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SubjectRe: Perf: WARNING: arch/x86/entry/common.c:624 idtentry_exit_cond_rcu+0x92/0xc0
Date
Andy Lutomirski <luto@amacapital.net> writes:
>> On Jun 12, 2020, at 2:01 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
>> There is no IST on 32bit, never was. We do software stack switching for
>> device interrupts, but that's a different story.
>>
>
> DEFINE_IDTENTRY does the idtentry_enter_cond_rcu() dance, which isn’t
> intended to be safe from NMI context. It should probably map to
> DEFINE_IDTENTRY_RAW() instead. The specific issue is that NMI ends up
> there, and at least DEFINE_IDTENTRY_NMI should be raw.

Yes, you are right. That's clearly broken.

> I haven’t tried this at all, nor have I dug through all the users of
> these macros to check what they expect. Perhaps we should not have
> the _IST one defined at all on 32 bit and rename it to
> DEFINE_IDTENTRY_IST_RAW on 64 bit to make it more clear what’s going
> on when reading the C code.

Let me go over it with a fine comb.

> Or maybe I’m too sleepy and I’m nuts. But I don’t think I am.

/me politely refrains from commenting

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