Re: [RFC patch V2 2/7] kthread: Implement park/unpark facility

Namhyung Kim
2012-06-18T08:47:13Z

On Fri, 15 Jun 2012 14:13:21 -0000, Thomas Gleixner wrote:
> To avoid the full teardown/setup of per cpu kthreads in the case of
> cpu hot(un)plug, provide a facility which allows to put the kthread
> into a park position and unpark it when the cpu comes online again.
>

Please see a comment below. Other than that, you can add my

Reviewed-by: Namhyung Kim <namhyung@kernel.org>

if you want.

> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
> include/linux/kthread.h | 11 ++
> kernel/kthread.c | 184 +++++++++++++++++++++++++++++++++++++++++++-----
> 2 files changed, 175 insertions(+), 20 deletions(-)
[snip]
> /**
> + * kthread_create_on_cpu - Create a cpu bound kthread
> + * @threadfn: the function to run until signal_pending(current).
> + * @data: data ptr for @threadfn.
> + * @cpu: The cpu on which the thread should be bound,
> + * @namefmt: printf-style name for the thread.

How about adding a comment that @namefmt can handle a single %u only
for the cpu number in the current implementation?

Thanks,
Namhyung

> + *
> + * Description: This helper function creates and names a kernel thread
> + * The thread will be woken and put into park mode.
> + */
> +struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
> + void *data, unsigned int cpu,
> + const char *namefmt)
> +{
> + struct task_struct *p;
> +
> + p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
> + cpu);
> + if (IS_ERR(p))
> + return p;
> + set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags);
> + to_kthread(p)->cpu = cpu;
> + /* Park the thread to get it out of TASK_UNINTERRUPTIBLE state */
> + kthread_park(p);
> + return p;
> +}
> +