Re: regression in 2.6.23-rc8 - power off failed

From: Mark Lord
Date: Sat Sep 29 2007 - 08:40:50 EST

Wolfgang Erig wrote:
On Sat, Sep 29, 2007 at 01:30:33AM -0700, H. Peter Anvin wrote:
Wolfgang Erig wrote:
Both are bad.
Two different systems and two different bisections.
I sent the last step of each.
$ git bisect good Bisecting: 0 revisions left to test after this [626073132b381684c4983e0d911e9aceb32e2cbc] Assembly header and main routine for new x86 setup code
OK, so which one is the bad one?
This problem (no power off) persists after pull some minutes ago.
Sorry for the confusion.

I believe there must have been something wrong here (possibly
inconsistent experiments?) This checkin has *zero code changes* from
the previous one (and next one) -- the kernel should have been binarily
identical to the previous one. The code introduced in this checkin
doesn't even get compiled until two checkins later,

I have done two bisections simultanously and it was late at night.
I start again with a fresh tree and better controlled experiments.

If this is an SMP system, then you could just be getting random results,
depending upon which CPU is attempting the poweroff.

I have a newish patch in Andrew's tree now to fix SMP poweroff
(has been broken forever), reproduced here below in case you missed it.

* * *
We need to disable all CPUs other than the boot CPU (usually 0)
before attempting to power-off modern SMP machines.
This fixes the hang-on-poweroff issue on my MythTV SMP box,
and also on Thomas Gleixner's new toybox.

Signed-off-by: Mark Lord <mlord@xxxxxxxxx>
Acked-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

--- linux/kernel/sys.c.orig 2007-09-13 09:49:11.000000000 -0400
+++ linux/kernel/sys.c 2007-09-28 15:48:54.000000000 -0400
@@ -32,6 +32,7 @@
#include <linux/getcpu.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/seccomp.h>
+#include <linux/cpu.h>

#include <linux/compat.h>
#include <linux/syscalls.h>
@@ -878,6 +879,7 @@
if (pm_power_off_prepare)
+ disable_nonboot_cpus();
printk(KERN_EMERG "Power down.\n");
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