From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756169Ab2ILXea (ORCPT ); Wed, 12 Sep 2012 19:34:30 -0400 Received: from mail-oa0-f46.google.com ([209.85.219.46]:59246 "EHLO mail-oa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756140Ab2ILXeZ (ORCPT ); Wed, 12 Sep 2012 19:34:25 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg KH , Anton Blanchard , Benjamin Herrenschmidt Subject: [ 078/108] powerpc: Update DSCR on all CPUs when writing sysfs dscr_default Date: Wed, 12 Sep 2012 16:29:16 -0700 Message-Id: <20120912232458.687292206@linuxfoundation.org> X-Mailer: git-send-email 1.7.10.1.362.g242cab3 In-Reply-To: <20120912232450.500619493@linuxfoundation.org> References: <20120912232816.GA1655@kroah.com> <20120912232450.500619493@linuxfoundation.org> User-Agent: quilt/0.60-2.1.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Greg KH 3.5-stable review patch. If anyone has any objections, please let me know. ------------------ From: Anton Blanchard commit 1b6ca2a6fe56e7697d57348646e07df08f43b1bb upstream. Writing to dscr_default in sysfs doesn't actually change the DSCR - we rely on a context switch on each CPU to do the work. There is no guarantee we will get a context switch in a reasonable amount of time so fire off an IPI to force an immediate change. This issue was found with the following test case: http://ozlabs.org/~anton/junkcode/dscr_explicit_test.c Signed-off-by: Anton Blanchard Signed-off-by: Benjamin Herrenschmidt Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/kernel/sysfs.c | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/arch/powerpc/kernel/sysfs.c +++ b/arch/powerpc/kernel/sysfs.c @@ -194,6 +194,12 @@ static ssize_t show_dscr_default(struct return sprintf(buf, "%lx\n", dscr_default); } +static void update_dscr(void *dummy) +{ + if (!current->thread.dscr_inherit) + mtspr(SPRN_DSCR, dscr_default); +} + static ssize_t __used store_dscr_default(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) @@ -206,6 +212,8 @@ static ssize_t __used store_dscr_default return -EINVAL; dscr_default = val; + on_each_cpu(update_dscr, NULL, 1); + return count; }