c++11 atomic template from libstdc++

d61e3535 · Nickolai Zeldovich · db8baf3d · d61e3535 · d61e3535 · d61e3535
--- a/atomic.hh
+++ b/atomic.hh
+#pragma once
+#define _GLIBCXX_VISIBILITY(x)
+#define _GLIBCXX_BEGIN_NAMESPACE_VERSION
+#define _GLIBCXX_END_NAMESPACE_VERSION
+#define _GLIBCXX_BEGIN_EXTERN_C extern "C" {
+#define _GLIBCXX_END_EXTERN_C }
+#define __glibcxx_assert(x)
+#include "atomic_base.h"
+#include "atomic_2.h"
+template<class T>
+struct atomic : public std::__atomic2::__atomic_base<T> {
+  atomic() = default;
+  ~atomic() = default;
+  atomic(const atomic&) = delete;
+  atomic& operator=(const atomic&) = delete;
+  atomic& operator=(const atomic&) volatile = delete;
+  constexpr atomic(T v) : std::__atomic2::__atomic_base<T>(v) {}
+  using std::__atomic2::__atomic_base<T>::operator T;
+  using std::__atomic2::__atomic_base<T>::operator=;
+};
--- a/atomic_2.h
+++ b/atomic_2.h
+// -*- C++ -*- header.
+// Copyright (C) 2008, 2009, 2010, 2011
+// 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 3, or (at your option)
+// any later version.
+// This library 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.
+// 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 bits/atomic_2.h
+ *  This is an internal header file, included by other library headers.
+ *  Do not attempt to use it directly. @headername{atomic}
+ */
+#ifndef _GLIBCXX_ATOMIC_2_H
+#define _GLIBCXX_ATOMIC_2_H 1
+#pragma GCC system_header
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+// 2 == __atomic2 == Always lock-free
+// Assumed:
+// _GLIBCXX_ATOMIC_BUILTINS_1
+// _GLIBCXX_ATOMIC_BUILTINS_2
+// _GLIBCXX_ATOMIC_BUILTINS_4
+// _GLIBCXX_ATOMIC_BUILTINS_8
+namespace __atomic2
+{
+  /// atomic_flag
+  struct atomic_flag : public __atomic_flag_base
+  {
+    atomic_flag() = default;
+    ~atomic_flag() = default;
+    atomic_flag(const atomic_flag&) = delete;
+    atomic_flag& operator=(const atomic_flag&) = delete;
+    atomic_flag& operator=(const atomic_flag&) volatile = delete;
+    // Conversion to ATOMIC_FLAG_INIT.
+    atomic_flag(bool __i): __atomic_flag_base({ __i }) { }
+    bool
+    test_and_set(memory_order __m = memory_order_seq_cst)
+    {
+      // Redundant synchronize if built-in for lock is a full barrier.
+      if (__m != memory_order_acquire && __m != memory_order_acq_rel)
+	__sync_synchronize();
+      return __sync_lock_test_and_set(&_M_i, 1);
+    }
+    bool
+    test_and_set(memory_order __m = memory_order_seq_cst) volatile
+    {
+      // Redundant synchronize if built-in for lock is a full barrier.
+      if (__m != memory_order_acquire && __m != memory_order_acq_rel)
+	__sync_synchronize();
+      return __sync_lock_test_and_set(&_M_i, 1);
+    }
+    void
+    clear(memory_order __m = memory_order_seq_cst)
+    {
+      __glibcxx_assert(__m != memory_order_consume);
+      __glibcxx_assert(__m != memory_order_acquire);
+      __glibcxx_assert(__m != memory_order_acq_rel);
+      __sync_lock_release(&_M_i);
+      if (__m != memory_order_acquire && __m != memory_order_acq_rel)
+	__sync_synchronize();
+    }
+    void
+    clear(memory_order __m = memory_order_seq_cst) volatile
+    {
+      __glibcxx_assert(__m != memory_order_consume);
+      __glibcxx_assert(__m != memory_order_acquire);
+      __glibcxx_assert(__m != memory_order_acq_rel);
+      __sync_lock_release(&_M_i);
+      if (__m != memory_order_acquire && __m != memory_order_acq_rel)
+	__sync_synchronize();
+    }
+  };
+  /// Base class for atomic integrals.
+  //
+  // For each of the integral types, define atomic_[integral type] struct
+  //
+  // atomic_bool     bool
+  // atomic_char     char
+  // atomic_schar    signed char
+  // atomic_uchar    unsigned char
+  // atomic_short    short
+  // atomic_ushort   unsigned short
+  // atomic_int      int
+  // atomic_uint     unsigned int
+  // atomic_long     long
+  // atomic_ulong    unsigned long
+  // atomic_llong    long long
+  // atomic_ullong   unsigned long long
+  // atomic_char16_t char16_t
+  // atomic_char32_t char32_t
+  // atomic_wchar_t  wchar_t
+  //
+  // NB: Assuming _ITp is an integral scalar type that is 1, 2, 4, or
+  // 8 bytes, since that is what GCC built-in functions for atomic
+  // memory access expect.
+  template<typename _ITp>
+    struct __atomic_base
+    {
+    private:
+      typedef _ITp 	__int_type;
+      __int_type 	_M_i;
+    public:
+      __atomic_base() = default;
+      ~__atomic_base() = default;
+      __atomic_base(const __atomic_base&) = delete;
+      __atomic_base& operator=(const __atomic_base&) = delete;
+      __atomic_base& operator=(const __atomic_base&) volatile = delete;
+      // Requires __int_type convertible to _M_i.
+      constexpr __atomic_base(__int_type __i): _M_i (__i) { }
+      operator __int_type() const
+      { return load(); }
+      operator __int_type() const volatile
+      { return load(); }
+      __int_type
+      operator=(__int_type __i)
+      {
+	store(__i);
+	return __i;
+      }
+      __int_type
+      operator=(__int_type __i) volatile
+      {
+	store(__i);
+	return __i;
+      }
+      __int_type
+      operator++(int)
+      { return fetch_add(1); }
+      __int_type
+      operator++(int) volatile
+      { return fetch_add(1); }
+      __int_type
+      operator--(int)
+      { return fetch_sub(1); }
+      __int_type
+      operator--(int) volatile
+      { return fetch_sub(1); }
+      __int_type
+      operator++()
+      { return __sync_add_and_fetch(&_M_i, 1); }
+      __int_type
+      operator++() volatile
+      { return __sync_add_and_fetch(&_M_i, 1); }
+      __int_type
+      operator--()
+      { return __sync_sub_and_fetch(&_M_i, 1); }
+      __int_type
+      operator--() volatile
+      { return __sync_sub_and_fetch(&_M_i, 1); }
+      __int_type
+      operator+=(__int_type __i)
+      { return __sync_add_and_fetch(&_M_i, __i); }
+      __int_type
+      operator+=(__int_type __i) volatile
+      { return __sync_add_and_fetch(&_M_i, __i); }
+      __int_type
+      operator-=(__int_type __i)
+      { return __sync_sub_and_fetch(&_M_i, __i); }
+      __int_type
+      operator-=(__int_type __i) volatile
+      { return __sync_sub_and_fetch(&_M_i, __i); }
+      __int_type
+      operator&=(__int_type __i)
+      { return __sync_and_and_fetch(&_M_i, __i); }
+      __int_type
+      operator&=(__int_type __i) volatile
+      { return __sync_and_and_fetch(&_M_i, __i); }
+      __int_type
+      operator|=(__int_type __i)
+      { return __sync_or_and_fetch(&_M_i, __i); }
+      __int_type
+      operator|=(__int_type __i) volatile
+      { return __sync_or_and_fetch(&_M_i, __i); }
+      __int_type
+      operator^=(__int_type __i)
+      { return __sync_xor_and_fetch(&_M_i, __i); }
+      __int_type
+      operator^=(__int_type __i) volatile
+      { return __sync_xor_and_fetch(&_M_i, __i); }
+      bool
+      is_lock_free() const
+      { return true; }
+      bool
+      is_lock_free() const volatile
+      { return true; }
+      void
+      store(__int_type __i, memory_order __m = memory_order_seq_cst)
+      {
+	__glibcxx_assert(__m != memory_order_acquire);
+	__glibcxx_assert(__m != memory_order_acq_rel);
+	__glibcxx_assert(__m != memory_order_consume);
+	if (__m == memory_order_relaxed)
+	  _M_i = __i;
+	else
+	  {
+	    // write_mem_barrier();
+	    _M_i = __i;
+	    if (__m == memory_order_seq_cst)
+	      __sync_synchronize();
+	  }
+      }
+      void
+      store(__int_type __i, memory_order __m = memory_order_seq_cst) volatile
+      {
+	__glibcxx_assert(__m != memory_order_acquire);
+	__glibcxx_assert(__m != memory_order_acq_rel);
+	__glibcxx_assert(__m != memory_order_consume);
+	if (__m == memory_order_relaxed)
+	  _M_i = __i;
+	else
+	  {
+	    // write_mem_barrier();
+	    _M_i = __i;
+	    if (__m == memory_order_seq_cst)
+	      __sync_synchronize();
+	  }
+      }
+      __int_type
+      load(memory_order __m = memory_order_seq_cst) const
+      {
+	__glibcxx_assert(__m != memory_order_release);
+	__glibcxx_assert(__m != memory_order_acq_rel);
+	__sync_synchronize();
+	__int_type __ret = _M_i;
+	__sync_synchronize();
+	return __ret;
+      }
+      __int_type
+      load(memory_order __m = memory_order_seq_cst) const volatile
+      {
+	__glibcxx_assert(__m != memory_order_release);
+	__glibcxx_assert(__m != memory_order_acq_rel);
+	__sync_synchronize();
+	__int_type __ret = _M_i;
+	__sync_synchronize();
+	return __ret;
+      }
+      __int_type
+      exchange(__int_type __i, memory_order __m = memory_order_seq_cst)
+      {
+	// XXX built-in assumes memory_order_acquire.
+	return __sync_lock_test_and_set(&_M_i, __i);
+      }
+      __int_type
+      exchange(__int_type __i, memory_order __m = memory_order_seq_cst) volatile
+      {
+	// XXX built-in assumes memory_order_acquire.
+	return __sync_lock_test_and_set(&_M_i, __i);
+      }
+      bool
+      compare_exchange_weak(__int_type& __i1, __int_type __i2,
+			    memory_order __m1, memory_order __m2)
+      { return compare_exchange_strong(__i1, __i2, __m1, __m2); }
+      bool
+      compare_exchange_weak(__int_type& __i1, __int_type __i2,
+			    memory_order __m1, memory_order __m2) volatile
+      { return compare_exchange_strong(__i1, __i2, __m1, __m2); }
+      bool
+      compare_exchange_weak(__int_type& __i1, __int_type __i2,
+			    memory_order __m = memory_order_seq_cst)
+      {
+	return compare_exchange_weak(__i1, __i2, __m,
+				     __calculate_memory_order(__m));
+      }
+      bool
+      compare_exchange_weak(__int_type& __i1, __int_type __i2,
+			    memory_order __m = memory_order_seq_cst) volatile
+      {
+	return compare_exchange_weak(__i1, __i2, __m,
+				     __calculate_memory_order(__m));
+      }
+      bool
+      compare_exchange_strong(__int_type& __i1, __int_type __i2,
+			      memory_order __m1, memory_order __m2)
+      {
+	__glibcxx_assert(__m2 != memory_order_release);
+	__glibcxx_assert(__m2 != memory_order_acq_rel);
+	__glibcxx_assert(__m2 <= __m1);
+	__int_type __i1o = __i1;
+	__int_type __i1n = __sync_val_compare_and_swap(&_M_i, __i1o, __i2);
+	// Assume extra stores (of same value) allowed in true case.
+	__i1 = __i1n;
+	return __i1o == __i1n;
+      }
+      bool
+      compare_exchange_strong(__int_type& __i1, __int_type __i2,
+			      memory_order __m1, memory_order __m2) volatile
+      {
+	__glibcxx_assert(__m2 != memory_order_release);
+	__glibcxx_assert(__m2 != memory_order_acq_rel);
+	__glibcxx_assert(__m2 <= __m1);
+	__int_type __i1o = __i1;
+	__int_type __i1n = __sync_val_compare_and_swap(&_M_i, __i1o, __i2);
+	// Assume extra stores (of same value) allowed in true case.
+	__i1 = __i1n;
+	return __i1o == __i1n;
+      }
+      bool
+      compare_exchange_strong(__int_type& __i1, __int_type __i2,
+			      memory_order __m = memory_order_seq_cst)
+      {
+	return compare_exchange_strong(__i1, __i2, __m,
+				       __calculate_memory_order(__m));
+      }
+      bool
+      compare_exchange_strong(__int_type& __i1, __int_type __i2,
+			      memory_order __m = memory_order_seq_cst) volatile
+      {
+	return compare_exchange_strong(__i1, __i2, __m,
+				       __calculate_memory_order(__m));
+      }
+      __int_type
+      fetch_add(__int_type __i, memory_order __m = memory_order_seq_cst)
+      { return __sync_fetch_and_add(&_M_i, __i); }
+      __int_type
+      fetch_add(__int_type __i,
+		memory_order __m = memory_order_seq_cst) volatile
+      { return __sync_fetch_and_add(&_M_i, __i); }
+      __int_type
+      fetch_sub(__int_type __i, memory_order __m = memory_order_seq_cst)
+      { return __sync_fetch_and_sub(&_M_i, __i); }
+      __int_type
+      fetch_sub(__int_type __i,
+		memory_order __m = memory_order_seq_cst) volatile
+      { return __sync_fetch_and_sub(&_M_i, __i); }
+      __int_type
+      fetch_and(__int_type __i, memory_order __m = memory_order_seq_cst)
+      { return __sync_fetch_and_and(&_M_i, __i); }
+      __int_type
+      fetch_and(__int_type __i,
+		memory_order __m = memory_order_seq_cst) volatile
+      { return __sync_fetch_and_and(&_M_i, __i); }
+      __int_type
+      fetch_or(__int_type __i, memory_order __m = memory_order_seq_cst)
+      { return __sync_fetch_and_or(&_M_i, __i); }
+      __int_type
+      fetch_or(__int_type __i,
+	       memory_order __m = memory_order_seq_cst) volatile
+      { return __sync_fetch_and_or(&_M_i, __i); }
+      __int_type
+      fetch_xor(__int_type __i, memory_order __m = memory_order_seq_cst)
+      { return __sync_fetch_and_xor(&_M_i, __i); }
+      __int_type
+      fetch_xor(__int_type __i,
+		memory_order __m = memory_order_seq_cst) volatile
+      { return __sync_fetch_and_xor(&_M_i, __i); }
+    };
+  /// Partial specialization for pointer types.
+  template<typename _PTp>
+    struct __atomic_base<_PTp*>
+    {
+    private:
+      typedef _PTp* 	__pointer_type;
+      __pointer_type 	_M_p;
+    public:
+      __atomic_base() = default;
+      ~__atomic_base() = default;
+      __atomic_base(const __atomic_base&) = delete;
+      __atomic_base& operator=(const __atomic_base&) = delete;
+      __atomic_base& operator=(const __atomic_base&) volatile = delete;
+      // Requires __pointer_type convertible to _M_p.
+      constexpr __atomic_base(__pointer_type __p): _M_p (__p) { }
+      operator __pointer_type() const
+      { return load(); }
+      operator __pointer_type() const volatile
+      { return load(); }
+      __pointer_type
+      operator=(__pointer_type __p)
+      {
+	store(__p);
+	return __p;
+      }
+      __pointer_type
+      operator=(__pointer_type __p) volatile
+      {
+	store(__p);
+	return __p;
+      }
+      __pointer_type
+      operator++(int)
+      { return fetch_add(1); }
+      __pointer_type
+      operator++(int) volatile
+      { return fetch_add(1); }
+      __pointer_type
+      operator--(int)
+      { return fetch_sub(1); }
+      __pointer_type
+      operator--(int) volatile
+      { return fetch_sub(1); }
+      __pointer_type
+      operator++()
+      { return fetch_add(1) + 1; }
+      __pointer_type
+      operator++() volatile
+      { return fetch_add(1) + 1; }
+      __pointer_type
+      operator--()
+      { return fetch_sub(1) -1; }
+      __pointer_type
+      operator--() volatile
+      { return fetch_sub(1) -1; }
+      __pointer_type
+      operator+=(ptrdiff_t __d)
+      { return fetch_add(__d) + __d; }
+      __pointer_type
+      operator+=(ptrdiff_t __d) volatile
+      { return fetch_add(__d) + __d; }
+      __pointer_type
+      operator-=(ptrdiff_t __d)
+      { return fetch_sub(__d) - __d; }
+      __pointer_type
+      operator-=(ptrdiff_t __d) volatile
+      { return fetch_sub(__d) - __d; }
+      bool
+      is_lock_free() const
+      { return true; }
+      bool
+      is_lock_free() const volatile
+      { return true; }
+      void
+      store(__pointer_type __p, memory_order __m = memory_order_seq_cst)
+      {
+	__glibcxx_assert(__m != memory_order_acquire);
+	__glibcxx_assert(__m != memory_order_acq_rel);
+	__glibcxx_assert(__m != memory_order_consume);
+	if (__m == memory_order_relaxed)
+	  _M_p = __p;
+	else
+	  {
+	    // write_mem_barrier();
+	    _M_p = __p;
+	    if (__m == memory_order_seq_cst)
+	      __sync_synchronize();
+	  }
+      }
+      void
+      store(__pointer_type __p,
+	    memory_order __m = memory_order_seq_cst) volatile
+      {
+	__glibcxx_assert(__m != memory_order_acquire);
+	__glibcxx_assert(__m != memory_order_acq_rel);
+	__glibcxx_assert(__m != memory_order_consume);
+	if (__m == memory_order_relaxed)
+	  _M_p = __p;
+	else
+	  {
+	    // write_mem_barrier();
+	    _M_p = __p;
+	    if (__m == memory_order_seq_cst)
+	      __sync_synchronize();
+	  }
+      }
+      __pointer_type
+      load(memory_order __m = memory_order_seq_cst) const
+      {
+	__glibcxx_assert(__m != memory_order_release);
+	__glibcxx_assert(__m != memory_order_acq_rel);
+	__sync_synchronize();
+	__pointer_type __ret = _M_p;
+	__sync_synchronize();
+	return __ret;
+      }
+      __pointer_type
+      load(memory_order __m = memory_order_seq_cst) const volatile
+      {
+	__glibcxx_assert(__m != memory_order_release);
+	__glibcxx_assert(__m != memory_order_acq_rel);
+	__sync_synchronize();
+	__pointer_type __ret = _M_p;
+	__sync_synchronize();
+	return __ret;
+      }
+      __pointer_type
+      exchange(__pointer_type __p, memory_order __m = memory_order_seq_cst)
+      {
+	// XXX built-in assumes memory_order_acquire.
+	return __sync_lock_test_and_set(&_M_p, __p);
+      }
+      __pointer_type
+      exchange(__pointer_type __p,
+	       memory_order __m = memory_order_seq_cst) volatile
+      {
+	// XXX built-in assumes memory_order_acquire.
+	return __sync_lock_test_and_set(&_M_p, __p);
+      }
+      bool
+      compare_exchange_strong(__pointer_type& __p1, __pointer_type __p2,
+			      memory_order __m1, memory_order __m2)
+      {
+	__glibcxx_assert(__m2 != memory_order_release);
+	__glibcxx_assert(__m2 != memory_order_acq_rel);
+	__glibcxx_assert(__m2 <= __m1);
+	__pointer_type __p1o = __p1;
+	__pointer_type __p1n = __sync_val_compare_and_swap(&_M_p, __p1o, __p2);
+	// Assume extra stores (of same value) allowed in true case.
+	__p1 = __p1n;
+	return __p1o == __p1n;
+      }
+      bool
+      compare_exchange_strong(__pointer_type& __p1, __pointer_type __p2,
+			      memory_order __m1, memory_order __m2) volatile
+      {
+	__glibcxx_assert(__m2 != memory_order_release);
+	__glibcxx_assert(__m2 != memory_order_acq_rel);
+	__glibcxx_assert(__m2 <= __m1);
+	__pointer_type __p1o = __p1;
+	__pointer_type __p1n = __sync_val_compare_and_swap(&_M_p, __p1o, __p2);
+	// Assume extra stores (of same value) allowed in true case.
+	__p1 = __p1n;
+	return __p1o == __p1n;
+      }
+      __pointer_type
+      fetch_add(ptrdiff_t __d, memory_order __m = memory_order_seq_cst)
+      { return __sync_fetch_and_add(&_M_p, __d); }
+      __pointer_type
+      fetch_add(ptrdiff_t __d,
+		memory_order __m = memory_order_seq_cst) volatile
+      { return __sync_fetch_and_add(&_M_p, __d); }
+      __pointer_type
+      fetch_sub(ptrdiff_t __d, memory_order __m = memory_order_seq_cst)
+      { return __sync_fetch_and_sub(&_M_p, __d); }
+      __pointer_type
+      fetch_sub(ptrdiff_t __d,
+		memory_order __m = memory_order_seq_cst) volatile
+      { return __sync_fetch_and_sub(&_M_p, __d); }
+    };
+} // namespace __atomic2
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace std
+#endif
--- a/atomic_base.h
+++ b/atomic_base.h
+// -*- C++ -*- header.
+// Copyright (C) 2008, 2009, 2010, 2011 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 3, or (at your option)
+// any later version.
+// This library 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.
+// 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 bits/atomic_base.h
+ *  This is an internal header file, included by other library headers.
+ *  Do not attempt to use it directly. @headername{atomic}
+ */
+#ifndef _GLIBCXX_ATOMIC_BASE_H
+#define _GLIBCXX_ATOMIC_BASE_H 1
+#pragma GCC system_header
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+  /**
+   * @defgroup atomics Atomics
+   *
+   * Components for performing atomic operations.
+   * @{
+   */
+  /// Enumeration for memory_order
+  typedef enum memory_order
+    {
+      memory_order_relaxed,
+      memory_order_consume,
+      memory_order_acquire,
+      memory_order_release,
+      memory_order_acq_rel,
+      memory_order_seq_cst
+    } memory_order;
+  inline memory_order
+  __calculate_memory_order(memory_order __m)
+  {
+    const bool __cond1 = __m == memory_order_release;
+    const bool __cond2 = __m == memory_order_acq_rel;
+    memory_order __mo1(__cond1 ? memory_order_relaxed : __m);
+    memory_order __mo2(__cond2 ? memory_order_acquire : __mo1);
+    return __mo2;
+  }
+  void
+  atomic_thread_fence(memory_order);
+  void
+  atomic_signal_fence(memory_order);
+  /// kill_dependency
+  template<typename _Tp>
+    inline _Tp
+    kill_dependency(_Tp __y)
+    {
+      _Tp __ret(__y);
+      return __ret;
+    }
+  /**
+   *  @brief Base type for atomic_flag.
+   *
+   *  Base type is POD with data, allowing atomic_flag to derive from
+   *  it and meet the standard layout type requirement. In addition to
+   *  compatibilty with a C interface, this allows different
+   *  implementations of atomic_flag to use the same atomic operation
+   *  functions, via a standard conversion to the __atomic_flag_base
+   *  argument.
+  */
+  _GLIBCXX_BEGIN_EXTERN_C
+  struct __atomic_flag_base
+  {
+    bool _M_i;
+  };
+  _GLIBCXX_END_EXTERN_C
+#define ATOMIC_FLAG_INIT { false }
+  // Base types for atomics.
+  //
+  // Three nested namespaces for atomic implementation details.
+  //
+  // The nested namespace inlined into std:: is determined by the value
+  // of the _GLIBCXX_ATOMIC_PROPERTY macro and the resulting
+  // ATOMIC_*_LOCK_FREE macros.
+  //
+  // 0 == __atomic0 == Never lock-free
+  // 1 == __atomic1 == Best available, sometimes lock-free
+  // 2 == __atomic2 == Always lock-free
+  namespace __atomic0
+  {
+    struct atomic_flag;
+    template<typename _IntTp>
+      struct __atomic_base;
+  }
+  namespace __atomic2
+  {
+    struct atomic_flag;
+    template<typename _IntTp>
+      struct __atomic_base;
+  }
+  namespace __atomic1
+  {
+    using __atomic2::atomic_flag;
+    using __atomic0::__atomic_base;
+  }
+  /// Lock-free Property
+#if defined(_GLIBCXX_ATOMIC_BUILTINS_1) && defined(_GLIBCXX_ATOMIC_BUILTINS_2) \
+  && defined(_GLIBCXX_ATOMIC_BUILTINS_4) && defined(_GLIBCXX_ATOMIC_BUILTINS_8)
+# define _GLIBCXX_ATOMIC_PROPERTY 2
+# define _GLIBCXX_ATOMIC_NAMESPACE __atomic2
+#elif defined(_GLIBCXX_ATOMIC_BUILTINS_1)
+# define _GLIBCXX_ATOMIC_PROPERTY 1
+# define _GLIBCXX_ATOMIC_NAMESPACE __atomic1
+#else
+# define _GLIBCXX_ATOMIC_PROPERTY 0
+# define _GLIBCXX_ATOMIC_NAMESPACE __atomic0
+#endif
+#define ATOMIC_CHAR_LOCK_FREE _GLIBCXX_ATOMIC_PROPERTY
+#define ATOMIC_CHAR16_T_LOCK_FREE _GLIBCXX_ATOMIC_PROPERTY
+#define ATOMIC_CHAR32_T_LOCK_FREE _GLIBCXX_ATOMIC_PROPERTY
+#define ATOMIC_WCHAR_T_LOCK_FREE _GLIBCXX_ATOMIC_PROPERTY
+#define ATOMIC_SHORT_LOCK_FREE _GLIBCXX_ATOMIC_PROPERTY
+#define ATOMIC_INT_LOCK_FREE _GLIBCXX_ATOMIC_PROPERTY
+#define ATOMIC_LONG_LOCK_FREE _GLIBCXX_ATOMIC_PROPERTY
+#define ATOMIC_LLONG_LOCK_FREE _GLIBCXX_ATOMIC_PROPERTY
+  inline namespace _GLIBCXX_ATOMIC_NAMESPACE { }
+#define ATOMIC_VAR_INIT(_VI) { _VI }
+  template<typename _Tp>
+    struct atomic;
+  template<typename _Tp>
+    struct atomic<_Tp*>;
+  // @} group atomics
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace std
+#endif
--- a/bio.cc
+++ b/bio.cc
@@ -135,7 +135,7 @@ bread(u32 dev, u64 sector, int writer)
  if(!(b->flags & B_VALID))
    iderw(b);
  if (writer && !origwriter) {
-    __sync_fetch_and_and(&b->flags, ~B_BUSY);
+    b->flags &= ~B_BUSY;
    cv_wakeup(&b->cv);
  }
  return b;
@@ -159,7 +159,7 @@ brelse(struct buf *b, int writer)
  if (writer) {
    if((b->flags & B_BUSY) == 0)
      panic("brelse");
-    __sync_fetch_and_and(&b->flags, ~B_BUSY);
+    b->flags &= ~B_BUSY;
    cv_wakeup(&b->cv);
  }
  // rcu_begin_read() happens in bread

--- a/buf.hh
+++ b/buf.hh
 #include "gc.hh"
+#include "atomic.hh"
 struct buf : public rcu_freed {
-  int flags;
+  atomic<int> flags;
  u32 dev;
  u64 sector;
  struct buf *prev; // LRU cache list

--- a/file.cc
+++ b/file.cc
@@ -28,7 +28,7 @@ filealloc(void)
 struct file*
 filedup(struct file *f)
 {
-  if (__sync_fetch_and_add(&f->ref, 1) < 1)
+  if (f->ref++ < 1)
    panic("filedup");
  return f;
 }
@@ -37,7 +37,7 @@ filedup(struct file *f)
 void
 fileclose(struct file *f)
 {
-  if (subfetch(&f->ref, 1) > 0)
+  if (--f->ref > 0)
    return;
  if(f->type == file::FD_PIPE)

--- a/file.hh
+++ b/file.hh
 #include "cpputil.hh"
 #include "ns.hh"
 #include "gc.hh"
+#include "atomic.hh"
 u64 namehash(const strbuf<DIRSIZ>&);
 struct file {
  enum { FD_NONE, FD_PIPE, FD_INODE, FD_SOCKET } type;
-  int ref; // reference count
+  atomic<int> ref; // reference count
  char readable;
  char writable;

--- a/types.h
+++ b/types.h
@@ -18,4 +18,5 @@ typedef pme_t           pml4e_t;
 typedef s64             ssize_t;
 typedef u64             size_t;
 typedef u64             off_t;
+typedef s64             ptrdiff_t;
 #endif