From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752955Ab0IXQwZ (ORCPT ); Fri, 24 Sep 2010 12:52:25 -0400 Received: from kroah.org ([198.145.64.141]:38397 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932710Ab0IXQ2d (ORCPT ); Fri, 24 Sep 2010 12:28:33 -0400 X-Mailbox-Line: From gregkh@clark.site Fri Sep 24 09:26:18 2010 Message-Id: <20100924162618.880742629@clark.site> User-Agent: quilt/0.48-11.2 Date: Fri, 24 Sep 2010 09:24:34 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Tejun Heo Subject: [46/80] percpu: fix pcpu_last_unit_cpu In-Reply-To: <20100924162706.GA7381@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.35-stable review patch. If anyone has any objections, please let us know. ------------------ From: Tejun Heo commit 46b30ea9bc3698bc1d1e6fd726c9601d46fa0a91 upstream. pcpu_first/last_unit_cpu are used to track which cpu has the first and last units assigned. This in turn is used to determine the span of a chunk for man/unmap cache flushes and whether an address belongs to the first chunk or not in per_cpu_ptr_to_phys(). When the number of possible CPUs isn't power of two, a chunk may contain unassigned units towards the end of a chunk. The logic to determine pcpu_last_unit_cpu was incorrect when there was an unused unit at the end of a chunk. It failed to ignore the unused unit and assigned the unused marker NR_CPUS to pcpu_last_unit_cpu. This was discovered through kdump failure which was caused by malfunctioning per_cpu_ptr_to_phys() on a kvm setup with 50 possible CPUs by CAI Qian. Signed-off-by: Tejun Heo Reported-by: CAI Qian Signed-off-by: Greg Kroah-Hartman --- mm/percpu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/percpu.c +++ b/mm/percpu.c @@ -1413,9 +1413,9 @@ int __init pcpu_setup_first_chunk(const 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)