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McKenney wrote: >> On Tue, Oct 25, 2022 at 01:00:02PM -0300, Jason Gunthorpe wrote: >>> On Tue, Oct 25, 2022 at 08:24:20AM -0700, Yonghong Song wrote: >>>> The current uverbs_api_ioctl_method definition: >>>> struct uverbs_api_ioctl_method { >>>> int(__rcu *handler)(struct uverbs_attr_bundle *attrs); >>>> DECLARE_BITMAP(attr_mandatory, UVERBS_API_ATTR_BKEY_LEN); >>>> ... >>>> }; >>>> The struct member 'handler' is marked with __rcu. But unless >>>> the function body pointed by 'handler' is changing (e.g., jited) >>>> during runtime, there is no need with __rcu. >>> >>> Huh? This is a sparse marker, it says that the pointer must always be >>> loaded with rcu_dereference >>> >>> It has nothing to do with JIT, this patch is not correct >> >> OK, I will bite... >> >> This is a pointer to a function. Given that this function's code is >> generated at compile time, what sequence of changes is rcu_dereference() >> protecting against? > > Module unload. We set the value to NULL and then synchronize_rcu > before unloading the code it points at. Okay. Thanks for explanation. I forgot the module unload case. I will look at compiler side then. > > Jason