cpu/hotplug: Convert to a state machine for the control processor
Move the split out steps into a callback array and let the cpu_up/down
code iterate through the array functions. For now most of the
callbacks are asymmetric to resemble the current hotplug maze.
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/20160226182340.671816690@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 0b5d259..3018519 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -22,10 +22,64 @@
#include <linux/lockdep.h>
#include <linux/tick.h>
#include <linux/irq.h>
+
#include <trace/events/power.h>
+#define CREATE_TRACE_POINTS
+#include <trace/events/cpuhp.h>
#include "smpboot.h"
+/**
+ * cpuhp_cpu_state - Per cpu hotplug state storage
+ * @state: The current cpu state
+ * @target: The target state
+ */
+struct cpuhp_cpu_state {
+ enum cpuhp_state state;
+ enum cpuhp_state target;
+};
+
+static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state);
+
+/**
+ * cpuhp_step - Hotplug state machine step
+ * @name: Name of the step
+ * @startup: Startup function of the step
+ * @teardown: Teardown function of the step
+ * @skip_onerr: Do not invoke the functions on error rollback
+ * Will go away once the notifiers are gone
+ */
+struct cpuhp_step {
+ const char *name;
+ int (*startup)(unsigned int cpu);
+ int (*teardown)(unsigned int cpu);
+ bool skip_onerr;
+};
+
+static struct cpuhp_step cpuhp_bp_states[];
+
+/**
+ * cpuhp_invoke_callback _ Invoke the callbacks for a given state
+ * @cpu: The cpu for which the callback should be invoked
+ * @step: The step in the state machine
+ * @cb: The callback function to invoke
+ *
+ * Called from cpu hotplug and from the state register machinery
+ */
+static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state step,
+ int (*cb)(unsigned int))
+{
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+ int ret = 0;
+
+ if (cb) {
+ trace_cpuhp_enter(cpu, st->target, step, cb);
+ ret = cb(cpu);
+ trace_cpuhp_exit(cpu, st->state, step, ret);
+ }
+ return ret;
+}
+
#ifdef CONFIG_SMP
/* Serializes the updates to cpu_online_mask, cpu_present_mask */
static DEFINE_MUTEX(cpu_add_remove_lock);
@@ -454,10 +508,29 @@
return 0;
}
+#else
+#define notify_down_prepare NULL
+#define takedown_cpu NULL
+#define notify_dead NULL
+#endif
+
+#ifdef CONFIG_HOTPLUG_CPU
+static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st)
+{
+ for (st->state++; st->state < st->target; st->state++) {
+ struct cpuhp_step *step = cpuhp_bp_states + st->state;
+
+ if (!step->skip_onerr)
+ cpuhp_invoke_callback(cpu, st->state, step->startup);
+ }
+}
+
/* Requires cpu_add_remove_lock to be held */
static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
{
- int err;
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+ int prev_state, ret = 0;
+ bool hasdied = false;
if (num_online_cpus() == 1)
return -EBUSY;
@@ -469,20 +542,25 @@
cpuhp_tasks_frozen = tasks_frozen;
- err = notify_down_prepare(cpu);
- if (err)
- goto out_release;
- err = takedown_cpu(cpu);
- if (err)
- goto out_release;
+ prev_state = st->state;
+ st->target = CPUHP_OFFLINE;
+ for (; st->state > st->target; st->state--) {
+ struct cpuhp_step *step = cpuhp_bp_states + st->state;
- notify_dead(cpu);
+ ret = cpuhp_invoke_callback(cpu, st->state, step->teardown);
+ if (ret) {
+ st->target = prev_state;
+ undo_cpu_down(cpu, st);
+ break;
+ }
+ }
+ hasdied = prev_state != st->state && st->state == CPUHP_OFFLINE;
-out_release:
cpu_hotplug_done();
- if (!err)
+ /* This post dead nonsense must die */
+ if (!ret && hasdied)
cpu_notify_nofail(CPU_POST_DEAD, cpu);
- return err;
+ return ret;
}
int cpu_down(unsigned int cpu)
@@ -537,11 +615,22 @@
register_cpu_notifier(&smpboot_thread_notifier);
}
+static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st)
+{
+ for (st->state--; st->state > st->target; st->state--) {
+ struct cpuhp_step *step = cpuhp_bp_states + st->state;
+
+ if (!step->skip_onerr)
+ cpuhp_invoke_callback(cpu, st->state, step->teardown);
+ }
+}
+
/* Requires cpu_add_remove_lock to be held */
static int _cpu_up(unsigned int cpu, int tasks_frozen)
{
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
struct task_struct *idle;
- int ret;
+ int prev_state, ret = 0;
cpu_hotplug_begin();
@@ -550,6 +639,7 @@
goto out;
}
+ /* Let it fail before we try to bring the cpu up */
idle = idle_thread_get(cpu);
if (IS_ERR(idle)) {
ret = PTR_ERR(idle);
@@ -558,22 +648,22 @@
cpuhp_tasks_frozen = tasks_frozen;
- ret = smpboot_create_threads(cpu);
- if (ret)
- goto out;
+ prev_state = st->state;
+ st->target = CPUHP_ONLINE;
+ while (st->state < st->target) {
+ struct cpuhp_step *step;
- ret = notify_prepare(cpu);
- if (ret)
- goto out;
-
- ret = bringup_cpu(cpu);
- if (ret)
- goto out;
-
- notify_online(cpu);
+ st->state++;
+ step = cpuhp_bp_states + st->state;
+ ret = cpuhp_invoke_callback(cpu, st->state, step->startup);
+ if (ret) {
+ st->target = prev_state;
+ undo_cpu_up(cpu, st);
+ break;
+ }
+ }
out:
cpu_hotplug_done();
-
return ret;
}
@@ -767,6 +857,44 @@
#endif /* CONFIG_SMP */
+/* Boot processor state steps */
+static struct cpuhp_step cpuhp_bp_states[] = {
+ [CPUHP_OFFLINE] = {
+ .name = "offline",
+ .startup = NULL,
+ .teardown = NULL,
+ },
+#ifdef CONFIG_SMP
+ [CPUHP_CREATE_THREADS]= {
+ .name = "threads:create",
+ .startup = smpboot_create_threads,
+ .teardown = NULL,
+ },
+ [CPUHP_NOTIFY_PREPARE] = {
+ .name = "notify:prepare",
+ .startup = notify_prepare,
+ .teardown = notify_dead,
+ .skip_onerr = true,
+ },
+ [CPUHP_BRINGUP_CPU] = {
+ .name = "cpu:bringup",
+ .startup = bringup_cpu,
+ .teardown = takedown_cpu,
+ .skip_onerr = true,
+ },
+ [CPUHP_NOTIFY_ONLINE] = {
+ .name = "notify:online",
+ .startup = notify_online,
+ .teardown = notify_down_prepare,
+ },
+#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.
@@ -826,3 +954,25 @@
{
cpumask_copy(&__cpu_online_mask, src);
}
+
+/*
+ * Activate the first processor.
+ */
+void __init boot_cpu_init(void)
+{
+ int cpu = smp_processor_id();
+
+ /* Mark the boot cpu "present", "online" etc for SMP and UP case */
+ set_cpu_online(cpu, true);
+ set_cpu_active(cpu, true);
+ set_cpu_present(cpu, true);
+ set_cpu_possible(cpu, true);
+}
+
+/*
+ * Must be called _AFTER_ setting up the per_cpu areas
+ */
+void __init boot_cpu_state_init(void)
+{
+ per_cpu_ptr(&cpuhp_state, smp_processor_id())->state = CPUHP_ONLINE;
+}