How to know when rendering to texture is done

[ChenTianSky]

Hello. I would like to ask, in ogre, how do I know that the current frame has been rendered by the gpu? For example, when I render to the texture, how do I know that the GPU has finished rendering, and I need to sample it back to do other processing at this time. I tried Ogre::FrameListener, but frameRenderingQueued doesn't sync gpu rendering complete event