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: Thomas 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: Thomas Gleixner <tglx@linutronix.de>
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145
kernel/cpu.c
145
kernel/cpu.c
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@ -22,6 +22,7 @@
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#include <linux/lockdep.h>
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#include <linux/tick.h>
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#include <linux/irq.h>
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#include <linux/smpboot.h>
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#include <trace/events/power.h>
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#define CREATE_TRACE_POINTS
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@ -33,10 +34,24 @@
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* cpuhp_cpu_state - Per cpu hotplug state storage
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* @state: The current cpu state
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* @target: The target state
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* @thread: Pointer to the hotplug thread
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* @should_run: Thread should execute
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* @cb_stat: The state for a single callback (install/uninstall)
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* @cb: Single callback function (install/uninstall)
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* @result: Result of the operation
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* @done: Signal completion to the issuer of the task
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*/
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struct cpuhp_cpu_state {
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enum cpuhp_state state;
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enum cpuhp_state target;
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#ifdef CONFIG_SMP
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struct task_struct *thread;
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bool should_run;
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enum cpuhp_state cb_state;
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int (*cb)(unsigned int cpu);
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int result;
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struct completion done;
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#endif
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};
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static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state);
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@ -394,6 +409,134 @@ static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
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return ret;
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}
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/*
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* The cpu hotplug threads manage the bringup and teardown of the cpus
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*/
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static void cpuhp_create(unsigned int cpu)
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{
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struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
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init_completion(&st->done);
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}
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static int cpuhp_should_run(unsigned int cpu)
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{
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struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
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return st->should_run;
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}
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/* Execute the teardown callbacks. Used to be CPU_DOWN_PREPARE */
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static int cpuhp_ap_offline(unsigned int cpu, struct cpuhp_cpu_state *st)
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{
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enum cpuhp_state target = max((int)st->target, CPUHP_AP_ONLINE);
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return cpuhp_down_callbacks(cpu, st, cpuhp_ap_states, target);
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}
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/* Execute the online startup callbacks. Used to be CPU_ONLINE */
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static int cpuhp_ap_online(unsigned int cpu, struct cpuhp_cpu_state *st)
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{
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return cpuhp_up_callbacks(cpu, st, cpuhp_ap_states, st->target);
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}
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/*
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* Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
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* callbacks when a state gets [un]installed at runtime.
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*/
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static void cpuhp_thread_fun(unsigned int cpu)
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{
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struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
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int ret = 0;
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/*
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* Paired with the mb() in cpuhp_kick_ap_work and
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* cpuhp_invoke_ap_callback, so the work set is consistent visible.
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*/
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smp_mb();
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if (!st->should_run)
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return;
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st->should_run = false;
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/* Single callback invocation for [un]install ? */
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if (st->cb) {
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if (st->cb_state < CPUHP_AP_ONLINE) {
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local_irq_disable();
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ret = cpuhp_invoke_callback(cpu, st->cb_state, st->cb);
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local_irq_enable();
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} else {
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ret = cpuhp_invoke_callback(cpu, st->cb_state, st->cb);
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}
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} else {
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/* Regular hotplug work */
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if (st->state < st->target)
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ret = cpuhp_ap_online(cpu, st);
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else if (st->state > st->target)
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ret = cpuhp_ap_offline(cpu, st);
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}
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st->result = ret;
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complete(&st->done);
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}
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/* Invoke a single callback on a remote cpu */
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static int cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state,
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int (*cb)(unsigned int))
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{
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struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
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if (!cpu_online(cpu))
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return 0;
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st->cb_state = state;
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st->cb = cb;
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/*
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* Make sure the above stores are visible before should_run becomes
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* true. Paired with the mb() above in cpuhp_thread_fun()
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*/
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smp_mb();
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st->should_run = true;
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wake_up_process(st->thread);
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wait_for_completion(&st->done);
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return st->result;
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}
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/* Regular hotplug invocation of the AP hotplug thread */
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static int cpuhp_kick_ap_work(unsigned int cpu)
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{
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struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
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enum cpuhp_state state = st->state;
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trace_cpuhp_enter(cpu, st->target, state, cpuhp_kick_ap_work);
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st->result = 0;
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st->cb = NULL;
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/*
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* Make sure the above stores are visible before should_run becomes
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* true. Paired with the mb() above in cpuhp_thread_fun()
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*/
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smp_mb();
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st->should_run = true;
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wake_up_process(st->thread);
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wait_for_completion(&st->done);
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trace_cpuhp_exit(cpu, st->state, state, st->result);
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return st->result;
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}
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static struct smp_hotplug_thread cpuhp_threads = {
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.store = &cpuhp_state.thread,
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.create = &cpuhp_create,
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.thread_should_run = cpuhp_should_run,
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.thread_fn = cpuhp_thread_fun,
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.thread_comm = "cpuhp/%u",
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.selfparking = true,
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};
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void __init cpuhp_threads_init(void)
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{
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BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
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kthread_unpark(this_cpu_read(cpuhp_state.thread));
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}
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#ifdef CONFIG_HOTPLUG_CPU
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EXPORT_SYMBOL(register_cpu_notifier);
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EXPORT_SYMBOL(__register_cpu_notifier);
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@ -997,7 +1140,7 @@ static int cpuhp_cb_check(enum cpuhp_state state)
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static bool cpuhp_is_ap_state(enum cpuhp_state state)
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{
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return (state > CPUHP_AP_OFFLINE && state < CPUHP_AP_ONLINE);
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return (state >= CPUHP_AP_OFFLINE && state <= CPUHP_AP_ONLINE);
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}
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static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
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@ -569,6 +569,7 @@ void __init smp_init(void)
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unsigned int cpu;
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idle_threads_init();
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cpuhp_threads_init();
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/* FIXME: This should be done in userspace --RR */
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for_each_present_cpu(cpu) {
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@ -17,4 +17,6 @@ int smpboot_create_threads(unsigned int cpu);
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int smpboot_park_threads(unsigned int cpu);
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int smpboot_unpark_threads(unsigned int cpu);
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void __init cpuhp_threads_init(void);
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#endif
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