On 5/14/19 7:27 PM, Alexei Starovoitov wrote: > what about activate_effective_progs() ? > I wouldn't want to lose the annotation there. > but then array_free will lose it? > in some cases it's called without mutex in a destruction path. > also how do you propose to solve different 'mtx' in > lockdep_is_held(&mtx)); ? > passing it through the call chain is imo not clean. > Usage of RCU api in BPF is indeed a bit strange and lacks lockdep support. Looking at bpf_prog_array_copy_core() for example, it looks like the __rcu in the first argument is not needed, since the caller must have done the proper dereference already, and the caller knows which mutex is protecting its rcu_dereference_protected() for the writer sides. bpf_prog_array_copy_core() should manipulate standard pointers, with no __rcu stuff. The analogy in net/ are probably the rtnl_dereference() users.
