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Commit 4baa0afc authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

cpu/hotplug: Convert the hotplugged cpu work to a state machine 



Move the functions which need to run on the hotplugged processor into
a state machine array and let the code iterate through these functions.

In a later state, this will grow synchronization points between the
control processor and the hotplugged processor, so we can move the
various architecture implementations of the synchronizations to the
core.

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/20160226182340.770651526@linutronix.de


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent cff7d378

include/linux/cpuhotplug.h

+4 −0
Original line number Diff line number Diff line
@@ -6,6 +6,10 @@ enum cpuhp_state { 
	CPUHP_CREATE_THREADS,

	CPUHP_NOTIFY_PREPARE,

	CPUHP_BRINGUP_CPU,

	CPUHP_AP_OFFLINE,

	CPUHP_AP_NOTIFY_STARTING,

	CPUHP_AP_ONLINE,

	CPUHP_TEARDOWN_CPU,

	CPUHP_NOTIFY_ONLINE,

	CPUHP_ONLINE,

};

kernel/cpu.c

+66 −15
Original line number Diff line number Diff line
@@ -57,6 +57,7 @@ struct cpuhp_step { 
};



static struct cpuhp_step cpuhp_bp_states[];

static struct cpuhp_step cpuhp_ap_states[];



/**

 * cpuhp_invoke_callback _ Invoke the callbacks for a given state
@@ -304,6 +305,12 @@ static int notify_online(unsigned int cpu) 
	return 0;

}



static int notify_starting(unsigned int cpu)

{

	cpu_notify(CPU_STARTING, cpu);

	return 0;

}



static int bringup_cpu(unsigned int cpu)

{

	struct task_struct *idle = idle_thread_get(cpu);
@@ -421,9 +428,17 @@ static int notify_down_prepare(unsigned int cpu) 
	return err;

}



static int notify_dying(unsigned int cpu)

{

	cpu_notify(CPU_DYING, cpu);

	return 0;

}



/* Take this CPU down. */

static int take_cpu_down(void *_param)

{

	struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);

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

	int err, cpu = smp_processor_id();



	/* Ensure this CPU doesn't handle any more interrupts. */
@@ -431,7 +446,12 @@ static int take_cpu_down(void *_param) 
	if (err < 0)

		return err;



	cpu_notify(CPU_DYING, cpu);

	/* Invoke the former CPU_DYING callbacks */

	for (; st->state > target; st->state--) {

		struct cpuhp_step *step = cpuhp_ap_states + st->state;



		cpuhp_invoke_callback(cpu, st->state, step->teardown);

	}

	/* Give up timekeeping duties */

	tick_handover_do_timer();

	/* Park the stopper thread */
@@ -512,6 +532,7 @@ static int notify_dead(unsigned int cpu) 
#define notify_down_prepare	NULL

#define takedown_cpu		NULL

#define notify_dead		NULL

#define notify_dying		NULL

#endif



#ifdef CONFIG_HOTPLUG_CPU
@@ -615,6 +636,28 @@ void smpboot_thread_init(void) 
	register_cpu_notifier(&smpboot_thread_notifier);

}



/**

 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers

 * @cpu: cpu that just started

 *

 * This function calls the cpu_chain notifiers with CPU_STARTING.

 * It must be called by the arch code on the new cpu, before the new cpu

 * enables interrupts and before the "boot" cpu returns from __cpu_up().

 */

void notify_cpu_starting(unsigned int cpu)

{

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

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



	while (st->state < target) {

		struct cpuhp_step *step;



		st->state++;

		step = cpuhp_ap_states + st->state;

		cpuhp_invoke_callback(cpu, st->state, step->startup);

	}

}



static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st)

{

	for (st->state--; st->state > st->target; st->state--) {
@@ -842,19 +885,6 @@ core_initcall(cpu_hotplug_pm_sync_init); 


#endif /* CONFIG_PM_SLEEP_SMP */



/**

 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers

 * @cpu: cpu that just started

 *

 * This function calls the cpu_chain notifiers with CPU_STARTING.

 * It must be called by the arch code on the new cpu, before the new cpu

 * enables interrupts and before the "boot" cpu returns from __cpu_up().

 */

void notify_cpu_starting(unsigned int cpu)

{

	cpu_notify(CPU_STARTING, cpu);

}



#endif /* CONFIG_SMP */



/* Boot processor state steps */
@@ -879,8 +909,12 @@ static struct cpuhp_step cpuhp_bp_states[] = { 
	[CPUHP_BRINGUP_CPU] = {

		.name			= "cpu:bringup",

		.startup		= bringup_cpu,

		.teardown		= NULL,

	},

	[CPUHP_TEARDOWN_CPU] = {

		.name			= "cpu:teardown",

		.startup		= NULL,

		.teardown		= takedown_cpu,

		.skip_onerr		= true,

	},

	[CPUHP_NOTIFY_ONLINE] = {

		.name			= "notify:online",
@@ -895,6 +929,23 @@ static struct cpuhp_step cpuhp_bp_states[] = { 
	},

};



/* Application processor state steps */

static struct cpuhp_step cpuhp_ap_states[] = {

#ifdef CONFIG_SMP

	[CPUHP_AP_NOTIFY_STARTING] = {

		.name			= "notify:starting",

		.startup		= notify_starting,

		.teardown		= notify_dying,

		.skip_onerr		= true,

	},

#endif

	[CPUHP_ONLINE] = {

		.name			= "online",

		.startup		= NULL,

		.teardown		= NULL,

	},

};



/*

 * cpu_bit_bitmap[] is a special, "compressed" data structure that

 * represents all NR_CPUS bits binary values of 1<<nr.