powerpc: Fix DSCR inheritance in copy_thread()
If the default DSCR is non zero we set thread.dscr_inherit in
copy_thread() meaning the new thread and all its children will ignore
future updates to the default DSCR. This is not intended and is
a change in behaviour that a number of our users have hit.
We just need to inherit thread.dscr and thread.dscr_inherit from
the parent which ends up being much simpler.
This was found with the following test case:
http://ozlabs.org/~anton/junkcode/dscr_default_test.c
Signed-off-by: Anton Blanchard <anton@samba.org>
Cc: <stable@kernel.org> # 3.0+
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 710f400..1a1f2dd 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -802,16 +802,8 @@
#endif /* CONFIG_PPC_STD_MMU_64 */
#ifdef CONFIG_PPC64
if (cpu_has_feature(CPU_FTR_DSCR)) {
- if (current->thread.dscr_inherit) {
- p->thread.dscr_inherit = 1;
- p->thread.dscr = current->thread.dscr;
- } else if (0 != dscr_default) {
- p->thread.dscr_inherit = 1;
- p->thread.dscr = dscr_default;
- } else {
- p->thread.dscr_inherit = 0;
- p->thread.dscr = 0;
- }
+ p->thread.dscr_inherit = current->thread.dscr_inherit;
+ p->thread.dscr = current->thread.dscr;
}
#endif