[libcamera-devel] [PATCH v2 09/11] android: camera_device: Fix variables access without protection

[Laurent Pinchart]

Hi Hiro,

Thank you for the patch.

On Mon, Nov 29, 2021 at 08:44:51PM +0900, Hirokazu Honda wrote:
> This fixes the code accessing descriptors and
> Camera3RequestDescriptor::pendingStreamsToProcess_ without holding
> descriptorsMutex_ and Camera3RequestDescriptor::streamProcessMutex_
> in CameraDevice.
> 
> Signed-off-by: Hirokazu Honda <hiroh at chromium.org>
> ---
>  src/android/camera_device.cpp | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/src/android/camera_device.cpp b/src/android/camera_device.cpp
> index f2e0bdbd..59185e7f 100644
> --- a/src/android/camera_device.cpp
> +++ b/src/android/camera_device.cpp
> @@ -422,7 +422,11 @@ void CameraDevice::stop()
>  	worker_.stop();
>  	camera_->stop();
>  
> -	descriptors_ = {};
> +	{
> +		MutexLocker descriptorsLock(descriptorsMutex_);
> +		descriptors_ = {};
> +	}
> +
>  	streams_.clear();
>  
>  	state_ = State::Stopped;
> @@ -919,6 +923,8 @@ int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
>  		 */
>  		FrameBuffer *frameBuffer = nullptr;
>  		int acquireFence = -1;
> +
> +		MutexLocker lock(descriptor->streamsProcessMutex_);

I'd add a blank line here.

It's annoying to take a lock here, when we know that there can be no
concurrent access. Is there any way to tell the thread analyzer that we
know what we're doing ? If not, I really hope std::mutex is backed by
futexes, and very cheap to lock and unlock when there's no contention.

>  		switch (cameraStream->type()) {
>  		case CameraStream::Type::Mapped:
>  			/*

-- 
Regards,

Laurent Pinchart