linux-kernel - highres timers break cpu hotplug in 2.6.23-rc5 [was Re: cpu hotplug support broken in 2.6.23-rc3]

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Message-ID: <20070903035644.GC3655@ucw.cz>
Date:	Mon, 3 Sep 2007 03:56:44 +0000
From:	Pavel Machek <pavel@....cz>
To:	Jeff Chua <jeff.chua.linux@...il.com>
Cc:	rusty@...tycorp.com.au, vatsa@...ibm.com, zwane@....linux.org.uk,
	kernel list <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, tglx@...utronix.de
Subject: highres timers break cpu hotplug in 2.6.23-rc5 [was Re: cpu hotplug support broken in 2.6.23-rc3]

Hi!

> > Can you try 20-or-so tests? Mine hangs randomly, so it survived 4 or
> > so cycles at one point.
> 
> Mine still survives with this ... with sleep 1 ...
> 
> # for((i=0; i<100; i++)); do echo $i; echo $((i % 2))
> >/sys/devices/system/cpu/cpu1/online; sleep 1; done
> 
> and this as well ... without sleep ...
> 
> # for((i=0; i<100; i++)); do echo $i; echo $((i % 2))
> >/sys/devices/system/cpu/cpu1/online; done
> 
> I'm on reiserfs. gcc 3.4.5. Config sent to you seperately so as not to
> cloud lkml. If anyone wants the config, please let me know. Is mime
> "attachment" acceptable now on lkml?

It gets weirder. With "nohz=off" on commandline, I have to press any
key (generate interrupt?) for echo 1  > online to finish. 2.6.23-rc5
kernel... but hotplug/unplug works reliably now.

With nohz=off highres=off I can unplug/replug cpus as much as I
want... running in tight loop now.
								Pavel

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