SurfaceTexture: fix an error check in dequeueBuffer.

This change fixes the MIN_UNDEQUEUED_BUFFERS error check in
dequeueBuffer.  The check should only be performed if a buffer has been
queued since the last time the buffer count was changed by the client.
The check must be applied conditionally because video decoders require
all the bufferes to be dequeued and registered before beginning the
decode.

Change-Id: I08d96b380544e395c2fcf0f3983a199bfd695b09

2 files changed, 21 insertions, 10 deletions

diff --git a/libs/gui/SurfaceTexture.cpp b/libs/gui/SurfaceTexture.cpp
index bcf7a63..ee97dcf 100644
--- a/libs/gui/SurfaceTexture.cpp
+++ b/libs/gui/SurfaceTexture.cpp
@@ -285,15 +285,19 @@ status_t SurfaceTexture::dequeueBuffer(int *outBuf, uint32_t w, uint32_t h,
             return -EINVAL;
         }
 
-        // make sure the client is not trying to dequeue more buffers
-        // than allowed.
-        const int avail = mBufferCount - (dequeuedCount+1);
-        if (avail < (MIN_UNDEQUEUED_BUFFERS-int(mSynchronousMode))) {
-            LOGE("dequeueBuffer: MIN_UNDEQUEUED_BUFFERS=%d exceeded (dequeued=%d)",
-                    MIN_UNDEQUEUED_BUFFERS-int(mSynchronousMode),
-                    dequeuedCount);
-            // TODO: Enable this error report after we fix issue 4435022
-            // return -EBUSY;
+        // See whether a buffer has been queued since the last setBufferCount so
+        // we know whether to perform the MIN_UNDEQUEUED_BUFFERS check below.
+        bool bufferHasBeenQueued = mCurrentTexture != INVALID_BUFFER_SLOT;
+        if (bufferHasBeenQueued) {
+            // make sure the client is not trying to dequeue more buffers
+            // than allowed.
+            const int avail = mBufferCount - (dequeuedCount+1);
+            if (avail < (MIN_UNDEQUEUED_BUFFERS-int(mSynchronousMode))) {
+                LOGE("dequeueBuffer: MIN_UNDEQUEUED_BUFFERS=%d exceeded (dequeued=%d)",
+                        MIN_UNDEQUEUED_BUFFERS-int(mSynchronousMode),
+                        dequeuedCount);
+                return -EBUSY;
+            }
         }
 
         // we're in synchronous mode and didn't find a buffer, we need to wait
diff --git a/libs/gui/tests/SurfaceTextureClient_test.cpp b/libs/gui/tests/SurfaceTextureClient_test.cpp
index 8340337..8000bde 100644
--- a/libs/gui/tests/SurfaceTextureClient_test.cpp
+++ b/libs/gui/tests/SurfaceTextureClient_test.cpp
@@ -431,10 +431,13 @@ TEST_F(SurfaceTextureClientTest, SurfaceTextureSyncModeMinUndequeued) {
     android_native_buffer_t* buf[3];
     ASSERT_EQ(OK, st->setSynchronousMode(true));
     ASSERT_EQ(OK, native_window_set_buffer_count(anw.get(), 3));
+
+    // We should be able to dequeue all the buffers before we've queued any.
     EXPECT_EQ(OK, anw->dequeueBuffer(anw.get(), &buf[0]));
     EXPECT_EQ(OK, anw->dequeueBuffer(anw.get(), &buf[1]));
-    EXPECT_EQ(-EBUSY, anw->dequeueBuffer(anw.get(), &buf[2]));
+    EXPECT_EQ(OK, anw->dequeueBuffer(anw.get(), &buf[2]));
 
+    ASSERT_EQ(OK, anw->cancelBuffer(anw.get(), buf[2]));
     ASSERT_EQ(OK, anw->queueBuffer(anw.get(), buf[1]));
 
     EXPECT_EQ(OK, st->updateTexImage());
@@ -442,6 +445,10 @@ TEST_F(SurfaceTextureClientTest, SurfaceTextureSyncModeMinUndequeued) {
 
     EXPECT_EQ(OK, anw->dequeueBuffer(anw.get(), &buf[2]));
 
+    // Once we've queued a buffer, however we should not be able to dequeue more
+    // than (buffer-count - MIN_UNDEQUEUED_BUFFERS), which is 2 in this case.
+    EXPECT_EQ(-EBUSY, anw->dequeueBuffer(anw.get(), &buf[1]));
+
     ASSERT_EQ(OK, anw->cancelBuffer(anw.get(), buf[0]));
     ASSERT_EQ(OK, anw->cancelBuffer(anw.get(), buf[2]));
 }