linux-kernel - Re: [PATCH -rt 1/4] x86_64: send NMI after nmi_show

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Message-ID: <Pine.LNX.4.58.0804281457330.4615@gandalf.stny.rr.com>
Date:	Mon, 28 Apr 2008 15:00:36 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org
Subject: Re: [PATCH -rt 1/4] x86_64: send NMI after nmi_show_regs on



On Mon, 28 Apr 2008, Hiroshi Shimamoto wrote:
> diff --git a/arch/x86/kernel/nmi_64.c b/arch/x86/kernel/nmi_64.c
> index d187ab9..69cc737 100644
> --- a/arch/x86/kernel/nmi_64.c
> +++ b/arch/x86/kernel/nmi_64.c
> @@ -327,11 +327,11 @@ void nmi_show_all_regs(void)
>  	if (system_state == SYSTEM_BOOTING)
>  		return;
>
> -	smp_send_nmi_allbutself();
> -
>  	for_each_online_cpu(i)
>  		nmi_show_regs[i] = 1;

Hi Hiroshi,

I know this wasn't your code to begin with but, how does this function
exit?  I mean, we set an array where each index per online cpu is set to
one, then do an "nmi_allbutself", and then wait on those indexes to turn
zero, one at a time.  If we are CPU 0 here, we set that index to 1, then
enter the loop, and will block forever on this "while" loop below.

Am I missing something?

Thanks,

-- Steve



> +	smp_send_nmi_allbutself();
> +
>  	for_each_online_cpu(i) {
>  		while (nmi_show_regs[i] == 1)
>  			barrier();
> --
> 1.5.4.1
>
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