1 files changed, 16 insertions, 26 deletions

diff --git a/libs/gui/BufferQueueConsumer.cpp b/libs/gui/BufferQueueConsumer.cpp
index 336ddb667d..4174676c76 100644
--- a/libs/gui/BufferQueueConsumer.cpp
+++ b/libs/gui/BufferQueueConsumer.cpp
@@ -36,7 +36,7 @@ BufferQueueConsumer::BufferQueueConsumer(const sp<BufferQueueCore>& core) :
 BufferQueueConsumer::~BufferQueueConsumer() {}
 
 status_t BufferQueueConsumer::acquireBuffer(BufferItem* outBuffer,
-        nsecs_t expectedPresent) {
+        nsecs_t expectedPresent, uint64_t maxFrameNumber) {
     ATRACE_CALL();
     Mutex::Autolock lock(mCore->mMutex);
 
@@ -89,17 +89,12 @@ status_t BufferQueueConsumer::acquireBuffer(BufferItem* outBuffer,
         // the timestamps are being auto-generated by Surface. If the app isn't
         // generating timestamps explicitly, it probably doesn't want frames to
         // be discarded based on them.
-        //
-        // If the consumer is shadowing our queue, we also make sure that we
-        // don't drop so many buffers that the consumer hasn't received the
-        // onFrameAvailable callback for the buffer it acquires. That is, we
-        // want the buffer we return to be in the consumer's shadow queue.
-        size_t droppableBuffers = mCore->mConsumerShadowQueueSize > 1 ?
-                mCore->mConsumerShadowQueueSize - 1 : 0;
         while (mCore->mQueue.size() > 1 && !mCore->mQueue[0].mIsAutoTimestamp) {
-            if (mCore->mConsumerHasShadowQueue && droppableBuffers == 0) {
-                BQ_LOGV("acquireBuffer: no droppable buffers in consumer's"
-                        " shadow queue, continuing");
+            const BufferItem& bufferItem(mCore->mQueue[1]);
+
+            // If dropping entry[0] would leave us with a buffer that the
+            // consumer is not yet ready for, don't drop it.
+            if (maxFrameNumber && bufferItem.mFrameNumber > maxFrameNumber) {
                 break;
             }
 
@@ -112,7 +107,6 @@ status_t BufferQueueConsumer::acquireBuffer(BufferItem* outBuffer,
             //
             // We may want to add an additional criterion: don't drop the
             // earlier buffer if entry[1]'s fence hasn't signaled yet.
-            const BufferItem& bufferItem(mCore->mQueue[1]);
             nsecs_t desiredPresent = bufferItem.mTimestamp;
             if (desiredPresent < expectedPresent - MAX_REASONABLE_NSEC ||
                     desiredPresent > expectedPresent) {
@@ -137,18 +131,22 @@ status_t BufferQueueConsumer::acquireBuffer(BufferItem* outBuffer,
             }
             mCore->mQueue.erase(front);
             front = mCore->mQueue.begin();
-            --droppableBuffers;
         }
 
-        // See if the front buffer is due
+        // See if the front buffer is ready to be acquired
         nsecs_t desiredPresent = front->mTimestamp;
-        if (desiredPresent > expectedPresent &&
-                desiredPresent < expectedPresent + MAX_REASONABLE_NSEC) {
+        bool bufferIsDue = desiredPresent <= expectedPresent ||
+                desiredPresent > expectedPresent + MAX_REASONABLE_NSEC;
+        bool consumerIsReady = maxFrameNumber > 0 ?
+                front->mFrameNumber <= maxFrameNumber : true;
+        if (!bufferIsDue || !consumerIsReady) {
             BQ_LOGV("acquireBuffer: defer desire=%" PRId64 " expect=%" PRId64
-                    " (%" PRId64 ") now=%" PRId64,
+                    " (%" PRId64 ") now=%" PRId64 " frame=%" PRIu64
+                    " consumer=%" PRIu64,
                     desiredPresent, expectedPresent,
                     desiredPresent - expectedPresent,
-                    systemTime(CLOCK_MONOTONIC));
+                    systemTime(CLOCK_MONOTONIC),
+                    front->mFrameNumber, maxFrameNumber);
             return PRESENT_LATER;
         }
 
@@ -553,14 +551,6 @@ sp<NativeHandle> BufferQueueConsumer::getSidebandStream() const {
     return mCore->mSidebandStream;
 }
 
-void BufferQueueConsumer::setShadowQueueSize(size_t size) {
-    ATRACE_CALL();
-    BQ_LOGV("setShadowQueueSize: %zu", size);
-    Mutex::Autolock lock(mCore->mMutex);
-    mCore->mConsumerHasShadowQueue = true;
-    mCore->mConsumerShadowQueueSize = size;
-}
-
 void BufferQueueConsumer::dump(String8& result, const char* prefix) const {
     mCore->dump(result, prefix);
 }