linux-kernel - Re: [stable] [patch 09/12] Fix SMP poweroff hangs

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Date:	Wed, 10 Oct 2007 05:06:05 -0500 (CDT)
From:	Milton Miller <miltonm@....com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Mark Lord <lkml@....ca>
Cc:	<linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	<linux-pm@...ts.linux-foundation.org>
Subject:  Re: [stable] [patch 09/12] Fix SMP poweroff hangs


On Tue, Oct 9 2007 Thomas Gleixner wrote:
>On Tue, 9 Oct 2007, Linus Torvalds wrote:
>>On Wed, 10 Oct 2007, Thomas Gleixner wrote:
>>>
>>> Wrapping it into a #ifdef CONFIG_X86 would be sufficient.
>>
>> Well, the ppc oops seems to be a ppc bug regardless.
>>
>> If CPU_HOTPLUG isn't defined, the thing does nothing. And if it is
>> defined, I don't see why/how ppc can validly oops. So I think the first
>> thing to do is to try to figure out why it oopses, not to disable it for
>> ppc.
>
>Fair enough. OTOH for the affected PPC users it's a regression and that's
>what I'm concerned of.
>
>tglx

I agree this exposes a ppc arch bug (and the reason has been diagnosed),
but might not other archs have similar problems?  The patch ties
power-off code to suspend and hibernate cpu hotplug code.

Why not put this ACPI requirement in the ACPI code?   There is already
a hook called at the same place this function was called that is only
used for power off.

Also, the code is compiled for CONFIG_PM_SLEEP_SMP, which is not
CONFIG_HOTPLUG_CPU, it requires the selection of either CONFIG_HIBERNATION
or CONFIG_SUSPEND.  I confirmed that both of these can be disabled
on i386 without disabling acpi.  In such a kernel the existing patch
is insufficient.


 drivers/acpi/sleep/main.c |    2 ++
 kernel/sys.c              |    1 -
 2 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/acpi/sleep/main.c b/drivers/acpi/sleep/main.c
index 2cbb9aa..79589bd 100644
--- a/drivers/acpi/sleep/main.c
+++ b/drivers/acpi/sleep/main.c
@@ -15,6 +15,7 @@
 #include <linux/dmi.h>
 #include <linux/device.h>
 #include <linux/suspend.h>
+#include <linux/cpu.h>
 
 #include <asm/io.h>
 
@@ -382,6 +383,7 @@ static void acpi_power_off_prepare(void)
 {
 	/* Prepare to power off the system */
 	acpi_sleep_prepare(ACPI_STATE_S5);
+	disable_nonboot_cpus();
 }
 
 static void acpi_power_off(void)
diff --git a/kernel/sys.c b/kernel/sys.c
index 8ae2e63..138f5c8 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -879,7 +879,6 @@ void kernel_power_off(void)
 	kernel_shutdown_prepare(SYSTEM_POWER_OFF);
 	if (pm_power_off_prepare)
 		pm_power_off_prepare();
-	disable_nonboot_cpus();
 	sysdev_shutdown();
 	printk(KERN_EMERG "Power down.\n");
 	machine_power_off();
-
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