diff options
authorAnton Blanchard <>2012-09-03 16:47:56 +0000
committerGreg Kroah-Hartman <>2012-09-14 10:00:22 -0700
commit652f43702b224351b790fd9182744d7946d4cdf6 (patch)
parenta9959bb7e1510edb3326beb354e59da0a6a0dab1 (diff)
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: Signed-off-by: Anton Blanchard <> Signed-off-by: Benjamin Herrenschmidt <> Signed-off-by: Greg Kroah-Hartman <>
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
index 3529446c2ab..d4cbbd1fa75 100644
--- a/arch/powerpc/kernel/sysfs.c
+++ b/arch/powerpc/kernel/sysfs.c
@@ -194,6 +194,12 @@ static ssize_t show_dscr_default(struct device *dev,
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(struct device *dev,
return -EINVAL;
dscr_default = val;
+ on_each_cpu(update_dscr, NULL, 1);
return count;