From 089f9fba56faf33cc6dd2a6442b7ac92c58b8209 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Mon, 16 Apr 2012 22:48:15 +0200 Subject: [PATCH] i387: ptrace breaks the lazy-fpu-restore logic Starting from 7e16838d "i387: support lazy restore of FPU state" we assume that fpu_owner_task doesn't need restore_fpu_checking() on the context switch, its FPU state should match what we already have in the FPU on this CPU. However, debugger can change the tracee's FPU state, in this case we should reset fpu.last_cpu to ensure fpu_lazy_restore() can't return true. Change init_fpu() to do this, it is called by user_regset->set() methods. Reported-by: Jan Kratochvil Suggested-by: Linus Torvalds Signed-off-by: Oleg Nesterov Link: http://lkml.kernel.org/r/20120416204815.GB24884@redhat.com Cc: v3.3 Signed-off-by: H. Peter Anvin --- arch/x86/kernel/i387.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c index 7734bcbb5a3a..2d6e6498c176 100644 --- a/arch/x86/kernel/i387.c +++ b/arch/x86/kernel/i387.c @@ -235,6 +235,7 @@ int init_fpu(struct task_struct *tsk) if (tsk_used_math(tsk)) { if (HAVE_HWFP && tsk == current) unlazy_fpu(tsk); + tsk->thread.fpu.last_cpu = ~0; return 0; } -- 2.39.5