powerpc: Update DSCR on all CPUs when writing sysfs dscr_default

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 <[email protected]> Cc: <[email protected]> # 3.0+ Signed-off-by: Benjamin Herrenschmidt <[email protected]>
dokyukim · Sep 5, 2012 · 1b6ca2a · 1b6ca2a
1 parent 375f561
commit 1b6ca2a
Showing 1 changed file with 8 additions and 0 deletions.
diff --git 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;
 }