Re: [Bug 12492] Re: [patch 1/2] stop_machine: introduce stop_machine_create/destroy.

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 27 Jan 2009 00:04:32 -0800 Andrew Morton <akpm@linux-foundation.org> wrote:

> On Mon, 22 Dec 2008 12:36:30 +0100 Heiko Carstens <heiko.carstens@de.ibm.com> wrote:
> 
> > Introduce stop_machine_create/destroy. With this interface subsystems
> > that need a non-failing stop_machine environment can create the
> > stop_machine machine threads before actually calling stop_machine.
> > When the threads aren't needed anymore they can be killed with
> > stop_machine_destroy again.
> > 
> > When stop_machine gets called and the threads aren't present they
> > will be created and destroyed automatically. This restores the old
> > behaviour of stop_machine.
> > 
> > This patch also converts cpu hotplug to the new interface since it
> > is special: cpu_down calls __stop_machine instead of stop_machine.
> > However the kstop threads will only be created when stop_machine
> > gets called.
> > 
> > Changing the code so that the threads would be created automatically
> > on __stop_machine is currently not possible: when __stop_machine gets
> > called we hold cpu_add_remove_lock, which is the same lock that
> > create_rt_workqueue would take. So the workqueue needs to be created
> > before the cpu hotplug code locks cpu_add_remove_lock.
> 
> In http://bugzilla.kernel.org/show_bug.cgi?id=12492, Thomas (cc'ed
> here) reports
> 
>   Commit 9ea09af3bd3090e8349ca2899ca2011bd94cda85 introduced a
>   regression that caused the kernel to fail to suspend.  The 'sleeping'
>   LED on the laptop just keeps blinking and the laptop never shuts
>   down.  I think this was eventually fixed because with 2.6.29-rc1 and
>   -rc2 the laptop suspends fine, but fails to resume.  When I try to
>   resume, all I see is a blinking cursor in the top left corner of the
>   screen.
> 
>   I'm using acpi_sleep=s3_bios,s3_mode, suspending using a script
>   that does: echo mem > /sys/power/state.
> 

hm.  Re-reading this, it seems to be saying that
9ea09af3bd3090e8349ca2899ca2011bd94cda85 might be innocent, and that
some other patch might have caused the resume regression?