On 2023-10-31 17:14:01 [+0100], Oliver Hartkopp wrote: > Hi Sebastian, Hi Oliver, > The content of gwj->mod can be overwritten with new modification rules at > runtime. But this update (with memcpy) has to take place when there is no > incoming network traffic. This is my assumption. But "no incoming network traffic" is not ensured, right? > > If not, my suggestion would be replacing the bh-off, memcpy part with: > > | old_mod = rcu_replace_pointer(gwj->mod, new_mod, true); > > | kfree_rcu_mightsleep(old_mod); > > > > and doing the needed pointer replacement with for struct cgw_job::mod > > and RCU annotation. > > Replacing a pointer does not copy any data to the cf_mod structure, right? Yes. The cf_mod data structure is embedded into cgw_job. So it would have to become a pointer. Then cgw_create_job() would create a new cf_mod via cgw_parse_attr() but it would be a new allocated structure instead on stack like it is now. And then in the existing case you would do the swap. Otherwise (non-existing, brand new) it becomes part of the new created cgw_job. The point is to replace/ update cf_mod at runtime while following RCU rules so always either new or the old object is observed. Never an intermediate step. > Best regards, > Oliver Sebastian
