path: root/arch
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authorAnton Blanchard <anton@samba.org>2012-09-03 16:48:46 +0000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2012-09-05 16:05:21 +1000
commit00ca0de02f80924dfff6b4f630e1dff3db005e35 (patch)
treec3e314e7804d634f926e319bf46ef101f777caf8 /arch
parent1b6ca2a6fe56e7697d57348646e07df08f43b1bb (diff)
powerpc: Keep thread.dscr and thread.dscr_inherit in sync
When we update the DSCR either via emulation of mtspr(DSCR) or via a change to dscr_default in sysfs we don't update thread.dscr. We will eventually update it at context switch time but there is a period where thread.dscr is incorrect. If we fork at this point we will copy the old value of thread.dscr into the child. To avoid this, always keep thread.dscr in sync with reality. This issue was found with the following testcase: http://ozlabs.org/~anton/junkcode/dscr_inherit_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>
Diffstat (limited to 'arch')
2 files changed, 5 insertions, 2 deletions
diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
index d4cbbd1fa75f..8302af649219 100644
--- a/arch/powerpc/kernel/sysfs.c
+++ b/arch/powerpc/kernel/sysfs.c
@@ -196,8 +196,10 @@ static ssize_t show_dscr_default(struct device *dev,
static void update_dscr(void *dummy)
- if (!current->thread.dscr_inherit)
+ if (!current->thread.dscr_inherit) {
+ current->thread.dscr = dscr_default;
mtspr(SPRN_DSCR, dscr_default);
+ }
static ssize_t __used store_dscr_default(struct device *dev,
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 158972341a2d..ae0843fa7a61 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -972,8 +972,9 @@ static int emulate_instruction(struct pt_regs *regs)
cpu_has_feature(CPU_FTR_DSCR)) {
PPC_WARN_EMULATED(mtdscr, regs);
rd = (instword >> 21) & 0x1f;
- mtspr(SPRN_DSCR, regs->gpr[rd]);
+ current->thread.dscr = regs->gpr[rd];
current->thread.dscr_inherit = 1;
+ mtspr(SPRN_DSCR, current->thread.dscr);
return 0;