From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f54.google.com (mail-pa0-f54.google.com [209.85.220.54]) by kanga.kvack.org (Postfix) with ESMTP id 073266B0255 for ; Wed, 18 Nov 2015 13:57:04 -0500 (EST) Received: by padhx2 with SMTP id hx2so53111511pad.1 for ; Wed, 18 Nov 2015 10:57:03 -0800 (PST) Received: from mail-pa0-x22e.google.com (mail-pa0-x22e.google.com. [2607:f8b0:400e:c03::22e]) by mx.google.com with ESMTPS id c15si6156776pbu.93.2015.11.18.10.57.03 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 18 Nov 2015 10:57:03 -0800 (PST) Received: by padhx2 with SMTP id hx2so53111299pad.1 for ; Wed, 18 Nov 2015 10:57:03 -0800 (PST) Message-ID: <564CC9FD.3080307@linaro.org> Date: Wed, 18 Nov 2015 10:57:01 -0800 From: "Shi, Yang" MIME-Version: 1.0 Subject: Re: [PATCH] writeback: initialize m_dirty to avoid compile warning References: <1447439201-32009-1-git-send-email-yang.shi@linaro.org> <20151117153855.99d2acd0568d146c29defda5@linux-foundation.org> <20151118181142.GC11496@mtj.duckdns.org> <564CC314.1090904@linaro.org> <20151118183344.GD11496@mtj.duckdns.org> <564CC5DB.8000104@linaro.org> <20151118105517.2947aaa2.akpm@linux-foundation.org> In-Reply-To: <20151118105517.2947aaa2.akpm@linux-foundation.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Tejun Heo , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linaro-kernel@lists.linaro.org On 11/18/2015 10:55 AM, Andrew Morton wrote: > On Wed, 18 Nov 2015 10:39:23 -0800 "Shi, Yang" wrote: > >> On 11/18/2015 10:33 AM, Tejun Heo wrote: >>> Hello, >>> >>> On Wed, Nov 18, 2015 at 10:27:32AM -0800, Shi, Yang wrote: >>>>> This was the main reason the code was structured the way it is. If >>>>> cgroup writeback is not enabled, any derefs of mdtc variables should >>>>> trigger warnings. Ugh... I don't know. Compiler really should be >>>>> able to tell this much. >>>> >>>> Thanks for the explanation. It sounds like a compiler problem. >>>> >>>> If you think it is still good to cease the compile warning, maybe we could >>> >>> If this is gonna be a problem with new gcc versions, I don't think we >>> have any other options. :( >>> >>>> just assign it to an insane value as what Andrew suggested, maybe >>>> 0xdeadbeef. >>> >>> I'd just keep it at zero. Whatever we do, the effect is gonna be >>> difficult to track down - it's not gonna blow up in an obvious way. >>> Can you please add a comment tho explaining that this is to work >>> around compiler deficiency? >> >> Sure. >> >> Other than this, in v2, I will just initialize m_dirty since compiler >> just reports it is uninitialized. > > gcc-4.4.4 and gcc-4.8.4 warn about all three variables. It sounds 5.x is smarter :-) > > > --- a/mm/page-writeback.c~writeback-initialize-m_dirty-to-avoid-compile-warning-fix > +++ a/mm/page-writeback.c > @@ -1542,7 +1542,9 @@ static void balance_dirty_pages(struct a > for (;;) { > unsigned long now = jiffies; > unsigned long dirty, thresh, bg_thresh; > - unsigned long m_dirty = 0, m_thresh = 0, m_bg_thresh = 0; > + unsigned long m_dirty = 0; /* stop bogus uninit warnings */ > + unsigned long m_thresh = 0; > + unsigned long m_bg_thresh = 0; Still need v2? Thanks, Yang > > /* > * Unstable writes are a feature of certain networked > _ > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org