From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , alan@lxorguk.ukuu.org.uk, Anton Blanchard , Benjamin Herrenschmidt , Haren Myneni Subject: [ 21/22] powerpc: Update DSCR on all CPUs when writing sysfs dscr_default Date: Fri, 14 Dec 2012 14:26:06 -0800 Message-Id: <20121214222254.729285780@linuxfoundation.org> In-Reply-To: <20121214222249.889051473@linuxfoundation.org> References: <20121214222249.889051473@linuxfoundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.0-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: Haren Myneni 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 @@ -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; }