From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [PATCH 2/2] x86/tbl/trace: Do not trace on CPU that is offline Date: Sat, 7 Feb 2015 14:14:07 -0800 Message-ID: <20150207221407.GF5418@linux.vnet.ibm.com> References: <20150206200653.009919583@goodmis.org> <20150206200800.689573476@goodmis.org> <20150206232754.GA17751@linux.vnet.ibm.com> <20150206230206.0733828d@grimm.local.home> <20150207102002.4edc054c@grimm.local.home> <20150207200948.GA5418@linux.vnet.ibm.com> <20150207165205.3d9d5cde@gandalf.local.home> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from e33.co.us.ibm.com ([32.97.110.151]:58374 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756069AbbBGWON (ORCPT ); Sat, 7 Feb 2015 17:14:13 -0500 Received: from /spool/local by e33.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sat, 7 Feb 2015 15:14:13 -0700 Content-Disposition: inline In-Reply-To: <20150207165205.3d9d5cde@gandalf.local.home> Sender: linux-next-owner@vger.kernel.org List-ID: To: Steven Rostedt Cc: Sedat Dilek , LKML , Dave Hansen , "Rafael J. Wysocki" , linux-next , Stephen Rothwell , Kristen Carlson Accardi , "H. Peter Anvin" , Rik van Riel , Mel Gorman , Andrew Morton On Sat, Feb 07, 2015 at 04:52:05PM -0500, Steven Rostedt wrote: > On Sat, 7 Feb 2015 12:09:48 -0800 > "Paul E. McKenney" wrote: > > > The tag sequence has the meaning of: > > git cherry-pick a1f84a3 > > git cherry-pick 1b9508f > > git cherry-pick fd21073 > > git cherry-pick > > > > Does that do what you need? > > Note, for this case it really doesn't apply, because one patch does not > depend on the other. > > The real bug is that a tracepoint can be called when RCU is not > watching (cpu is offline). That bug was introduced in 3.17 and is fixed > by patch 2 with the conditional trace event. > > When that bug was fixed, it showed that another bug exists. That is > that lockdep should not complain if the conditional prevents the bad > RCU from happening, and this bug was introduced in 3.18. This was fixed > by the first patch. > > They really are two entirely separate bugs, it just happens that the > test case Sedat had happened to trigger both of them. This is why I > really don't see why the two need to reference each other. > > I'm also going to modify patch 1 to not mention porting the other > commit (that patch 1 fixes) to 3.17 (from 3.18), as that other commit is > just a debugging tool and not something that satisfies being > backported, and the patch that fixes it shouldn't be backported to 3.17 > either, only to 3.18. Thank you for the explanation! I guess I needed to have kept a scorecard on this one. ;-) Thanx, Paul