Hello, On Wed, Oct 04, 2017 at 03:20:40AM +0800, Ming Lei wrote: > On Tue, Oct 03, 2017 at 07:14:59AM -0700, Tejun Heo wrote: > > Hello, > > > > On Tue, Oct 03, 2017 at 10:04:03PM +0800, Ming Lei wrote: > > > Block layer need to call this function after holding > > > rcu lock in a real hot path, so introduce this helper. > > > > The patch description is too anemic. It doesn't even describe what > > changes are being made, let alone justifying them. > > Sorry for Cc you, and this change is needed by the following > patch: > > https://marc.info/?l=linux-scsi&m=150703956929333&w=2 > > Block layer need to call percpu_ref_tryget_live() > with holding RCU read lock, given it is a hot I/O > path, that is why I make this patch so that we can > avoid nested RCU read lock and save a bit cost. I'm not necessarily against it but please name it sth like percpu_ref_tryget_live_locked(), add lockdep assertions in the inner function and document properly. Thanks. -- tejun
