linux-kernel - Re: [PATCH 1/3] x86/entry/64: Refactor IRQ stacks and make then NMI-safe

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Message-ID: <CALCETrXc9iagtEZQRDgu_-xA3e2ak5NVSeQ6WirsdpNteibTkg@mail.gmail.com>
Date:	Wed, 5 Aug 2015 11:32:08 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Ingo Molnar <mingo@...nel.org>, Andy Lutomirski <luto@...nel.org>,
	X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Brian Gerst <brgerst@...il.com>, Willy Tarreau <w@....eu>,
	Borislav Petkov <bp@...en8.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 1/3] x86/entry/64: Refactor IRQ stacks and make then NMI-safe

On Wed, Aug 5, 2015 at 11:27 AM, Steven Rostedt <rostedt@...dmis.org> wrote:
> On Wed, 5 Aug 2015 11:24:54 -0700
> Andy Lutomirski <luto@...capital.net> wrote:
>
>> On Wed, Aug 5, 2015 at 1:59 AM, Ingo Molnar <mingo@...nel.org> wrote:
>> >
>> > * Andy Lutomirski <luto@...nel.org> wrote:
>> >
>> >> --- a/arch/x86/kernel/process_64.c
>> >> +++ b/arch/x86/kernel/process_64.c
>> >> @@ -280,6 +280,10 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
>> >>       unsigned fsindex, gsindex;
>> >>       fpu_switch_t fpu_switch;
>> >>
>> >> +#ifdef CONFIG_DEBUG_ENTRY
>> >> +     WARN_ON(this_cpu_read(irq_count));
>> >> +#endif
>> >
>> > Please introduce a less noisy (to the eyes) version of this, something like:
>> >
>> >         WARN_ON_DEBUG_ENTRY(this_cpu_read(irq_count));
>> >
>> > or so, similar to WARN_ON_FPU().
>>
>> I can do that (or "DEBUG_ENTRY_WARN_ON"?  we seem to be inconsistent
>> about ordering).
>>
>> Or would if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) WARN_ON(...) be better?
>>
>
> Does WARN_ON(IS_ENABLED(CONFIG_DEBUG_ENTRY) && this_cpu_read(irq_count))
> work?

I'd be okay with it.  Ingo?

(Except that that line of code is from v1, and v2 looks slightly
different here, but that's beside the point.)

--Andy

>
> -- Steve



-- 
Andy Lutomirski
AMA Capital Management, LLC
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