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Commit a2e0cc09 authored by Michael Bestas's avatar Michael Bestas
Browse files

FlingTracker can divide by zero and hang StatusBar in an infinite loop 



if 2 events have the same timestamp then FlingTracker in PanelView will divide
by zero causing NaNs. the bug is usually triggered by rapid StatusBar up/down
dragging activity and updateCarrierLabelVisibility can then loop indefinitely
looking at NaNs. the user visible symptom is that StatusBar refuses to pull
down and is burning cpu time.

Signed-off-by: default avatarMichael Bestas <mikeioannina@gmail.com>

Change-Id: I0791c6bea953bf03346185fc6aaf44aaea79aace
parent da062dc6

packages/SystemUI/src/com/android/systemui/statusbar/phone/PanelView.java

+10 −2
Original line number Diff line number Diff line
@@ -114,6 +114,7 @@ public class PanelView extends FrameLayout { 
            mVX = mVY = 0;

            MotionEventCopy last = null;

            int i = 0;

            int j = 0;

            float totalweight = 0f;

            float weight = 10f;

            for (final Iterator<MotionEventCopy> iter = mEventBuf.descendingIterator();
@@ -121,6 +122,10 @@ public class PanelView extends FrameLayout { 
                final MotionEventCopy event = iter.next();

                if (last != null) {

                    final float dt = (float) (event.t - last.t) / timebase;

                    if (dt == 0) {

                        last = event;

                        continue;

                    }

                    final float dx = (event.x - last.x);

                    final float dy = (event.y - last.y);

                    if (FlingTracker.DEBUG) {
@@ -135,12 +140,15 @@ public class PanelView extends FrameLayout { 
                    mVY += weight * dy / dt;

                    totalweight += weight;

                    weight *= DECAY;

                    j++;

                }

                last = event;

                i++;

            }

            if (j != 0) {

                mVX /= totalweight;

                mVY /= totalweight;

            }



            if (FlingTracker.DEBUG) {

                Slog.v("FlingTracker", "computed: vx=" + mVX + " vy=" + mVY);