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atomic_futex.h: Use mutex and condition_variable when atomic int is not lock-free.

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* 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
This commit is contained in:
Jonathan Wakely 2015-01-18 14:25:22 +00:00 committed by Jonathan Wakely
parent e207c52262
commit 87361f3098
3 changed files with 52 additions and 47 deletions
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6
libstdc++-v3/ChangeLog
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@ -1,3 +1,9 @@
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> 2015-01-17 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/64638 PR libstdc++/64638

91
libstdc++-v3/include/bits/atomic_futex.h
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@ -35,7 +35,7 @@
#include <bits/c++config.h> #include <bits/c++config.h>
#include <atomic> #include <atomic>
#include <chrono> #include <chrono>
#if !defined(_GLIBCXX_HAVE_LINUX_FUTEX) #if ! (defined(_GLIBCXX_HAVE_LINUX_FUTEX) && ATOMIC_INT_LOCK_FREE > 1)
#include <mutex> #include <mutex>
#include <condition_variable> #include <condition_variable>
#endif #endif
@ -49,7 +49,7 @@ namespace std _GLIBCXX_VISIBILITY(default)
_GLIBCXX_BEGIN_NAMESPACE_VERSION _GLIBCXX_BEGIN_NAMESPACE_VERSION
#if defined(_GLIBCXX_HAS_GTHREADS) && defined(_GLIBCXX_USE_C99_STDINT_TR1) #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 struct __atomic_futex_unsigned_base
{ {
// Returns false iff a timeout occurred. // Returns false iff a timeout occurred.
@ -62,16 +62,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}; };
template <unsigned _Waiter_bit = 0x80000000> 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; typedef chrono::system_clock __clock_t;
// XXX We expect this to be lock-free, and having the payload at offset 0. // This must be lock-free and at offset 0.
#if ATOMIC_INT_LOCK_FREE < 2
# error We require lock-free atomic operations on int
#endif
atomic<unsigned> _M_data; atomic<unsigned> _M_data;
public:
explicit
__atomic_futex_unsigned(unsigned __data) : _M_data(__data) __atomic_futex_unsigned(unsigned __data) : _M_data(__data)
{ } { }
@ -82,7 +81,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
} }
private: private:
// If a timeout occurs, returns a current value after the timeout; // If a timeout occurs, returns a current value after the timeout;
// otherwise, returns the operand's value if equal is true or a different // otherwise, returns the operand's value if equal is true or a different
// value if equal is false. // value if equal is false.
@ -165,26 +163,27 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// Returns false iff a timeout occurred. // Returns false iff a timeout occurred.
template<typename _Rep, typename _Period> template<typename _Rep, typename _Period>
_GLIBCXX_ALWAYS_INLINE bool _GLIBCXX_ALWAYS_INLINE bool
_M_load_when_equal_for(unsigned __val, memory_order __mo, _M_load_when_equal_for(unsigned __val, memory_order __mo,
const chrono::duration<_Rep, _Period>& __rtime) const chrono::duration<_Rep, _Period>& __rtime)
{ {
return _M_load_when_equal_until(__val, __mo, __clock_t::now() + __rtime); return _M_load_when_equal_until(__val, __mo,
} __clock_t::now() + __rtime);
}
// Returns false iff a timeout occurred. // Returns false iff a timeout occurred.
template<typename _Clock, typename _Duration> template<typename _Clock, typename _Duration>
_GLIBCXX_ALWAYS_INLINE bool _GLIBCXX_ALWAYS_INLINE bool
_M_load_when_equal_until(unsigned __val, memory_order __mo, _M_load_when_equal_until(unsigned __val, memory_order __mo,
const chrono::time_point<_Clock, _Duration>& __atime) const chrono::time_point<_Clock, _Duration>& __atime)
{ {
// DR 887 - Sync unknown clock to known clock. // DR 887 - Sync unknown clock to known clock.
const typename _Clock::time_point __c_entry = _Clock::now(); const typename _Clock::time_point __c_entry = _Clock::now();
const __clock_t::time_point __s_entry = __clock_t::now(); const __clock_t::time_point __s_entry = __clock_t::now();
const auto __delta = __atime - __c_entry; const auto __delta = __atime - __c_entry;
const auto __s_atime = __s_entry + __delta; const auto __s_atime = __s_entry + __delta;
return _M_load_when_equal_until(__val, __mo, __s_atime); return _M_load_when_equal_until(__val, __mo, __s_atime);
} }
// Returns false iff a timeout occurred. // Returns false iff a timeout occurred.
template<typename _Duration> template<typename _Duration>
@ -207,16 +206,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
if (_M_data.exchange(__val, __mo) & _Waiter_bit) if (_M_data.exchange(__val, __mo) & _Waiter_bit)
_M_futex_notify_all(__futex); _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. // If futexes are not available, use a mutex and a condvar to wait.
// Because we access the data only within critical sections, all accesses // Because we access the data only within critical sections, all accesses
// are sequentially consistent; thus, we satisfy any provided memory_order. // are sequentially consistent; thus, we satisfy any provided memory_order.
template <unsigned _Waiter_bit = 0x80000000> template <unsigned _Waiter_bit = 0x80000000>
struct __atomic_futex_unsigned class __atomic_futex_unsigned
{ {
typedef chrono::system_clock __clock_t; typedef chrono::system_clock __clock_t;
@ -224,6 +222,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
mutex _M_mutex; mutex _M_mutex;
condition_variable _M_condvar; condition_variable _M_condvar;
public:
explicit
__atomic_futex_unsigned(unsigned __data) : _M_data(__data) __atomic_futex_unsigned(unsigned __data) : _M_data(__data)
{ } { }
@ -252,24 +252,24 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
} }
template<typename _Rep, typename _Period> template<typename _Rep, typename _Period>
_GLIBCXX_ALWAYS_INLINE bool _GLIBCXX_ALWAYS_INLINE bool
_M_load_when_equal_for(unsigned __val, memory_order __mo, _M_load_when_equal_for(unsigned __val, memory_order __mo,
const chrono::duration<_Rep, _Period>& __rtime) const chrono::duration<_Rep, _Period>& __rtime)
{ {
unique_lock<mutex> __lock(_M_mutex); unique_lock<mutex> __lock(_M_mutex);
return _M_condvar.wait_for(__lock, __rtime, return _M_condvar.wait_for(__lock, __rtime,
[&] { return _M_data == __val;}); [&] { return _M_data == __val;});
} }
template<typename _Clock, typename _Duration> template<typename _Clock, typename _Duration>
_GLIBCXX_ALWAYS_INLINE bool _GLIBCXX_ALWAYS_INLINE bool
_M_load_when_equal_until(unsigned __val, memory_order __mo, _M_load_when_equal_until(unsigned __val, memory_order __mo,
const chrono::time_point<_Clock, _Duration>& __atime) const chrono::time_point<_Clock, _Duration>& __atime)
{ {
unique_lock<mutex> __lock(_M_mutex); unique_lock<mutex> __lock(_M_mutex);
return _M_condvar.wait_until(__lock, __atime, return _M_condvar.wait_until(__lock, __atime,
[&] { return _M_data == __val;}); [&] { return _M_data == __val;});
} }
_GLIBCXX_ALWAYS_INLINE void _GLIBCXX_ALWAYS_INLINE void
_M_store_notify_all(unsigned __val, memory_order __mo) _M_store_notify_all(unsigned __val, memory_order __mo)
@ -278,10 +278,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_M_data = __val; _M_data = __val;
_M_condvar.notify_all(); _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 #endif // _GLIBCXX_HAS_GTHREADS && _GLIBCXX_USE_C99_STDINT_TR1
_GLIBCXX_END_NAMESPACE_VERSION _GLIBCXX_END_NAMESPACE_VERSION

2
libstdc++-v3/src/c++11/futex.cc
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@ -23,7 +23,7 @@
// <http://www.gnu.org/licenses/>. // <http://www.gnu.org/licenses/>.
#include <bits/c++config.h> #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 <bits/atomic_futex.h>
#include <chrono> #include <chrono>
#include <climits> #include <climits>