From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757292AbaEPOh1 (ORCPT ); Fri, 16 May 2014 10:37:27 -0400 Received: from mail-qg0-f54.google.com ([209.85.192.54]:62170 "EHLO mail-qg0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756355AbaEPOhV (ORCPT ); Fri, 16 May 2014 10:37:21 -0400 Date: Fri, 16 May 2014 10:37:18 -0400 From: Tejun Heo To: Stephen Warren Cc: lizefan@huawei.com, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, "linux-tegra@vger.kernel.org" , ARM kernel mailing list Subject: Re: [PATCH 9/9] cgroup: use cgroup->self.refcnt for cgroup refcnting Message-ID: <20140516143718.GA5379@htj.dyndns.org> References: <1399670015-23463-1-git-send-email-tj@kernel.org> <1399670015-23463-10-git-send-email-tj@kernel.org> <53751062.2050401@wwwdotorg.org> <53753823.2090402@wwwdotorg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53753823.2090402@wwwdotorg.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Stephen. On Thu, May 15, 2014 at 03:56:51PM -0600, Stephen Warren wrote: > On 05/15/2014 01:07 PM, Stephen Warren wrote: > > On 05/09/2014 03:13 PM, Tejun Heo wrote: > >> Currently cgroup implements refcnting separately using atomic_t > >> cgroup->refcnt. The destruction paths of cgroup and css are rather > >> complex and bear a lot of similiarities including the use of RCU and > >> bouncing to a work item. > >> > >> This patch makes cgroup use the refcnt of self css for refcnting > >> instead of using its own. This makes cgroup refcnting use css's > >> percpu refcnt and share the destruction mechanism. > >> ... > > > > In next-20150515, this patch causes silent boot failures on NVIDIA Tegra > > ARM systems. There isn't even any earlyprintk. Reverting this one patch > > solves this. > > > > I was a bit surprised that cgroups would cause such an issue, but > > looking at a normal kernel boot, I guess cgroup does get initialized > > very early: > > > > Uncompressing Linux... done, booting the kernel. > > [ 0.000000] Booting Linux on physical CPU 0x0 > > [ 0.000000] Initializing cgroup subsys cpu > > [ 0.000000] Initializing cgroup subsys cpuacct > > > > Anyway, I'll try to track down what the problem is, but if someone > > familiar with this patch could give it a look, that'd be very useful, > > since I'm not at all familiar with this code or feature. > > It looks like this has something to do with the new code using percpu_ > functions from within cgroup_init_early, yet that function being called > before init/main.c calls setup_per_cpu_areas() etc.? Unfortunately I > have to run to some meetings now, so won't look at this until tomorrow. Yeap, I know where the issue is. Will post a fix soon. Thanks. -- tejun