From 00ca0de02f80924dfff6b4f630e1dff3db005e35 Mon Sep 17 00:00:00 2001 From: Anton Blanchard Date: Mon, 3 Sep 2012 16:48:46 +0000 Subject: 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 Cc: # 3.0+ Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/kernel/traps.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'arch/powerpc/kernel/traps.c') 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; } #endif -- cgit v1.2.3