Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752074AbaB1LcG (ORCPT ); Fri, 28 Feb 2014 06:32:06 -0500 Received: from merlin.infradead.org ([205.233.59.134]:53124 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751967AbaB1LcC (ORCPT ); Fri, 28 Feb 2014 06:32:02 -0500 Date: Fri, 28 Feb 2014 12:31:46 +0100 From: Peter Zijlstra To: "Aneesh Kumar K.V" Cc: benh@kernel.crashing.org, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Liu Ping Fan Subject: Re: [PATCH V3] mm: numa: bugfix for LAST_CPUPID_NOT_IN_PAGE_FLAGS Message-ID: <20140228113146.GJ27965@twins.programming.kicks-ass.net> References: <1393578122-6500-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1393578122-6500-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 28, 2014 at 02:32:02PM +0530, Aneesh Kumar K.V wrote: > From: Liu Ping Fan > > When doing some numa tests on powerpc, I triggered an oops bug. I find > it is caused by using page->_last_cpupid. It should be initialized as > "-1 & LAST_CPUPID_MASK", but not "-1". Otherwise, in task_numa_fault(), > we will miss the checking (last_cpupid == (-1 & LAST_CPUPID_MASK)). > And finally cause an oops bug in task_numa_group(), since the online cpu is > less than possible cpu. This happen with CONFIG_SPARSE_VMEMMAP disabled > > Signed-off-by: Liu Ping Fan > Signed-off-by: Aneesh Kumar K.V Acked-by: Peter Zijlstra > --- > > include/linux/mm.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index f28f46eade6a..86245839c9fa 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -757,7 +757,7 @@ static inline bool __cpupid_match_pid(pid_t task_pid, int cpupid) > #ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS > static inline int page_cpupid_xchg_last(struct page *page, int cpupid) > { > - return xchg(&page->_last_cpupid, cpupid); > + return xchg(&page->_last_cpupid, cpupid & LAST_CPUPID_MASK); > } > > static inline int page_cpupid_last(struct page *page) > @@ -766,7 +766,7 @@ static inline int page_cpupid_last(struct page *page) > } > static inline void page_cpupid_reset_last(struct page *page) > { > - page->_last_cpupid = -1; > + page->_last_cpupid = -1 & LAST_CPUPID_MASK; > } > #else > static inline int page_cpupid_last(struct page *page) > -- > 1.8.3.2 > -- 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/