diff --git a/libs/gui/SurfaceTexture.cpp b/libs/gui/SurfaceTexture.cpp
index beb23f6..fcd287c 100644
--- a/libs/gui/SurfaceTexture.cpp
+++ b/libs/gui/SurfaceTexture.cpp
@@ -36,6 +36,12 @@
 #include <utils/Log.h>
 #include <utils/String8.h>
 
+// This compile option causes SurfaceTexture to return the buffer that is currently
+// attached to the GL texture from dequeueBuffer when no other buffers are
+// available.  It requires the drivers (Gralloc, GL, OMX IL, and Camera) to do
+// implicit cross-process synchronization to prevent the buffer from being
+// written to before the buffer has (a) been detached from the GL texture and
+// (b) all GL reads from the buffer have completed.
 #ifdef ALLOW_DEQUEUE_CURRENT_BUFFER
 #define FLAG_ALLOW_DEQUEUE_CURRENT_BUFFER    true
 #warning "ALLOW_DEQUEUE_CURRENT_BUFFER enabled"
@@ -43,6 +49,16 @@
 #define FLAG_ALLOW_DEQUEUE_CURRENT_BUFFER    false
 #endif
 
+// This compile option makes SurfaceTexture use the EGL_KHR_fence_sync extension
+// to synchronize access to the buffers.  It will cause dequeueBuffer to stall,
+// waiting for the GL reads for the buffer being dequeued to complete before
+// allowing the buffer to be dequeued.
+#ifdef USE_FENCE_SYNC
+#ifdef ALLOW_DEQUEUE_CURRENT_BUFFER
+#error "USE_FENCE_SYNC and ALLOW_DEQUEUE_CURRENT_BUFFER are incompatible"
+#endif
+#endif
+
 // Macros for including the SurfaceTexture name in log messages
 #define ST_LOGV(x, ...) LOGV("[%s] "x, mName.string(), ##__VA_ARGS__)
 #define ST_LOGD(x, ...) LOGD("[%s] "x, mName.string(), ##__VA_ARGS__)
@@ -99,7 +115,7 @@
 }
 
 SurfaceTexture::SurfaceTexture(GLuint tex, bool allowSynchronousMode,
-        GLenum texTarget) :
+        GLenum texTarget, bool useFenceSync) :
     mDefaultWidth(1),
     mDefaultHeight(1),
     mPixelFormat(PIXEL_FORMAT_RGBA_8888),
@@ -116,6 +132,11 @@
     mAllowSynchronousMode(allowSynchronousMode),
     mConnectedApi(NO_CONNECTED_API),
     mAbandoned(false),
+#ifdef USE_FENCE_SYNC
+    mUseFenceSync(useFenceSync),
+#else
+    mUseFenceSync(false),
+#endif
     mTexTarget(texTarget),
     mFrameCounter(0) {
     // Choose a name using the PID and a process-unique ID.
@@ -261,195 +282,225 @@
         return BAD_VALUE;
     }
 
-    Mutex::Autolock lock(mMutex);
-
     status_t returnFlags(OK);
+    EGLDisplay dpy = EGL_NO_DISPLAY;
+    EGLSyncKHR fence = EGL_NO_SYNC_KHR;
 
-    int found = -1;
-    int foundSync = -1;
-    int dequeuedCount = 0;
-    bool tryAgain = true;
-    while (tryAgain) {
-        if (mAbandoned) {
-            ST_LOGE("dequeueBuffer: SurfaceTexture has been abandoned!");
-            return NO_INIT;
-        }
+    { // Scope for the lock
+        Mutex::Autolock lock(mMutex);
 
-        // We need to wait for the FIFO to drain if the number of buffer
-        // needs to change.
-        //
-        // The condition "number of buffers needs to change" is true if
-        // - the client doesn't care about how many buffers there are
-        // - AND the actual number of buffer is different from what was
-        //   set in the last setBufferCountServer()
-        //                         - OR -
-        //   setBufferCountServer() was set to a value incompatible with
-        //   the synchronization mode (for instance because the sync mode
-        //   changed since)
-        //
-        // As long as this condition is true AND the FIFO is not empty, we
-        // wait on mDequeueCondition.
-
-        const int minBufferCountNeeded = mSynchronousMode ?
-                MIN_SYNC_BUFFER_SLOTS : MIN_ASYNC_BUFFER_SLOTS;
-
-        const bool numberOfBuffersNeedsToChange = !mClientBufferCount &&
-                ((mServerBufferCount != mBufferCount) ||
-                        (mServerBufferCount < minBufferCountNeeded));
-
-        if (!mQueue.isEmpty() && numberOfBuffersNeedsToChange) {
-            // wait for the FIFO to drain
-            mDequeueCondition.wait(mMutex);
-            // NOTE: we continue here because we need to reevaluate our
-            // whole state (eg: we could be abandoned or disconnected)
-            continue;
-        }
-
-        if (numberOfBuffersNeedsToChange) {
-            // here we're guaranteed that mQueue is empty
-            freeAllBuffersLocked();
-            mBufferCount = mServerBufferCount;
-            if (mBufferCount < minBufferCountNeeded)
-                mBufferCount = minBufferCountNeeded;
-            mCurrentTexture = INVALID_BUFFER_SLOT;
-            returnFlags |= ISurfaceTexture::RELEASE_ALL_BUFFERS;
-        }
-
-        // look for a free buffer to give to the client
-        found = INVALID_BUFFER_SLOT;
-        foundSync = INVALID_BUFFER_SLOT;
-        dequeuedCount = 0;
-        for (int i = 0; i < mBufferCount; i++) {
-            const int state = mSlots[i].mBufferState;
-            if (state == BufferSlot::DEQUEUED) {
-                dequeuedCount++;
+        int found = -1;
+        int foundSync = -1;
+        int dequeuedCount = 0;
+        bool tryAgain = true;
+        while (tryAgain) {
+            if (mAbandoned) {
+                ST_LOGE("dequeueBuffer: SurfaceTexture has been abandoned!");
+                return NO_INIT;
             }
 
-            // if buffer is FREE it CANNOT be current
-            LOGW_IF((state == BufferSlot::FREE) && (mCurrentTexture==i),
-                    "dequeueBuffer: buffer %d is both FREE and current!", i);
+            // We need to wait for the FIFO to drain if the number of buffer
+            // needs to change.
+            //
+            // The condition "number of buffers needs to change" is true if
+            // - the client doesn't care about how many buffers there are
+            // - AND the actual number of buffer is different from what was
+            //   set in the last setBufferCountServer()
+            //                         - OR -
+            //   setBufferCountServer() was set to a value incompatible with
+            //   the synchronization mode (for instance because the sync mode
+            //   changed since)
+            //
+            // As long as this condition is true AND the FIFO is not empty, we
+            // wait on mDequeueCondition.
 
-            if (FLAG_ALLOW_DEQUEUE_CURRENT_BUFFER) {
-                if (state == BufferSlot::FREE || i == mCurrentTexture) {
-                    foundSync = i;
-                    if (i != mCurrentTexture) {
-                        found = i;
-                        break;
-                    }
+            const int minBufferCountNeeded = mSynchronousMode ?
+                    MIN_SYNC_BUFFER_SLOTS : MIN_ASYNC_BUFFER_SLOTS;
+
+            const bool numberOfBuffersNeedsToChange = !mClientBufferCount &&
+                    ((mServerBufferCount != mBufferCount) ||
+                            (mServerBufferCount < minBufferCountNeeded));
+
+            if (!mQueue.isEmpty() && numberOfBuffersNeedsToChange) {
+                // wait for the FIFO to drain
+                mDequeueCondition.wait(mMutex);
+                // NOTE: we continue here because we need to reevaluate our
+                // whole state (eg: we could be abandoned or disconnected)
+                continue;
+            }
+
+            if (numberOfBuffersNeedsToChange) {
+                // here we're guaranteed that mQueue is empty
+                freeAllBuffersLocked();
+                mBufferCount = mServerBufferCount;
+                if (mBufferCount < minBufferCountNeeded)
+                    mBufferCount = minBufferCountNeeded;
+                mCurrentTexture = INVALID_BUFFER_SLOT;
+                returnFlags |= ISurfaceTexture::RELEASE_ALL_BUFFERS;
+            }
+
+            // look for a free buffer to give to the client
+            found = INVALID_BUFFER_SLOT;
+            foundSync = INVALID_BUFFER_SLOT;
+            dequeuedCount = 0;
+            for (int i = 0; i < mBufferCount; i++) {
+                const int state = mSlots[i].mBufferState;
+                if (state == BufferSlot::DEQUEUED) {
+                    dequeuedCount++;
                 }
-            } else {
-                if (state == BufferSlot::FREE) {
-                    /** For Asynchronous mode, we need to return the oldest of free buffers
-                    * There is only one instance when the Framecounter overflows, this logic
-                    * might return the earlier buffer to client. Which is a negligible impact
-                    **/
-                    if (found < 0 || mSlots[i].mFrameNumber < mSlots[found].mFrameNumber) {
+
+                // if buffer is FREE it CANNOT be current
+                LOGW_IF((state == BufferSlot::FREE) && (mCurrentTexture==i),
+                        "dequeueBuffer: buffer %d is both FREE and current!",
+                        i);
+
+                if (FLAG_ALLOW_DEQUEUE_CURRENT_BUFFER) {
+                    if (state == BufferSlot::FREE || i == mCurrentTexture) {
                         foundSync = i;
-                        found = i;
+                        if (i != mCurrentTexture) {
+                            found = i;
+                            break;
+                        }
+                    }
+                } else {
+                    if (state == BufferSlot::FREE) {
+                        /* We return the oldest of the free buffers to avoid
+                         * stalling the producer if possible.  This is because
+                         * the consumer may still have pending reads of the
+                         * buffers in flight.
+                         */
+                        bool isOlder = mSlots[i].mFrameNumber <
+                                mSlots[found].mFrameNumber;
+                        if (found < 0 || isOlder) {
+                            foundSync = i;
+                            found = i;
+                        }
                     }
                 }
             }
-        }
 
-        // clients are not allowed to dequeue more than one buffer
-        // if they didn't set a buffer count.
-        if (!mClientBufferCount && dequeuedCount) {
-            ST_LOGE("dequeueBuffer: can't dequeue multiple buffers without "
-                    "setting the buffer count");
-            return -EINVAL;
-        }
+            // clients are not allowed to dequeue more than one buffer
+            // if they didn't set a buffer count.
+            if (!mClientBufferCount && dequeuedCount) {
+                ST_LOGE("dequeueBuffer: can't dequeue multiple buffers without "
+                        "setting the buffer count");
+                return -EINVAL;
+            }
 
-        // 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))) {
-                ST_LOGE("dequeueBuffer: MIN_UNDEQUEUED_BUFFERS=%d exceeded "
-                        "(dequeued=%d)",
-                        MIN_UNDEQUEUED_BUFFERS-int(mSynchronousMode),
-                        dequeuedCount);
-                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))) {
+                    ST_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 for some buffers to be consumed
+            tryAgain = mSynchronousMode && (foundSync == INVALID_BUFFER_SLOT);
+            if (tryAgain) {
+                mDequeueCondition.wait(mMutex);
             }
         }
 
-        // we're in synchronous mode and didn't find a buffer, we need to wait
-        // for some buffers to be consumed
-        tryAgain = mSynchronousMode && (foundSync == INVALID_BUFFER_SLOT);
-        if (tryAgain) {
-            mDequeueCondition.wait(mMutex);
+        if (mSynchronousMode && found == INVALID_BUFFER_SLOT) {
+            // foundSync guaranteed to be != INVALID_BUFFER_SLOT
+            found = foundSync;
         }
-    }
 
-    if (mSynchronousMode && found == INVALID_BUFFER_SLOT) {
-        // foundSync guaranteed to be != INVALID_BUFFER_SLOT
-        found = foundSync;
-    }
-
-    if (found == INVALID_BUFFER_SLOT) {
-        // This should not happen.
-        ST_LOGE("dequeueBuffer: no available buffer slots");
-        return -EBUSY;
-    }
-
-    const int buf = found;
-    *outBuf = found;
-
-    const bool useDefaultSize = !w && !h;
-    if (useDefaultSize) {
-        // use the default size
-        w = mDefaultWidth;
-        h = mDefaultHeight;
-    }
-
-    const bool updateFormat = (format != 0);
-    if (!updateFormat) {
-        // keep the current (or default) format
-        format = mPixelFormat;
-    }
-
-    // buffer is now in DEQUEUED (but can also be current at the same time,
-    // if we're in synchronous mode)
-    mSlots[buf].mBufferState = BufferSlot::DEQUEUED;
-
-    const sp<GraphicBuffer>& buffer(mSlots[buf].mGraphicBuffer);
-    if ((buffer == NULL) ||
-        (uint32_t(buffer->width)  != w) ||
-        (uint32_t(buffer->height) != h) ||
-        (uint32_t(buffer->format) != format) ||
-        ((uint32_t(buffer->usage) & usage) != usage))
-    {
-        usage |= GraphicBuffer::USAGE_HW_TEXTURE;
-        status_t error;
-        sp<GraphicBuffer> graphicBuffer(
-                mGraphicBufferAlloc->createGraphicBuffer(
-                        w, h, format, usage, &error));
-        if (graphicBuffer == 0) {
-            ST_LOGE("dequeueBuffer: SurfaceComposer::createGraphicBuffer "
-                    "failed");
-            return error;
+        if (found == INVALID_BUFFER_SLOT) {
+            // This should not happen.
+            ST_LOGE("dequeueBuffer: no available buffer slots");
+            return -EBUSY;
         }
-        if (updateFormat) {
-            mPixelFormat = format;
+
+        const int buf = found;
+        *outBuf = found;
+
+        const bool useDefaultSize = !w && !h;
+        if (useDefaultSize) {
+            // use the default size
+            w = mDefaultWidth;
+            h = mDefaultHeight;
         }
-        mSlots[buf].mGraphicBuffer = graphicBuffer;
-        mSlots[buf].mRequestBufferCalled = false;
-        if (mSlots[buf].mEglImage != EGL_NO_IMAGE_KHR) {
-            eglDestroyImageKHR(mSlots[buf].mEglDisplay, mSlots[buf].mEglImage);
-            mSlots[buf].mEglImage = EGL_NO_IMAGE_KHR;
-            mSlots[buf].mEglDisplay = EGL_NO_DISPLAY;
+
+        const bool updateFormat = (format != 0);
+        if (!updateFormat) {
+            // keep the current (or default) format
+            format = mPixelFormat;
         }
-        if (mCurrentTexture == buf) {
-            // The current texture no longer references the buffer in this slot
-            // since we just allocated a new buffer.
-            mCurrentTexture = INVALID_BUFFER_SLOT;
+
+        // buffer is now in DEQUEUED (but can also be current at the same time,
+        // if we're in synchronous mode)
+        mSlots[buf].mBufferState = BufferSlot::DEQUEUED;
+
+        const sp<GraphicBuffer>& buffer(mSlots[buf].mGraphicBuffer);
+        if ((buffer == NULL) ||
+            (uint32_t(buffer->width)  != w) ||
+            (uint32_t(buffer->height) != h) ||
+            (uint32_t(buffer->format) != format) ||
+            ((uint32_t(buffer->usage) & usage) != usage))
+        {
+            usage |= GraphicBuffer::USAGE_HW_TEXTURE;
+            status_t error;
+            sp<GraphicBuffer> graphicBuffer(
+                    mGraphicBufferAlloc->createGraphicBuffer(
+                            w, h, format, usage, &error));
+            if (graphicBuffer == 0) {
+                ST_LOGE("dequeueBuffer: SurfaceComposer::createGraphicBuffer "
+                        "failed");
+                return error;
+            }
+            if (updateFormat) {
+                mPixelFormat = format;
+            }
+            mSlots[buf].mGraphicBuffer = graphicBuffer;
+            mSlots[buf].mRequestBufferCalled = false;
+            mSlots[buf].mFence = EGL_NO_SYNC_KHR;
+            if (mSlots[buf].mEglImage != EGL_NO_IMAGE_KHR) {
+                eglDestroyImageKHR(mSlots[buf].mEglDisplay,
+                        mSlots[buf].mEglImage);
+                mSlots[buf].mEglImage = EGL_NO_IMAGE_KHR;
+                mSlots[buf].mEglDisplay = EGL_NO_DISPLAY;
+            }
+            if (mCurrentTexture == buf) {
+                // The current texture no longer references the buffer in this slot
+                // since we just allocated a new buffer.
+                mCurrentTexture = INVALID_BUFFER_SLOT;
+            }
+            returnFlags |= ISurfaceTexture::BUFFER_NEEDS_REALLOCATION;
         }
-        returnFlags |= ISurfaceTexture::BUFFER_NEEDS_REALLOCATION;
+
+        dpy = mSlots[buf].mEglDisplay;
+        fence = mSlots[buf].mFence;
+        mSlots[buf].mFence = EGL_NO_SYNC_KHR;
     }
+
+    if (fence != EGL_NO_SYNC_KHR) {
+        EGLint result = eglClientWaitSyncKHR(dpy, fence, 0, 1000000000);
+        // If something goes wrong, log the error, but return the buffer without
+        // synchronizing access to it.  It's too late at this point to abort the
+        // dequeue operation.
+        if (result == EGL_FALSE) {
+            LOGE("dequeueBuffer: error waiting for fence: %#x", eglGetError());
+        } else if (result == EGL_TIMEOUT_EXPIRED_KHR) {
+            LOGE("dequeueBuffer: timeout waiting for fence");
+        }
+        eglDestroySyncKHR(dpy, fence);
+    }
+
     ST_LOGV("dequeueBuffer: returning slot=%d buf=%p flags=%#x", buf,
             mSlots[buf].mGraphicBuffer->handle, returnFlags);
+
     return returnFlags;
 }
 
@@ -712,8 +763,8 @@
 
         // Update the GL texture object.
         EGLImageKHR image = mSlots[buf].mEglImage;
+        EGLDisplay dpy = eglGetCurrentDisplay();
         if (image == EGL_NO_IMAGE_KHR) {
-            EGLDisplay dpy = eglGetCurrentDisplay();
             if (mSlots[buf].mGraphicBuffer == 0) {
                 ST_LOGE("buffer at slot %d is null", buf);
                 return BAD_VALUE;
@@ -746,16 +797,32 @@
             return -EINVAL;
         }
 
-        ST_LOGV("updateTexImage: (slot=%d buf=%p) -> (slot=%d buf=%p)", mCurrentTexture,
-                mCurrentTextureBuf != NULL ? mCurrentTextureBuf->handle : 0, buf,
-                mSlots[buf].mGraphicBuffer->handle);
+        if (mCurrentTexture != INVALID_BUFFER_SLOT) {
+            if (mUseFenceSync) {
+                EGLSyncKHR fence = eglCreateSyncKHR(dpy, EGL_SYNC_FENCE_KHR,
+                        NULL);
+                if (fence == EGL_NO_SYNC_KHR) {
+                    LOGE("updateTexImage: error creating fence: %#x",
+                            eglGetError());
+                    return -EINVAL;
+                }
+                glFlush();
+                mSlots[mCurrentTexture].mFence = fence;
+            }
+        }
+
+        ST_LOGV("updateTexImage: (slot=%d buf=%p) -> (slot=%d buf=%p)",
+                mCurrentTexture,
+                mCurrentTextureBuf != NULL ? mCurrentTextureBuf->handle : 0,
+                buf, mSlots[buf].mGraphicBuffer->handle);
 
         if (mCurrentTexture != INVALID_BUFFER_SLOT) {
             // The current buffer becomes FREE if it was still in the queued
             // state. If it has already been given to the client
             // (synchronous mode), then it stays in DEQUEUED state.
-            if (mSlots[mCurrentTexture].mBufferState == BufferSlot::QUEUED)
+            if (mSlots[mCurrentTexture].mBufferState == BufferSlot::QUEUED) {
                 mSlots[mCurrentTexture].mBufferState = BufferSlot::FREE;
+            }
         }
 
         // Update the SurfaceTexture state.