From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754797Ab2IQA47 (ORCPT ); Sun, 16 Sep 2012 20:56:59 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:33928 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753957Ab2IQAv2 (ORCPT ); Sun, 16 Sep 2012 20:51:28 -0400 Message-Id: <20120917003631.247940408@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Mon, 17 Sep 2012 01:37:01 +0100 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Anton Blanchard , Benjamin Herrenschmidt Subject: [ 036/135] powerpc: Update DSCR on all CPUs when writing sysfs dscr_default In-Reply-To: <20120917003625.784119135@decadent.org.uk> X-SA-Exim-Connect-IP: 2001:470:1f08:1539:21c:bfff:fe03:f805 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2-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 [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- arch/powerpc/kernel/sysfs.c | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/arch/powerpc/kernel/sysfs.c +++ b/arch/powerpc/kernel/sysfs.c @@ -192,6 +192,12 @@ 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 sysdev_class *class, struct sysdev_class_attribute *attr, const char *buf, size_t count) @@ -204,6 +210,8 @@ static ssize_t __used store_dscr_default return -EINVAL; dscr_default = val; + on_each_cpu(update_dscr, NULL, 1); + return count; }