| Date | Tue, 13 Jan 2015 11:33:46 -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 11:19 AM, Oleg Nesterov wrote: > On 01/11, riel@redhat.com 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?
> Plus "is_stopped" is not needed, ptracer no longer can do STOPPED > -> TRACED transition.
I will remove _is_stopped.
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