From aad3371b3d1831dd0525a51e40f637f00be6ff87 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sat, 20 Apr 2013 17:47:50 +0300
Subject: [PATCH] Fix Timer to use is Semaphore correctly

Besides still assuming the old condvar-style semantics, it was also
horribly broken and contained potential deadlocks and race conditions.
Not to mention unusable due to a missing constructor.
---
 source/time/timer.cpp | 32 +++++++++++++++++++++++---------
 source/time/timer.h   |  2 ++
 2 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/source/time/timer.cpp b/source/time/timer.cpp
index 59360b6..f26900b 100644
--- a/source/time/timer.cpp
+++ b/source/time/timer.cpp
@@ -7,6 +7,11 @@ using namespace std;
 namespace Msp {
 namespace Time {
 
+Timer::Timer():
+	sem(1),
+	blocking(false)
+{ }
+
 Timer::~Timer()
 {
 	for(vector<SlotProxy>::iterator i=slots.begin(); i!=slots.end(); ++i)
@@ -16,23 +21,22 @@ Timer::~Timer()
 Timer::Slot &Timer::add(const TimeDelta &td)
 {
 	Slot *s = new Slot(td);
-	mutex.lock();
+	MutexLock l(mutex);
 	slots.push_back(s);
 	push_heap(slots.begin(), slots.end());
-	mutex.unlock();
-	sem.signal();
+	if(blocking)
+		sem.signal();
 	return *s;
 }
 
 Timer::Slot &Timer::add(const TimeStamp &ts)
 {
 	Slot *s = new Slot(ts);
-	{
-		MutexLock l(mutex);
-		slots.push_back(s);
-		push_heap(slots.begin(), slots.end());
-	}
-	sem.signal();
+	MutexLock l(mutex);
+	slots.push_back(s);
+	push_heap(slots.begin(), slots.end());
+	if(blocking)
+		sem.signal();
 	return *s;
 }
 
@@ -59,7 +63,12 @@ void Timer::tick(bool block)
 			if(slots.empty())
 			{
 				if(block)
+				{
+					blocking = true;
+					mutex.unlock();
 					sem.wait();
+					mutex.lock();
+				}
 				else
 					return;
 			}
@@ -70,7 +79,12 @@ void Timer::tick(bool block)
 			if(stamp<=t)
 				break;
 			else if(block)
+			{
+				blocking = true;
+				mutex.unlock();
 				sem.wait(stamp-t);
+				mutex.lock();
+			}
 			else
 				return;
 		}
diff --git a/source/time/timer.h b/source/time/timer.h
index 7566c3d..90d870c 100644
--- a/source/time/timer.h
+++ b/source/time/timer.h
@@ -49,8 +49,10 @@ private:
 	std::vector<SlotProxy> slots;
 	Semaphore sem;
 	Mutex mutex;
+	bool blocking;
 
 public:
+	Timer();
 	~Timer();
 
 	/** Adds a timer that will be executed periodically as long as the timeout
-- 
2.45.2