make the cached current time thread-safe

bindings/python/src/session.cpp

@@ -383,7 +383,7 @@ namespace
        }
 
        list pieces;
-       ptime now = time_now();
+       time_point now = clock_type::now();
        for (std::vector<cached_piece_info>::iterator i = ret.begin()
           , end(ret.end()); i != end; ++i)
        {

include/libtorrent/aux_/time.hpp

@@ -35,14 +35,12 @@ POSSIBILITY OF SUCH DAMAGE.
 
 #include "libtorrent/config.hpp"
 #include "libtorrent/time.hpp"
-#include <string>
-#include <boost/cstdint.hpp>
 
 namespace libtorrent { namespace aux
 {
 	// returns the current time, as represented by time_point. The
 	// resolution of this timer is about 100 ms.
-	time_point const& time_now();
+	time_point time_now();
 
 	TORRENT_EXTRA_EXPORT void update_time_now();
 

include/libtorrent/config.hpp

@@ -106,6 +106,10 @@ POSSIBILITY OF SUCH DAMAGE.
 #  define TORRENT_DEPRECATED __attribute__ ((deprecated))
 # endif
 
+# if __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ <= 8)
+#  define TORRENT_NO_ATOMIC_DURATION 1
+# endif
+
 // ======= SUNPRO =========
 
 #elif defined __SUNPRO_CC
@@ -542,6 +546,12 @@ int snprintf(char* buf, int len, char const* fmt, ...)
 #define TORRENT_NO_FPU 0
 #endif
 
+// defined to 1 if the compiler does not support putting
+// std::chrono::time_point in a std::atomic (which it's supposed to)
+#ifndef TORRENT_NO_ATOMIC_DURATION
+#define TORRENT_NO_ATOMIC_DURATION 0
+#endif
+
 #ifndef TORRENT_USE_IOSTREAM
 #ifndef BOOST_NO_IOSTREAM
 #define TORRENT_USE_IOSTREAM 1

src/time.cpp

@@ -30,30 +30,29 @@ POSSIBILITY OF SUCH DAMAGE.
 
 */
 
-#include <ctime>
-#include <string>
-#include <cstdio>
-#include <boost/limits.hpp>
-#include <boost/version.hpp>
-#include "libtorrent/config.hpp"
 #include "libtorrent/time.hpp"
 #include "libtorrent/aux_/time.hpp"
+#include <atomic>
 
 namespace libtorrent { namespace aux
 {
-	// used to cache the current time
-	// every 100 ms. This is cheaper
-	// than a system call and can be
-	// used where more accurate time
-	// is not necessary
+	// used to cache the current time regularly (update_time_now() is called by
+	// the session_impl main thread). This is cheaper than a system call and can
+	// be used where more accurate time is not necessary
+#if !TORRENT_NO_ATOMIC_DURATION
 	namespace {
-		time_point g_current_time = clock_type::now();
+		std::atomic<time_point> g_current_time(clock_type::now());
 	}
-
-	time_point const& time_now() { return aux::g_current_time; }
-
-	void update_time_now() { g_current_time = clock_type::now(); }
-
+	time_point time_now() { return aux::g_current_time.load(); }
+	void update_time_now() { g_current_time.store(clock_type::now()); }
+#else
+	// work-around for not being able to put time_point in std::atomic
+	namespace {
+		std::atomic<time_duration::rep> g_current_time(clock_type::now().time_since_epoch().count());
+	}
+	time_point time_now() { return time_point(clock_type::duration(aux::g_current_time.load())); }
+	void update_time_now() { g_current_time.store(clock_type::now().time_since_epoch().count()); }
+#endif
 
 } }