smpboot: Allow selfparking per cpu threads

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 <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Arjan van de Veen <arjan@infradead.org>
Cc: Paul Turner <pjt@google.com>
Cc: Richard Weinberger <rw@linutronix.de>
Cc: Magnus Damm <magnus.damm@gmail.com>
Link: http://lkml.kernel.org/r/20130131120741.553993267@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/include/linux/smpboot.h b/include/linux/smpboot.h
index e0106d8581d380c2bee45d10141297cb8ac0b4b0..c65dee059913c8d429a614bf3c9b16e088369216 100644 (file)
--- a/include/linux/smpboot.h
+++ b/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;
 };
 

diff --git a/kernel/smpboot.c b/kernel/smpboot.c
index d6c5fc0542428dae4fffc7546e06b0f6dd4ac4f5..d4abac261779e037b2396b80f5b4fe3ec6efad71 100644 (file)
--- a/kernel/smpboot.c
+++ b/kernel/smpboot.c
@@ -183,9 +183,10 @@ __smpboot_create_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
                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 smp_hotplug_thread *ht, unsigned int cpu)
 {
        struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
 
-       if (tsk)
+       if (tsk && !ht->selfparking)
                kthread_park(tsk);
 }