Re: [PATCH] cgroup/cpuset: fix circular locking dependency

From: Paul E. McKenney
Date: Tue Jan 09 2018 - 11:00:55 EST


On Tue, Jan 09, 2018 at 07:37:52AM -0800, Tejun Heo wrote:
> Hello, Paul.
>
> On Tue, Jan 09, 2018 at 07:21:12AM -0800, Paul E. McKenney wrote:
> > > The code was previously using both system_power_efficient_wq and
> > > system_workqueue (for the expedited path). I guess the options were
> > > either using two workqueues or dropping POWER_EFFICIENT. I have no
> > > idea how big an impact this will make or whether it'd even be
> > > noticeable but maybe it'd be worthwhile to mention that in the
> > > description?
> >
> > Good point! How about if I change the last paragraph of the commit
> > log to read as follows?
> >
> > Thanx, Paul
> >
> > ------------------------------------------------------------------------
> >
> > This commit also causes SRCU to use this new RCU-specific
> > workqueue_struct. Note that SRCU's use of workqueues never blocks them
> > waiting for readers, so this should be safe from a forward-progress
> > viewpoint. Note that this moves SRCU from system_power_efficient_wq
> > to a normal workqueue. In the unlikely event that this results in
> > measurable degradation, a separate power-efficient workqueue will be
> > creates for SRCU.
>
> Sounds good. Please feel free to add
>
> Acked-by: Tejun Heo <tj@xxxxxxxxxx>

Done, thank you!

Thanx, Paul