[PATCH v2] libcamera: software_isp: Clean up pending requests on stop

[Milan Zamazal]

Hi Robert,

thank you for testing and review.

Robert Mader <robert.mader at collabora.com> writes:

> Hi, thanks for the patch!
>
> On 09.10.24 10:39, Milan Zamazal wrote:
>> Milan Zamazal <mzamazal at redhat.com> writes:
>>
>>> PipelineHandler::stop() calls stopDevice() method to perform pipeline
>>> specific cleanup and then completes waiting requests.  If any queued
>>> requests remain, an assertion error is raised.
>>>
>>> Software ISP stores request buffers in
>>> SimpleCameraData::conversionQueue_ and queues them as V4L2 signals
>>> bufferReady.  stopDevice() cleanup forgets to clean up the buffers and
>>> their requests from conversionQueue_, possibly resulting in the
>>> assertion error.
>>>
>>> This patch fixes the omission.  The request must be also canceled, which
>>> requires introducing a little PipelineHandler::cancelRequest helper in
>>> order to be able to access the private cancel() method.
>>>
>>> The problem wasn't very visible when
>>> SimplePipelineHandler::kNumInternalBuffers (the number of buffers
>>> allocated in V4L2) was equal to the number of buffers exported from
>>> software ISP.  But when the number of the exported buffers was increased
>>> by one in commit abe2ec64f9e4e97bbdfe3a50372611bd7b5315c2, the assertion
>>> error started pop up in some environments.  Increasing the number of the
>>> buffers much more, e.g. to 9, makes the problem very reproducible.
>>>
>>> Each pipeline uses its own mechanism to track the requests to clean up
>>> and it can't be excluded that similar omissions are present in other
>>> places.  But there is no obvious way to make a common cleanup for all
>>> the pipelines (except for doing it instead of raising the assertion
>>> error, which is probably undesirable, in order not to hide incomplete
>>> pipeline specific cleanups).
>>>
>>> Bug: https://bugs.libcamera.org/show_bug.cgi?id=234
>>> Signed-off-by: Milan Zamazal <mzamazal at redhat.com>
>> Changes in v2:
>> - The request is additionally canceled.
>> - New helper method PipelineHandler::cancelRequest() introduced.
>>
>> Robert, could you please test v2?
>
> I gave it a quick go for 5 minutes - generally it seems to work great, however trying enough quick camera
> switching I still run into the assert.
>
> So probably, on top of this, we'll need something implementing what Kieran suggested:
>
>> (Though I think we should reject any incoming requests as soon as we hit stop())
>
>>> ---
>>>   include/libcamera/internal/pipeline_handler.h |  1 +
>>>   src/libcamera/pipeline/simple/simple.cpp      | 14 +++++++++++
>>>   src/libcamera/pipeline_handler.cpp            | 23 +++++++++++++------
>>>   3 files changed, 31 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/include/libcamera/internal/pipeline_handler.h b/include/libcamera/internal/pipeline_handler.h
>>> index 0d3808036..fb28a18d0 100644
>>> --- a/include/libcamera/internal/pipeline_handler.h
>>> +++ b/include/libcamera/internal/pipeline_handler.h
>>> @@ -60,6 +60,7 @@ public:
>>>     	bool completeBuffer(Request *request, FrameBuffer *buffer);
>>>   	void completeRequest(Request *request);
>>> +	void cancelRequest(Request *request);
>>>     	std::string configurationFile(const std::string &subdir,
>>>   				      const std::string &name) const;
>>> diff --git a/src/libcamera/pipeline/simple/simple.cpp b/src/libcamera/pipeline/simple/simple.cpp
>>> index 3ddce71d3..e862ef00f 100644
>>> --- a/src/libcamera/pipeline/simple/simple.cpp
>>> +++ b/src/libcamera/pipeline/simple/simple.cpp
>>> @@ -284,6 +284,7 @@ public:
>>>   	std::vector<std::unique_ptr<FrameBuffer>> conversionBuffers_;
>>>   	std::queue<std::map<const Stream *, FrameBuffer *>> conversionQueue_;
>>>   	bool useConversion_;
>>> +	void clearIncompleteRequests();
>>>     	std::unique_ptr<Converter> converter_;
>>>   	std::unique_ptr<SoftwareIsp> swIsp_;
>>> @@ -897,6 +898,18 @@ void SimpleCameraData::conversionOutputDone(FrameBuffer *buffer)
>>>   		pipe->completeRequest(request);
>>>   }
>>>   +void SimpleCameraData::clearIncompleteRequests()
>>> +{
>>> +	while (!conversionQueue_.empty()) {
>>> +		for (auto &item : conversionQueue_.front()) {
>>> +			FrameBuffer *outputBuffer = item.second;
>>> +			Request *request = outputBuffer->request();
>>> +			pipe()->cancelRequest(request);
>>> +		}
>>> +		conversionQueue_.pop();
>>> +	}
>>> +}
>>> +
>>>   void SimpleCameraData::ispStatsReady(uint32_t frame, uint32_t bufferId)
>>>   {
>>>   	swIsp_->processStats(frame, bufferId,
>>> @@ -1407,6 +1420,7 @@ void SimplePipelineHandler::stopDevice(Camera *camera)
>>>   	video->bufferReady.disconnect(data, &SimpleCameraData::bufferReady);
>>>     	data->conversionBuffers_.clear();
>>> +	data->clearIncompleteRequests();
>>>     	releasePipeline(data);
>>>   }
>>> diff --git a/src/libcamera/pipeline_handler.cpp b/src/libcamera/pipeline_handler.cpp
>>> index e59404691..c9cb11f0f 100644
>>> --- a/src/libcamera/pipeline_handler.cpp
>>> +++ b/src/libcamera/pipeline_handler.cpp
>>> @@ -367,9 +367,7 @@ void PipelineHandler::stop(Camera *camera)
>>>   	while (!waitingRequests_.empty()) {
>>>   		Request *request = waitingRequests_.front();
>>>   		waitingRequests_.pop();
>>> -
>>> -		request->_d()->cancel();
>>> -		completeRequest(request);
>>> +		cancelRequest(request);
>>>   	}
>>>     	/* Make sure no requests are pending. */
>>> @@ -470,10 +468,8 @@ void PipelineHandler::doQueueRequest(Request *request)
>>>   	}
>>>     	int ret = queueRequestDevice(camera, request);
>>> -	if (ret) {
>>> -		request->_d()->cancel();
>>> -		completeRequest(request);
>>> -	}
>>> +	if (ret)
>>> +		cancelRequest(request);
>>>   }
>>>     /**
>>> @@ -568,6 +564,19 @@ void PipelineHandler::completeRequest(Request *request)
>>>   	}
>>>   }
>>>   +/**
>>> + * \brief Cancel request and signal its completion
>>> + * \param[in] request The request to cancel
>
> Small typo here

Sorry, I can't spot the typo, what typo exactly?

>>> + *
>>> + * This function cancels the request in addition to its completion. The same
>>> + * rules as for completeRequest() apply.
>>> + */
>>> +void PipelineHandler::cancelRequest(Request *request)
>>> +{
>>> +	request->_d()->cancel();
>>> +	completeRequest(request);
>>> +}
>>> +
>>>   /**
>>>    * \brief Retrieve the absolute path to a platform configuration file
>>>    * \param[in] subdir The pipeline handler specific subdirectory name