From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH] cgroup/cpuset: fix circular locking dependency Date: Tue, 9 Jan 2018 07:37:52 -0800 Message-ID: <20180109153752.GI3668920@devbig577.frc2.facebook.com> References: <20180102161656.GD3668920@devbig577.frc2.facebook.com> <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> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=z0k/ytaEmce44GZjz/Bvhg/RN6wShJMjhMBnBa7LjCU=; b=K3R7p1KQifbtyXIAdpzo3giKqa4lNq5jVCzVRDGPgO7EfsjoNJD2HJ+m+kiKEQoTjx Vc7ifgjeeVlTWtDmmihJ9U8zvb+6QnhA2Lwr8svtG3sNpAEO2O7aDnSVy3JsCMjHgjXD LPak5xvTueOt4wvNr57mEag0CGSsooU36UgcPMMHG3azoLgHCuochCaV0nFhZ3jlDVxQ k2wcxMssLrMwrw1lVdlxmKHvrLPCoWETcUEhhXYd6wJua3Om4icN2bKxl3gQckFe0uWZ ulWJM5zEeG5QpQgpY45uQdHswekR9uYBhb9eUzlHVoyFa/RyHAurIbfYByzdgE0G2y/4 09WQ== Content-Disposition: inline In-Reply-To: <20180109152112.GT9671@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: "Paul E. McKenney" Cc: Prateek Sood , Peter Zijlstra , avagin@gmail.com, mingo@kernel.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, sramana@codeaurora.org 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 Thanks. -- tejun