From: "Paul E. McKenney" Subject: Re: [PATCH] cgroup/cpuset: fix circular locking dependency Date: Tue, 9 Jan 2018 08:00:22 -0800 Message-ID: <20180109160022.GW9671@linux.vnet.ibm.com> References: <20180102174408.GM7829@linux.vnet.ibm.com> <20180102180119.GA1355@linux.vnet.ibm.com> <20180108122823.GL3668920@devbig577.frc2.facebook.com> <20180108225238.GN9671@linux.vnet.ibm.com> <20180109003127.GA30224@linux.vnet.ibm.com> <20180109034211.GC3668920@devbig577.frc2.facebook.com> <20180109042016.GR9671@linux.vnet.ibm.com> <20180109134448.GE3668920@devbig577.frc2.facebook.com> <20180109152112.GT9671@linux.vnet.ibm.com> <20180109153752.GI3668920@devbig577.frc2.facebook.com> Reply-To: paulmck-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <20180109153752.GI3668920-4dN5La/x3IkLX0oZNxdnEQ2O0Ztt9esIQQ4Iyu8u01E@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Tejun Heo Cc: Prateek Sood , Peter Zijlstra , avagin-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, sramana-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org 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 Done, thank you! Thanx, Paul