linux-kernel - Re: [PATCH] ACPI: idle: fix init-time TSC check regression

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Date:	Fri, 15 May 2009 00:31:54 +0200
From:	Frans Pop <elendil@...net.nl>
To:	Len Brown <lenb@...nel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Janne Kulmala <janne.t.kulmala@....fi>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...e.hu>, johnstul@...ibm.com
Subject: Re: [PATCH] ACPI: idle: fix init-time TSC check regression

On Thursday 14 May 2009, Len Brown wrote:
> From: Len Brown <len.brown@...el.com>
>
> A previous 2.6.30 patch, a71e4917dc0ebbcb5a0ecb7ca3486643c1c9a6e2,
> (ACPI: idle: mark_tsc_unstable() at init-time, not run-time)
> erroneously disabled the TSC on systems that did not actually
> have valid deep C-states.
>
> Move the check after the deep-C-states are validated,
> via new helper, tsc_check_state(), hich replaces tsc_halts_in_c().

[...]

> @@ -603,6 +602,8 @@ static int acpi_processor_power_verify(struct
> acpi_processor *pr) 
>                                acpi_timer_check_state(i, pr, cx);
>                        break;
>                }
>+               if (cx->valid)
>+                       tsc_check_state(cx->type);
> 
>                if (cx->valid)
>                        working++;

Shouldn't those last two ifs not simply be combined?
Hmm. I guess not if tsc_check_state can change cx->valid, but that might 
be worth a comment.

But even with that I'll give the patch a try tomorrow.

Cheers,
FJP
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