From: Anton Blanchard Date: Mon, 3 Sep 2012 16:47:56 +0000 (+0000) Subject: powerpc: Update DSCR on all CPUs when writing sysfs dscr_default X-Git-Tag: firefly_0821_release~7541^2~221 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=1758e55fd05e042e873f6d54657552ee1730bb32;p=firefly-linux-kernel-4.4.55.git powerpc: Update DSCR on all CPUs when writing sysfs dscr_default 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 --- diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c index f0f2199e64e1..d62af950695b 100644 --- a/arch/powerpc/kernel/sysfs.c +++ b/arch/powerpc/kernel/sysfs.c @@ -192,6 +192,12 @@ static ssize_t show_dscr_default(struct sysdev_class *class, 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(struct sysdev_class *class, return -EINVAL; dscr_default = val; + on_each_cpu(update_dscr, NULL, 1); + return count; }