mDirtyRegion is single threaded, but could be accessed from a hwc thread

We now have mInvalidateRegion which holds the region to invalidate, it
can be set from any thread as long as mInvalidateLock is held. We use
fine-grained locking here because mInvalidateRegion can be set from anywhere,
in particular frmo HWC callbacks.

Bug: 5466774
Change-Id: Iafca20aa3f5b25a87755e65bde7b769aa8f997bc

services/surfaceflinger/SurfaceFlinger.cpp

@@ -788,6 +788,8 @@ void SurfaceFlinger::handlePageFlip()
         }
 
     unlockPageFlip(currentLayers);
+
+    mDirtyRegion.orSelf(getAndClearInvalidateRegion());
     mDirtyRegion.andSelf(screenRegion);
 }
 
@@ -1798,12 +1800,24 @@ status_t SurfaceFlinger::onTransact(
 }
 
 void SurfaceFlinger::repaintEverything() {
-    Mutex::Autolock _l(mStateLock);
     const DisplayHardware& hw(graphicPlane(0).displayHardware());
-    mDirtyRegion.set(hw.bounds());
+    const Rect bounds(hw.getBounds());
+    setInvalidateRegion(Region(bounds));
     signalEvent();
 }
 
+void SurfaceFlinger::setInvalidateRegion(const Region& reg) {
+    Mutex::Autolock _l(mInvalidateLock);
+    mInvalidateRegion = reg;
+}
+
+Region SurfaceFlinger::getAndClearInvalidateRegion() {
+    Mutex::Autolock _l(mInvalidateLock);
+    Region reg(mInvalidateRegion);
+    mInvalidateRegion.clear();
+    return reg;
+}
+
 // ---------------------------------------------------------------------------
 
 status_t SurfaceFlinger::renderScreenToTexture(DisplayID dpy,

services/surfaceflinger/SurfaceFlinger.h

@@ -308,6 +308,9 @@ private:
             void        composeSurfaces(const Region& dirty);
 
 
+            void        setInvalidateRegion(const Region& reg);
+            Region      getAndClearInvalidateRegion();
+
             ssize_t     addClientLayer(const sp<Client>& client,
                     const sp<LayerBaseClient>& lbc);
             status_t    addLayer_l(const sp<LayerBase>& layer);
@@ -367,6 +370,10 @@ private:
                 bool                        mLayersRemoved;
                 DefaultKeyedVector< wp<IBinder>, wp<Layer> > mLayerMap;
 
+                // access must be protected by mInvalidateLock
+    mutable     Mutex                       mInvalidateLock;
+                Region                      mInvalidateRegion;
+
                 // constant members (no synchronization needed for access)
                 sp<IMemoryHeap>             mServerHeap;
                 surface_flinger_cblk_t*     mServerCblk;