On Mon, Oct 12, 2020 at 10:44:38PM +0200, Pavel Reichl wrote: > > > On 10/12/20 6:04 PM, Brian Foster wrote: > > ... > >> @@ -2863,8 +2875,20 @@ xfs_btree_split( > >> args.done = &done; > >> args.kswapd = current_is_kswapd(); > >> INIT_WORK_ONSTACK(&args.work, xfs_btree_split_worker); > >> + /* > >> + * Update lockdep's ownership information to reflect that we > >> + * will be transferring the ilock from this thread to the > >> + * worker. > >> + */ > > > > Can we update this comment to explain why we need to do this? E.g., I'm > > assuming there's a lockdep splat somewhere down in the split worker > > without it, but it's not immediately clear where and so it might not be > > obvious if we're ever able to remove this. > > Hi, would something like this work for you? > > /* > + * Update lockdep's ownership information to reflect that we > + * will be transferring the ilock from this thread to the > + * worker (xfs_btree_split_worker() run via queue_work()). > + * If the ownership transfer would not happen lockdep would > + * assert in the worker thread because the ilock would be owned > + * by the original thread. > + */ > That doesn't really answer the question. Do you have a record of the lockdep error message that occurs without this state transfer, by chance? Brian >
