[libcamera-devel] [RFC PATCH] android: CameraWorker: Cancel pending messages in queue in stop()

[Hirokazu Honda]

Gentle ping for review.

On Mon, May 10, 2021 at 3:03 PM Hirokazu Honda <hiroh at chromium.org> wrote:

> Gentle ping for review.
>
> On Fri, Apr 23, 2021 at 1:04 PM Hirokazu Honda <hiroh at chromium.org> wrote:
>
>> CameraWorker::stop() executes Thread::exit() and Thread::wait().
>> However, intuitively, the two functions doesn't clean up pending
>> messages in the message queue of the thread. They are rather
>> cleaned in the destruction of CameraWorker, but CameraWorker's
>> life time is the same as CameraDevice and thus CameraManager,
>> which is never destroyed. On the other hand,
>> Camera3RequestDescriptors are destroyed in CameraDevice::stop().
>>
>> This causes CameraWorker::Worker::queueRequest() starts to be
>> executed after CameraWorker::start(), which is after
>> CameraDevice::stop(). This obviously causes a segmentation fault,
>> because CameraWorker::Worker::queueRequest() touches
>> CaptureRequest which is owned by Camera3RequestDescriptor.
>>
>> This fixes the issue by cancel pending message in thread queue in
>> CameraWorker::stop() with Thread::dispatchMessages().
>>
>> Signed-off-by: Hirokazu Honda <hiroh at chromium.org>
>> ---
>>  src/android/camera_worker.cpp | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/src/android/camera_worker.cpp b/src/android/camera_worker.cpp
>> index 300ddde0..b68ce9d5 100644
>> --- a/src/android/camera_worker.cpp
>> +++ b/src/android/camera_worker.cpp
>> @@ -62,6 +62,7 @@ void CameraWorker::start()
>>
>>  void CameraWorker::stop()
>>  {
>> +       thread_.dispatchMessages(Message::Type::InvokeMessage);
>>         thread_.exit();
>>         thread_.wait();
>>  }
>> --
>> 2.31.1.498.g6c1eba8ee3d-goog
>>
>>
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