SurfaceFlinger: Fix PTS on stale buffers

SurfaceFlinger's (Layer's) shadow copy of the BufferQueue queue was
getting out of sync for a few reasons. This change fixes these by
doing the following:

- Adds a check to re-synchronize the shadow copy every time we
  successfully acquire a buffer by first dropping stale buffers before
  removing the current buffer.
- Avoids trying to perform updates for buffers which have been rejected
  (for incorrect dimensions) by SurfaceFlinger.
- Adds IGraphicBufferConsumer::setShadowQueueSize, which allows the
  consumer to notify the BufferQueue that it is maintaining a shadow
  copy of the queue and prevents it from dropping so many buffers
  during acquireBuffer that it ends up returning a buffer for which the
  consumer has not yet received an onFrameAvailable call.

Bug: 20096136
Change-Id: I78d0738428005fc19b3be85cc8f1db498043612f

3 files changed, 15 insertions, 0 deletions

diff --git a/include/gui/BufferQueueConsumer.h b/include/gui/BufferQueueConsumer.h
index 9c91fc7..0f42613 100644
--- a/include/gui/BufferQueueConsumer.h
+++ b/include/gui/BufferQueueConsumer.h
@@ -148,6 +148,9 @@ public:
     // Retrieve the sideband buffer stream, if any.
     virtual sp<NativeHandle> getSidebandStream() const;
 
+    // See IGraphicBufferConsumer::setShadowQueueSize
+    virtual void setShadowQueueSize(size_t size);
+
     // dump our state in a String
     virtual void dump(String8& result, const char* prefix) const;
 
diff --git a/include/gui/BufferQueueCore.h b/include/gui/BufferQueueCore.h
index e3624b7..a22015c 100644
--- a/include/gui/BufferQueueCore.h
+++ b/include/gui/BufferQueueCore.h
@@ -274,6 +274,13 @@ private:
     // mBufferAge tracks the age of the contents of the most recently dequeued
     // buffer as the number of frames that have elapsed since it was last queued
     uint64_t mBufferAge;
+
+    // mConsumerHasShadowQueue determines if acquireBuffer should be more
+    // cautious about dropping buffers so that it always returns a buffer that
+    // is represented in the consumer's shadow queue.
+    bool mConsumerHasShadowQueue;
+    size_t mConsumerShadowQueueSize;
+
 }; // class BufferQueueCore
 
 } // namespace android
diff --git a/include/gui/IGraphicBufferConsumer.h b/include/gui/IGraphicBufferConsumer.h
index 8f31b55..0be09a2 100644
--- a/include/gui/IGraphicBufferConsumer.h
+++ b/include/gui/IGraphicBufferConsumer.h
@@ -248,6 +248,11 @@ public:
     // Retrieve the sideband buffer stream, if any.
     virtual sp<NativeHandle> getSidebandStream() const = 0;
 
+    // setShadowQueueSize notifies the BufferQueue that the consumer is
+    // shadowing its queue and allows it to limit the number of buffers it is
+    // permitted to drop during acquire so as to not get out of sync.
+    virtual void setShadowQueueSize(size_t size) = 0;
+
     // dump state into a string
     virtual void dump(String8& result, const char* prefix) const = 0;