Subject: [Boost-commit] svn:boost r85809 - in trunk/boost/sync: . detail/event
From: tim_at_[hidden]
Date: 2013-09-21 05:21:30
Author: timblechmann
Date: 2013-09-21 05:21:30 EDT (Sat, 21 Sep 2013)
New Revision: 85809
URL: http://svn.boost.org/trac/boost/changeset/85809
Log:
sync: event - prototype futex-based event
Added:
trunk/boost/sync/detail/event/event_futex.hpp (contents, props changed)
Text files modified:
trunk/boost/sync/detail/event/event_futex.hpp | 217 ++++++++++++++++++++++++++++++++++++++++
trunk/boost/sync/event.hpp | 3
2 files changed, 220 insertions(+), 0 deletions(-)
Added: trunk/boost/sync/detail/event/event_futex.hpp
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ trunk/boost/sync/detail/event/event_futex.hpp 2013-09-21 05:21:30 EDT (Sat, 21 Sep 2013) (r85809)
@@ -0,0 +1,217 @@
+// event.hpp, futex-based event
+//
+// Copyright (C) 2013 Tim Blechmann
+//
+// Distributed under the Boost Software License, Version 1.0. (See
+// accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_SYNC_DETAIL_EVENT_EVENT_FUTEX_HPP_INCLUDED
+#define BOOST_SYNC_DETAIL_EVENT_EVENT_FUTEX_HPP_INCLUDED
+
+#include <boost/thread/condition_variable.hpp>
+#include <boost/thread/shared_mutex.hpp>
+#include <boost/thread/locks.hpp>
+
+#include <boost/sync/detail/config.hpp>
+#include <boost/sync/detail/header.hpp>
+
+#include <boost/atomic.hpp>
+
+#include <sys/time.h>
+#include <linux/futex.h>
+#include <unistd.h>
+#include <sys/syscall.h>
+
+namespace boost {
+namespace sync {
+BOOST_SYNC_DETAIL_OPEN_ABI_NAMESPACE {
+
+class event
+{
+ BOOST_DELETED_FUNCTION(event(event const&));
+ BOOST_DELETED_FUNCTION(event& operator=(event const&));
+
+public:
+ explicit event(bool auto_reset = false) BOOST_NOEXCEPT :
+ m_auto_reset(auto_reset), m_state(0)
+ {}
+
+ void post() BOOST_NOEXCEPT
+ {
+ if (m_auto_reset) {
+ int32_t old_state = m_state.load();
+ if (old_state >= 0) {
+ for(;;) {
+ if (m_state.compare_exchange_weak(old_state, old_state - 1))
+ break;
+ }
+ futex(&m_state, FUTEX_WAKE_PRIVATE, std::numeric_limits<int>::max() ); // wake all threads
+ }
+
+ } else {
+ int old_state = m_state.exchange(1); // set state
+ if (old_state == 0)
+ futex(&m_state, FUTEX_WAKE_PRIVATE, std::numeric_limits<int>::max() ); // wake all threads
+ }
+ }
+
+ void wait() BOOST_NOEXCEPT
+ {
+ if (m_auto_reset) {
+ int32_t old_state = m_state.fetch_add(1) + 1;
+
+ for (;;) {
+ long status = futex(&m_state, FUTEX_WAIT_PRIVATE, old_state);
+ if (status == 0)
+ return;
+
+ switch (errno) {
+ case EINTR: // signal received
+ continue;
+
+ case EWOULDBLOCK: // another thread changed the state, reread and retry
+ old_state = m_state.load();
+ continue;
+
+ default:
+ BOOST_ASSERT(false);
+ }
+ }
+ } else {
+ try_again:
+
+ if ( m_state.load(memory_order_acquire) == 1 )
+ return; // fast-path
+
+ const long status = futex(&m_state, FUTEX_WAIT_PRIVATE, 0);
+ if (status == 0)
+ return;
+
+ switch (errno)
+ {
+ case EINTR:
+ // signal received
+ goto try_again;
+
+ case EWOULDBLOCK:
+ // another thread has reset the event
+ goto try_again;
+ }
+ }
+ }
+
+ bool try_wait()
+ {
+ if (m_auto_reset) {
+ int32_t old_state = m_state.load();
+
+ if (old_state < 0) {
+ for(;;) {
+ int32_t new_state = old_state + 1;
+ bool cas_successful = m_state.compare_exchange_weak(old_state, new_state);
+ if (cas_successful) // we succeeded and reset the wait count
+ return true;
+ if (old_state >= 0) // another thread a succeeded
+ return false;
+ }
+ }
+ return false;
+
+ } else {
+ if ( m_state.load(memory_order_acquire) == 1 )
+ return true; // fast-path
+ else
+ return false;
+ }
+ }
+
+ void reset() BOOST_NOEXCEPT
+ {
+ m_state.store( 0 );
+ }
+
+ template <class Rep, class Period>
+ bool try_wait_for(const chrono::duration<Rep, Period> & duration) BOOST_NOEXCEPT
+ {
+ timespec ts = boost::detail::to_timespec( duration );
+ return do_wait_for(ts);
+ }
+
+ template <class Clock, class Duration>
+ bool try_wait_until(const chrono::time_point<Clock, Duration> & timeout ) BOOST_NOEXCEPT
+ {
+ return try_wait_for( timeout - Clock::now() );
+ }
+
+private:
+ bool do_wait_for(const struct timespec & timeout)
+ {
+ if (m_auto_reset) {
+ int32_t old_state = m_state.fetch_add(1) + 1;
+
+ for (;;) {
+ long status = futex(&m_state, FUTEX_WAIT_PRIVATE, old_state, &timeout);
+ if (status == 0)
+ return true;
+
+ switch (errno) {
+ case ETIMEDOUT:
+ return false;
+
+ case EINTR: // signal received
+ continue;
+
+ case EWOULDBLOCK: // another thread changed the state, reread and retry
+ old_state = m_state.load();
+ continue;
+
+ default:
+ BOOST_ASSERT(false);
+ }
+ }
+ } else {
+ try_again:
+
+ if ( m_state.load(memory_order_acquire) == 1 )
+ return true; // fast-path
+
+ const long status = futex(&m_state, FUTEX_WAIT_PRIVATE, 0, &timeout);
+ if (status == 0)
+ return true;
+
+ switch (errno)
+ {
+ case ETIMEDOUT:
+ return false;
+
+ case EINTR:
+ // signal received
+ goto try_again;
+
+ case EWOULDBLOCK:
+ // another thread has reset the event
+ goto try_again;
+ }
+ }
+ BOOST_ASSERT(false);
+ return false;
+ }
+
+ static long futex(void *addr1, int op, int val1, const struct timespec *timeout = NULL, void *addr2 = NULL, int val3 = 0)
+ {
+ return syscall(SYS_futex, addr1, op, val1, timeout, addr2, val3);
+ }
+
+ const bool m_auto_reset;
+
+ atomic<int32_t> m_state;
+};
+
+}
+}
+}
+
+#include <boost/sync/detail/footer.hpp>
+
+#endif // BOOST_SYNC_DETAIL_EVENT_EVENT_FUTEX_HPP_INCLUDED
Modified: trunk/boost/sync/event.hpp
==============================================================================
--- trunk/boost/sync/event.hpp Fri Sep 20 16:06:32 2013 (r85808)
+++ trunk/boost/sync/event.hpp 2013-09-21 05:21:30 EDT (Sat, 21 Sep 2013) (r85809)
@@ -115,6 +115,9 @@
#if defined(BOOST_SYNC_DETAIL_PLATFORM_WINAPI)
#include <boost/sync/detail/event/event_windows.hpp>
+#elif defined(__linux__)
+#include <boost/sync/detail/event/event_futex.hpp>
+
#elif defined(BOOST_SYNC_DETAIL_PLATFORM_MACH)
#include <boost/sync/detail/event/event_mach.hpp>