[GIT PULL] smp/hotplug changes for v3.9

From: Ingo Molnar
Date: Tue Feb 19 2013 - 09:28:45 EST

Linus,

Please pull the latest smp-hotplug-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git smp-hotplug-for-linus

HEAD: 14e568e78f6f80ca1e27256641ddf524c7dbdc51 stop_machine: Use smpboot threads

Some early preparatory changes for the WIP hotplug rework by
Thomas Gleixner.

Thanks,

Ingo

------------------>
Thomas Gleixner (3):
smpboot: Allow selfparking per cpu threads
stop_machine: Store task reference in a separate per cpu variable
stop_machine: Use smpboot threads


include/linux/smpboot.h | 5 ++
kernel/cpu.c | 2 +
kernel/smpboot.c | 5 +-
kernel/stop_machine.c | 156 +++++++++++++++++++-----------------------------
4 files changed, 70 insertions(+), 98 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/cpu.c b/kernel/cpu.c
index 3046a50..c91e30d 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -254,6 +254,8 @@ static int __ref take_cpu_down(void *_param)
return err;

cpu_notify(CPU_DYING | param->mod, param->hcpu);
+ /* Park the stopper thread */
+ kthread_park(current);
return 0;
}

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)
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);
}

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 2f194e9..95d178c 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -18,7 +18,7 @@
#include <linux/stop_machine.h>
#include <linux/interrupt.h>
#include <linux/kallsyms.h>
-
+#include <linux/smpboot.h>
#include <linux/atomic.h>

/*
@@ -37,10 +37,10 @@ struct cpu_stopper {
spinlock_t lock;
bool enabled; /* is this stopper enabled? */
struct list_head works; /* list of pending works */
- struct task_struct *thread; /* stopper thread */
};

static DEFINE_PER_CPU(struct cpu_stopper, cpu_stopper);
+static DEFINE_PER_CPU(struct task_struct *, cpu_stopper_task);
static bool stop_machine_initialized = false;

static void cpu_stop_init_done(struct cpu_stop_done *done, unsigned int nr_todo)
@@ -62,16 +62,18 @@ static void cpu_stop_signal_done(struct cpu_stop_done *done, bool executed)
}

/* queue @work to @stopper. if offline, @work is completed immediately */
-static void cpu_stop_queue_work(struct cpu_stopper *stopper,
- struct cpu_stop_work *work)
+static void cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work)
{
+ struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
+ struct task_struct *p = per_cpu(cpu_stopper_task, cpu);
+
unsigned long flags;

spin_lock_irqsave(&stopper->lock, flags);

if (stopper->enabled) {
list_add_tail(&work->list, &stopper->works);
- wake_up_process(stopper->thread);
+ wake_up_process(p);
} else
cpu_stop_signal_done(work->done, false);

@@ -108,7 +110,7 @@ int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
struct cpu_stop_work work = { .fn = fn, .arg = arg, .done = &done };

cpu_stop_init_done(&done, 1);
- cpu_stop_queue_work(&per_cpu(cpu_stopper, cpu), &work);
+ cpu_stop_queue_work(cpu, &work);
wait_for_completion(&done.completion);
return done.executed ? done.ret : -ENOENT;
}
@@ -130,7 +132,7 @@ void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
struct cpu_stop_work *work_buf)
{
*work_buf = (struct cpu_stop_work){ .fn = fn, .arg = arg, };
- cpu_stop_queue_work(&per_cpu(cpu_stopper, cpu), work_buf);
+ cpu_stop_queue_work(cpu, work_buf);
}

/* static data for stop_cpus */
@@ -159,8 +161,7 @@ static void queue_stop_cpus_work(const struct cpumask *cpumask,
*/
preempt_disable();
for_each_cpu(cpu, cpumask)
- cpu_stop_queue_work(&per_cpu(cpu_stopper, cpu),
- &per_cpu(stop_cpus_work, cpu));
+ cpu_stop_queue_work(cpu, &per_cpu(stop_cpus_work, cpu));
preempt_enable();
}

@@ -244,20 +245,25 @@ int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg)
return ret;
}

-static int cpu_stopper_thread(void *data)
+static int cpu_stop_should_run(unsigned int cpu)
+{
+ struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
+ unsigned long flags;
+ int run;
+
+ spin_lock_irqsave(&stopper->lock, flags);
+ run = !list_empty(&stopper->works);
+ spin_unlock_irqrestore(&stopper->lock, flags);
+ return run;
+}
+
+static void cpu_stopper_thread(unsigned int cpu)
{
- struct cpu_stopper *stopper = data;
+ struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
struct cpu_stop_work *work;
int ret;

repeat:
- set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
-
- if (kthread_should_stop()) {
- __set_current_state(TASK_RUNNING);
- return 0;
- }
-
work = NULL;
spin_lock_irq(&stopper->lock);
if (!list_empty(&stopper->works)) {
@@ -273,8 +279,6 @@ repeat:
struct cpu_stop_done *done = work->done;
char ksym_buf[KSYM_NAME_LEN] __maybe_unused;

- __set_current_state(TASK_RUNNING);
-
/* cpu stop callbacks are not allowed to sleep */
preempt_disable();

@@ -290,88 +294,55 @@ repeat:
ksym_buf), arg);

cpu_stop_signal_done(done, true);
- } else
- schedule();
-
- goto repeat;
+ goto repeat;
+ }
}

extern void sched_set_stop_task(int cpu, struct task_struct *stop);

-/* manage stopper for a cpu, mostly lifted from sched migration thread mgmt */
-static int __cpuinit cpu_stop_cpu_callback(struct notifier_block *nfb,
- unsigned long action, void *hcpu)
+static void cpu_stop_create(unsigned int cpu)
+{
+ sched_set_stop_task(cpu, per_cpu(cpu_stopper_task, cpu));
+}
+
+static void cpu_stop_park(unsigned int cpu)
{
- unsigned int cpu = (unsigned long)hcpu;
struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
- struct task_struct *p;
-
- switch (action & ~CPU_TASKS_FROZEN) {
- case CPU_UP_PREPARE:
- BUG_ON(stopper->thread || stopper->enabled ||
- !list_empty(&stopper->works));
- p = kthread_create_on_node(cpu_stopper_thread,
- stopper,
- cpu_to_node(cpu),
- "migration/%d", cpu);
- if (IS_ERR(p))
- return notifier_from_errno(PTR_ERR(p));
- get_task_struct(p);
- kthread_bind(p, cpu);
- sched_set_stop_task(cpu, p);
- stopper->thread = p;
- break;
-
- case CPU_ONLINE:
- /* strictly unnecessary, as first user will wake it */
- wake_up_process(stopper->thread);
- /* mark enabled */
- spin_lock_irq(&stopper->lock);
- stopper->enabled = true;
- spin_unlock_irq(&stopper->lock);
- break;
-
-#ifdef CONFIG_HOTPLUG_CPU
- case CPU_UP_CANCELED:
- case CPU_POST_DEAD:
- {
- struct cpu_stop_work *work;
-
- sched_set_stop_task(cpu, NULL);
- /* kill the stopper */
- kthread_stop(stopper->thread);
- /* drain remaining works */
- spin_lock_irq(&stopper->lock);
- list_for_each_entry(work, &stopper->works, list)
- cpu_stop_signal_done(work->done, false);
- stopper->enabled = false;
- spin_unlock_irq(&stopper->lock);
- /* release the stopper */
- put_task_struct(stopper->thread);
- stopper->thread = NULL;
- break;
- }
-#endif
- }
+ struct cpu_stop_work *work;
+ unsigned long flags;

- return NOTIFY_OK;
+ /* drain remaining works */
+ spin_lock_irqsave(&stopper->lock, flags);
+ list_for_each_entry(work, &stopper->works, list)
+ cpu_stop_signal_done(work->done, false);
+ stopper->enabled = false;
+ spin_unlock_irqrestore(&stopper->lock, flags);
}

-/*
- * Give it a higher priority so that cpu stopper is available to other
- * cpu notifiers. It currently shares the same priority as sched
- * migration_notifier.
- */
-static struct notifier_block __cpuinitdata cpu_stop_cpu_notifier = {
- .notifier_call = cpu_stop_cpu_callback,
- .priority = 10,
+static void cpu_stop_unpark(unsigned int cpu)
+{
+ struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
+
+ spin_lock_irq(&stopper->lock);
+ stopper->enabled = true;
+ spin_unlock_irq(&stopper->lock);
+}
+
+static struct smp_hotplug_thread cpu_stop_threads = {
+ .store = &cpu_stopper_task,
+ .thread_should_run = cpu_stop_should_run,
+ .thread_fn = cpu_stopper_thread,
+ .thread_comm = "migration/%u",
+ .create = cpu_stop_create,
+ .setup = cpu_stop_unpark,
+ .park = cpu_stop_park,
+ .unpark = cpu_stop_unpark,
+ .selfparking = true,
};

static int __init cpu_stop_init(void)
{
- void *bcpu = (void *)(long)smp_processor_id();
unsigned int cpu;
- int err;

for_each_possible_cpu(cpu) {
struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
@@ -380,15 +351,8 @@ static int __init cpu_stop_init(void)
INIT_LIST_HEAD(&stopper->works);
}

- /* start one for the boot cpu */
- err = cpu_stop_cpu_callback(&cpu_stop_cpu_notifier, CPU_UP_PREPARE,
- bcpu);
- BUG_ON(err != NOTIFY_OK);
- cpu_stop_cpu_callback(&cpu_stop_cpu_notifier, CPU_ONLINE, bcpu);
- register_cpu_notifier(&cpu_stop_cpu_notifier);
-
+ BUG_ON(smpboot_register_percpu_thread(&cpu_stop_threads));
stop_machine_initialized = true;
-
return 0;
}
early_initcall(cpu_stop_init);
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/