From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753926Ab0IWI6d (ORCPT ); Thu, 23 Sep 2010 04:58:33 -0400 Received: from hera.kernel.org ([140.211.167.34]:59307 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752124Ab0IWI6c (ORCPT ); Thu, 23 Sep 2010 04:58:32 -0400 Message-ID: <4C9B168A.9000702@kernel.org> Date: Thu, 23 Sep 2010 10:57:46 +0200 From: Tejun Heo User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); en-US; rv:1.9.2.9) Gecko/20100915 Lightning/1.0b2 Thunderbird/3.1.4 MIME-Version: 1.0 To: Linus Torvalds , lkml , CAI Qian Subject: [GIT PULL] percpu: fixes for v2.6.36-rc5 X-Enigmail-Version: 1.1.1 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Thu, 23 Sep 2010 08:57:47 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Linus. Please pull from the following branch to receive a percpu fix for v2.6.36-rc5. git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu.git for-linus It contains only one patch to fix incorrect pcpu_last_unit_cpu initialization. When the number of possible CPUs isn't power of two, there can be unused holes at the end of each percpu chunk. Percpu init code uses NR_CPUS to mark these holes. pcpu_last_unit_cpu should contain the CPU which maps to the last unit in the chunk but when the above condition occurs, it contained NR_CPUS instead, which makes percpu code miscalculate the address range covered by a chunk for per_cpu_ptr_to_phys() and tlb and v[un]map flushses and has potential to cause weird issues especially on virtual cache architectures. This problem was discovered by CAI Qian during kvm kdump testing. Kudos to him for finding this subtle problem. Thanks. Tejun Heo (1): percpu: fix pcpu_last_unit_cpu mm/percpu.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/mm/percpu.c b/mm/percpu.c index 58c572b..c76ef38 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -1401,9 +1401,9 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai, if (pcpu_first_unit_cpu == NR_CPUS) pcpu_first_unit_cpu = cpu; + pcpu_last_unit_cpu = cpu; } } - pcpu_last_unit_cpu = cpu; pcpu_nr_units = unit; for_each_possible_cpu(cpu)