Re: [PATCH] sched/x86: Save [ER]FLAGS on context switch

Andy Lutomirski
2019-02-15T18:28:13Z

> On Feb 15, 2019, at 9:40 AM, Peter Zijlstra <peterz@infradead.org> wrote:
>
>> On Fri, Feb 15, 2019 at 09:18:00AM -0800, Linus Torvalds wrote:
>>> On Thu, Feb 14, 2019 at 11:34 AM Peter Zijlstra <peterz@infradead.org> wrote:
>>>
>>> Something like the below, right?
>>>
>>> + frame->flags = 0;
>>> + frame->flags = 0;
>>
>> Those are not valid flag values.
>>
>> Can you popf them? Yes.
>>
>> Do they make sense? No.
>>
>> It has the IF flag clear, for example. Is that intentional? If it is,
>
> Uhmm. yeah, that's bonkers. We should have interrupts disabled here.
> I'll go read up on the eflags and figure out what they _should_ be right
> about there.

And probably add a comment near the POPF explaining that it will keep IRQs off :)