Prevent onImageAvailable from being called on stale listeners

ImageReader queues up calls to OnImageAvailableListener#onImageAvailable
(one for each frame) by wrapping them in Runnables and passing the
Runnables to an Executor, which in turn executes Runnables in order.
Before queuing the Runnable, ImageReader reads the value of listener
and passes a reference to the listener that is current at the time of
queueing to the Runnable. This reference is used when calling
onImageAvailable.

If the listener changes between when a Runnable is queued and when the
Runnable is executed, it is possible for the Runnable to call into a
stale listener.

This CL replaces the mutex used to guard the state of ImageReader with a
StampedLock behaving as a Read-Write Lock. The Runnables wrapping calls
to OnImageAvailableListener#onImageAvailable grab a read lock and calls
the onImageAvailable method of the listener referenced by ImageReader at
the time of Runnable's execution. Any call to modify the listener grabs
the write lock.

Bug: 204438677
Test: Existing CTS tests pass

Change-Id: I7b11243962595e8c41912a483a80ecd8d3c3e945

0 files changed, 0 insertions, 0 deletions