[libcamera-devel] [RFC v1 4/7] py: Create PyCameraManager
Laurent Pinchart
laurent.pinchart at ideasonboard.com
Mon Jun 27 12:25:17 CEST 2022
Hi Tomi,
On Mon, Jun 27, 2022 at 11:52:17AM +0300, Tomi Valkeinen wrote:
> On 24/06/2022 16:47, Laurent Pinchart wrote:
> > On Fri, Jun 24, 2022 at 11:05:11AM +0100, Kieran Bingham wrote:
> >> Quoting Tomi Valkeinen (2022-06-23 15:47:33)
> >>> Wrap the CameraManager with a PyCameraManager class and move the related
> >>> code inside the new class.
> >>>
> >>> This helps understanding the life times of the used-to-be global
> >>> variables, gets rid of static handleRequestCompleted function, and
> >>> allows us to simplify the binding code as the more complex pieces are
> >>> inside the class.
> >>>
> >>> There should be no user visible functional changes.
> >>>
> >>> Note that attaching to requestCompleted signal is a bit funny, as
> >>> apparently the only way to use a lambda with a signal is to provide an
> >>> object instance pointer as the first parameter, even if there's really
> >>> no instance.
> >>>
> >>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen at ideasonboard.com>
> >>> ---
> >>> src/py/libcamera/meson.build | 1 +
> >>> src/py/libcamera/py_camera_manager.cpp | 115 ++++++++++++++++++++++++
> >>> src/py/libcamera/py_camera_manager.h | 39 ++++++++
> >>> src/py/libcamera/py_main.cpp | 120 ++++++-------------------
> >>> 4 files changed, 181 insertions(+), 94 deletions(-)
> >>> create mode 100644 src/py/libcamera/py_camera_manager.cpp
> >>> create mode 100644 src/py/libcamera/py_camera_manager.h
> >>>
> >>> diff --git a/src/py/libcamera/meson.build b/src/py/libcamera/meson.build
> >>> index 04578bac..ad2a6858 100644
> >>> --- a/src/py/libcamera/meson.build
> >>> +++ b/src/py/libcamera/meson.build
> >>> @@ -13,6 +13,7 @@ pybind11_proj = subproject('pybind11')
> >>> pybind11_dep = pybind11_proj.get_variable('pybind11_dep')
> >>>
> >>> pycamera_sources = files([
> >>> + 'py_camera_manager.cpp',
> >>> 'py_enums.cpp',
> >>> 'py_geometry.cpp',
> >>> 'py_helpers.cpp',
> >>> diff --git a/src/py/libcamera/py_camera_manager.cpp b/src/py/libcamera/py_camera_manager.cpp
> >>> new file mode 100644
> >>> index 00000000..c9e5a99c
> >>> --- /dev/null
> >>> +++ b/src/py/libcamera/py_camera_manager.cpp
> >>> @@ -0,0 +1,115 @@
> >>> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> >>> +/*
> >>> + * Copyright (C) 2022, Tomi Valkeinen <tomi.valkeinen at ideasonboard.com>
> >>> + */
> >>> +
> >>> +#include "py_camera_manager.h"
> >>> +
> >>> +#include <sys/eventfd.h>
> >>> +#include <unistd.h>
> >>> +
> >>> +#include "py_main.h"
> >>> +
> >>> +namespace py = pybind11;
> >>> +
> >>> +using namespace libcamera;
> >>> +
> >>> +PyCameraManager::PyCameraManager()
> >>> +{
> >>> + int fd = eventfd(0, 0);
> >
> > In a separate patch I'd set at least the EFD_CLOEXEC flag.
>
> Ok.
>
> >>> + if (fd == -1)
> >>> + throw std::system_error(errno, std::generic_category(),
> >
> > #include <errno.h>
> > #include <system_error>
>
> Ok.
>
> >>> + "Failed to create eventfd");
> >>> +
> >>> + eventFd_ = fd;
> >>> +
> >>> + int ret = start();
> >>> + if (ret) {
> >>> + close(fd);
> >>> + eventFd_ = -1;
> >
> > You could use the UniqueFD class for eventFd_, this could when then
> > disappear. Same for the destructor.
>
> Yep. I'll do that in a separate patch, as here I'm just trying to move
> the code.
>
> >>> + throw std::system_error(-ret, std::generic_category(),
> >>> + "Failed to start CameraManager");
> >>> + }
> >>> +}
> >>> +
> >>> +PyCameraManager::~PyCameraManager()
> >>> +{
> >>> + if (eventFd_ != -1) {
> >>> + close(eventFd_);
> >>> + eventFd_ = -1;
> >>> + }
> >>> +}
> >>> +
> >>> +py::list PyCameraManager::getCameras()
> >
> > s/getCameras()/cameras()/ ?
>
> CameraManager already has cameras()...
>
> >>> +{
> >>> + /* Create a list of Cameras, where each camera has a keep-alive to CameraManager */
> >
> > Line wrap.
>
> Ok.
>
> >>> + py::list l;
> >>> +
> >>> + for (auto &c : cameras()) {
> >
> > We usually try not to shorten names too much. s/c/camera/ would read
> > nicely.
>
> Ok.
>
> >>> + py::object py_cm = py::cast(this);
> >>> + py::object py_cam = py::cast(c);
> >>> + py::detail::keep_alive_impl(py_cam, py_cm);
> >>> + l.append(py_cam);
> >>> + }
> >>> +
> >>> + return l;
> >>> +}
> >>> +
> >>> +std::vector<py::object> PyCameraManager::getReadyRequests()
> >>> +{
> >>> + readFd();
> >>
> >> Is this blocking? Does it need any kind of time out of cancellation
> >> support? (What happens if a ctrl-c happens while blocked here etc..)
> >
> > I expect this to be rework in the next patches of the series, but maybe
> > some of these concerns could be addressed already.
>
> I take it the concern was about ctrl-c, and that works?
Any of them, as reasonably feasible :-)
> >>> +
> >>> + std::vector<Request *> v;
> >
> > s/v/requests/
>
> Ok.
>
> >>> + getRequests(v);
> >
> > You can make getRequests() return the vector instead of passing it as a
> > reference, and then even do
> >
> > for (Request *req : getRequests()) {
>
> Ok. I usually keep away from those as I don't seem to ever exactly know
> when copies are made and when not...
With copy elision the vector returned by getRequest() will not be copied.
> >>> +
> >>> + std::vector<py::object> ret;
> >>> +
> >>> + for (Request *req : v) {
> >
> > s/req/request/
>
> Ok.
>
> >>> + py::object o = py::cast(req);
> >>> + /* Decrease the ref increased in Camera.queue_request() */
> >>> + o.dec_ref();
> >>> + ret.push_back(o);
> >>> + }
> >>> +
> >>> + return ret;
> >>> +}
> >>> +
> >>> +/* Note: Called from another thread */
> >>> +void PyCameraManager::handleRequestCompleted(Request *req)
> >>> +{
> >>> + pushRequest(req);
> >>> + writeFd();
> >>> +}
> >>> +
> >>> +void PyCameraManager::writeFd()
> >>> +{
> >>> + uint64_t v = 1;
> >>> +
> >>> + size_t s = write(eventFd_, &v, 8);
> >>> + /*
> >>> + * We should never fail, and have no simple means to manage the error,
> >>> + * so let's use LOG(Python, Fatal).
> >>> + */
> >>
> >> Trivial spacing is wrong here on the last line.
> >>
> >>> + if (s != 8)
> >>> + LOG(Python, Fatal) << "Unable to write to eventfd";
> >>
> >> Hrm ... should this tie in to throwing a python error to generate a
> >> python backtrace or such too ?
> >
> > We can't, as this isn't run from the Python thread.
> >
> >> It certainly shouldn't happen though indeed so ... it probably doesn't
> >> matter too much now.
> >>
> >>> +}
> >>> +
> >>> +void PyCameraManager::readFd()
> >>> +{
> >>> + uint8_t buf[8];
> >>> +
> >>> + if (read(eventFd_, buf, 8) != 8)
> >>> + throw std::system_error(errno, std::generic_category());
> >>> +}
> >>> +
> >>> +void PyCameraManager::pushRequest(Request *req)
> >>> +{
> >>> + std::lock_guard guard(reqlist_mutex_);
> >
> > Could you use the MutexLocker class ? That gives us access to
> > thread-safety annotations.
>
> Ok. I'll look at that in a separate patch.
>
> >> Aha, I was going to ask about locking up in
> >> PyCameraManager::handleRequestCompleted but now I see it's handled ...
> >>
> >>> + reqList_.push_back(req);
> >>> +}
> >>> +
> >>> +void PyCameraManager::getRequests(std::vector<Request *> &v)
> >>> +{
> >>> + std::lock_guard guard(reqlist_mutex_);
> >>> + swap(v, reqList_);
> >>> +}
> >>> diff --git a/src/py/libcamera/py_camera_manager.h b/src/py/libcamera/py_camera_manager.h
> >>> new file mode 100644
> >>> index 00000000..b0b971ad
> >>> --- /dev/null
> >>> +++ b/src/py/libcamera/py_camera_manager.h
> >>> @@ -0,0 +1,39 @@
> >>> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> >>> +/*
> >>> + * Copyright (C) 2022, Tomi Valkeinen <tomi.valkeinen at ideasonboard.com>
> >>> + */
> >>> +
> >>> +#pragma once
> >>> +
> >>> +#include <mutex>
> >>> +
> >>> +#include <libcamera/libcamera.h>
> >>> +
> >>> +#include <pybind11/smart_holder.h>
> >>> +
> >>> +using namespace libcamera;
> >>> +
> >>> +class PyCameraManager : public CameraManager
> >
> > CameraManager isn't meant to be inherited from (I'm surprised it's not
> > marked as final). You can keep this for now, but we should soon switch
> > to encapsulating the CameraManager instead.
>
> Hmm that may be problematic. At the moment if there's a CameraManager
> pointer, the pybind11 bindings can easily convert that instance to a
> Python instance. But if we encapsulate it, that's no longer the case, as
> you need something extra to associate the CameraManager pointer to the
> encapsulating class.
>
> I tried to do that with Cameras at some point (trying to sort out the
> destructor issue), but I didn't get it working. Maybe I'll try again
> with CameraManager this time.
Given that both the CameraManager and the PyCameraManager can only be
instantiated once, the Python code could unconditionally use the
PyCameraManager, without ever using the CameraManager pointer directly.
Do we even have any event that passes the CameraManager as an argument ?
For Camera instances we do, so that's indeed more problematic.
> >>> +{
> >>> +public:
> >>> + PyCameraManager();
> >>> + virtual ~PyCameraManager();
> >>> +
> >>> + pybind11::list getCameras();
> >>> +
> >>> + int eventFd() const { return eventFd_; }
> >>> +
> >>> + std::vector<pybind11::object> getReadyRequests();
> >>> +
> >>> + void handleRequestCompleted(Request *req);
> >>> +
> >>> +private:
> >>> + int eventFd_ = -1;
> >>> + std::mutex reqlist_mutex_;
> >
> > Mutex instead of std::mutex, and s/reqlist_mutex_/requestsListMutex_/
> > (or similar). You can also call it just lock_, and use the
> > LIBCAMERA_TSA_ macros to annotate the fields it protects, that's even
> > more explicit.
>
> Ok. I'll look at that in a separate patch.
>
> >>> + std::vector<Request *> reqList_;
> >
> > completedRequests_
>
> Ok.
>
> >>> +
> >>> + void writeFd();
> >>> + void readFd();
> >>> + void pushRequest(Request *req);
> >>> + void getRequests(std::vector<Request *> &v);
> >
> > getCompletedRequests()
>
> Ok.
>
> >>> +};
> >>> diff --git a/src/py/libcamera/py_main.cpp b/src/py/libcamera/py_main.cpp
> >>> index 5a423ece..23018288 100644
> >>> --- a/src/py/libcamera/py_main.cpp
> >>> +++ b/src/py/libcamera/py_main.cpp
> >>> @@ -7,10 +7,7 @@
> >>>
> >>> #include "py_main.h"
> >>>
> >>> -#include <mutex>
> >>> #include <stdexcept>
> >>> -#include <sys/eventfd.h>
> >>> -#include <unistd.h>
> >>>
> >>> #include <libcamera/base/log.h>
> >>>
> >>> @@ -21,6 +18,7 @@
> >>> #include <pybind11/stl.h>
> >>> #include <pybind11/stl_bind.h>
> >>>
> >>> +#include "py_camera_manager.h"
> >>> #include "py_helpers.h"
> >>>
> >>> namespace py = pybind11;
> >>> @@ -29,27 +27,11 @@ using namespace libcamera;
> >>>
> >>> LOG_DEFINE_CATEGORY(Python)
> >>>
> >>> -static std::weak_ptr<CameraManager> gCameraManager;
> >>> -static int gEventfd;
> >>> -static std::mutex gReqlistMutex;
> >>> -static std::vector<Request *> gReqList;
> >>> -
> >>> -static void handleRequestCompleted(Request *req)
> >>> -{
> >>> - {
> >>> - std::lock_guard guard(gReqlistMutex);
> >>> - gReqList.push_back(req);
> >>> - }
> >>> -
> >>> - uint64_t v = 1;
> >>> - size_t s = write(gEventfd, &v, 8);
> >>> - /*
> >>> - * We should never fail, and have no simple means to manage the error,
> >>> - * so let's use LOG(Python, Fatal).
> >>> - */
> >>> - if (s != 8)
> >>> - LOG(Python, Fatal) << "Unable to write to eventfd";
> >>> -}
> >>> +/*
> >>> + * XXX Note: global C++ destructors can be ran on this before the py module is
> >>
> >> XXX or Todo ... or Warning (WARNING!)? Even if this is just a highglight
> >> for review, I think it should stay in the code.
> >>
> >>> + * destructed.
> >>> + */
> >>> +static std::weak_ptr<PyCameraManager> gCameraManager;
> >>>
> >>> void init_py_enums(py::module &m);
> >>> void init_py_controls_generated(py::module &m);
> >>> @@ -72,7 +54,7 @@ PYBIND11_MODULE(_libcamera, m)
> >>> * https://pybind11.readthedocs.io/en/latest/advanced/misc.html#avoiding-c-types-in-docstrings
> >>> */
> >>>
> >>> - auto pyCameraManager = py::class_<CameraManager>(m, "CameraManager");
> >>> + auto pyCameraManager = py::class_<PyCameraManager>(m, "CameraManager");
> >>> auto pyCamera = py::class_<Camera>(m, "Camera");
> >>> auto pyCameraConfiguration = py::class_<CameraConfiguration>(m, "CameraConfiguration");
> >>> auto pyCameraConfigurationStatus = py::enum_<CameraConfiguration::Status>(pyCameraConfiguration, "Status");
> >>> @@ -106,78 +88,22 @@ PYBIND11_MODULE(_libcamera, m)
> >>> /* Classes */
> >>> pyCameraManager
> >>> .def_static("singleton", []() {
> >>> - std::shared_ptr<CameraManager> cm = gCameraManager.lock();
> >>> - if (cm)
> >>> - return cm;
> >>> -
> >>> - int fd = eventfd(0, 0);
> >>> - if (fd == -1)
> >>> - throw std::system_error(errno, std::generic_category(),
> >>> - "Failed to create eventfd");
> >>> -
> >>> - cm = std::shared_ptr<CameraManager>(new CameraManager, [](auto p) {
> >>> - close(gEventfd);
> >>> - gEventfd = -1;
> >>> - delete p;
> >>> - });
> >>> -
> >>> - gEventfd = fd;
> >>> - gCameraManager = cm;
> >>> -
> >>> - int ret = cm->start();
> >>> - if (ret)
> >>> - throw std::system_error(-ret, std::generic_category(),
> >>> - "Failed to start CameraManager");
> >>> -
> >>> - return cm;
> >>> - })
> >>> -
> >>> - .def_property_readonly("version", &CameraManager::version)
> >>> -
> >>> - .def_property_readonly("event_fd", [](CameraManager &) {
> >>> - return gEventfd;
> >>> - })
> >>> + std::shared_ptr<PyCameraManager> cm = gCameraManager.lock();
> >>>
> >>> - .def("get_ready_requests", [](CameraManager &) {
> >>> - uint8_t buf[8];
> >>> -
> >>> - if (read(gEventfd, buf, 8) != 8)
> >>> - throw std::system_error(errno, std::generic_category());
> >>> -
> >>> - std::vector<Request *> v;
> >>> -
> >>> - {
> >>> - std::lock_guard guard(gReqlistMutex);
> >>> - swap(v, gReqList);
> >>> + if (!cm) {
> >>> + cm = std::make_shared<PyCameraManager>();
> >>> + gCameraManager = cm;
> >>> }
> >>>
> >>> - std::vector<py::object> ret;
> >>> -
> >>> - for (Request *req : v) {
> >>> - py::object o = py::cast(req);
> >>> - /* Decrease the ref increased in Camera.queue_request() */
> >>> - o.dec_ref();
> >>> - ret.push_back(o);
> >>> - }
> >>> -
> >>> - return ret;
> >>> + return cm;
> >>> })
> >>>
> >>> - .def("get", py::overload_cast<const std::string &>(&CameraManager::get), py::keep_alive<0, 1>())
> >>> + .def_property_readonly("version", &PyCameraManager::version)
> >>> + .def("get", py::overload_cast<const std::string &>(&PyCameraManager::get), py::keep_alive<0, 1>())
> >>> + .def_property_readonly("cameras", &PyCameraManager::getCameras)
> >>>
> >>> - /* Create a list of Cameras, where each camera has a keep-alive to CameraManager */
> >>> - .def_property_readonly("cameras", [](CameraManager &self) {
> >>> - py::list l;
> >>> -
> >>> - for (auto &c : self.cameras()) {
> >>> - py::object py_cm = py::cast(self);
> >>> - py::object py_cam = py::cast(c);
> >>> - py::detail::keep_alive_impl(py_cam, py_cm);
> >>> - l.append(py_cam);
> >>> - }
> >>> -
> >>> - return l;
> >>> - });
> >>> + .def_property_readonly("event_fd", &PyCameraManager::eventFd)
> >>> + .def("get_ready_requests", &PyCameraManager::getReadyRequests);
> >>>
> >>> pyCamera
> >>> .def_property_readonly("id", &Camera::id)
> >>> @@ -187,7 +113,13 @@ PYBIND11_MODULE(_libcamera, m)
> >>> const std::unordered_map<const ControlId *, py::object> &controls) {
> >>> /* \todo What happens if someone calls start() multiple times? */
> >>>
> >>> - self.requestCompleted.connect(handleRequestCompleted);
> >>> + auto cm = gCameraManager.lock();
> >>> + assert(cm);
> >>> +
> >>> + self.requestCompleted.connect(&self, [cm=std::move(cm)](Request *req) {
> >>> +
> >
> > Extra blank line.
>
> Yep.
>
> >>> + cm->handleRequestCompleted(req);
> >>> + });
> >
> > So the following didn't work ?
> >
> > self.requestCompleted.connect(cm.get(), &PyCameraManager::handleRequestCompleted);
> >
> > ? I can investigate.
>
> I didn't try that. I don't think what you have above is the same. Note
> that in my version I store a shared_ptr<CameraManager> to make sure it
> stays alive.
Is there a way we could avoid that ?
> The issue I had (which I asked about in the chat) was in the "New event
> handling", when connecting the cameraAdded signal.
I recall you had trouble receiving the cameraAdded signal even when
testing with cam, due to udev support being disabled. Have you retested
after fixing that ?
--
Regards,
Laurent Pinchart
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