From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753865AbcAGUwT (ORCPT ); Thu, 7 Jan 2016 15:52:19 -0500 Received: from e31.co.us.ibm.com ([32.97.110.149]:48913 "EHLO e31.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753757AbcAGUwQ (ORCPT ); Thu, 7 Jan 2016 15:52:16 -0500 X-IBM-Helo: d03dlp01.boulder.ibm.com X-IBM-MailFrom: paulmck@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org;linux-next@vger.kernel.org Date: Thu, 7 Jan 2016 12:52:20 -0800 From: "Paul E. McKenney" To: Stephen Rothwell Cc: linux-next@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: linux-next: build failure after merge of the rcu tree Message-ID: <20160107205220.GU3818@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20160107195725.3a130b4d@canb.auug.org.au> <20160107180244.GR3818@linux.vnet.ibm.com> <20160108071932.060a9bcc@canb.auug.org.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160108071932.060a9bcc@canb.auug.org.au> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16010720-8236-0000-0000-000014F94A50 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 08, 2016 at 07:19:32AM +1100, Stephen Rothwell wrote: > Hi Paul, > > On Thu, 7 Jan 2016 10:02:44 -0800 "Paul E. McKenney" wrote: > > > > On Thu, Jan 07, 2016 at 07:57:25PM +1100, Stephen Rothwell wrote: > > > Hi Paul, > > > > > > [I found this a few days ago, but I think I forgot to send the email, > > > sorry.] > > > > > > After merging the rcu tree, today's linux-next build (powerpc > > > allyesconfig) failed like this: > > > > > > kernel/rcu/rcuperf.o:(.discard+0x0): multiple definition of `__pcpu_unique_srcu_ctl_srcu_array' > > > kernel/rcu/rcutorture.o:(.discard+0x0): first defined here > > > > > > Caused by commit > > > > > > abcd7ec0808e ("rcutorture: Add RCU grace-period performance tests") > > > > > > I have reverted that commit for today. > > > > Hello, Stephen, > > > > Very strange. The "static" keyword does not mean anything here? > > Easy enough to use different symbols in the two different files, > > but this situation is not so good for information hiding. > > > > Happy to update rcuperf.c to use a different name, but in the > > immortal words of MSDOS, "Are you sure?" :-) > > I have no idea why it happens, but I do get the error above unless I > revert that commit. So, yes, I am sure :-) > > OK, I looked further and > > DEFINE_STATIC_SRCU(srcu_ctl); > > becomes this (NLs added for clarity): > > static __attribute__((section(".discard"), unused)) char __pcpu_scope_srcu_ctl_srcu_array; > extern __attribute__((section(".discard"), unused)) char __pcpu_unique_srcu_ctl_srcu_array; > __attribute__((section(".discard"), unused)) char __pcpu_unique_srcu_ctl_srcu_array; > extern __attribute__((section(".data..percpu" ""))) __typeof__(struct srcu_struct_array) srcu_ctl_srcu_array; > __attribute__((section(".data..percpu" ""))) __attribute__((weak)) __typeof__(struct srcu_struct_array) srcu_ctl_srcu_array; > static struct srcu_struct srcu_ctl = { > . > . > }; > > So, the "static" is not very effective :-( Oddly enough, this appears to be toolchain dependent. No idea why. Here is a patch that I will be merging in. Thanx, Paul ------------------------------------------------------------------------ commit d81f900405de0dc6152692a2088258b8b35d740d Author: Paul E. McKenney Date: Thu Jan 7 12:39:10 2016 -0800 Merge with abcd7ec0808e (rcutorture: Add RCU grace-period performance tests) Signed-off-by: Paul E. McKenney diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c index eef82a9460d8..4c8d99aa4f5e 100644 --- a/kernel/rcu/rcuperf.c +++ b/kernel/rcu/rcuperf.c @@ -188,8 +188,8 @@ static struct rcu_perf_ops rcu_bh_ops = { * Definitions for srcu perf testing. */ -DEFINE_STATIC_SRCU(srcu_ctl); -static struct srcu_struct *srcu_ctlp = &srcu_ctl; +DEFINE_STATIC_SRCU(srcu_ctl_perf); +static struct srcu_struct *srcu_ctlp = &srcu_ctl_perf; static int srcu_perf_read_lock(void) __acquires(srcu_ctlp) {