linux-kernel - Re: cpu hotplug support broken in 2.6.23-rc3

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Date:	Tue, 2 Oct 2007 11:45:59 +0200
From:	Pavel Machek <pavel@....cz>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Jeff Chua <jeff.chua.linux@...il.com>, rusty@...tycorp.com.au,
	vatsa@...ibm.com, zwane@....linux.org.uk,
	kernel list <linux-kernel@...r.kernel.org>,
	Len Brown <lenb@...nel.org>
Subject: Re: cpu hotplug support broken in 2.6.23-rc3

Hi!

> > > Venki sent me an initial patch, but it has issues with the notify
> > > ordering. Find below my "cache the broadcast flags" version for testing.
> > 
> > Hmmpf, the flag is still cleared when the cpu goes offline. Need to take
> > a closer look.
> 
> I finally tracked it down. There were several ways to turn the box into
> a brick. Sigh !
> 
> Can you please test the combo patch below ?

Sorry, I was on holidays. I assume this is in -rc9 or so, already?
Yes, seems so.

Unfortunately, cpu hotplug seems to be still behaving strangely in
-rc9. I can echo 0 > online (and cpu will go down). I do echo 0 >
online, again, and I get -EBUSY. Good. But I try to do echo 1 >
online, and get -EBUSY, too... and that's bad :-(.

root@amd:/sys/devices/system/cpu/cpu1# echo 0 > online
root@amd:/sys/devices/system/cpu/cpu1# echo 0 > online
-bash: echo: write error: Device or resource busy
root@amd:/sys/devices/system/cpu/cpu1# echo 1 > online
-bash: echo: write error: Device or resource busy
root@amd:/sys/devices/system/cpu/cpu1# uname -a
Linux amd 2.6.23-rc9 #507 SMP Tue Oct 2 09:58:40 CEST 2007 i686
GNU/Linux

Kernel says:

Oct  2 11:42:12 amd log1n[1436]: ROOT LOGIN on `tty1'
Oct  2 11:42:56 amd kernel: CPU 1 is now offline
Oct  2 11:42:56 amd kernel: SMP alternatives: switching to UP code

								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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