[libcamera-devel] [PATCH v5 3/4] android: post_processor: Make post processing async
Umang Jain
umang.jain at ideasonboard.com
Thu Oct 21 07:53:04 CEST 2021
Hi Laurent,
On 10/21/21 7:03 AM, Laurent Pinchart wrote:
> Hi Umang,
>
> Thank you for the patch.
>
> On Wed, Oct 20, 2021 at 04:12:11PM +0530, Umang Jain 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.
>>
>> To get access to the source and destination buffers in the worker
>> thread, we also need to save a pointer to them in the
> s/a pointer/pointers/
>
>> Camera3RequestDescriptor.
>>
>> 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 scnearios 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 | 46 +++++----------
>> src/android/camera_request.h | 4 ++
>> src/android/camera_stream.cpp | 107 +++++++++++++++++++++++++++++++---
>> src/android/camera_stream.h | 38 +++++++++++-
>> 4 files changed, 156 insertions(+), 39 deletions(-)
>>
>> diff --git a/src/android/camera_device.cpp b/src/android/camera_device.cpp
>> index 541c2c81..b14416ce 100644
>> --- a/src/android/camera_device.cpp
>> +++ b/src/android/camera_device.cpp
>> @@ -1020,29 +1020,8 @@ 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.
>> @@ -1120,12 +1099,7 @@ void CameraDevice::requestComplete(Request *request)
>> bool needsPostProcessing = false;
>> Camera3RequestDescriptor::Status processingStatus =
>> Camera3RequestDescriptor::Status::Pending;
>> - /*
>> - * \todo Apply streamsProcessMutex_ when post-processing is adapted to run
>> - * asynchronously. If we introduce the streamsProcessMutex_ right away, the
>> - * lock will be held forever since it is synchronous at this point
>> - * (see streamProcessingComplete).
>> - */
>> +
>> for (auto &buffer : descriptor->buffers_) {
>> CameraStream *stream = buffer.stream;
>>
>> @@ -1145,7 +1119,13 @@ void CameraDevice::requestComplete(Request *request)
>> buffer.internalBuffer = src;
>>
>> needsPostProcessing = true;
>> - int ret = stream->process(*src, buffer, descriptor);
>> +
>> + int ret;
>> + {
>> + MutexLocker locker(descriptor->streamsProcessMutex_);
> It may be possible (see my review of 2/4) to only lock access to the
> data structures and not cover the process() call. Let's see how it turns
> out.
Yes, I need to draft the code and then only I'll be able to confirm. My
deep-code visual skills are kinda limited.
>
>> + ret = stream->process(*src, buffer, descriptor);
>> + }
>> +
>> if (ret) {
>> setBufferStatus(stream, buffer, descriptor,
>> Camera3RequestDescriptor::Status::Error);
>> @@ -1156,6 +1136,12 @@ void CameraDevice::requestComplete(Request *request)
>> if (needsPostProcessing) {
>> if (processingStatus == Camera3RequestDescriptor::Status::Error) {
>> descriptor->status_ = processingStatus;
>> + /*
>> + * \todo This is problematic when some streams are
>> + * queued successfully, but some fail to get queued.
>> + * We might end up with use-after-free situation for
>> + * descriptor in streamProcessingComplete().
>> + */
> Hopefully this will be fixed in v6 of 2/4 :-)
>
>> sendCaptureResults();
>> }
>>
>> diff --git a/src/android/camera_request.h b/src/android/camera_request.h
>> index 3a2774e0..85274414 100644
>> --- a/src/android/camera_request.h
>> +++ b/src/android/camera_request.h
>> @@ -18,6 +18,7 @@
>>
>> #include <hardware/camera3.h>
>>
>> +#include "camera_buffer.h"
>> #include "camera_metadata.h"
>> #include "camera_worker.h"
>>
>> @@ -39,6 +40,9 @@ public:
>> int fence;
>> Status status;
>> libcamera::FrameBuffer *internalBuffer = nullptr;
>> + std::unique_ptr<CameraBuffer> destBuffer;
>> + const libcamera::FrameBuffer *srcBuffer;
>> + Camera3RequestDescriptor *request = nullptr;
>> };
>>
>> Camera3RequestDescriptor(libcamera::Camera *camera,
>> diff --git a/src/android/camera_stream.cpp b/src/android/camera_stream.cpp
>> index b3cb06a2..a29ce33b 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 *request, PostProcessor::Status status) {
>> Camera3RequestDescriptor::Status bufferStatus =
>> @@ -110,6 +111,7 @@ int CameraStream::configure()
>> cameraDevice_->streamProcessingComplete(this, request,
>> bufferStatus);
>> });
>> + worker_->start();
>> }
>>
>> if (type_ == Type::Internal) {
>> @@ -179,23 +181,31 @@ int CameraStream::process(const FrameBuffer &source,
>> if (!postProcessor_)
>> return 0;
>>
>> - /*
>> - * \todo Buffer mapping and processing should be moved to a
>> - * separate thread.
>> - */
>> const StreamConfiguration &output = configuration();
>> - CameraBuffer destBuffer(*dest.camera3Buffer, output.pixelFormat,
>> - output.size, PROT_READ | PROT_WRITE);
>> - if (!destBuffer.isValid()) {
>> + dest.destBuffer = std::make_unique<CameraBuffer>(
>> + *dest.camera3Buffer, output.pixelFormat, output.size, PROT_READ | PROT_WRITE);
> dest.destBuffer = std::make_unique<CameraBuffer>(
> *dest.camera3Buffer, output.pixelFormat, output.size,
> PROT_READ | PROT_WRITE);
>
>> + if (!dest.destBuffer->isValid()) {
>> LOG(HAL, Error) << "Failed to create destination buffer";
>> return -EINVAL;
>> }
>>
>> - postProcessor_->process(source, &destBuffer, request);
>> + dest.srcBuffer = &source;
>> + dest.request = request;
>> +
>> + /* Push the postProcessor request to the worker queue. */
>> + worker_->queueRequest(&dest);
>>
>> return 0;
>> }
>>
>> +void CameraStream::flush()
>> +{
>> + if (!postProcessor_)
>> + return;
>> +
>> + worker_->flush();
>> +}
>> +
>> FrameBuffer *CameraStream::getBuffer()
>> {
>> if (!allocator_)
>> @@ -223,3 +233,84 @@ 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_);
> Could you add a
>
> ASSERT(state_ != State::Running);
>
> here ? I'm worried that a future refactoring will call
> CameraStream::configure() multiple times, and that would result in the
> worker being start multiple times too.
Ack
>
>> + 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 *stream = requests_.front();
>> + requests_.pop();
>> + locker.unlock();
>> +
>> + postProcessor_->process(*stream->srcBuffer, stream->destBuffer.get(),
>> + stream->request);
>> +
>> + locker.lock();
>> + }
>> +
>> + if (state_ == State::Flushing) {
>> + while (!requests_.empty()) {
>> + postProcessor_->processComplete.emit(
>> + requests_.front()->request,
>> + PostProcessor::Status::Error);
> I'm also a tiny bit concerned here that we're emitting the signal with
> the lock held, while for requests that complete normally we don't. The
> behaviour isn't consistent and could cause issues in the CameraStream or
> CameraDevice classes. I think it's harmless for now, but maybe we could
> drop the lock around the emit(à call ? One option to avoid dropping and
> taking the lock in every iteration would be
>
> std::queue<Camera3RequestDescriptor::StreamBuffer *> requests = std::move(requests_);
>
> locker.unlock();
>
> while (!requests.empty()) {
> postProcessor_->processComplete.emit(
> requests.front()->request,
> PostProcessor::Status::Error);
> requests.pop();
> }
>
> locker.lock();
>
> And now that I think about it, given that we now have a StreamBuffer
> object, wouldn't it be simpler to pass the StreamBuffer instead of the
> Camera3RequestDescriptor to the signal ?
Yesteday, Jacopo might have suggested the same. I'll try to accomodate this.
>> + }
>> +
>> + state_ = State::Stopped;
>> + locker.unlock();
> You can drop the unlock() call here.
Ack. Shouldn't be here
>
>> + }
>> +}
>> +
>> +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 f242336e..64e32c77 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
>> {
>> @@ -126,8 +130,38 @@ public:
>> Camera3RequestDescriptor *request);
>> 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_;
>> + };
>> +
>> int waitFence(int fence);
>>
>> CameraDevice *const cameraDevice_;
>> @@ -144,6 +178,8 @@ private:
>> */
>> std::unique_ptr<std::mutex> mutex_;
>> std::unique_ptr<PostProcessor> postProcessor_;
>> +
>> + std::unique_ptr<PostProcessorWorker> worker_;
>> };
>>
>> #endif /* __ANDROID_CAMERA_STREAM__ */
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