DRTVWR-494: Defend LLInstanceTracker against multi-thread usage.

The previous implementation went to some effort to crash if anyone attempted
to create or destroy an LLInstanceTracker subclass instance during traversal.
That restriction is manageable within a single thread, but becomes unworkable
if it's possible that a given subclass might be used on more than one thread.

Remove LLInstanceTracker::instance_iter, beginInstances(), endInstances(),
also key_iter, beginKeys() and endKeys(). Instead, introduce key_snapshot()
and instance_snapshot(), the only means of iterating over LLInstanceTracker
instances. (These are intended to resemble functions, but in fact the current
implementation simply presents the classes.) Iterating over a captured
snapshot defends against container modifications during traversal. The term
'snapshot' reminds the coder that a new instance created during traversal will
not be considered. To defend against instance deletion during traversal, a
snapshot stores std::weak_ptrs which it lazily dereferences, skipping on the
fly any that have expired.

Dereferencing instance_snapshot::iterator gets you a reference rather than a
pointer. Because some use cases want to delete all existing instances, add an
instance_snapshot::deleteAll() method that extracts the pointer. Those cases
used to require explicitly copying instance pointers into a separate
container; instance_snapshot() now takes care of that. It remains the caller's
responsibility to ensure that all instances of that LLInstanceTracker subclass
were allocated on the heap.

Replace unkeyed static LLInstanceTracker::getInstance(T*) -- which returned
nullptr if that instance had been destroyed -- with new getWeak() method
returning std::weak_ptr<T>. Caller must detect expiration of that weak_ptr.

Adjust tests accordingly.

Use of std::weak_ptr to detect expired instances requires engaging
std::shared_ptr in the constructor. We now store shared_ptrs in the static
containers (std::map for keyed, std::set for unkeyed).

Make LLInstanceTrackerBase a template parameterized on the type of the static
data it manages. For that reason, hoist static data class declarations out of
the class definitions to an LLInstanceTrackerStuff namespace.

Remove the static atomic sIterationNestDepth and its methods incrementDepth(),
decrementDepth() and getDepth(), since they were used only to forbid creation
and destruction during traversal.

Add a std::mutex to static data. Introduce an internal LockStatic class that
locks the mutex while providing a pointer to static data, making that the only
way to access the static data.

The LLINSTANCETRACKER_DTOR_NOEXCEPT macro goes away because we no longer
expect ~LLInstanceTracker() to throw an exception in test programs.
That affects LLTrace::StatBase as well as LLInstanceTracker itself.

Adapt consumers to the new LLInstanceTracker API.

6 files changed, 31 insertions, 82 deletions

diff --git a/indra/newview/llappviewer.cpp b/indra/newview/llappviewer.cpp
index b232a8c3bb..a76ac58724 100644
--- a/indra/newview/llappviewer.cpp
+++ b/indra/newview/llappviewer.cpp
@@ -1681,24 +1681,9 @@ bool LLAppViewer::cleanup()
 		gDirUtilp->deleteFilesInDir(logdir, "*-*-*-*-*.dmp");
 	}
 
-	{
-		// Kill off LLLeap objects. We can find them all because LLLeap is derived
-		// from LLInstanceTracker. But collect instances first: LLInstanceTracker
-		// specifically forbids adding/deleting instances while iterating.
-		std::vector<LLLeap*> leaps;
-		leaps.reserve(LLLeap::instanceCount());
-		for (LLLeap::instance_iter li(LLLeap::beginInstances()), lend(LLLeap::endInstances());
-			 li != lend; ++li)
-		{
-			leaps.push_back(&*li);
-		}
-		// Okay, now trash them all. We don't have to NULL or erase the entry
-		// in 'leaps' because the whole vector is going away momentarily.
-		BOOST_FOREACH(LLLeap* leap, leaps)
-		{
-			delete leap;
-		}
-	} // destroy 'leaps'
+	// Kill off LLLeap objects. We can find them all because LLLeap is derived
+	// from LLInstanceTracker.
+	LLLeap::instance_snapshot().deleteAll();
 
 	//flag all elements as needing to be destroyed immediately
 	// to ensure shutdown order
@@ -2858,12 +2843,11 @@ bool LLAppViewer::initConfiguration()
 
 	// Let anyone else who cares know that we've populated our settings
 	// variables.
-	for (LLControlGroup::key_iter ki(LLControlGroup::beginKeys()), kend(LLControlGroup::endKeys());
-		 ki != kend; ++ki)
+	for (const auto& key : LLControlGroup::key_snapshot())
 	{
 		// For each named instance of LLControlGroup, send an event saying
 		// we've initialized an LLControlGroup instance by that name.
-		LLEventPumps::instance().obtain("LLControlGroup").post(LLSDMap("init", *ki));
+		LLEventPumps::instance().obtain("LLControlGroup").post(LLSDMap("init", key));
 	}
 
 	return true; // Config was successful.
diff --git a/indra/newview/llchathistory.cpp b/indra/newview/llchathistory.cpp
index 1099d4bc09..4131af828e 100644
--- a/indra/newview/llchathistory.cpp
+++ b/indra/newview/llchathistory.cpp
@@ -1344,10 +1344,8 @@ void LLChatHistory::appendMessage(const LLChat& chat, const LLSD &args, const LL
 				// We don't want multiple friendship offers to appear, this code checks if there are previous offers
 				// by iterating though all panels.
 				// Note: it might be better to simply add a "pending offer" flag somewhere
-				for (LLToastNotifyPanel::instance_iter ti(LLToastNotifyPanel::beginInstances())
-					, tend(LLToastNotifyPanel::endInstances()); ti != tend; ++ti)
+				for (auto& panel : LLToastNotifyPanel::instance_snapshot())
 				{
-					LLToastNotifyPanel& panel = *ti;
 					LLIMToastNotifyPanel * imtoastp = dynamic_cast<LLIMToastNotifyPanel *>(&panel);
 					const std::string& notification_name = panel.getNotificationName();
 					if (notification_name == "OfferFriendship"
diff --git a/indra/newview/llimprocessing.cpp b/indra/newview/llimprocessing.cpp
index c3375a3779..c1dcc61010 100644
--- a/indra/newview/llimprocessing.cpp
+++ b/indra/newview/llimprocessing.cpp
@@ -1404,10 +1404,8 @@ void LLIMProcessing::processNewMessage(LLUUID from_id,
             payload["sender"] = sender.getIPandPort();
 
             bool add_notification = true;
-            for (LLToastNotifyPanel::instance_iter ti(LLToastNotifyPanel::beginInstances())
-                , tend(LLToastNotifyPanel::endInstances()); ti != tend; ++ti)
+            for (auto& panel : LLToastNotifyPanel::instance_snapshot())
             {
-                LLToastNotifyPanel& panel = *ti;
                 const std::string& notification_name = panel.getNotificationName();
                 if (notification_name == "OfferFriendship" && panel.isControlPanelEnabled())
                 {
diff --git a/indra/newview/llscenemonitor.cpp b/indra/newview/llscenemonitor.cpp
index 5ab0013055..2c0c38dc75 100644
--- a/indra/newview/llscenemonitor.cpp
+++ b/indra/newview/llscenemonitor.cpp
@@ -559,16 +559,14 @@ void LLSceneMonitor::dumpToFile(std::string file_name)
 
 
 	typedef StatType<CountAccumulator> trace_count;
-	for (trace_count::instance_iter it = trace_count::beginInstances(), end_it = trace_count::endInstances();
-		it != end_it;
-		++it)
+	for (auto& it : trace_count::instance_snapshot())
 	{
 		std::ostringstream row;
 		row << std::setprecision(10);
 
-		row << it->getName();
+		row << it.getName();
 
-		const char* unit_label = it->getUnitLabel();
+		const char* unit_label = it.getUnitLabel();
 		if(unit_label[0])
 		{
 			row << "(" << unit_label << ")";
@@ -579,8 +577,8 @@ void LLSceneMonitor::dumpToFile(std::string file_name)
 		for (S32 frame = 1; frame <= frame_count; frame++)
 		{
 			Recording& recording = scene_load_recording.getPrevRecording(frame_count - frame);
-			samples += recording.getSampleCount(*it);
-			row << ", " << recording.getSum(*it);
+			samples += recording.getSampleCount(it);
+			row << ", " << recording.getSum(it);
 		}
 
 		row << '\n';
@@ -593,15 +591,13 @@ void LLSceneMonitor::dumpToFile(std::string file_name)
 
 	typedef StatType<EventAccumulator> trace_event;
 
-	for (trace_event::instance_iter it = trace_event::beginInstances(), end_it = trace_event::endInstances();
-		it != end_it;
-		++it)
+	for (auto& it : trace_event::instance_snapshot())
 	{
 		std::ostringstream row;
 		row << std::setprecision(10);
-		row << it->getName();
+		row << it.getName();
 
-		const char* unit_label = it->getUnitLabel();
+		const char* unit_label = it.getUnitLabel();
 		if(unit_label[0])
 		{
 			row << "(" << unit_label << ")";
@@ -612,8 +608,8 @@ void LLSceneMonitor::dumpToFile(std::string file_name)
 		for (S32 frame = 1; frame <= frame_count; frame++)
 		{
 			Recording& recording = scene_load_recording.getPrevRecording(frame_count - frame);
-			samples += recording.getSampleCount(*it);
-			F64 mean = recording.getMean(*it);
+			samples += recording.getSampleCount(it);
+			F64 mean = recording.getMean(it);
 			if (llisnan(mean))
 			{
 				row << ", n/a";
@@ -634,15 +630,13 @@ void LLSceneMonitor::dumpToFile(std::string file_name)
 
 	typedef StatType<SampleAccumulator> trace_sample;
 
-	for (trace_sample::instance_iter it = trace_sample::beginInstances(), end_it = trace_sample::endInstances();
-		it != end_it;
-		++it)
+	for (auto& it : trace_sample::instance_snapshot())
 	{
 		std::ostringstream row;
 		row << std::setprecision(10);
-		row << it->getName();
+		row << it.getName();
 
-		const char* unit_label = it->getUnitLabel();
+		const char* unit_label = it.getUnitLabel();
 		if(unit_label[0])
 		{
 			row << "(" << unit_label << ")";
@@ -653,8 +647,8 @@ void LLSceneMonitor::dumpToFile(std::string file_name)
 		for (S32 frame = 1; frame <= frame_count; frame++)
 		{
 			Recording& recording = scene_load_recording.getPrevRecording(frame_count - frame);
-			samples += recording.getSampleCount(*it);
-			F64 mean = recording.getMean(*it);
+			samples += recording.getSampleCount(it);
+			F64 mean = recording.getMean(it);
 			if (llisnan(mean))
 			{
 				row << ", n/a";
@@ -674,15 +668,13 @@ void LLSceneMonitor::dumpToFile(std::string file_name)
 	}
 
 	typedef StatType<MemAccumulator> trace_mem;
-	for (trace_mem::instance_iter it = trace_mem::beginInstances(), end_it = trace_mem::endInstances();
-		it != end_it;
-		++it)
+	for (auto& it : trace_mem::instance_snapshot())
 	{
-		os << it->getName() << "(KiB)";
+		os << it.getName() << "(KiB)";
 
 		for (S32 frame = 1; frame <= frame_count; frame++)
 		{
-			os << ", " << scene_load_recording.getPrevRecording(frame_count - frame).getMax(*it).valueInUnits<LLUnits::Kilobytes>();
+			os << ", " << scene_load_recording.getPrevRecording(frame_count - frame).getMax(it).valueInUnits<LLUnits::Kilobytes>();
 		}
 
 		os << '\n';
diff --git a/indra/newview/lltoast.cpp b/indra/newview/lltoast.cpp
index 870e0d94f0..bf56a10d4d 100644
--- a/indra/newview/lltoast.cpp
+++ b/indra/newview/lltoast.cpp
@@ -612,11 +612,8 @@ S32	LLToast::notifyParent(const LLSD& info)
 //static
 void LLToast::updateClass()
 {
-	for (LLInstanceTracker<LLToast>::instance_iter iter = LLInstanceTracker<LLToast>::beginInstances(); 
-			iter != LLInstanceTracker<LLToast>::endInstances(); ) 
+	for (auto& toast : LLInstanceTracker<LLToast>::instance_snapshot())
 	{
-		LLToast& toast = *iter++;
-		
 		toast.updateHoveredState();
 	}
 }
@@ -624,22 +621,6 @@ void LLToast::updateClass()
 // static 
 void LLToast::cleanupToasts()
 {
-	LLToast * toastp = NULL;
-
-	while (LLInstanceTracker<LLToast>::instanceCount() > 0)
-	{
-		{	// Need to scope iter to allow deletion
-			LLInstanceTracker<LLToast>::instance_iter iter = LLInstanceTracker<LLToast>::beginInstances(); 
-			toastp = &(*iter);
-		}
-
-		//LL_INFOS() << "Cleaning up toast id " << toastp->getNotificationID() << LL_ENDL;
-
-		// LLToast destructor will remove it from the LLInstanceTracker.
-		if (!toastp)
-			break;		// Don't get stuck in the loop if a null pointer somehow got on the list
-
-		delete toastp;
-	}
+	LLInstanceTracker<LLToast>::instance_snapshot().deleteAll();
 }
 
diff --git a/indra/newview/llviewercontrollistener.cpp b/indra/newview/llviewercontrollistener.cpp
index d2484b2b23..3443bb644a 100644
--- a/indra/newview/llviewercontrollistener.cpp
+++ b/indra/newview/llviewercontrollistener.cpp
@@ -50,11 +50,9 @@ LLViewerControlListener::LLViewerControlListener()
 	std::ostringstream groupnames;
 	groupnames << "[\"group\"] is one of ";
 	const char* delim = "";
-	for (LLControlGroup::key_iter cgki(LLControlGroup::beginKeys()),
-								  cgkend(LLControlGroup::endKeys());
-		 cgki != cgkend; ++cgki)
+	for (const auto& key : LLControlGroup::key_snapshot())
 	{
-		groupnames << delim << '"' << *cgki << '"';
+		groupnames << delim << '"' << key << '"';
 		delim = ", ";
 	}
 	groupnames << '\n';
@@ -181,11 +179,9 @@ void LLViewerControlListener::groups(LLSD const & request)
 {
 	// No Info, we're not looking up either a group or a control name.
 	Response response(LLSD(), request);
-	for (LLControlGroup::key_iter cgki(LLControlGroup::beginKeys()),
-								  cgkend(LLControlGroup::endKeys());
-		 cgki != cgkend; ++cgki)
+	for (const auto& key : LLControlGroup::key_snapshot())
 	{
-		response["groups"].append(*cgki);
+		response["groups"].append(key);
 	}
 }