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It does not invoke an >>>>>> extra >>>>>> + * dma_fence_get() on it. Consequently, this callback >>>>>> must return a >>>>>> + * fence whose refcount is at least 2: One for the >>>>>> scheduler's >>>>>> + * reference returned here, another one for the >>>>>> reference kept by the >>>>>> + * driver. >>>>> Well the driver actually doesn't need any extra reference. The >>>>> scheduler >>>>> just needs to guarantee that this reference isn't dropped before >>>>> it is >>>>> signaled. >>>> I think he means the reference the driver's fence context has to >>>> have in order >>>> to signal that thing eventually. >>> Yeah, but this is usually a weak reference. IIRC most drivers don't >>> increment the reference count for the reference they keep to signal a >>> fence. >>> >>> It's expected that the consumers of the dma_fence keep the fence >>> alive >>> at least until it is signaled. >> So are you saying that the driver having an extra reference (without >> having obtained it with dma_fence_get()) is not an issue because the >> driver is the one who will signal the fence [and then be done with it]? > It's never a "real" issue if you have multiple pointers to a reference counted > object as long as you can ensure that you hold at least one reference for the > time you have pointers to the object. Well, I'm not saying that this isn't an issue. I'm just pointing out that this is the current practice :) > But, that's bad design. For every pointer to an object a separate reference > should be taken. Yeah, completely agree. Weak references are usually a bad idea if you don't absolutely need them for something. Regards, Christian.