Fix bug in GrCachedLayer reuse

src/gpu/GrLayerCache.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrAtlas.h"
 #include "GrGpu.h"
 #include "GrLayerCache.h"
 
 DECLARE_SKMESSAGEBUS_MESSAGE(GrPictureDeletedMessage);
 
 #ifdef SK_DEBUG
 void GrCachedLayer::validate(const GrTexture* backingTexture) const {
     SkASSERT(SK_InvalidGenID != fKey.pictureID());
     SkASSERT(fKey.start() >= 0);
 
-
     if (fTexture) {
         // If the layer is in some texture then it must occupy some rectangle
         SkASSERT(!fRect.isEmpty());
         if (!this->isAtlased()) {
             // If it isn't atlased then the rectangle should start at the origin
             SkASSERT(0.0f == fRect.fLeft && 0.0f == fRect.fTop);
         }
     } else {
         SkASSERT(fRect.isEmpty());
         SkASSERT(NULL == fPlot);
         SkASSERT(!fLocked);     // layers without a texture cannot be locked
     }
 
     if (fPlot) {
         // If a layer has a plot (i.e., is atlased) then it must point to
         // the backing texture. Additionally, its rect should be non-empty.
         SkASSERT(fTexture && backingTexture == fTexture);
         SkASSERT(!fRect.isEmpty());
     }
 
     if (fLocked) {
         // If a layer is locked it must have a texture (though it need not be
         // the atlas-backing texture) and occupy some space.
         SkASSERT(fTexture);
         SkASSERT(!fRect.isEmpty());
     }
+
+    // Unfortunately there is a brief time where a layer can be locked
+    // but not used.

[jvanverth1, 2014/10/10 18:21:44]

This comment is a little confusing. Maybe "There is a brief time where a layer
can be locked, but not used, so we can only verify that fUses >= 0"? Not sure
that's better.

[robertphillips, 2014/10/10 18:37:43]

Done.

+    if (fUses > 0) {
+        SkASSERT(fLocked);
+    } else {
+        SkASSERT(0 == fUses);
+    }
 }
 
 class GrAutoValidateLayer : ::SkNoncopyable {
 public:
     GrAutoValidateLayer(GrTexture* backingTexture, const GrCachedLayer* layer) 
         : fBackingTexture(backingTexture)
         , fLayer(layer) {
         if (fLayer) {
             fLayer->validate(backingTexture);
         }
@@ skipping 18 matching lines @@
     : fContext(context) {
     this->initAtlas();
     memset(fPlotLocks, 0, sizeof(fPlotLocks));
 }
 
 GrLayerCache::~GrLayerCache() {
 
     SkTDynamicHash<GrCachedLayer, GrCachedLayer::Key>::Iter iter(&fLayerHash);
     for (; !iter.done(); ++iter) {
         GrCachedLayer* layer = &(*iter);
+        SkASSERT(0 == layer->uses());
         this->unlock(layer);
         SkDELETE(layer);
     }
 
     // The atlas only lets go of its texture when the atlas is deleted. 
     fAtlas.free();    
 }
 
 void GrLayerCache::initAtlas() {
     SkASSERT(NULL == fAtlas.get());
@@ skipping 67 matching lines @@
             SkASSERT(layer->rect().height() == desc.fHeight);
         }
 #endif
         return false;
     }
 
     if (layer->isAtlased()) {
         // Hooray it is still in the atlas - make sure it stays there
         SkASSERT(!dontAtlas);
         layer->setLocked(true);
-        fPlotLocks[layer->plot()->id()]++;
+        this->incPlotLock(layer->plot()->id());
         return false;
     } else if (!dontAtlas && PlausiblyAtlasable(desc.fWidth, desc.fHeight)) {
         // Not in the atlas - will it fit?
         GrPictureInfo* pictInfo = fPictureHash.find(layer->pictureID());
         if (NULL == pictInfo) {
             pictInfo = SkNEW_ARGS(GrPictureInfo, (layer->pictureID()));
             fPictureHash.add(pictInfo);
         }
 
         SkIPoint16 loc;
         for (int i = 0; i < 2; ++i) { // extra pass in case we fail to add but are able to purge
             GrPlot* plot = fAtlas->addToAtlas(&pictInfo->fPlotUsage,
                                               desc.fWidth, desc.fHeight,
                                               NULL, &loc);
             // addToAtlas can allocate the backing texture
             SkDEBUGCODE(avl.setBackingTexture(fAtlas->getTexture()));
             if (plot) {
                 // The layer was successfully added to the atlas
                 GrIRect16 bounds = GrIRect16::MakeXYWH(loc.fX, loc.fY,
                                                        SkToS16(desc.fWidth),
                                                        SkToS16(desc.fHeight));
                 layer->setTexture(fAtlas->getTexture(), bounds);
                 layer->setPlot(plot);
                 layer->setLocked(true);
-                fPlotLocks[layer->plot()->id()]++;
+                this->incPlotLock(layer->plot()->id());
                 return true;
             }
 
             // The layer was rejected by the atlas (even though we know it is 
             // plausibly atlas-able). See if a plot can be purged and try again.
             if (!this->purgePlot()) {
                 break;  // We weren't able to purge any plots
             }
         }
     }
@@ skipping 13 matching lines @@
     SkDEBUGCODE(GrAutoValidateLayer avl(fAtlas->getTexture(), layer);)
 
     if (NULL == layer || !layer->locked()) {
         // invalid or not locked
         return;
     }
 
     if (layer->isAtlased()) {
         const int plotID = layer->plot()->id();
 
-        SkASSERT(fPlotLocks[plotID] > 0);
-        fPlotLocks[plotID]--;
+        this->decPlotLock(plotID);
         // At this point we could aggressively clear out un-locked plots but
         // by delaying we may be able to reuse some of the atlased layers later.
 #if DISABLE_CACHING
         // This testing code aggressively removes the atlased layers. This
         // can be used to separate the performance contribution of less
         // render target pingponging from that due to the re-use of cached layers
         GrPictureInfo* pictInfo = fPictureHash.find(layer->pictureID());
         SkASSERT(pictInfo);
         
         GrAtlas::RemovePlot(&pictInfo->fPlotUsage, layer->plot());
@@ skipping 21 matching lines @@
         layer->validate(fAtlas->getTexture());
 
         const GrPictureInfo* pictInfo = fPictureHash.find(layer->pictureID());
         if (pictInfo) {
             // In aggressive cleanup mode a picture info should only exist if
             // it has some atlased layers
 #if !DISABLE_CACHING
             SkASSERT(!pictInfo->fPlotUsage.isEmpty());
 #endif
         } else {
-            // If there is no picture info for this layer then all of its
+            // If there is no picture info for this picture then all of its
             // layers should be non-atlased.
             SkASSERT(!layer->isAtlased());
         }
 
         if (layer->plot()) {
             SkASSERT(pictInfo);
             SkASSERT(pictInfo->fPictureID == layer->pictureID());
 
             SkASSERT(pictInfo->fPlotUsage.contains(layer->plot()));
 
@@ skipping 30 matching lines @@
     SkTDArray<GrCachedLayer*> toBeRemoved;
 
     SkTDynamicHash<GrCachedLayer, GrCachedLayer::Key>::Iter iter(&fLayerHash);
     for (; !iter.done(); ++iter) {
         if (pictureID == (*iter).pictureID()) {
             *toBeRemoved.append() = &(*iter);
         }
     }
 
     for (int i = 0; i < toBeRemoved.count(); ++i) {
+        SkASSERT(0 == toBeRemoved[i]->uses());
         this->unlock(toBeRemoved[i]);
         fLayerHash.remove(GrCachedLayer::GetKey(*toBeRemoved[i]));
         SkDELETE(toBeRemoved[i]);
     }
 
     GrPictureInfo* pictInfo = fPictureHash.find(pictureID);
     if (pictInfo) {
         fPictureHash.remove(pictureID);
         SkDELETE(pictInfo);
     }
@@ skipping 25 matching lines @@
     SkTDArray<GrCachedLayer*> toBeRemoved;
 
     SkTDynamicHash<GrCachedLayer, GrCachedLayer::Key>::Iter iter(&fLayerHash);
     for (; !iter.done(); ++iter) {
         if (plot == (*iter).plot()) {
             *toBeRemoved.append() = &(*iter);
         }
     }
 
     for (int i = 0; i < toBeRemoved.count(); ++i) {
+        SkASSERT(0 == toBeRemoved[i]->uses());
         SkASSERT(!toBeRemoved[i]->locked());
 
         uint32_t pictureIDToRemove = toBeRemoved[i]->pictureID();
 
         // Aggressively remove layers and, if it becomes totally uncached, delete the picture info
         fLayerHash.remove(GrCachedLayer::GetKey(*toBeRemoved[i]));
         SkDELETE(toBeRemoved[i]);
 
         GrPictureInfo* pictInfo = fPictureHash.find(pictureIDToRemove);
         if (pictInfo) {
@@ skipping 38 matching lines @@
 
 void GrLayerCache::processDeletedPictures() {
     SkTDArray<GrPictureDeletedMessage> deletedPictures;
     fPictDeletionInbox.poll(&deletedPictures);
 
     for (int i = 0; i < deletedPictures.count(); i++) {
         this->purge(deletedPictures[i].pictureID);
     }
 }