Re: [PATCH 4/6] x86,fpu: use disable_task_lazy_fpu_restore helper

[Rik van Riel]

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On 02/02/2015 02:21 PM, Oleg Nesterov wrote:
> I'll try to read this patch tomorrow. Too late for me.
> 
> I think it is fine, but
> 
> On 02/02, riel@xxxxxxxxxx wrote:
>> 
>> This also fixes the lazy FPU restore disabling in drop_fpu,
>> which only really works when !use_eager_fpu(). ...
>> 
>> --- a/arch/x86/include/asm/fpu-internal.h +++
>> b/arch/x86/include/asm/fpu-internal.h @@ -396,7 +396,7 @@ static
>> inline void drop_fpu(struct task_struct *tsk) * Forget
>> coprocessor state.. */ preempt_disable(); -
>> tsk->thread.fpu_counter = 0; +
>> task_disable_lazy_fpu_restore(tsk); __drop_fpu(tsk); 
>> clear_used_math();
> 
> perhaps this makes sense anyway, but I am not sure if the changelog
> is right.
> 
> Note that we clear PF_USED_MATH, last_fpu/has_fpu have no effect
> after this.

After a few days on the RCU code, I'm back to this :)

You are right, I should drop the change above from the patch,
and disable lazy fpu restore explicitly in places where we
need it.

I will send a v2 of these patches, without patch 6/6.

Ingo, would you like me to also re-send Oleg's FPU patches that are
not in -tip yet?

- -- 
All rights reversed
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