From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yk0-f169.google.com (mail-yk0-f169.google.com [209.85.160.169]) by kanga.kvack.org (Postfix) with ESMTP id 58F276B0038 for ; Wed, 18 Nov 2015 13:11:47 -0500 (EST) Received: by ykdr82 with SMTP id r82so78016616ykd.3 for ; Wed, 18 Nov 2015 10:11:47 -0800 (PST) Received: from mail-yk0-x22e.google.com (mail-yk0-x22e.google.com. [2607:f8b0:4002:c07::22e]) by mx.google.com with ESMTPS id q8si3707844ywb.43.2015.11.18.10.11.46 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 18 Nov 2015 10:11:46 -0800 (PST) Received: by ykdr82 with SMTP id r82so78016303ykd.3 for ; Wed, 18 Nov 2015 10:11:46 -0800 (PST) Date: Wed, 18 Nov 2015 13:11:42 -0500 From: Tejun Heo Subject: Re: [PATCH] writeback: initialize m_dirty to avoid compile warning Message-ID: <20151118181142.GC11496@mtj.duckdns.org> References: <1447439201-32009-1-git-send-email-yang.shi@linaro.org> <20151117153855.99d2acd0568d146c29defda5@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151117153855.99d2acd0568d146c29defda5@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Yang Shi , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linaro-kernel@lists.linaro.org Hello, On Tue, Nov 17, 2015 at 03:38:55PM -0800, Andrew Morton wrote: > > --- a/mm/page-writeback.c > > +++ b/mm/page-writeback.c > > @@ -1542,7 +1542,7 @@ static void balance_dirty_pages(struct address_space *mapping, > > for (;;) { > > unsigned long now = jiffies; > > unsigned long dirty, thresh, bg_thresh; > > - unsigned long m_dirty, m_thresh, m_bg_thresh; > > + unsigned long m_dirty = 0, m_thresh = 0, m_bg_thresh = 0; > > > > /* > > * Unstable writes are a feature of certain networked > > Adding runtime overhead to suppress a compile-time warning is Just > Wrong. > > With gcc-4.4.4 the above patch actually reduces page-writeback.o's > .text by 36 bytes, lol. With gcc-4.8.4 the patch saves 19 bytes. No > idea what's going on there... > > > And initializing locals in the above fashion can hide real bugs - > looky: 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. -- tejun -- 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