From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933314AbcASWRN (ORCPT ); Tue, 19 Jan 2016 17:17:13 -0500 Received: from mail-pa0-f54.google.com ([209.85.220.54]:33277 "EHLO mail-pa0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933070AbcASWRF (ORCPT ); Tue, 19 Jan 2016 17:17:05 -0500 Date: Tue, 19 Jan 2016 14:17:03 -0800 (PST) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: "Kirill A. Shutemov" cc: Arnd Bergmann , Andrew Morton , Ebru Akagunduz , dan.carpenter@oracle.com, linux-mm@kvack.org, Linus Torvalds , "Kirill A. Shutemov" , Rik van Riel , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] mm: avoid uninitialized variable in tracepoint In-Reply-To: <20160118230324.GF14531@node.shutemov.name> Message-ID: References: <4117363.Ys1FTDH7Wz@wuerfel> <20160118230324.GF14531@node.shutemov.name> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 19 Jan 2016, Kirill A. Shutemov wrote: > > A newly added tracepoint in the hugepage code uses a variable in the > > error handling that is not initialized at that point: > > > > include/trace/events/huge_memory.h:81:230: error: 'isolated' may be used uninitialized in this function [-Werror=maybe-uninitialized] > > > > The result is relatively harmless, as the trace data will in rare > > cases contain incorrect data. > > > > This works around the problem by adding an explicit initialization. > > > > Signed-off-by: Arnd Bergmann > > Fixes: 7d2eba0557c1 ("mm: add tracepoint for scanning pages") > > There's the same patch in mm tree, but it got lost on the way to Linus' > tree: > > https://ozlabs.org/~akpm/mmots/broken-out/mm-make-optimistic-check-for-swapin-readahead-fix.patch > > Andrew? > Looks like the patch got the wrong title, mm-make-optimistic-check-for-swapin-readahead-fix.patch, since the subject is "khugepaged: avoid usage of uninitialized variable 'isolated'". Anyway, feel free to add Acked-by: David Rientjes to either patch. > > > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > > index b2db98136af9..bb3b763b1829 100644 > > --- a/mm/huge_memory.c > > +++ b/mm/huge_memory.c > > @@ -2320,7 +2320,7 @@ static void collapse_huge_page(struct mm_struct *mm, > > pgtable_t pgtable; > > struct page *new_page; > > spinlock_t *pmd_ptl, *pte_ptl; > > - int isolated, result = 0; > > + int isolated = 0, result = 0; > > unsigned long hstart, hend; > > struct mem_cgroup *memcg; > > unsigned long mmun_start; /* For mmu_notifiers */ > >