Re: [mm PATCH 4/6] RCU: preemptible RCU

[Andrew Morton <akpm@osdl.org>]

On Tue, 16 Jan 2007 00:58:58 +0530
Dipankar Sarma <dipankar@in.ibm.com> wrote:

> +/*
> + * Wait for CPUs to acknowledge the flip.
> + */
> +static int rcu_try_flip_waitack(int flipctr)
> +{
> +	int cpu;
> +
> +	for_each_possible_cpu(cpu)
> +		if (per_cpu(rcu_flip_flag, cpu) != RCU_FLIP_SEEN) 
> +			return 1;
> +
> +	/*
> +	 * Make sure our checks above don't bleed into subsequent
> +	 * waiting for the sum of the counters to reach zero.
> +	 */
> +	smp_mb();
> +	return 0;
> +}

Confused.  If some of the possible cpus aren't online, doesn't the 
state machine get stuck??
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