4 files changed, 50 insertions, 10 deletions
diff --git a/indra/llcommon/llapp.cpp b/indra/llcommon/llapp.cpp
index a90b294550..34f6ba140a 100644
--- a/indra/llcommon/llapp.cpp
+++ b/indra/llcommon/llapp.cpp
@@ -113,7 +113,8 @@ BOOL LLApp::sDisableCrashlogger = FALSE;
 BOOL LLApp::sLogInSignal = FALSE;
 
 // static
-LLApp::EAppStatus LLApp::sStatus = LLApp::APP_STATUS_STOPPED; // Keeps track of application status
+// Keeps track of application status
+LLScalarCond<LLApp::EAppStatus> LLApp::sStatus{LLApp::APP_STATUS_STOPPED};
 LLAppErrorHandler LLApp::sErrorHandler = NULL;
 BOOL LLApp::sErrorThreadRunning = FALSE;
 
@@ -579,7 +580,8 @@ static std::map<LLApp::EAppStatus, const char*> statusDesc
 // static
 void LLApp::setStatus(EAppStatus status)
 {
-    sStatus = status;
+    // notify everyone waiting on sStatus any time its value changes
+    sStatus.set_all(status);
 
     // This can also happen very late in the application lifecycle -- don't
     // resurrect a deleted LLSingleton
@@ -609,6 +611,12 @@ void LLApp::setError()
 	setStatus(APP_STATUS_ERROR);
 }
 
+// static
+bool LLApp::sleep(F32Milliseconds duration)
+{
+    return ! sStatus.wait_for_unequal(duration, APP_STATUS_RUNNING);
+}
+
 void LLApp::setMiniDumpDir(const std::string &path)
 {
 	if (path.empty())
@@ -668,28 +676,28 @@ void LLApp::setStopped()
 // static
 bool LLApp::isStopped()
 {
-	return (APP_STATUS_STOPPED == sStatus);
+	return (APP_STATUS_STOPPED == sStatus.get());
 }
 
 
 // static
 bool LLApp::isRunning()
 {
-	return (APP_STATUS_RUNNING == sStatus);
+	return (APP_STATUS_RUNNING == sStatus.get());
 }
 
 
 // static
 bool LLApp::isError()
 {
-	return (APP_STATUS_ERROR == sStatus);
+	return (APP_STATUS_ERROR == sStatus.get());
 }
 
 
 // static
 bool LLApp::isQuitting()
 {
-	return (APP_STATUS_QUITTING == sStatus);
+	return (APP_STATUS_QUITTING == sStatus.get());
 }
 
 // static
diff --git a/indra/llcommon/llapp.h b/indra/llcommon/llapp.h
index 245c73e3a2..e95929b865 100644
--- a/indra/llcommon/llapp.h
+++ b/indra/llcommon/llapp.h
@@ -28,9 +28,11 @@
 #define LL_LLAPP_H
 
 #include <map>
+#include "llcond.h"
 #include "llrun.h"
 #include "llsd.h"
 #include <atomic>
+#include <chrono>
 // Forward declarations
 class LLErrorThread;
 class LLLiveFile;
@@ -211,6 +213,36 @@ public:
 	static bool isExiting(); // Either quitting or error (app is exiting, cleanly or not)
 	static int getPid();
 
+	//
+	// Sleep for specified time while still running
+	//
+	// For use by a coroutine or thread that performs some maintenance on a
+	// periodic basis. (See also LLEventTimer.) This method supports the
+	// pattern of an "infinite" loop that sleeps for some time, performs some
+	// action, then sleeps again. The trouble with literally sleeping a worker
+	// thread is that it could potentially sleep right through attempted
+	// application shutdown. This method avoids that by returning false as
+	// soon as the application status changes away from APP_STATUS_RUNNING
+	// (isRunning()).
+	//
+	// sleep() returns true if it sleeps undisturbed for the entire specified
+	// duration. The idea is that you can code 'while sleep(duration) ...',
+	// which will break the loop once shutdown begins.
+	//
+	// Since any time-based LLUnit should be implicitly convertible to
+	// F32Milliseconds, accept that specific type as a proxy.
+	static bool sleep(F32Milliseconds duration);
+	// Allow any duration defined in terms of <chrono>.
+	// One can imagine a wonderfully general bidirectional conversion system
+	// between any type derived from LLUnits::LLUnit<T, LLUnits::Seconds> and
+	// any std::chrono::duration -- but that doesn't yet exist.
+	template <typename Rep, typename Period>
+	bool sleep(const std::chrono::duration<Rep, Period>& duration)
+	{
+		// wait_for_unequal() has the opposite bool return convention
+		return ! sStatus.wait_for_unequal(duration, APP_STATUS_RUNNING);
+	}
+
 	/** @name Error handling methods */
 	//@{
 	/**
@@ -241,8 +273,8 @@ public:
 
 	// Return the Google Breakpad minidump filename after a crash.
 	char *getMiniDumpFilename() { return mMinidumpPath; }
-    std::string* getStaticDebugFile() { return &mStaticDebugFileName; }
-    std::string* getDynamicDebugFile() { return &mDynamicDebugFileName; }
+	std::string* getStaticDebugFile() { return &mStaticDebugFileName; }
+	std::string* getDynamicDebugFile() { return &mDynamicDebugFileName; }
 
 	// Write out a Google Breakpad minidump file.
 	void writeMiniDump();
@@ -266,7 +298,7 @@ public:
 protected:
 
 	static void setStatus(EAppStatus status);		// Use this to change the application status.
-	static EAppStatus sStatus; // Reflects current application status
+	static LLScalarCond<EAppStatus> sStatus; // Reflects current application status
 	static BOOL sErrorThreadRunning; // Set while the error thread is running
 	static BOOL sDisableCrashlogger; // Let the OS handle crashes for us.
 	std::wstring mCrashReportPipeStr;  //Name of pipe to use for crash reporting.
diff --git a/indra/llcommon/llthread.h b/indra/llcommon/llthread.h
index 5cd0731f6c..50202631e7 100644
--- a/indra/llcommon/llthread.h
+++ b/indra/llcommon/llthread.h
@@ -27,7 +27,6 @@
 #ifndef LL_LLTHREAD_H
 #define LL_LLTHREAD_H
 
-#include "llapp.h"
 #include "llapr.h"
 #include "boost/intrusive_ptr.hpp"
 #include "llrefcount.h"
diff --git a/indra/llcommon/lluuid.cpp b/indra/llcommon/lluuid.cpp
index b05630c6b5..b4879c2489 100644
--- a/indra/llcommon/lluuid.cpp
+++ b/indra/llcommon/lluuid.cpp
@@ -33,6 +33,7 @@
 #include <iphlpapi.h>
 #endif
 
+#include "llapp.h"
 #include "lldefs.h"
 #include "llerror.h"