[PATCH v2 3/3] test: gstreamer: Test memory lifetime
Kieran Bingham
kieran.bingham at ideasonboard.com
Thu May 9 18:07:51 CEST 2024
Quoting Nicolas Dufresne (2024-05-09 16:28:14)
> Hi,
>
> Le jeudi 09 mai 2024 à 15:57 +0100, Kieran Bingham a écrit :
> > Quoting Nicolas Dufresne (2024-03-05 15:30:58)
> > > From: Nicolas Dufresne <nicolas.dufresne at collabora.com>
> > >
> > > Test that everything works fine if a buffer outlives the pipeline.
> > >
> > > Signed-off-by: Nicolas Dufresne <nicolas.dufresne at collabora.com>
> > > ---
> > > .../gstreamer_memory_lifetime_test.cpp | 75 +++++++++++++++++++
> > > test/gstreamer/meson.build | 4 +-
> > > 2 files changed, 78 insertions(+), 1 deletion(-)
> > > create mode 100644 test/gstreamer/gstreamer_memory_lifetime_test.cpp
> > >
> > > diff --git a/test/gstreamer/gstreamer_memory_lifetime_test.cpp b/test/gstreamer/gstreamer_memory_lifetime_test.cpp
> > > new file mode 100644
> > > index 00000000..6d932e9e
> > > --- /dev/null
> > > +++ b/test/gstreamer/gstreamer_memory_lifetime_test.cpp
> > > @@ -0,0 +1,75 @@
> > > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> > > +/*
> > > + * Copyright (C) 2024, Nicolas Dufresne
> > > + *
> > > + * gstreamer_memory_lifetime_test.cpp - GStreamer memory lifetime test
> > > + */
> > > +
> > > +#include <iostream>
> > > +#include <unistd.h>
> > > +
> > > +#include <gst/app/app.h>
> > > +#include <gst/gst.h>
> > > +
> > > +#include "gstreamer_test.h"
> > > +#include "test.h"
> > > +
> > > +using namespace std;
> > > +
> > > +class GstreamerMemoryLifetimeTest : public GstreamerTest, public Test
> > > +{
> > > +public:
> > > + GstreamerMemoryLifetimeTest()
> > > + : GstreamerTest()
> > > + {
> > > + }
> > > +
> > > +protected:
> > > + int init() override
> > > + {
> > > + if (status_ != TestPass)
> > > + return status_;
> > > +
> > > + appsink_ = gst_element_factory_make("appsink", nullptr);
> > > + if (!appsink_) {
> > > + g_printerr("Your installation is missing 'appsink'\n");
> > > + return TestFail;
> > > + }
> > > + g_object_ref_sink(appsink_);
> > > +
> > > + return createPipeline();
> > > + }
> > > +
> > > + int run() override
> > > + {
> > > + /* Build the pipeline */
> > > + gst_bin_add_many(GST_BIN(pipeline_), libcameraSrc_, appsink_, nullptr);
> > > + if (gst_element_link(libcameraSrc_, appsink_) != TRUE) {
> > > + g_printerr("Elements could not be linked.\n");
> > > + return TestFail;
> > > + }
> > > +
> > > + if (startPipeline() != TestPass)
> > > + return TestFail;
>
> Did not add a comment here, since "startPipeline()" should be obvious that we
> start the pipeline. It will raise the state to PLAYING state.
Yes, startPipeline is obvious enough ;-)
> > > +
> > > + sample_ = gst_app_sink_try_pull_sample(GST_APP_SINK(appsink_), GST_SECOND * 5);
>
> This is also a bit trivial, it pulls a sample from the pipeline.
Agreed, but what's the impact in lifetime. do we expect a single buffer?
I think you're covering it on the comment below though.
>
> > > + gst_element_set_state(pipeline_, GST_STATE_NULL);
>
> Here though, I should probably add a comment (well before the change to NULL
> state).
>
> /*
> * Stop the pipeline without releasing sample_. This ensures that we can hold
> * on memory while elements can release all their internal resources as required
> * by the NULL state definition.
> */
Yes, that's what I think the test needs to document.
>
> > > +
> > > + if (!sample_)
> > > + return TestFail;
> >
> > Is this the part that does the test? I don't really know how this test
> > is working.
>
> This is memory safety. As the doc says:
>
> https://gstreamer.freedesktop.org/documentation/applib/gstappsink.html?gi-language=c#gst_app_sink_pull_sample
>
> > Returns ( [transfer: full][nullable]) – a GstSample or NULL ...
>
> As it annoted nullable, not doing a null check if not safe. I'd, say, it would
> be annormal, so failing the test make sense, but its not really the expected
> failure spot for when the code was broken.
Which is the point that spots the code is broken then? I seem to still
miss it ?
>
> >
> > Is it pulling a single buffer? Does set_state(GST_STATE_NULL) destroy
> > the pipeline?
>
> No, when moving to STATE_NULL, its is required
>
> >
> > Any comments we can add here to make it clearer what is actually being
> > tested or happening? The code doesn't really tell me what's going on
> > under the hood.
>
> https://gstreamer.freedesktop.org/documentation/application-development/basics/elements.html?gi-language=c#element-states
>
> > GST_STATE_NULL: this is the default state. No resources are allocated in this
> state, so, transitioning to it will free all resources. The element must be in
> this state when its refcount reaches 0 and it is freed.
>
> Let me know if the suggested comment above would do for you.
>
> >
> > Does the test for !sample_ really mean the buffer still exists and is
> > valid? Does the test need to do anything to /access/ the buffer to make
> > sure the test proves it succeeded?
> >
> > I expect it probably does as otherwise you'd have added more - but it's
> > just not obvious from the above.
> >
> >
>
> The bug being that libcamera crash when the memory is released, in this specific
> case it crash in cleanup(). But I suspect that we can drop the sample_ member,
> and simple manually unref the sample here (avoiding smart pointer, as it would
> be equally confusing).
>
> p.s. Btw, its hard for me to efficiently comment back on 2 months old patch, I
> don't remember much about it, I'm just reading the patch to reply here.
Sounds like a great reason to make sure we have comments in the code
that explain the 'why' :-)
I'm fine with whatever comments you believe are appropriate. 'You' two
months later are probably the best reviewer here ;-)
>
> Nicolas
>
> >
> > > +
> > > + return TestPass;
> > > + }
> > > +
> > > + void cleanup() override
> > > + {
Are you saying the test is actually testing the issue /here/ ? If so -
can we add a comment explicitly saying that ?
Otherwise this is just 'cleanup' code to me. That's why I was looking at
the null check of sample_ trying to figure out if that's how you were
determining if the test had failed (Becuase that's the only time you
return TestFail after the test actually starts).
I guess the failure point is that the test will crash, rather than
detect a failure. Would that also be noteworthy?
> > > + g_clear_pointer(&sample_, gst_sample_unref);
> > > + g_clear_object(&appsink_);
> > > + }
> > > +
> > > +private:
> > > + GstElement *appsink_;
> > > + GstSample *sample_;
> > > +};
> > > +
> > > +TEST_REGISTER(GstreamerMemoryLifetimeTest)
> > > diff --git a/test/gstreamer/meson.build b/test/gstreamer/meson.build
> > > index f3ba5a23..70609b88 100644
> > > --- a/test/gstreamer/meson.build
> > > +++ b/test/gstreamer/meson.build
> > > @@ -8,12 +8,14 @@ gstreamer_tests = [
> > > {'name': 'single_stream_test', 'sources': ['gstreamer_single_stream_test.cpp']},
> > > {'name': 'multi_stream_test', 'sources': ['gstreamer_multi_stream_test.cpp']},
> > > {'name': 'device_provider_test', 'sources': ['gstreamer_device_provider_test.cpp']},
> > > + {'name': 'memory_lifetime_test', 'sources': ['gstreamer_memory_lifetime_test.cpp']},
> > > ]
> > > gstreamer_dep = dependency('gstreamer-1.0', required : true)
> > > +gstapp_dep = dependency('gstreamer-app-1.0', required : true)
> > >
> > > foreach test : gstreamer_tests
> > > exe = executable(test['name'], test['sources'], 'gstreamer_test.cpp',
> > > - dependencies : [libcamera_private, gstreamer_dep],
> > > + dependencies : [libcamera_private, gstreamer_dep, gstapp_dep],
> > > link_with : test_libraries,
> > > include_directories : test_includes_internal)
> > >
> > > --
> > > 2.43.2
> > >
>
More information about the libcamera-devel
mailing list