On Fri, Apr 21, 2017 at 02:57:17PM +0100, David Howells wrote: > Eric Biggers <ebigge...@gmail.com> wrote: > > > - kfree_rcu(zap, rcu); > > + call_rcu(&zap->rcu, user_free_payload_rcu); > > Add kzfree_rcu()? > > David
We could, but it's not trivial because the way kfree_rcu() works is to store the offset of the rcu_head as the callback function, then have a special case in RCU reclaim that recognizes "function pointers" with value < 4096 and call kfree() rather than the function. To support kzfree_rcu() we'd need to reserve another 4096 bytes of the address space (maybe at the end?), then check for the special kzfree value on every RCU reclaim. Or equivalently it could be a flag. It's possible, but it may be best to just use a custom callback for now. Then if it can be shown later that there are a lot of users who would like a "kzfree_rcu()", it can be added. - Eric
