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SubjectRe: Perf: WARNING: arch/x86/entry/common.c:624 idtentry_exit_cond_rcu+0x92/0xc0
Date
Andy Lutomirski <luto@kernel.org> writes:
> On Thu, Jun 11, 2020 at 4:22 PM Andy Lutomirski <luto@kernel.org> wrote:
>
> Two bugs here.
>
> 1. We had an issue with WARN. Patch sent.

Grabbed it

> 2. idtentry.h has, for x86_32:
>
> # define DEFINE_IDTENTRY_IST DEFINE_IDTENTRY
>
> This is nonsense. It's getting late over here and I'd rather focus on
> the more interesting RCU issue, so that's all from me today.

Well, this might be nonsense, but it's exactly matching the current code
in mainline which, e.g. for #DB does:

SYM_CODE_START(debug)
/*
* Entry from sysenter is now handled in common_exception
*/
ASM_CLAC
pushl $0
pushl $do_debug
jmp common_exception
SYM_CODE_END(debug)

There is no IST on 32bit, never was. We do software stack switching for
device interrupts, but that's a different story.

Thanks,

tglx

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