On 10/13/20 1:04 PM, Brian Foster wrote: > 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 Hi, please see this mail from Darrick - he hit the issue first - http://mail.spinics.net/lists/linux-xfs/msg38967.html > >> >
