From: Christian Borntraeger <borntraeger@de.ibm.com>
To: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Subject: Re: [PATCH] stopmachine: add stopmachine_timeout
Date: Mon, 14 Jul 2008 13:51:25 +0200
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Cc: linux-kernel@vger.kernel.org, Rusty Russell <rusty@rustcorp.com.au>,
       Heiko Carstens <heiko.carstens@de.ibm.com>
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Am Montag, 14. Juli 2008 schrieb Hidetoshi Seto:
> +	/* Wait all others come to life */
> +	while (cpus_weight(prepared_cpus) != num_online_cpus() - 1) {
> +		if (time_is_before_jiffies(limit))
> +			goto timeout;
> +		cpu_relax();
> +	}
> +

Hmm. I think this could become interesting on virtual machines. The hypervisor 
might be to busy to schedule a specific cpu at certain load scenarios. This 
would cause a failure even if the cpu is not really locked up. We had similar 
problems with the soft lockup daemon on s390. 

It would be good to not-use wall-clock time, but really used cpu time instead. 
Unfortunately I have no idea, if that is possible in a generic way.
Heiko, any ideas?
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