[tip:smp/hotplug] smpboot: Allow selfparking per cpu threads

From: tip-bot for Thomas Gleixner
Date: Thu Feb 14 2013 - 12:49:24 EST

Commit-ID: 7d7e499f7333f68b7e7f67d14b9c1480913b4afb
Gitweb: http://git.kernel.org/tip/7d7e499f7333f68b7e7f67d14b9c1480913b4afb
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Thu, 31 Jan 2013 12:11:12 +0000
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Thu, 14 Feb 2013 15:29:37 +0100

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@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Paul McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
Cc: Arjan van de Veen <arjan@xxxxxxxxxxxxx>
Cc: Paul Turner <pjt@xxxxxxxxxx>
Cc: Richard Weinberger <rw@xxxxxxxxxxxxx>
Cc: Magnus Damm <magnus.damm@xxxxxxxxx>
Link: http://lkml.kernel.org/r/20130131120741.553993267@xxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
include/linux/smpboot.h | 5 +++++
kernel/smpboot.c | 5 +++--
2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/include/linux/smpboot.h b/include/linux/smpboot.h
index e0106d8..c65dee0 100644
--- 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 d6c5fc0..d4abac2 100644
--- a/kernel/smpboot.c
+++ b/kernel/smpboot.c
@@ -183,9 +183,10 @@ __smpboot_create_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
return PTR_ERR(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)

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