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Commit 757c989b authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

cpu/hotplug: Make target state writeable 



Make it possible to write a target state to the per cpu state file, so we can
switch between states.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182341.022814799@linutronix.de


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 98f8cdce

kernel/cpu.c

+65 −8
Original line number Diff line number Diff line
@@ -48,12 +48,14 @@ static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state); 
 * @teardown:	Teardown function of the step

 * @skip_onerr:	Do not invoke the functions on error rollback

 *		Will go away once the notifiers	are gone

 * @cant_stop:	Bringup/teardown can't be stopped at this step

 */

struct cpuhp_step {

	const char	*name;

	int		(*startup)(unsigned int cpu);

	int		(*teardown)(unsigned int cpu);

	bool		skip_onerr;

	bool		cant_stop;

};



static DEFINE_MUTEX(cpuhp_state_mutex);
@@ -558,7 +560,7 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen, 
	if (num_online_cpus() == 1)

		return -EBUSY;



	if (!cpu_online(cpu))

	if (!cpu_present(cpu))

		return -EINVAL;



	cpu_hotplug_begin();
@@ -683,17 +685,26 @@ static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target) 


	cpu_hotplug_begin();



	if (cpu_online(cpu) || !cpu_present(cpu)) {

	if (!cpu_present(cpu)) {

		ret = -EINVAL;

		goto out;

	}



	/*

	 * The caller of do_cpu_up might have raced with another

	 * caller. Ignore it for now.

	 */

	if (st->state >= target)

		goto out;



	if (st->state == CPUHP_OFFLINE) {

		/* Let it fail before we try to bring the cpu up */

		idle = idle_thread_get(cpu);

		if (IS_ERR(idle)) {

			ret = PTR_ERR(idle);

			goto out;

		}

	}



	cpuhp_tasks_frozen = tasks_frozen;
@@ -909,27 +920,32 @@ static struct cpuhp_step cpuhp_bp_states[] = { 
		.name			= "threads:create",

		.startup		= smpboot_create_threads,

		.teardown		= NULL,

		.cant_stop		= true,

	},

	[CPUHP_NOTIFY_PREPARE] = {

		.name			= "notify:prepare",

		.startup		= notify_prepare,

		.teardown		= notify_dead,

		.skip_onerr		= true,

		.cant_stop		= true,

	},

	[CPUHP_BRINGUP_CPU] = {

		.name			= "cpu:bringup",

		.startup		= bringup_cpu,

		.teardown		= NULL,

		.cant_stop		= true,

	},

	[CPUHP_TEARDOWN_CPU] = {

		.name			= "cpu:teardown",

		.startup		= NULL,

		.teardown		= takedown_cpu,

		.cant_stop		= true,

	},

	[CPUHP_NOTIFY_ONLINE] = {

		.name			= "notify:online",

		.startup		= notify_online,

		.teardown		= notify_down_prepare,

		.cant_stop		= true,

	},

#endif

	[CPUHP_ONLINE] = {
@@ -947,6 +963,7 @@ static struct cpuhp_step cpuhp_ap_states[] = { 
		.startup		= notify_starting,

		.teardown		= notify_dying,

		.skip_onerr		= true,

		.cant_stop		= true,

	},

#endif

	[CPUHP_ONLINE] = {
@@ -979,6 +996,46 @@ static ssize_t show_cpuhp_state(struct device *dev, 
}

static DEVICE_ATTR(state, 0444, show_cpuhp_state, NULL);



static ssize_t write_cpuhp_target(struct device *dev,

				  struct device_attribute *attr,

				  const char *buf, size_t count)

{

	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);

	struct cpuhp_step *sp;

	int target, ret;



	ret = kstrtoint(buf, 10, &target);

	if (ret)

		return ret;



#ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL

	if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)

		return -EINVAL;

#else

	if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)

		return -EINVAL;

#endif



	ret = lock_device_hotplug_sysfs();

	if (ret)

		return ret;



	mutex_lock(&cpuhp_state_mutex);

	sp = cpuhp_get_step(target);

	ret = !sp->name || sp->cant_stop ? -EINVAL : 0;

	mutex_unlock(&cpuhp_state_mutex);

	if (ret)

		return ret;



	if (st->state < target)

		ret = do_cpu_up(dev->id, target);

	else

		ret = do_cpu_down(dev->id, target);



	unlock_device_hotplug();

	return ret ? ret : count;

}



static ssize_t show_cpuhp_target(struct device *dev,

				 struct device_attribute *attr, char *buf)

{
@@ -986,7 +1043,7 @@ static ssize_t show_cpuhp_target(struct device *dev, 


	return sprintf(buf, "%d\n", st->target);

}

static DEVICE_ATTR(target, 0444, show_cpuhp_target, NULL);

static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);



static struct attribute *cpuhp_cpu_attrs[] = {

	&dev_attr_state.attr,
@@ -1007,7 +1064,7 @@ static ssize_t show_cpuhp_states(struct device *dev, 
	int i;



	mutex_lock(&cpuhp_state_mutex);

	for (i = 0; i <= CPUHP_ONLINE; i++) {

	for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {

		struct cpuhp_step *sp = cpuhp_get_step(i);



		if (sp->name) {

lib/Kconfig.debug

+13 −0
Original line number Diff line number Diff line
@@ -1442,6 +1442,19 @@ config DEBUG_BLOCK_EXT_DEVT 


	  Say N if you are unsure.



config CPU_HOTPLUG_STATE_CONTROL

	bool "Enable CPU hotplug state control"

	depends on DEBUG_KERNEL

	depends on HOTPLUG_CPU

	default n

	help

	  Allows to write steps between "offline" and "online" to the CPUs

	  sysfs target file so states can be stepped granular. This is a debug

	  option for now as the hotplug machinery cannot be stopped and

	  restarted at arbitrary points yet.



	  Say N if your are unsure.



config NOTIFIER_ERROR_INJECTION

	tristate "Notifier error injection"

	depends on DEBUG_KERNEL