SL-16202: Streamline WorkQueues in LLImageGLThread.

Use the new WorkQueue::postIfOpen() method in LLImageGLThread::post(). That
makes the LLImageGLThread method a trivial wrapper, which can accept templated
work items and pass them through to the WorkQueue method, eliminating double
indirection due to multiple layers of std::function.

Eliminate LLImageGLThread's WorkQueue intended for work on the main queue.
Since the main loop already has a WorkQueue of its own, post work directly to
that WorkQueue instead of using a separate WorkQueue misleadingly embedded in
LLImageGLThread.

Instead of looking up the main thread's WorkQueue every time, capture a
pointer in LLImageGL's constructor.

We no longer need a fallback queue for when the main thread's WorkQueue is
full. We no longer need the main loop to poll LLImageGL to service the local
main-thread-targeted WorkQueue, or to copy work from the fallback queue to the
main queue. That eliminates LLImageGLThread::postCallback(), mCallbackQueue,
mPendingCallbackQ, executeCallbacks() -- and even LLImageGL::updateClass() and
LLAppViewer's call to it.

Change LLViewerFetchedTexture::scheduleCreateTexture() to post work to the
main thread's WorkQueue instead of calling LLImageGLThread::postCallback().

2 files changed, 12 insertions, 75 deletions

diff --git a/indra/llrender/llimagegl.cpp b/indra/llrender/llimagegl.cpp
index cbc5392882..71c48801ac 100644
--- a/indra/llrender/llimagegl.cpp
+++ b/indra/llrender/llimagegl.cpp
@@ -183,13 +183,6 @@ void LLImageGL::initClass(LLWindow* window, S32 num_catagories, BOOL skip_analyz
     LLImageGLThread::sInstance->start();
 }
 
-//static
-void LLImageGL::updateClass()
-{
-    LL_PROFILE_ZONE_SCOPED;
-    LLImageGLThread::sInstance->executeCallbacks();
-}
-
 //static 
 void LLImageGL::cleanupClass() 
 {
@@ -504,6 +497,9 @@ void LLImageGL::init(BOOL usemipmaps)
 #endif
 
 	mCategory = -1;
+
+	// Sometimes we have to post work for the main thread.
+	mMainQueue = LL::WorkQueue::getInstance("mainloop");
 }
 
 void LLImageGL::cleanup()
@@ -1554,7 +1550,9 @@ BOOL LLImageGL::createGLTexture(S32 discard_level, const U8* data_in, BOOL data_
         }
 
         ref();
-        LLImageGLThread::sInstance->postCallback([=]()
+        LL::WorkQueue::postMaybe(
+            mMainQueue,
+            [=]()
             {
                 LL_PROFILE_ZONE_NAMED("cglt - delete callback");
                 if (old_texname != 0)
@@ -2266,61 +2264,6 @@ LLImageGLThread::LLImageGLThread(LLWindow* window)
     mContext = mWindow->createSharedContext();
 }
 
-// post a function to be executed on the LLImageGL background thread
-
-bool LLImageGLThread::post(const std::function<void()>& func)
-{
-    try
-    {
-        mFunctionQueue.post(func);
-    }
-    catch (LLThreadSafeQueueInterrupt e)
-    {
-        return false;
-    }
-
-    return true;
-}
-
-//post a callback to be executed on the main thread
-
-bool LLImageGLThread::postCallback(const std::function<void()>& callback)
-{
-    try
-    {
-        if (!mCallbackQueue.tryPost(callback))
-        {
-            mPendingCallbackQ.push(callback);
-        }
-    }
-    catch (LLThreadSafeQueueInterrupt e)
-    {
-        //thread is closing, drop request
-        return false;
-    }
-
-    return true;
-}
-
-void LLImageGLThread::executeCallbacks()
-{
-    LL_PROFILE_ZONE_SCOPED;
-    //executed from main thread
-    mCallbackQueue.runPending();
-
-    while (!mPendingCallbackQ.empty())
-    {
-        if (mCallbackQueue.tryPost(mPendingCallbackQ.front()))
-        {
-            mPendingCallbackQ.pop();
-        }
-        else
-        {
-            break;
-        }
-    }
-}
-
 void LLImageGLThread::run()
 {
     mWindow->makeContextCurrent(mContext);
diff --git a/indra/llrender/llimagegl.h b/indra/llrender/llimagegl.h
index 8264e4a5f2..b9de481aae 100644
--- a/indra/llrender/llimagegl.h
+++ b/indra/llrender/llimagegl.h
@@ -198,6 +198,7 @@ private:
 	void freePickMask();
 
 	LLPointer<LLImageRaw> mSaveData; // used for destroyGL/restoreGL
+	LL::WorkQueue::weak_t mMainQueue;
 	U8* mPickMask;  //downsampled bitmap approximation of alpha channel.  NULL if no alpha channel
 	U16 mPickMaskWidth;
 	U16 mPickMaskHeight;
@@ -271,7 +272,6 @@ public:
 
 public:
 	static void initClass(LLWindow* window, S32 num_catagories, BOOL skip_analyze_alpha = false); 
-    static void updateClass();
 	static void cleanupClass() ;
 
 private:
@@ -313,27 +313,21 @@ public:
     LLImageGLThread(LLWindow* window);
 
     // post a function to be executed on the LLImageGL background thread
-    bool post(const std::function<void()>& func);
-
-    //post a callback to be executed on the main thread
-    bool postCallback(const std::function<void()>& callback);
-
-    void executeCallbacks();
+    template <typename CALLABLE>
+    bool post(CALLABLE&& func)
+    {
+        return mFunctionQueue.postIfOpen(std::forward<CALLABLE>(func));
+    }
 
     void run() override;
 
     // Work Queue for background thread
     LL::WorkQueue mFunctionQueue;
 
-    // Work Queue for main thread (run from updateClass)
-    LL::WorkQueue mCallbackQueue;
-
     LLWindow* mWindow;
     void* mContext;
     LLAtomicBool mFinished;
 
-    std::queue<std::function<void()>> mPendingCallbackQ;
-
     static LLImageGLThread* sInstance;
 };