On Mon, May 31, 2010 at 04:57:15PM -0700, Kevin Cernekee wrote:
> /**
> + * console_cpu_notify - print deferred console messages after CPU hotplug
> + *
> + * If printk() is called from a CPU that is not online yet, the messages
> + * will be spooled but will not show up on the console. This function is
> + * called when a new CPU comes online and ensures that any such output
> + * gets printed.
> + */
> +static int __cpuinit console_cpu_notify(struct notifier_block *self,
> + unsigned long action, void *hcpu)
> +{
> + switch (action) {
> + case CPU_ONLINE:
> + case CPU_UP_CANCELED:
> + if (try_acquire_console_sem() == 0)
> + release_console_sem();
> + }
> + return NOTIFY_OK;
> +}
> +
> +static struct notifier_block __cpuinitdata console_nb = {
> + .notifier_call = console_cpu_notify,
> +};
> +
> +static int __init console_notifier_init(void)
> +{
> + register_cpu_notifier(&console_nb);
> + return 0;
> +}
If this is to be entirely restricted to CPU hotplug then you could use
the hotcpu notifier here instead of the open-coded cpu notifier directly,
the former wraps to the latter in the CPU hotplug case and is simply a
nop for the regular SMP case.
