Commit bcbd818c authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull preparatory smp/hotplug patches from Ingo Molnar:
 "Some early preparatory changes for the WIP hotplug rework by Thomas
  Gleixner."

* 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  stop_machine: Use smpboot threads
  stop_machine: Store task reference in a separate per cpu variable
  smpboot: Allow selfparking per cpu threads
parents d652e1eb 14e568e7
......@@ -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;
};
......
......@@ -256,6 +256,8 @@ 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;
}
......
......@@ -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);
}
......
......@@ -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 @@ static int cpu_stopper_thread(void *data)
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 @@ static int cpu_stopper_thread(void *data)
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);
......
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