Messages in this thread Patch in this message | | | Date | Tue, 13 Jan 2015 11:57:41 -0500 | From | Rik van Riel <> | Subject | Re: [RFC PATCH 05/11] x86,fpu: ensure FPU state is reloaded from memory if task is traced |
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On 01/13/2015 11:50 AM, Oleg Nesterov wrote: > On 01/13, Rik van Riel wrote: >> >>>> @@ -412,8 +412,14 @@ static inline void >>>> switch_fpu_prepare(struct task_struct *old, struct task_struc >>>> bool preload = tsk_used_math(new) && (use_eager_fpu() || >>>> new->thread.fpu_counter >>>>> 5); if (__thread_has_fpu(old)) { - if >>>>> (!__save_init_fpu(old)) >>>> + /* + * Make sure the FPU state is restored from memory >>>> next time, + * if the task has an FPU exception pending, or >>>> the task's in + * memory FPU state could be changed by a >>>> debugger. + */ + if (!__save_init_fpu(old) || >>>> task_is_stopped_or_traced(old)) cpu = ~0; >>> >>> Well, if debugger wants to change FPU state, it should call >>> init_fpu() which resets .last_cpu ? >> >> Does the ptrace (and utrace, and ... ) code actually do that? > > Yes, see xfpregs_get/set. So I think this change is not needed (but > I didn't look at the next patches).
Excellent, I will drop this then.
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