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libcamera: camera: Use invokeMethod() for pipe_->acquire() and pipe_->release()
The uvcvideo driver needs to open / close its /dev/video# node from pipe_->acquireDevices() / pipe_->releaseDevices(). V4L2VideoDevice::open() creates an EventNotifier and this notifier needs to be created from the CameraManager thread. Use invokeMethod() for pipe_->acquire() and pipe_->release() so that the EventNotifiers are created from the CameraManager thread context. Running pipe_->acquire() and pipe_->release() from the CameraManager thread context serializes all calls to them. Drop PipelineHandler::lock_ this now is no longer necessary and update the "\context" part of the documentation for acquire[Device]() and release[Device]() to match. Note the delayed opening of /dev/video# is a special case because the kernel uvcvideo driver powers on the USB device as soon as /dev/video# is opened. This behavior should *not* be copied by other pipeline handlers. Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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3 changed files with 11 additions and 12 deletions
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@ -14,7 +14,6 @@
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#include <sys/types.h>
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#include <vector>
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#include <libcamera/base/mutex.h>
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#include <libcamera/base/object.h>
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#include <libcamera/controls.h>
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@ -99,9 +98,7 @@ private:
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std::queue<Request *> waitingRequests_;
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const char *name_;
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Mutex lock_;
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unsigned int useCount_ LIBCAMERA_TSA_GUARDED_BY(lock_);
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unsigned int useCount_;
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friend class PipelineHandlerFactoryBase;
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};
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@ -995,7 +995,8 @@ int Camera::acquire()
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if (ret < 0)
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return ret == -EACCES ? -EBUSY : ret;
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if (!d->pipe_->acquire(this)) {
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if (!d->pipe_->invokeMethod(&PipelineHandler::acquire,
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ConnectionTypeBlocking, this)) {
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LOG(Camera, Info)
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<< "Pipeline handler in use by another process";
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return -EBUSY;
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@ -1030,7 +1031,8 @@ int Camera::release()
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return ret == -EACCES ? -EBUSY : ret;
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if (d->isAcquired())
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d->pipe_->release(this);
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d->pipe_->invokeMethod(&PipelineHandler::release,
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ConnectionTypeBlocking, this);
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d->setState(Private::CameraAvailable);
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@ -157,7 +157,7 @@ MediaDevice *PipelineHandler::acquireMediaDevice(DeviceEnumerator *enumerator,
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* Pipeline handlers shall not call this function directly as the Camera class
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* handles access internally.
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*
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* \context This function is \threadsafe.
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* \context This function is called from the CameraManager thread.
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*
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* \return True if the pipeline handler was acquired, false if another process
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* has already acquired it
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@ -165,8 +165,6 @@ MediaDevice *PipelineHandler::acquireMediaDevice(DeviceEnumerator *enumerator,
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*/
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bool PipelineHandler::acquire(Camera *camera)
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{
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MutexLocker locker(lock_);
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if (useCount_ == 0) {
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for (std::shared_ptr<MediaDevice> &media : mediaDevices_) {
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if (!media->lock()) {
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@ -199,14 +197,12 @@ bool PipelineHandler::acquire(Camera *camera)
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* Pipeline handlers shall not call this function directly as the Camera class
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* handles access internally.
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*
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* \context This function is \threadsafe.
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* \context This function is called from the CameraManager thread.
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*
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* \sa acquire()
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*/
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void PipelineHandler::release(Camera *camera)
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{
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MutexLocker locker(lock_);
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ASSERT(useCount_);
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releaseDevice(camera);
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@ -230,6 +226,8 @@ void PipelineHandler::release(Camera *camera)
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* powers on the USB device as soon as /dev/video# is opened. This behavior
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* should *not* be copied by other pipeline handlers.
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*
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* \context This function is called from the CameraManager thread.
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*
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* \return True on success, false on failure
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* \sa releaseDevice()
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*/
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@ -250,6 +248,8 @@ bool PipelineHandler::acquireDevice([[maybe_unused]] Camera *camera)
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* release them until releaseDevice() has been called for all previously
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* acquired cameras.
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*
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* \context This function is called from the CameraManager thread.
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*
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* \sa acquireDevice()
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*/
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void PipelineHandler::releaseDevice([[maybe_unused]] Camera *camera)
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