory")
+#define _GLIBCXX_WRITE_MEM_BARRIER __atomic_thread_fence (__ATOMIC_RELEASE)
#endif
#endif
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