Re: [PATCH] SGI XPC fails to load when cpu 0 is out of IRQ resources.

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

On Fri, 3 Aug 2012 14:46:29 -0500
Robin Holt <holt@sgi.com> wrote:

> On many of our larger systems, CPU 0 has had all of its IRQ resources
> consumed before XPC loads.  Worse cases on machines with multiple
> 10 GigE cards and multiple IB cards have depleted the entire first
> socket of IRQs.  That patch makes selecting the node upon which
> IRQs are allocated (as well as all the other GRU Message Queue
> structures) specifiable as a module load param and has a default
> behavior of searching all nodes/cpus for an available resource.
> 

Is this problem serious enough to warrant a -stable backport?  If you
want it to appear in vendor kernels then I guess "yes".

> +static int
> +xpc_init_mq_node(int nid)
> +{
> +	int cpu;
> +
> +	for_each_cpu(cpu, cpumask_of_node(nid)) {
> +		xpc_activate_mq_uv = xpc_create_gru_mq_uv(XPC_ACTIVATE_MQ_SIZE_UV, nid,
> +							  XPC_ACTIVATE_IRQ_NAME,
> +							  xpc_handle_activate_IRQ_uv);
> +		if (!IS_ERR(xpc_activate_mq_uv))
> +			break;
> +	}
> +	if (IS_ERR(xpc_activate_mq_uv))
> +		return PTR_ERR(xpc_activate_mq_uv);
> +
> +	for_each_cpu(cpu, cpumask_of_node(nid)) {
> +		xpc_notify_mq_uv = xpc_create_gru_mq_uv(XPC_NOTIFY_MQ_SIZE_UV, nid,
> +							XPC_NOTIFY_IRQ_NAME,
> +							xpc_handle_notify_IRQ_uv);
> +		if (!IS_ERR(xpc_notify_mq_uv))
> +			break;
> +	}
> +	if (IS_ERR(xpc_notify_mq_uv)) {
> +		xpc_destroy_gru_mq_uv(xpc_activate_mq_uv);
> +		return PTR_ERR(xpc_notify_mq_uv);
> +	}
> +
> +	return 0;
> +}

This seems to take the optimistic approach to CPU hotplug ;)
get_online_cpus(), perhaps?