From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from youngberry.canonical.com ([91.189.89.112]:43989 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753666AbcCNSOX (ORCPT ); Mon, 14 Mar 2016 14:14:23 -0400 Date: Mon, 14 Mar 2016 18:14:18 +0000 From: Luis Henriques To: Steven Rostedt Cc: gregkh@linuxfoundation.org, sudeep.holla@arm.com, stable@vger.kernel.org, stable-commits@vger.kernel.org Subject: Re: Patch "tracing: Fix check for cpu online when event is disabled" has been added to the 3.10-stable tree Message-ID: <20160314181418.GB18730@charon.olymp> References: <145776624055166@kroah.com> <20160314171852.GA13407@charon.olymp> <20160314132527.1195cde7@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20160314132527.1195cde7@gandalf.local.home> Sender: stable-owner@vger.kernel.org List-ID: On Mon, Mar 14, 2016 at 01:25:27PM -0400, Steven Rostedt wrote: > On Mon, 14 Mar 2016 17:18:52 +0000 > Luis Henriques wrote: > > > On Fri, Mar 11, 2016 at 11:04:00PM -0800, Greg Kroah-Hartman wrote: > > > > > > This is a note to let you know that I've just added the patch titled > > > > > > tracing: Fix check for cpu online when event is disabled > > > > > > to the 3.10-stable tree which can be found at: > > > http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary > > > > > > The filename of the patch is: > > > tracing-fix-check-for-cpu-online-when-event-is-disabled.patch > > > and it can be found in the queue-3.10 subdirectory. > > > > > > If you, or anyone else, feels it should not be added to the stable tree, > > > please let know about it. > > > > > > > Please note that this patch was tagged for stable 3.18+. > > > > Correct. That's because: > > > > > > > Commit f37755490fe9b ("tracepoints: Do not trace when cpu is offline") added > > > a check to make sure that tracepoints only get called when the cpu is > > > online, as it uses rcu_read_lock_sched() for protection. > > This was added much earlier and fixes a real bug in various places. > > > > > > > Commit 3a630178fd5f3 ("tracing: generate RCU warnings even when tracepoints > > > are disabled") added lockdep checks (including rcu checks) for events that > > > are not enabled to catch possible RCU issues that would only be triggered if > > > a trace event was enabled. Commit f37755490fe9b only stopped the warnings > > > when the trace event was enabled but did not prevent warnings if the trace > > > event was called when disabled. > > The above wasn't added till 3.18, which warns when the trace event is > not enabled. With the backported patch, it now triggers false warnings. > But the false warnings wont exist before 3.18. > > It doesn't hurt to backport this patch further, it's just not > necessary, unless 3a630178fd5f3 was backported too. Was it? > > -- Steve > Thanks for clarifying, Steve. I don't think commit 3a630178fd5f3 has been backport to stable kernels, so if you're saying it doesn't hurt to backport dc17147de328 I guess that's up to the stable maintainers to include it or not. Thanks! Cheers, -- Lu�s