> On Jan 30, 2023, at 1:09 AM, Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> wrote: > > On Tue, Jan 24, 2023 at 02:57:35PM +0000, Chuck Lever III wrote: >> >>> I could be wrong, but it looks like you're safe to traverse the list >>> even in the case of removals, assuming the objects themselves are >>> rcu-freed. AFAICT, the object's ->next pointer is not changed when it's >>> removed from the table. After all, we're not holding a "real" lock here >>> so the object could be removed by another task at any time. >>> >>> It would be nice if this were documented though. > > Yes this is correct. As long as rcu_read_lock is still held, > the list will continue to be valid for walking even if you remove > entries from it. > >> Is there a preferred approach for this with rhltable? Can we just >> hold rcu_read_lock and call rhltable_remove repeatedly without getting >> a fresh copy of the list these items reside on? > > Yes you can walk the whole returned list while removing the nodes > one by one, assuming that you hold the RCU read lock throughout. > The unhashed nodes are only freed after the RCU grace period so the > list remains valid after removal. Thanks for the feedback! -- Chuck Lever
