Fix possible races in vsync infrastructure.

Applications sometimes crashed on exit due to the display event
receiver pipe apparently being closed while still a member of the
Looper's epoll fd set.

This patch fixes a few different possible races related to
the display event receiver lifecycle.

1. The receiver used to play a little dance with the Looper,
registering and unregistering its callback after each vsync
request.  This code was a holdover from a time before the
surface flinger supported one-shot vsync requests, so we can
get rid of it and make things a lot simpler.

2. When the Choreographer is being accessed from outside the UI
thread, it needs to take great care that it does not touch
the display event receiver.  Bad things could happen if the receiver
is handling a vsync event on the Looper and the receiver is
disposed concurrently.

3. It was possible for the Choreographer to attempt to dispose
the receiver while handling a vsync message.  Now we defer disposing
the receiver for a little while, which is also nice because we
may be able to avoid disposing the receiver altogether if we find
that we need it again a little while later.

Bug: 5974105
Change-Id: I77a158f51b0b689af34d07aee4245b969e6260d6

0 files changed, 0 insertions, 0 deletions