commit: 089f9fba56faf33cc6dd2a6442b7ac92c58b8209 From: Oleg Nesterov <[email protected]> Date: Mon, 16 Apr 2012 22:48:15 +0200 Subject: 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 <[email protected]> Suggested-by: Linus Torvalds <[email protected]> Signed-off-by: Oleg Nesterov <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Cc: <[email protected]> v3.3 Signed-off-by: H. Peter Anvin <[email protected]> --- arch/x86/kernel/i387.c | 1 + 1 files changed, 1 insertions(+), 0 deletions(-) diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c index 7734bcb..2d6e649 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; } -- 1.7.3.4 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
