Some camera HALs spin up a preview thread and need to wait for
the thread to exit. This can create a potential deadlock. In
stopPreview, we take the main lock. If a preview callback occurs
while the lock is held, the preview thread will block. If the
camera HAL is waiting for the preview thread to exit, this will
cause a deadlock.
This patch breaks out the preview buffer heap into a separate
mutex. This mutex is never held when the main lock is held, thus
preventing the deadlock from occuring.
We weren't checking to see if there was a valid camera client when
calling the notify callback function. Now we grab a strong pointer
before the callback to guarantee that the client is not destroyed
before we complete the callback. This change also fixes other
places in the code where we weren't holding a local strong pointer.
The reason we need this count is a new CameraService::connect() request may
come in while the previous Client's destructor has not been run or is still
running. If the last strong reference of the previous Client is gone but
destructor has not been run, we should not allow the new Client to be created
because we need to wait for the previous Client to tear down the hardware
first.
to CameraService::onTransact() method during development. Later on
the entire onTransact() method was #ifdef'd out, which inadvertently
omitted the permissions check code. This change restores the code.
