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

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.deSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 2e1a3483
......@@ -22,6 +22,7 @@
#include <linux/lockdep.h>
#include <linux/tick.h>
#include <linux/irq.h>
#include <linux/smpboot.h>
#include <trace/events/power.h>
#define CREATE_TRACE_POINTS
......@@ -33,10 +34,24 @@
* cpuhp_cpu_state - Per cpu hotplug state storage
* @state: The current cpu 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 {
enum cpuhp_state state;
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);
......@@ -394,6 +409,134 @@ static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
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
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)
{
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)
......
......@@ -569,6 +569,7 @@ void __init smp_init(void)
unsigned int cpu;
idle_threads_init();
cpuhp_threads_init();
/* FIXME: This should be done in userspace --RR */
for_each_present_cpu(cpu) {
......
......@@ -17,4 +17,6 @@ int smpboot_create_threads(unsigned int cpu);
int smpboot_park_threads(unsigned int cpu);
int smpboot_unpark_threads(unsigned int cpu);
void __init cpuhp_threads_init(void);
#endif
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