From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:40998 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752065AbdFLUPG (ORCPT ); Mon, 12 Jun 2017 16:15:06 -0400 Received: from pps.filterd (m0098396.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v5CKDmHX142822 for ; Mon, 12 Jun 2017 16:15:06 -0400 Received: from e19.ny.us.ibm.com (e19.ny.us.ibm.com [129.33.205.209]) by mx0a-001b2d01.pphosted.com with ESMTP id 2b1w4rwfqn-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 12 Jun 2017 16:15:05 -0400 Received: from localhost by e19.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 12 Jun 2017 16:15:04 -0400 Date: Mon, 12 Jun 2017 13:15:03 -0700 From: "Paul E. McKenney" To: Greg KH Cc: pbonzini@redhat.com, linuc.decode@gmail.com, torvalds@linux-foundation.org, stable@vger.kernel.org Subject: Re: FAILED: patch "[PATCH] srcu: Allow use of Classic SRCU from both process and" failed to apply to 4.9-stable tree Reply-To: paulmck@linux.vnet.ibm.com References: <149726987911656@kroah.com> <20170612163151.GW3721@linux.vnet.ibm.com> <20170612191734.GB2114@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170612191734.GB2114@kroah.com> Message-Id: <20170612201503.GC3721@linux.vnet.ibm.com> Sender: stable-owner@vger.kernel.org List-ID: On Mon, Jun 12, 2017 at 09:17:34PM +0200, Greg KH wrote: > On Mon, Jun 12, 2017 at 09:31:51AM -0700, Paul E. McKenney wrote: > > On Mon, Jun 12, 2017 at 02:17:59PM +0200, gregkh@linuxfoundation.org wrote: > > > > > > The patch below does not apply to the 4.9-stable tree. > > > If someone wants it applied there, or to any other stable or longterm > > > tree, then please email the backport, including the original git commit > > > id to . > > > > Indeed, this won't apply cleanly to 4.9 and earlier because of some > > changes to the way SRCU works. And if you try to make the obvious > > adjustments to make the patch apply, you will break SRCU. > > Oh good, I was wondering about that, I thought I had backported it > properly, but then I figured I really don't know how rcu works in > detail, so decided to just punt and reject it :) If it makes you feel better, the reason I know that it breaks SRCU is because I backported the patches early this morning before I was fully awake. Fortunately, rcutorture protested vigorously, saying this about a 30-minute run: WARNING: Summary: Bugs: 3494 Call Traces: 3494 Paolo pointed out at least one of the additional patches that would have to be backported along with this one. If people start seeing failures on the older kernels, I will of course make sure that the backport happens. Thanx, Paul