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SubjectRe: [PATCH 1/7] work_on_cpu: helper for doing task on a CPU.
On Thu, Oct 23, 2008 at 01:01:28AM +0000, Rusty Russell wrote:
>
> Several places in the kernel do the following:
>
> saved_mask = current->cpus_allowed;
> set_cpus_allowed_ptr(current, &cpumask_of_cpu(pr->id));
> somefunc();
> /* restore the previous state */
> set_cpus_allowed_ptr(current, &saved_mask);
>
> This is bad, because a process's cpumask is observable and
> manipulatable by userspace and should not be toyed with.
>
> We have the infrastructure, this just creates a nice wrapper to
> encourage its use.
>
> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
> Cc: Ingo Molnar <mingo@elte.hu>
> ---
> include/linux/workqueue.h | 8 +++++++
> kernel/workqueue.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 56 insertions(+)
>
> diff -r b72e0cbdd249 include/linux/workqueue.h
> --- a/include/linux/workqueue.h Thu Oct 23 00:39:36 2008 +1100
> +++ b/include/linux/workqueue.h Thu Oct 23 10:53:51 2008 +1100
> @@ -240,4 +240,12 @@ void cancel_rearming_delayed_work(struct
> cancel_delayed_work_sync(work);
>

<snip>
> + */
> +long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
> +{
> + struct work_for_cpu wfc;
> +
> + INIT_WORK(&wfc.work, do_work_for_cpu);
> + init_completion(&wfc.done);
> + wfc.fn = fn;
> + wfc.arg = arg;
> + get_online_cpus();
> + if (unlikely(!cpu_online(cpu))) {
> + wfc.ret = -EINVAL;
> + complete(&wfc.done);
> + } else
> + schedule_work_on(cpu, &wfc.work);

Won't this cause priority inversion in case of real-time tasks ?

> + put_online_cpus();
> + wait_for_completion(&wfc.done);
> +
> + return wfc.ret;
> +}
> +EXPORT_SYMBOL_GPL(work_on_cpu);
> +#endif /* CONFIG_SMP */
> +
> void __init init_workqueues(void)
> {
> cpu_populated_map = cpu_online_map;
>
> --
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--
Thanks and Regards
gautham

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