From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751376Ab2DRF6h (ORCPT ); Wed, 18 Apr 2012 01:58:37 -0400 Received: from mail-lb0-f174.google.com ([209.85.217.174]:48445 "EHLO mail-lb0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750730Ab2DRF6g (ORCPT ); Wed, 18 Apr 2012 01:58:36 -0400 Message-ID: <4F8E5807.6080909@openvz.org> Date: Wed, 18 Apr 2012 09:58:31 +0400 From: Konstantin Khlebnikov User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.2) Gecko/20120217 Firefox/10.0.2 Iceape/2.7.2 MIME-Version: 1.0 To: Andrew Morton CC: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Mel Gorman Subject: Re: [PATCH linux-next] mm/hugetlb: fix warning in alloc_huge_page/dequeue_huge_page_vma References: <20120417122819.7438.26117.stgit@zurg> <20120417135726.05de2546.akpm@linux-foundation.org> In-Reply-To: <20120417135726.05de2546.akpm@linux-foundation.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andrew Morton wrote: > On Tue, 17 Apr 2012 16:28:19 +0400 > Konstantin Khlebnikov wrote: > >> This patch fixes gcc warning (and bug?) introduced in linux-next commit cc9a6c877 >> ("cpuset: mm: reduce large amounts of memory barrier related damage v3") >> >> Local variable "page" can be uninitialized if nodemask from vma policy does not >> intersects with nodemask from cpuset. Even if it wouldn't happens it's better to >> initialize this variable explicitly than to introduce kernel oops on weird corner case. >> >> mm/hugetlb.c: In function ___alloc_huge_page___: >> mm/hugetlb.c:1135:5: warning: ___page___ may be used uninitialized in this function >> >> ... >> >> --- a/mm/hugetlb.c >> +++ b/mm/hugetlb.c >> @@ -532,7 +532,7 @@ static struct page *dequeue_huge_page_vma(struct hstate *h, >> struct vm_area_struct *vma, >> unsigned long address, int avoid_reserve) >> { >> - struct page *page; >> + struct page *page = NULL; >> struct mempolicy *mpol; >> nodemask_t *nodemask; >> struct zonelist *zonelist; > > hm, that's a pretty blatant use-uninitialised bug. I wonder why so few > gcc versions report it. Mine doesn't. I'm using latest gcc-4.7 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/