On Thu, Jan 31, 2013 at 12:11:12PM -0000, Thomas Gleixner wrote:
> The stop machine threads are still killed when a cpu goes offline. The
> reason is that the thread is used to bring the cpu down, so it can't
> be parked along with the other per cpu threads.
>
> Allow a per cpu thread to be excluded from automatic parking, so it
> can park itself once it's done
>
> Add a create callback function as well.
>
> Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Reviewed-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
> ---
> include/linux/smpboot.h | 5 +++++
> kernel/smpboot.c | 5 +++--
> 2 files changed, 8 insertions(+), 2 deletions(-)
>
> Index: linux-2.6/include/linux/smpboot.h
> ===================================================================
> --- linux-2.6.orig/include/linux/smpboot.h
> +++ linux-2.6/include/linux/smpboot.h
> @@ -14,6 +14,8 @@ struct smpboot_thread_data;
> * @thread_should_run: Check whether the thread should run or not.
> Called with
> * preemption disabled.
> * @thread_fn: The associated thread function
> + * @create: Optional setup function, called when the thread gets
> + * created (Not called from the thread context)
> * @setup: Optional setup function, called when the thread gets
> * operational the first time
> * @cleanup: Optional cleanup function, called when the thread
> @@ -22,6 +24,7 @@ struct smpboot_thread_data;
> * parked (cpu offline)
> * @unpark: Optional unpark function, called when the thread is
> * unparked (cpu online)
> + * @selfparking: Thread is not parked by the park function.
> * @thread_comm: The base name of the thread
> */
> struct smp_hotplug_thread {
> @@ -29,10 +32,12 @@ struct smp_hotplug_thread {
> struct list_head list;
> int (*thread_should_run)(unsigned int cpu);
> void (*thread_fn)(unsigned int cpu);
> + void (*create)(unsigned int cpu);
> void (*setup)(unsigned int cpu);
> void (*cleanup)(unsigned int cpu, bool
> online);
> void (*park)(unsigned int cpu);
> void (*unpark)(unsigned int cpu);
> + bool selfparking;
> const char *thread_comm;
> };
>
> Index: linux-2.6/kernel/smpboot.c
> ===================================================================
> --- linux-2.6.orig/kernel/smpboot.c
> +++ linux-2.6/kernel/smpboot.c
> @@ -183,9 +183,10 @@ __smpboot_create_thread(struct smp_hotpl
> kfree(td);
> return PTR_ERR(tsk);
> }
> -
> get_task_struct(tsk);
> *per_cpu_ptr(ht->store, cpu) = tsk;
> + if (ht->create)
> + ht->create(cpu);
> return 0;
> }
>
> @@ -225,7 +226,7 @@ static void smpboot_park_thread(struct s
> {
> struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
>
> - if (tsk)
> + if (tsk && !ht->selfparking)
> kthread_park(tsk);
> }
>
>
>
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