Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 4cb28ced authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

cpu/hotplug: Create hotplug threads 



In order to let the hotplugged cpu take care of the setup/teardown, we need a
seperate hotplug thread.

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/20160226182341.454541272@linutronix.de


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 2e1a3483

kernel/cpu.c

+144 −1
Original line number Original line Diff line number Diff line
@@ -22,6 +22,7 @@ 
#include <linux/lockdep.h>

#include <linux/lockdep.h>

#include <linux/tick.h>

#include <linux/tick.h>

#include <linux/irq.h>

#include <linux/irq.h>

#include <linux/smpboot.h>





#include <trace/events/power.h>

#include <trace/events/power.h>

#define CREATE_TRACE_POINTS

#define CREATE_TRACE_POINTS
@@ -33,10 +34,24 @@ 
 * cpuhp_cpu_state - Per cpu hotplug state storage

 * cpuhp_cpu_state - Per cpu hotplug state storage

 * @state:	The current cpu state

 * @state:	The current cpu state

 * @target:	The target state

 * @target:	The target state

 * @thread:	Pointer to the hotplug thread

 * @should_run:	Thread should execute

 * @cb_stat:	The state for a single callback (install/uninstall)

 * @cb:		Single callback function (install/uninstall)

 * @result:	Result of the operation

 * @done:	Signal completion to the issuer of the task

 */

 */

struct cpuhp_cpu_state {

struct cpuhp_cpu_state {

	enum cpuhp_state	state;

	enum cpuhp_state	state;

	enum cpuhp_state	target;

	enum cpuhp_state	target;

#ifdef CONFIG_SMP

	struct task_struct	*thread;

	bool			should_run;

	enum cpuhp_state	cb_state;

	int			(*cb)(unsigned int cpu);

	int			result;

	struct completion	done;

#endif

};

};





static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state);

static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state);
@@ -394,6 +409,134 @@ static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st, 
	return ret;

	return ret;

}

}





/*

 * The cpu hotplug threads manage the bringup and teardown of the cpus

 */

static void cpuhp_create(unsigned int cpu)

{

	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);



	init_completion(&st->done);

}



static int cpuhp_should_run(unsigned int cpu)

{

	struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);



	return st->should_run;

}



/* Execute the teardown callbacks. Used to be CPU_DOWN_PREPARE */

static int cpuhp_ap_offline(unsigned int cpu, struct cpuhp_cpu_state *st)

{

	enum cpuhp_state target = max((int)st->target, CPUHP_AP_ONLINE);



	return cpuhp_down_callbacks(cpu, st, cpuhp_ap_states, target);

}



/* Execute the online startup callbacks. Used to be CPU_ONLINE */

static int cpuhp_ap_online(unsigned int cpu, struct cpuhp_cpu_state *st)

{

	return cpuhp_up_callbacks(cpu, st, cpuhp_ap_states, st->target);

}



/*

 * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke

 * callbacks when a state gets [un]installed at runtime.

 */

static void cpuhp_thread_fun(unsigned int cpu)

{

	struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);

	int ret = 0;



	/*

	 * Paired with the mb() in cpuhp_kick_ap_work and

	 * cpuhp_invoke_ap_callback, so the work set is consistent visible.

	 */

	smp_mb();

	if (!st->should_run)

		return;



	st->should_run = false;



	/* Single callback invocation for [un]install ? */

	if (st->cb) {

		if (st->cb_state < CPUHP_AP_ONLINE) {

			local_irq_disable();

			ret = cpuhp_invoke_callback(cpu, st->cb_state, st->cb);

			local_irq_enable();

		} else {

			ret = cpuhp_invoke_callback(cpu, st->cb_state, st->cb);

		}

	} else {

		/* Regular hotplug work */

		if (st->state < st->target)

			ret = cpuhp_ap_online(cpu, st);

		else if (st->state > st->target)

			ret = cpuhp_ap_offline(cpu, st);

	}

	st->result = ret;

	complete(&st->done);

}



/* Invoke a single callback on a remote cpu */

static int cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state,

				    int (*cb)(unsigned int))

{

	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);



	if (!cpu_online(cpu))

		return 0;



	st->cb_state = state;

	st->cb = cb;

	/*

	 * Make sure the above stores are visible before should_run becomes

	 * true. Paired with the mb() above in cpuhp_thread_fun()

	 */

	smp_mb();

	st->should_run = true;

	wake_up_process(st->thread);

	wait_for_completion(&st->done);

	return st->result;

}



/* Regular hotplug invocation of the AP hotplug thread */

static int cpuhp_kick_ap_work(unsigned int cpu)

{

	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);

	enum cpuhp_state state = st->state;



	trace_cpuhp_enter(cpu, st->target, state, cpuhp_kick_ap_work);

	st->result = 0;

	st->cb = NULL;

	/*

	 * Make sure the above stores are visible before should_run becomes

	 * true. Paired with the mb() above in cpuhp_thread_fun()

	 */

	smp_mb();

	st->should_run = true;

	wake_up_process(st->thread);

	wait_for_completion(&st->done);

	trace_cpuhp_exit(cpu, st->state, state, st->result);

	return st->result;

}



static struct smp_hotplug_thread cpuhp_threads = {

	.store			= &cpuhp_state.thread,

	.create			= &cpuhp_create,

	.thread_should_run	= cpuhp_should_run,

	.thread_fn		= cpuhp_thread_fun,

	.thread_comm		= "cpuhp/%u",

	.selfparking		= true,

};



void __init cpuhp_threads_init(void)

{

	BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));

	kthread_unpark(this_cpu_read(cpuhp_state.thread));

}



#ifdef CONFIG_HOTPLUG_CPU

#ifdef CONFIG_HOTPLUG_CPU

EXPORT_SYMBOL(register_cpu_notifier);

EXPORT_SYMBOL(register_cpu_notifier);

EXPORT_SYMBOL(__register_cpu_notifier);

EXPORT_SYMBOL(__register_cpu_notifier);
@@ -997,7 +1140,7 @@ static int cpuhp_cb_check(enum cpuhp_state state) 




static bool cpuhp_is_ap_state(enum cpuhp_state state)

static bool cpuhp_is_ap_state(enum cpuhp_state state)

{

{

	return (state > CPUHP_AP_OFFLINE && state < CPUHP_AP_ONLINE);

	return (state >= CPUHP_AP_OFFLINE && state <= CPUHP_AP_ONLINE);

}

}





static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)

static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)

kernel/smp.c

+1 −0
Original line number Original line Diff line number Diff line
@@ -569,6 +569,7 @@ void __init smp_init(void) 
	unsigned int cpu;

	unsigned int cpu;





	idle_threads_init();

	idle_threads_init();

	cpuhp_threads_init();





	/* FIXME: This should be done in userspace --RR */

	/* FIXME: This should be done in userspace --RR */

	for_each_present_cpu(cpu) {

	for_each_present_cpu(cpu) {

kernel/smpboot.h

+2 −0
Original line number Original line Diff line number Diff line
@@ -17,4 +17,6 @@ int smpboot_create_threads(unsigned int cpu); 
int smpboot_park_threads(unsigned int cpu);

int smpboot_park_threads(unsigned int cpu);

int smpboot_unpark_threads(unsigned int cpu);

int smpboot_unpark_threads(unsigned int cpu);





void __init cpuhp_threads_init(void);



#endif
 
#endif