Re: [PATCH][2.5] smp_call_function_mask

[Andrew Morton <akpm@digeo.com>]

Zwane Mwaikambo <zwane@holomorphy.com> wrote:
>
> This patch adds a smp_call_function which also accepts a cpu mask which is 
> needed for targetting specific or groups of cpus.

What is it needed for?

> Index: linux-2.5.58-cpu_hotplug/arch/i386/kernel/smp.c

ia32 only?

>  
> +int smp_call_function_mask (void (*func) (void *info), void *info, int nonatomic,
> +			int wait, unsigned long mask)
> +/*
> + * [SUMMARY] Run a function on specific CPUs, save self.
> + * <func> The function to run. This must be fast and non-blocking.
> + * <info> An arbitrary pointer to pass to the function.
> + * <nonatomic> currently unused.
> + * <wait> If true, wait (atomically) until function has completed on other CPUs.
> + * <mask> The bitmask of CPUs to call the function
> + * [RETURNS] 0 on success, else a negative status code. Does not return until
> + * remote CPUs are nearly ready to execute <<func>> or are or have executed.
> + *
> + * You must not call this function with disabled interrupts or from a
> + * hardware interrupt handler or from a bottom half handler.
> + */

Please don't invent new coding styles.  The comment block goes outside the
function.  Nice comment block though.

> +{
> +	struct call_data_struct data;
> +	int num_cpus = hweight32(mask);
> +
> +	if (num_cpus == 0)
> +		return -EINVAL;
> +
> +	if ((1UL << smp_processor_id()) & mask)
> +		return -EINVAL;

Preempt safety?