[libcamera-devel] [PATCH v6 7/7] android: post_processor: Make post processing async
Umang Jain
umang.jain at ideasonboard.com
Mon Oct 25 15:48:47 CEST 2021
Hi Hiro,
On 10/25/21 5:59 PM, Hirokazu Honda wrote:
> Hi Umang, thank you for the patch.
>
> On Sat, Oct 23, 2021 at 7:33 PM Umang Jain <umang.jain at ideasonboard.com> wrote:
>> Introduce a dedicated worker class derived from libcamera::Thread.
>> The worker class maintains a queue for post-processing requests
>> and waits for a post-processing request to become available.
>> It will process them as per FIFO before de-queuing it from the
>> queue.
>>
>> The post processing streams loop in CameraDevice::requestComplete()
>> is tweaked a bit to better suit asynchronous needs of post processing.
>> Also, the entire iteration is locked under streamProcessMutex_ which
>> helps us to queue all the post-processing request at once, before any
>> of the post-processing completion slot (streamProcessingComplete())
>> is allowed to run for post-processing requests completing in parallel.
>> This helps us to manage both synchronous and asynchronous errors
>> encountered during the entire post processing operation.
>>
>> This patch also implements a flush() for the PostProcessorWorker
>> class which is responsible to purge post-processing requests
>> queued up while a camera is stopping/flushing. It is hooked with
>> CameraStream::flush(), which isn't used currently but will be
>> used when we handle flush/stop scenarios in greater detail
>> subsequently (in a different patchset).
>>
>> The libcamera request completion handler CameraDevice::requestComplete()
>> assumes that the request that has just completed is at the front of the
>> queue. Now that the post-processor runs asynchronously, this isn't true
>> anymore, a request being post-processed will stay in the queue and a new
>> libcamera request may complete. Remove that assumption, and use the
>> request cookie to obtain the Camera3RequestDescriptor.
>>
>> Signed-off-by: Umang Jain <umang.jain at ideasonboard.com>
>> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
>> ---
>> src/android/camera_device.cpp | 49 +++++------------
>> src/android/camera_stream.cpp | 101 ++++++++++++++++++++++++++++++++--
>> src/android/camera_stream.h | 38 ++++++++++++-
>> 3 files changed, 148 insertions(+), 40 deletions(-)
>>
>> diff --git a/src/android/camera_device.cpp b/src/android/camera_device.cpp
>> index 3114def0..dc39467b 100644
>> --- a/src/android/camera_device.cpp
>> +++ b/src/android/camera_device.cpp
>> @@ -1026,29 +1026,8 @@ int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
>>
>> void CameraDevice::requestComplete(Request *request)
>> {
>> - Camera3RequestDescriptor *descriptor;
>> - {
>> - MutexLocker descriptorsLock(descriptorsMutex_);
>> - ASSERT(!descriptors_.empty());
>> - descriptor = descriptors_.front().get();
>> - }
>> -
>> - if (descriptor->request_->cookie() != request->cookie()) {
>> - /*
>> - * \todo Clarify if the Camera has to be closed on
>> - * ERROR_DEVICE.
>> - */
>> - LOG(HAL, Error)
>> - << "Out-of-order completion for request "
>> - << utils::hex(request->cookie());
>> -
>> - MutexLocker descriptorsLock(descriptorsMutex_);
>> - descriptors_.pop();
>> -
>> - notifyError(0, nullptr, CAMERA3_MSG_ERROR_DEVICE);
>> -
>> - return;
>> - }
>> + Camera3RequestDescriptor *descriptor =
>> + reinterpret_cast<Camera3RequestDescriptor *>(request->cookie());
>>
>> /*
>> * Prepare the capture result for the Android camera stack.
>> @@ -1124,12 +1103,16 @@ void CameraDevice::requestComplete(Request *request)
>>
>> /* Handle post-processing. */
>> bool needPostProcessing = false;
>> + MutexLocker locker(descriptor->streamsProcessMutex_);
>> +
>> /*
>> - * \todo Protect the loop below with streamProcessMutex_ when post
>> - * processor runs asynchronously.
>> + * Queue all the post-processing streams request at once. The completion
>> + * slot streamProcessingComplete() can only execute when we are out
>> + * this critical section. This helps to handle synchronous errors here
>> + * itself.
>> */
>> auto iter = descriptor->pendingStreamsToProcess_.begin();
>> - while (descriptor->pendingStreamsToProcess_.size() > 0) {
>> + while (iter != descriptor->pendingStreamsToProcess_.end()) {
>> CameraStream *stream = iter->first;
>> Camera3RequestDescriptor::StreamBuffer *buffer = iter->second;
>> needPostProcessing = true;
>> @@ -1151,18 +1134,16 @@ void CameraDevice::requestComplete(Request *request)
>> }
>>
>> if (needPostProcessing) {
>> - /*
>> - * \todo We will require to check if we failed to queue
>> - * post-processing requests when we migrate to post-processor
>> - * running asynchronously.
>> - *
>> - * if (descriptor->pendingStreamsToProcess_.size() == 0)
>> - * completeDescriptor(descriptor);
>> - */
>> + if (descriptor->pendingStreamsToProcess_.size() == 0) {
>> + locker.unlock();
>> + completeDescriptor(descriptor);
>> + }
> As Laurent suggested in other patch, I think the code would be cleaner
> if we remove needPostProcessing.
>
>> return;
>> }
>>
>> + locker.unlock();
>> +
>> completeDescriptor(descriptor);
>> }
>>
>> diff --git a/src/android/camera_stream.cpp b/src/android/camera_stream.cpp
>> index 45d0607d..68b916e9 100644
>> --- a/src/android/camera_stream.cpp
>> +++ b/src/android/camera_stream.cpp
>> @@ -99,6 +99,7 @@ int CameraStream::configure()
>> if (ret)
>> return ret;
>>
>> + worker_ = std::make_unique<PostProcessorWorker>(postProcessor_.get());
>> postProcessor_->processComplete.connect(
>> this, [&](Camera3RequestDescriptor::StreamBuffer *streamBuffer,
>> PostProcessor::Status status) {
>> @@ -112,6 +113,8 @@ int CameraStream::configure()
>> cameraDevice_->streamProcessingComplete(streamBuffer,
>> bufferStatus);
>> });
>> +
>> + worker_->start();
>> }
>>
>> if (type_ == Type::Internal) {
>> @@ -179,10 +182,6 @@ int CameraStream::process(const FrameBuffer &source,
>>
>> ASSERT(type_ != Type::Direct);
>>
>> - /*
>> - * \todo Buffer mapping and processing should be moved to a
>> - * separate thread.
>> - */
>> const StreamConfiguration &output = configuration();
>> dest.destBuffer = std::make_unique<CameraBuffer>(
>> *dest.camera3Buffer, output.pixelFormat, output.size,
>> @@ -194,11 +193,19 @@ int CameraStream::process(const FrameBuffer &source,
>>
>> dest.srcBuffer = &source;
>>
>> - postProcessor_->process(&dest);
>> + worker_->queueRequest(&dest);
>>
>> return 0;
>> }
>>
>> +void CameraStream::flush()
>> +{
>> + if (!postProcessor_)
>> + return;
>> +
>> + worker_->flush();
>> +}
>> +
>> FrameBuffer *CameraStream::getBuffer()
>> {
>> if (!allocator_)
>> @@ -226,3 +233,87 @@ void CameraStream::putBuffer(FrameBuffer *buffer)
>>
>> buffers_.push_back(buffer);
>> }
>> +
>> +CameraStream::PostProcessorWorker::PostProcessorWorker(PostProcessor *postProcessor)
>> + : postProcessor_(postProcessor)
>> +{
>> +}
>> +
>> +CameraStream::PostProcessorWorker::~PostProcessorWorker()
>> +{
>> + {
>> + libcamera::MutexLocker lock(mutex_);
>> + state_ = State::Stopped;
>> + }
>> +
>> + cv_.notify_one();
>> + wait();
>> +}
>> +
>> +void CameraStream::PostProcessorWorker::start()
>> +{
>> + {
>> + libcamera::MutexLocker lock(mutex_);
>> + ASSERT(state_ != State::Running);
>> + state_ = State::Running;
>> + }
>> +
>> + Thread::start();
>> +}
>> +
>> +void CameraStream::PostProcessorWorker::queueRequest(Camera3RequestDescriptor::StreamBuffer *dest)
>> +{
>> + {
>> + MutexLocker lock(mutex_);
>> + ASSERT(state_ == State::Running);
>> + requests_.push(dest);
>> + }
>> +
>> + cv_.notify_one();
>> +}
>> +
>> +void CameraStream::PostProcessorWorker::run()
>> +{
>> + MutexLocker locker(mutex_);
>> +
>> + while (1) {
>> + cv_.wait(locker, [&] {
>> + return state_ != State::Running || !requests_.empty();
>> + });
>> +
>> + if (state_ != State::Running)
>> + break;
>> +
>> + Camera3RequestDescriptor::StreamBuffer *streamBuffer = requests_.front();
>> + requests_.pop();
>> + locker.unlock();
>> +
>> + postProcessor_->process(streamBuffer);
>> +
>> + locker.lock();
>> + }
>> +
>> + if (state_ == State::Flushing) {
>> + std::queue<Camera3RequestDescriptor::StreamBuffer *> requests =
>> + std::move(requests_);
> Why is moving requests_ to a local variable necessary?
To avoid iterating under a lock.
>
> Reviewed-by: Hirokazu Honda<hiroh at chromium.org>
>> + locker.unlock();
>> +
>> + while (!requests.empty()) {
>> + postProcessor_->processComplete.emit(
>> + requests.front(), PostProcessor::Status::Error);
>> + requests.pop();
>> + }
>> +
>> + locker.lock();
>> + state_ = State::Stopped;
>> + }
>> +}
>> +
>> +void CameraStream::PostProcessorWorker::flush()
>> +{
>> + libcamera::MutexLocker lock(mutex_);
>> + state_ = State::Flushing;
>> + lock.unlock();
>> +
>> + cv_.notify_one();
>> +}
>> diff --git a/src/android/camera_stream.h b/src/android/camera_stream.h
>> index e9c320b1..7c6e887c 100644
>> --- a/src/android/camera_stream.h
>> +++ b/src/android/camera_stream.h
>> @@ -7,12 +7,16 @@
>> #ifndef __ANDROID_CAMERA_STREAM_H__
>> #define __ANDROID_CAMERA_STREAM_H__
>>
>> +#include <condition_variable>
>> #include <memory>
>> #include <mutex>
>> +#include <queue>
>> #include <vector>
>>
>> #include <hardware/camera3.h>
>>
>> +#include <libcamera/base/thread.h>
>> +
>> #include <libcamera/camera.h>
>> #include <libcamera/framebuffer.h>
>> #include <libcamera/framebuffer_allocator.h>
>> @@ -20,9 +24,9 @@
>> #include <libcamera/pixel_format.h>
>>
>> #include "camera_request.h"
>> +#include "post_processor.h"
>>
>> class CameraDevice;
>> -class PostProcessor;
>>
>> class CameraStream
>> {
>> @@ -125,8 +129,38 @@ public:
>> Camera3RequestDescriptor::StreamBuffer &dest);
>> libcamera::FrameBuffer *getBuffer();
>> void putBuffer(libcamera::FrameBuffer *buffer);
>> + void flush();
>>
>> private:
>> + class PostProcessorWorker : public libcamera::Thread
>> + {
>> + public:
>> + enum class State {
>> + Stopped,
>> + Running,
>> + Flushing,
>> + };
>> +
>> + PostProcessorWorker(PostProcessor *postProcessor);
>> + ~PostProcessorWorker();
>> +
>> + void start();
>> + void queueRequest(Camera3RequestDescriptor::StreamBuffer *request);
>> + void flush();
>> +
>> + protected:
>> + void run() override;
>> +
>> + private:
>> + PostProcessor *postProcessor_;
>> +
>> + libcamera::Mutex mutex_;
>> + std::condition_variable cv_;
>> +
>> + std::queue<Camera3RequestDescriptor::StreamBuffer *> requests_;
>> + State state_ = State::Stopped;
>> + };
>> +
>> int waitFence(int fence);
>>
>> CameraDevice *const cameraDevice_;
>> @@ -143,6 +177,8 @@ private:
>> */
>> std::unique_ptr<std::mutex> mutex_;
>> std::unique_ptr<PostProcessor> postProcessor_;
>> +
>> + std::unique_ptr<PostProcessorWorker> worker_;
>> };
>>
>> #endif /* __ANDROID_CAMERA_STREAM__ */
>> --
>> 2.31.1
>>
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