From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754793Ab1KUVK5 (ORCPT ); Mon, 21 Nov 2011 16:10:57 -0500 Received: from mail-vx0-f174.google.com ([209.85.220.174]:42248 "EHLO mail-vx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752787Ab1KUVK4 (ORCPT ); Mon, 21 Nov 2011 16:10:56 -0500 Date: Mon, 21 Nov 2011 13:10:50 -0800 From: Tejun Heo To: Dave Young Cc: tim@edgecast.com, WANG Cong , kexec@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] percpu: fix chunk range calculation Message-ID: <20111121211050.GK25776@google.com> References: <1321467647.2137.4.camel@boudreau> <4EC47FCA.5090908@redhat.com> <4EC491B3.705@redhat.com> <4EC4B60C.3030706@redhat.com> <1321548033.12208.12.camel@boudreau> <4EC61AB6.4090808@redhat.com> <4EC61B2A.7010000@redhat.com> <20111118185535.GA27152@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20111118185535.GA27152@google.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 18, 2011 at 10:55:35AM -0800, Tejun Heo wrote: > Percpu allocator recorded the cpus which map to the first and last > units in pcpu_first/last_unit_cpu respectively and used them to > determine the address range of a chunk - e.g. it assumed that the > first unit has the lowest address in a chunk while the last unit has > the highest address. > > This simply isn't true. Groups in a chunk can have arbitrary positive > or negative offsets from the previous one and there is no guarantee > that the first unit occupies the lowest offset while the last one the > highest. > > Fix it by actually comparing unit offsets to determine cpus occupying > the lowest and highest offsets. Also, rename pcu_first/last_unit_cpu > to pcpu_low/high_unit_cpu to avoid confusion. > > The chunk address range is used to flush cache on vmalloc area > map/unmap and decide whether a given address is in the first chunk by > per_cpu_ptr_to_phys() and the bug was discovered by invalid > per_cpu_ptr_to_phys() translation for crash_note. > > Kudos to Dave Young for tracking down the problem. > > Signed-off-by: Tejun Heo > Reported-by: WANG Cong > Reported-by: Dave Young > LKML-Reference: <4EC21F67.10905@redhat.com> > Cc: stable @kernel.org BTW, waiting for Tested-by. If someone gives me that, I'll push it through percpu/for-fixes. Thanks. -- tejun