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Commit 87361f30 by Jonathan Wakely Committed by Jonathan Wakely
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atomic_futex.h: Use mutex and condition_variable when atomic int is not lock-free. 

	* include/bits/atomic_futex.h: Use mutex and condition_variable when
	atomic int is not lock-free. Make member variables private.
	* src/c++11/futex.cc: Likewise.

From-SVN: r219815
parent e207c522
Showing with 52 additions and 47 deletions
libstdc++-v3/ChangeLog
2015-01-18 Jonathan Wakely <jwakely@redhat.com>
* include/bits/atomic_futex.h: Use mutex and condition_variable when
atomic int is not lock-free. Make member variables private.
* src/c++11/futex.cc: Likewise.
2015-01-17 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/64638
......
libstdc++-v3/include/bits/atomic_futex.h
......@@ -35,7 +35,7 @@
#include <bits/c++config.h>
#include <atomic>
#include <chrono>
#if !defined(_GLIBCXX_HAVE_LINUX_FUTEX)
#if ! (defined(_GLIBCXX_HAVE_LINUX_FUTEX) && ATOMIC_INT_LOCK_FREE > 1)
#include <mutex>
#include <condition_variable>
#endif
......@@ -49,7 +49,7 @@ namespace std _GLIBCXX_VISIBILITY(default)
_GLIBCXX_BEGIN_NAMESPACE_VERSION
#if defined(_GLIBCXX_HAS_GTHREADS) && defined(_GLIBCXX_USE_C99_STDINT_TR1)
#if defined(_GLIBCXX_HAVE_LINUX_FUTEX)
#if defined(_GLIBCXX_HAVE_LINUX_FUTEX) && ATOMIC_INT_LOCK_FREE > 1
struct __atomic_futex_unsigned_base
{
// Returns false iff a timeout occurred.
......@@ -62,16 +62,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
};
template <unsigned _Waiter_bit = 0x80000000>
struct __atomic_futex_unsigned : __atomic_futex_unsigned_base
class __atomic_futex_unsigned : __atomic_futex_unsigned_base
{
typedef chrono::system_clock __clock_t;
// XXX We expect this to be lock-free, and having the payload at offset 0.
#if ATOMIC_INT_LOCK_FREE < 2
# error We require lock-free atomic operations on int
#endif
// This must be lock-free and at offset 0.
atomic<unsigned> _M_data;
public:
explicit
__atomic_futex_unsigned(unsigned __data) : _M_data(__data)
{ }
......@@ -82,7 +81,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
private:
// If a timeout occurs, returns a current value after the timeout;
// otherwise, returns the operand's value if equal is true or a different
// value if equal is false.
......@@ -165,26 +163,27 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// Returns false iff a timeout occurred.
template<typename _Rep, typename _Period>
_GLIBCXX_ALWAYS_INLINE bool
_M_load_when_equal_for(unsigned __val, memory_order __mo,
const chrono::duration<_Rep, _Period>& __rtime)
{
return _M_load_when_equal_until(__val, __mo, __clock_t::now() + __rtime);
}
_GLIBCXX_ALWAYS_INLINE bool
_M_load_when_equal_for(unsigned __val, memory_order __mo,
const chrono::duration<_Rep, _Period>& __rtime)
{
return _M_load_when_equal_until(__val, __mo,
__clock_t::now() + __rtime);
}
// Returns false iff a timeout occurred.
template<typename _Clock, typename _Duration>
_GLIBCXX_ALWAYS_INLINE bool
_M_load_when_equal_until(unsigned __val, memory_order __mo,
const chrono::time_point<_Clock, _Duration>& __atime)
{
// DR 887 - Sync unknown clock to known clock.
const typename _Clock::time_point __c_entry = _Clock::now();
const __clock_t::time_point __s_entry = __clock_t::now();
const auto __delta = __atime - __c_entry;
const auto __s_atime = __s_entry + __delta;
return _M_load_when_equal_until(__val, __mo, __s_atime);
}
_GLIBCXX_ALWAYS_INLINE bool
_M_load_when_equal_until(unsigned __val, memory_order __mo,
const chrono::time_point<_Clock, _Duration>& __atime)
{
// DR 887 - Sync unknown clock to known clock.
const typename _Clock::time_point __c_entry = _Clock::now();
const __clock_t::time_point __s_entry = __clock_t::now();
const auto __delta = __atime - __c_entry;
const auto __s_atime = __s_entry + __delta;
return _M_load_when_equal_until(__val, __mo, __s_atime);
}
// Returns false iff a timeout occurred.
template<typename _Duration>
......@@ -207,16 +206,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
if (_M_data.exchange(__val, __mo) & _Waiter_bit)
_M_futex_notify_all(__futex);
}
};
#else // !_GLIBCXX_HAVE_LINUX_FUTEX
#else // ! (_GLIBCXX_HAVE_LINUX_FUTEX && ATOMIC_INT_LOCK_FREE > 1)
// If futexes are not available, use a mutex and a condvar to wait.
// Because we access the data only within critical sections, all accesses
// are sequentially consistent; thus, we satisfy any provided memory_order.
template <unsigned _Waiter_bit = 0x80000000>
struct __atomic_futex_unsigned
class __atomic_futex_unsigned
{
typedef chrono::system_clock __clock_t;
......@@ -224,6 +222,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
mutex _M_mutex;
condition_variable _M_condvar;
public:
explicit
__atomic_futex_unsigned(unsigned __data) : _M_data(__data)
{ }
......@@ -252,24 +252,24 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
template<typename _Rep, typename _Period>
_GLIBCXX_ALWAYS_INLINE bool
_M_load_when_equal_for(unsigned __val, memory_order __mo,
const chrono::duration<_Rep, _Period>& __rtime)
{
unique_lock<mutex> __lock(_M_mutex);
return _M_condvar.wait_for(__lock, __rtime,
[&] { return _M_data == __val;});
}
_GLIBCXX_ALWAYS_INLINE bool
_M_load_when_equal_for(unsigned __val, memory_order __mo,
const chrono::duration<_Rep, _Period>& __rtime)
{
unique_lock<mutex> __lock(_M_mutex);
return _M_condvar.wait_for(__lock, __rtime,
[&] { return _M_data == __val;});
}
template<typename _Clock, typename _Duration>
_GLIBCXX_ALWAYS_INLINE bool
_M_load_when_equal_until(unsigned __val, memory_order __mo,
const chrono::time_point<_Clock, _Duration>& __atime)
{
unique_lock<mutex> __lock(_M_mutex);
return _M_condvar.wait_until(__lock, __atime,
[&] { return _M_data == __val;});
}
_GLIBCXX_ALWAYS_INLINE bool
_M_load_when_equal_until(unsigned __val, memory_order __mo,
const chrono::time_point<_Clock, _Duration>& __atime)
{
unique_lock<mutex> __lock(_M_mutex);
return _M_condvar.wait_until(__lock, __atime,
[&] { return _M_data == __val;});
}
_GLIBCXX_ALWAYS_INLINE void
_M_store_notify_all(unsigned __val, memory_order __mo)
......@@ -278,10 +278,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_M_data = __val;
_M_condvar.notify_all();
}
};
#endif // _GLIBCXX_HAVE_LINUX_FUTEX
#endif // _GLIBCXX_HAVE_LINUX_FUTEX && ATOMIC_INT_LOCK_FREE > 1
#endif // _GLIBCXX_HAS_GTHREADS && _GLIBCXX_USE_C99_STDINT_TR1
_GLIBCXX_END_NAMESPACE_VERSION
......
libstdc++-v3/src/c++11/futex.cc
......@@ -23,7 +23,7 @@
// <http://www.gnu.org/licenses/>.
#include <bits/c++config.h>
#if defined(_GLIBCXX_HAVE_LINUX_FUTEX)
#if defined(_GLIBCXX_HAVE_LINUX_FUTEX) && ATOMIC_INT_LOCK_FREE > 1
#include <bits/atomic_futex.h>
#include <chrono>
#include <climits>
......
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