From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: linux-next: build warnings after merge of the akpm-current tree Date: Thu, 29 Aug 2013 12:42:08 -0700 Message-ID: <20130829124208.7b97594d8a8723d45d1bad34@linux-foundation.org> References: <20130829194741.ff75bb1ce06207d5d3a703de@canb.auug.org.au> <521F2F7E.8010702@parallels.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: Received: from mail.linuxfoundation.org ([140.211.169.12]:36213 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755556Ab3H2TmK (ORCPT ); Thu, 29 Aug 2013 15:42:10 -0400 In-Reply-To: <521F2F7E.8010702@parallels.com> Sender: linux-next-owner@vger.kernel.org List-ID: To: Maxim Patlasov Cc: Stephen Rothwell , linux-next@vger.kernel.org, linux-kernel@vger.kernel.org On Thu, 29 Aug 2013 15:24:46 +0400 Maxim Patlasov wrote: > Hi Stephen, > > 08/29/2013 01:47 PM, Stephen Rothwell __________: > > Hi Andrew, > > > > After merging the akpm tree, today's linux-next build (sparc64 defconfig > > and others) produced these warnings: > > > > mm/page-writeback.c: In function 'balance_dirty_pages_ratelimited': > > mm/page-writeback.c:1450:13: warning: 'bdi_thresh' may be used uninitialized in this function [-Wuninitialized] > > mm/page-writeback.c:1372:16: note: 'bdi_thresh' was declared here > > mm/page-writeback.c:1226:16: warning: 'bdi_dirty' may be used uninitialized in this function [-Wuninitialized] > > mm/page-writeback.c:1369:16: note: 'bdi_dirty' was declared here > > > > Possibly introduced by commit 34c547af1e23 ("mm/page-writeback.c: add > > strictlimit feature"), but I am not sure anything can be done about them. > > > > This looks as gcc glitch. So far as I didn't observe the warnings, the > version of gcc does matter. May be moving the definitions of the two > variables into for(;;){...} would help. Could you please give it a try? Shuffling the definitions around won't help. To fix this we'll need to add more code and I hate adding runtime overhead to address compile-time issues. So... --- a/mm/page-writeback.c~a +++ a/mm/page-writeback.c @@ -1366,10 +1366,8 @@ static void balance_dirty_pages(struct a { unsigned long nr_reclaimable; /* = file_dirty + unstable_nfs */ unsigned long nr_dirty; /* = file_dirty + writeback + unstable_nfs */ - unsigned long bdi_dirty; unsigned long background_thresh; unsigned long dirty_thresh; - unsigned long bdi_thresh; long period; long pause; long max_pause; @@ -1385,8 +1383,10 @@ static void balance_dirty_pages(struct a for (;;) { unsigned long now = jiffies; - unsigned long dirty; + unsigned long uninitialized_var(bdi_thresh); unsigned long thresh; + unsigned long uninitialized_var(bdi_dirty); + unsigned long dirty; unsigned long bg_thresh; /* _