Time: Remove serverside getter, and use atomic operations

It isn't possible to use atomic operations for floats, so don't use them there. Having a lock is good out of other reasons too, because this way the float time and the integer time both match, and can't get different values in a race, e.g. when two setTimeofDay() get executed simultaneously.
minetest · Nov 3, 2015 · f9b0936 · f9b0936
1 parent abc354a
commit f9b0936
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Showing 4 changed files with 31 additions and 43 deletions.
diff --git a/src/environment.cpp b/src/environment.cpp
@@ -52,9 +52,8 @@ Environment::Environment():
 	m_time_of_day(9000),
 	m_time_of_day_f(9000./24000),
 	m_time_of_day_speed(0),
-	m_time_counter(0),
-	m_enable_day_night_ratio_override(false),
-	m_day_night_ratio_override(0.0f)
+	m_time_conversion_skew(0),
+	m_day_night_ratio_override_storage(0)
 {
 	m_cache_enable_shaders = g_settings->getBool("enable_shaders");
 }
@@ -180,53 +179,46 @@ std::vector<Player*> Environment::getPlayers(bool ignore_disconnected)
 
 u32 Environment::getDayNightRatio()
 {
-	MutexAutoLock(this->m_time_lock);
-	if (m_enable_day_night_ratio_override)
-		return m_day_night_ratio_override;
+	u64 day_night_st = m_day_night_ratio_override_storage;
+	if (day_night_st & ((u64)1 << 63))
+		return day_night_st & U32_MAX;
+	MutexAutoLock lock(this->m_time_floats_lock);
 	return time_to_daynight_ratio(m_time_of_day_f * 24000, m_cache_enable_shaders);
 }
 
 void Environment::setTimeOfDaySpeed(float speed)
 {
-	MutexAutoLock(this->m_time_lock);
 	m_time_of_day_speed = speed;
 }
 
 float Environment::getTimeOfDaySpeed()
 {
-	MutexAutoLock(this->m_time_lock);
-	float retval = m_time_of_day_speed;
-	return retval;
+	return m_time_of_day_speed;
 }
 
 void Environment::setTimeOfDay(u32 time)
 {
-	MutexAutoLock(this->m_time_lock);
+	MutexAutoLock lock(this->m_time_floats_lock);
 	m_time_of_day = time;
 	m_time_of_day_f = (float)time / 24000.0;
 }
 
 u32 Environment::getTimeOfDay()
 {
-	MutexAutoLock(this->m_time_lock);
-	u32 retval = m_time_of_day;
-	return retval;
+	return m_time_of_day;
 }
 
 float Environment::getTimeOfDayF()
 {
-	MutexAutoLock(this->m_time_lock);
-	float retval = m_time_of_day_f;
-	return retval;
+	MutexAutoLock lock(this->m_time_floats_lock);
+	return m_time_of_day_f;
 }
 
 void Environment::stepTimeOfDay(float dtime)
 {
-	MutexAutoLock(this->m_time_lock);
-
-	m_time_counter += dtime;
+	MutexAutoLock lock(this->m_time_floats_lock);
 	f32 speed = m_time_of_day_speed * 24000. / (24. * 3600);
-	u32 units = (u32)(m_time_counter * speed);
+	u32 units = (u32)((dtime + m_time_conversion_skew) * speed);
 	bool sync_f = false;
 	if (units > 0) {
 		// Sync at overflow
@@ -237,10 +229,10 @@ void Environment::stepTimeOfDay(float dtime)
 			m_time_of_day_f = (float)m_time_of_day / 24000.0;
 	}
 	if (speed > 0) {
-		m_time_counter -= (f32)units / speed;
+		m_time_conversion_skew -= (f32)units / speed;
 	}
 	if (!sync_f) {
-		m_time_of_day_f += m_time_of_day_speed / 24 / 3600 * dtime;
+		m_time_of_day_f += m_time_of_day_speed / (24. * 3600.) * dtime;
 		if (m_time_of_day_f > 1.0)
 			m_time_of_day_f -= 1.0;
 		if (m_time_of_day_f < 0.0)

diff --git a/src/environment.h b/src/environment.h
@@ -40,6 +40,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "mapnode.h"
 #include "mapblock.h"
 #include "threading/mutex.h"
+#include "threading/atomic.h"
 #include "network/networkprotocol.h" // for AccessDeniedCode
 
 class ServerEnvironment;
@@ -94,8 +95,7 @@ class Environment
 
 	void setDayNightRatioOverride(bool enable, u32 value)
 	{
-		m_enable_day_night_ratio_override = enable;
-		m_day_night_ratio_override = value;
+		m_day_night_ratio_override_storage = value | ((u64)enable << 63);
 	}
 
 	// counter used internally when triggering ABMs
@@ -105,23 +105,25 @@ class Environment
 	// peer_ids in here should be unique, except that there may be many 0s
 	std::vector<Player*> m_players;
 
+	// Time of day in milli-hours (0-23999); determines day and night
+	Atomic<u32> m_time_of_day;
 
 	/*
-	 *  Below: values under m_time_lock
-	 */
-	// Time of day in milli-hours (0-23999); determines day and night
-	u32 m_time_of_day;
+	 * Below: values managed by m_time_floats_lock
+	*/
 	// Time of day in 0...1
 	float m_time_of_day_f;
 	float m_time_of_day_speed;
-	// Used to buffer dtime for adding to m_time_of_day
-	float m_time_counter;
-	// Overriding the day-night ratio is useful for custom sky visuals
-	bool m_enable_day_night_ratio_override;
-	u32 m_day_night_ratio_override;
+	// Stores the skew created by the float -> u32 conversion
+	// to be applied at next conversion, so that there is no real skew.
+	float m_time_conversion_skew;
 	/*
-	 * Above: values under m_time_lock
-	 */
+	 * Above: values managed by m_time_floats_lock
+	*/
+
+	// Overriding the day-night ratio is useful for custom sky visuals
+	// lowest 32 bits store the overriden ratio, highest bit stores whether its enabled
+	Atomic<u64> m_day_night_ratio_override_storage;
 
 	/* TODO: Add a callback function so these can be updated when a setting
 	 *       changes.  At this point in time it doesn't matter (e.g. /set
@@ -135,7 +137,7 @@ class Environment
 	bool m_cache_enable_shaders;
 
 private:
-	Mutex m_time_lock;
+	Mutex m_time_floats_lock;
 
 	DISABLE_CLASS_COPY(Environment);
 };

diff --git a/src/server.cpp b/src/server.cpp
@@ -1232,11 +1232,6 @@ void Server::setTimeOfDay(u32 time)
 	m_time_of_day_send_timer = 0;
 }
 
-u32 Server::getTimeOfDay()
-{
-	return m_env->getTimeOfDay();
-}
-
 void Server::onMapEditEvent(MapEditEvent *event)
 {
 	if(m_ignore_map_edit_events)

diff --git a/src/server.h b/src/server.h
@@ -223,7 +223,6 @@ class Server : public con::PeerHandler, public MapEventReceiver,
 	// Both setter and getter need no envlock,
 	// can be called freely from threads
 	void setTimeOfDay(u32 time);
-	inline u32 getTimeOfDay();
 
 	/*
 		Shall be called with the environment locked.