linux-kernel - Re: [patch] i386/x86_64: ACPI cpu_idle

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Date:	Fri, 17 Nov 2006 20:26:26 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Andrew Morton <akpm@...l.org>
Cc:	linux-kernel@...r.kernel.org,
	Wolfgang Erig <Wolfgang.Erig@...itsu-siemens.com>,
	Andreas Friedrich <andreas.friedrich@...itsu-siemens.com>,
	Adrian Bunk <bunk@...sta.de>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Linus Torvalds <torvalds@...l.org>,
	"Brown, Len" <len.brown@...el.com>, linux-acpi@...r.kernel.org
Subject: Re: [patch] i386/x86_64: ACPI cpu_idle_wait() fix


* Andrew Morton <akpm@...l.org> wrote:

> > correction: the last known working kernel was 2.6.8. The bug 
> > predates our GIT history so it's older than 1.5 years.
> 
> How come nobody noticed?  Maybe it improved things ;)
> 
> I spose it's 2.6.19 material, although it's a bit of a leap into the 
> unknown.

i think it's 2.6.19 material. A kernel release that will speed up some 
systems quite noticeably ;-)

> How many systems will this affect?

dont know - it should be relatively rare - maybe the ACPI guys know when 
this has a chance to trigger?

> CPU#1: set_cpus_allowed(), swapper:1, 3 -> 2
>  [<c0103bbe>] show_trace_log_lvl+0x34/0x4a
>  [<c0103ceb>] show_trace+0x2c/0x2e
>  [<c01045f8>] dump_stack+0x2b/0x2d
>  [<c0116a77>] set_cpus_allowed+0x52/0xec
>  [<c0101d86>] cpu_idle_wait+0x2e/0x100
>  [<c0259c57>] acpi_processor_power_exit+0x45/0x58
>  [<c0259752>] acpi_processor_remove+0x46/0xea
>  [<c025c6fb>] acpi_start_single_object+0x47/0x54
>  [<c025cee5>] acpi_bus_register_driver+0xa4/0xd3
>  [<c04ab2d7>] acpi_processor_init+0x57/0x77
>  [<c01004d7>] init+0x146/0x2fd
>  [<c0103a87>] kernel_thread_helper+0x7/0x10
> 
> It seems strange that the kernel is calling 
> acpi_processor_power_exit() at this stage.  It'll have happened 
> because acpi_start_single_object()'s call to acpi_processor_start() 
> returned non-zero.  Why did that happen?

ah, maybe due to:

 BIOS reported wrong ACPI idfor the processor

google gives 4 hits, so i guess it's relatively rare.

> > 	/*
> > 	 * Buggy BIOS check
> > 	 * ACPI id of processors can be reported wrongly by the BIOS.
> > 	 * Don't trust it blindly
> > 	 */
> > 	if (processor_device_array[pr->id] != NULL &&
> > 	    processor_device_array[pr->id] != device) {
> > 		printk(KERN_WARNING "BIOS reported wrong ACPI id"
> > 			"for the processor\n");
> > 		return -ENODEV;
> 
> Andreas wasn't seeing that, right?

he was actually! dmesg.txt attached.

	Ingo

View attachment "dmesg.txt" of type "text/plain" (14372 bytes)