[patch 07/40] cpu: hotplug: Convert to a state machine for thecontrol processor
From: Thomas Gleixner
Date: Thu Jan 31 2013 - 07:20:12 EST
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 asymetric to resemble the current hotplug maze.
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
include/linux/cpu.h | 4 +
include/linux/cpuhotplug.h | 16 ++++
init/main.c | 15 ---
kernel/cpu.c | 180 ++++++++++++++++++++++++++++++++++++---------
kernel/smpboot.c | 6 +
kernel/smpboot.h | 4 -
6 files changed, 173 insertions(+), 52 deletions(-)
Index: linux-2.6/include/linux/cpu.h
===================================================================
--- linux-2.6.orig/include/linux/cpu.h
+++ linux-2.6/include/linux/cpu.h
@@ -26,6 +26,9 @@ struct cpu {
struct device dev;
};
+extern void boot_cpu_init(void);
+extern void boot_cpu_state_init(void);
+
extern int register_cpu(struct cpu *cpu, int num);
extern struct device *get_cpu_device(unsigned cpu);
extern bool cpu_is_hotpluggable(unsigned cpu);
@@ -112,6 +115,7 @@ enum {
#ifdef CONFIG_SMP
+extern bool cpuhp_tasks_frozen;
/* Need to know about CPUs going up/down? */
#if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE)
#define cpu_notifier(fn, pri) { \
Index: linux-2.6/include/linux/cpuhotplug.h
===================================================================
--- /dev/null
+++ linux-2.6/include/linux/cpuhotplug.h
@@ -0,0 +1,16 @@
+#ifndef __CPUHOTPLUG_H
+#define __CPUHOTPLUG_H
+
+enum cpuhp_states {
+ CPUHP_OFFLINE,
+ CPUHP_CREATE_THREADS,
+ CPUHP_NOTIFY_PREPARE,
+ CPUHP_NOTIFY_DEAD,
+ CPUHP_BRINGUP_CPU,
+ CPUHP_TEARDOWN_CPU,
+ CPUHP_PERCPU_THREADS,
+ CPUHP_NOTIFY_ONLINE,
+ CPUHP_NOTIFY_DOWN_PREPARE,
+ CPUHP_MAX,
+};
+#endif
Index: linux-2.6/init/main.c
===================================================================
--- linux-2.6.orig/init/main.c
+++ linux-2.6/init/main.c
@@ -424,20 +424,6 @@ void __init parse_early_param(void)
done = 1;
}
-/*
- * Activate the first processor.
- */
-
-static 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);
-}
-
void __init __weak smp_setup_processor_id(void)
{
}
@@ -502,6 +488,7 @@ asmlinkage void __init start_kernel(void
setup_command_line(command_line);
setup_nr_cpu_ids();
setup_per_cpu_areas();
+ boot_cpu_state_init();
smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */
build_all_zonelists(NULL, NULL);
Index: linux-2.6/kernel/cpu.c
===================================================================
--- linux-2.6.orig/kernel/cpu.c
+++ linux-2.6/kernel/cpu.c
@@ -19,13 +19,24 @@
#include <linux/mutex.h>
#include <linux/gfp.h>
#include <linux/suspend.h>
+#include <linux/cpuhotplug.h>
#include "smpboot.h"
+/* CPU state */
+static DEFINE_PER_CPU(enum cpuhp_states, cpuhp_state);
+
+struct cpuhp_step {
+ int (*startup)(unsigned int cpu);
+ int (*teardown)(unsigned int cpu);
+};
+
+static struct cpuhp_step cpuhp_bp_states[];
+
#ifdef CONFIG_SMP
/* Serializes the updates to cpu_online_mask, cpu_present_mask */
static DEFINE_MUTEX(cpu_add_remove_lock);
-static bool cpuhp_tasks_frozen;
+bool cpuhp_tasks_frozen;
/*
* The following two API's must be used when attempting
@@ -310,13 +321,10 @@ static int __ref take_cpu_down(void *_pa
static int takedown_cpu(unsigned int cpu)
{
- int err;
+ int err = __stop_machine(take_cpu_down, NULL, cpumask_of(cpu));
- smpboot_park_threads(cpu);
- err = __stop_machine(take_cpu_down, NULL, cpumask_of(cpu));
if (err) {
/* CPU didn't die: tell everyone. Can't complain. */
- smpboot_unpark_threads(cpu);
cpu_notify_nofail(CPU_DOWN_FAILED, cpu);
return err;
}
@@ -345,10 +353,32 @@ static int notify_dead(unsigned int cpu)
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, int step)
+{
+ while (step++ < CPUHP_MAX) {
+ /*
+ * Transitional check. Will be removed when we have a
+ * fully symetric mechanism
+ */
+ if (!cpuhp_bp_states[step].teardown)
+ continue;
+
+ if (cpuhp_bp_states[step].startup)
+ cpuhp_bp_states[step].startup(cpu);
+ }
+}
+
/* Requires cpu_add_remove_lock to be held */
static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
{
- int err;
+ int ret = 0, step;
if (num_online_cpus() == 1)
return -EBUSY;
@@ -360,20 +390,23 @@ static int __ref _cpu_down(unsigned int
cpuhp_tasks_frozen = tasks_frozen;
- err = notify_down_prepare(cpu);
- if (err)
- goto out_release;
- err = takedown_cpu(cpu);
- if (err)
- goto out_release;
-
- notify_dead(cpu);
+ for (step = per_cpu(cpuhp_state, cpu); step > 0; step--) {
+ if (cpuhp_bp_states[step].teardown) {
+ ret = cpuhp_bp_states[step].teardown(cpu);
+ if (ret) {
+ undo_cpu_down(cpu, step + 1);
+ step = CPUHP_MAX;
+ break;
+ }
+ }
+ }
+ /* Store the current cpu state */
+ per_cpu(cpuhp_state, cpu) = step;
-out_release:
cpu_hotplug_done();
- if (!err)
+ if (!ret)
cpu_notify_nofail(CPU_POST_DEAD, cpu);
- return err;
+ return ret;
}
int __ref cpu_down(unsigned int cpu)
@@ -396,11 +429,25 @@ out:
EXPORT_SYMBOL(cpu_down);
#endif /*CONFIG_HOTPLUG_CPU*/
+static void undo_cpu_up(unsigned int cpu, int step)
+{
+ while (step--) {
+ /*
+ * Transitional check. Will be removed when we have a
+ * fully symetric mechanism
+ */
+ if (!cpuhp_bp_states[step].startup)
+ continue;
+ if (cpuhp_bp_states[step].teardown)
+ cpuhp_bp_states[step].teardown(cpu);
+ }
+}
+
/* Requires cpu_add_remove_lock to be held */
static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
{
+ int ret = 0, step;
struct task_struct *idle;
- int ret;
cpu_hotplug_begin();
@@ -409,6 +456,7 @@ static int __cpuinit _cpu_up(unsigned in
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);
@@ -417,24 +465,20 @@ static int __cpuinit _cpu_up(unsigned in
cpuhp_tasks_frozen = tasks_frozen;
- ret = smpboot_create_threads(cpu);
- if (ret)
- goto out;
-
- ret = notify_prepare(cpu);
- if (ret)
- goto out;
-
- ret = bringup_cpu(cpu);
- if (ret)
- goto out;
-
- /* Wake the per cpu threads */
- smpboot_unpark_threads(cpu);
- notify_online(cpu);
+ for (step = per_cpu(cpuhp_state, cpu); step < CPUHP_MAX; step++) {
+ if (cpuhp_bp_states[step].startup) {
+ ret = cpuhp_bp_states[step].startup(cpu);
+ if (ret) {
+ undo_cpu_up(cpu, step - 1);
+ step = 0;
+ break;
+ }
+ }
+ }
+ /* Store the current cpu state */
+ per_cpu(cpuhp_state, cpu) = step;
out:
cpu_hotplug_done();
-
return ret;
}
@@ -674,6 +718,52 @@ void __cpuinit notify_cpu_starting(unsig
#endif /* CONFIG_SMP */
+/* Boot processor state steps */
+static struct cpuhp_step cpuhp_bp_states[] = {
+ [CPUHP_OFFLINE] = {
+ .startup = NULL,
+ .teardown = NULL,
+ },
+#ifdef CONFIG_SMP
+ [CPUHP_CREATE_THREADS] = {
+ .startup = smpboot_create_threads,
+ .teardown = NULL,
+ },
+ [CPUHP_NOTIFY_PREPARE] = {
+ .startup = notify_prepare,
+ .teardown = NULL,
+ },
+ [CPUHP_NOTIFY_DEAD] = {
+ .startup = NULL,
+ .teardown = notify_dead,
+ },
+ [CPUHP_BRINGUP_CPU] = {
+ .startup = bringup_cpu,
+ .teardown = NULL,
+ },
+ [CPUHP_TEARDOWN_CPU] = {
+ .startup = NULL,
+ .teardown = takedown_cpu,
+ },
+ [CPUHP_PERCPU_THREADS] = {
+ .startup = smpboot_unpark_threads,
+ .teardown = smpboot_park_threads,
+ },
+ [CPUHP_NOTIFY_ONLINE] = {
+ .startup = notify_online,
+ .teardown = NULL,
+ },
+ [CPUHP_NOTIFY_DOWN_PREPARE] = {
+ .startup = NULL,
+ .teardown = notify_down_prepare,
+ },
+#endif
+ [CPUHP_MAX] = {
+ .startup = NULL,
+ .teardown = NULL,
+ },
+};
+
/*
* cpu_bit_bitmap[] is a special, "compressed" data structure that
* represents all NR_CPUS bits binary values of 1<<nr.
@@ -769,3 +859,25 @@ void init_cpu_online(const struct cpumas
{
cpumask_copy(to_cpumask(cpu_online_bits), 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(cpuhp_state, smp_processor_id()) = CPUHP_MAX;
+}
Index: linux-2.6/kernel/smpboot.c
===================================================================
--- linux-2.6.orig/kernel/smpboot.c
+++ linux-2.6/kernel/smpboot.c
@@ -212,7 +212,7 @@ static void smpboot_unpark_thread(struct
kthread_unpark(tsk);
}
-void smpboot_unpark_threads(unsigned int cpu)
+int smpboot_unpark_threads(unsigned int cpu)
{
struct smp_hotplug_thread *cur;
@@ -220,6 +220,7 @@ void smpboot_unpark_threads(unsigned int
list_for_each_entry(cur, &hotplug_threads, list)
smpboot_unpark_thread(cur, cpu);
mutex_unlock(&smpboot_threads_lock);
+ return 0;
}
static void smpboot_park_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
@@ -230,7 +231,7 @@ static void smpboot_park_thread(struct s
kthread_park(tsk);
}
-void smpboot_park_threads(unsigned int cpu)
+int smpboot_park_threads(unsigned int cpu)
{
struct smp_hotplug_thread *cur;
@@ -238,6 +239,7 @@ void smpboot_park_threads(unsigned int c
list_for_each_entry_reverse(cur, &hotplug_threads, list)
smpboot_park_thread(cur, cpu);
mutex_unlock(&smpboot_threads_lock);
+ return 0;
}
static void smpboot_destroy_threads(struct smp_hotplug_thread *ht)
Index: linux-2.6/kernel/smpboot.h
===================================================================
--- linux-2.6.orig/kernel/smpboot.h
+++ linux-2.6/kernel/smpboot.h
@@ -14,7 +14,7 @@ static inline void idle_threads_init(voi
#endif
int smpboot_create_threads(unsigned int cpu);
-void smpboot_park_threads(unsigned int cpu);
-void smpboot_unpark_threads(unsigned int cpu);
+int smpboot_park_threads(unsigned int cpu);
+int smpboot_unpark_threads(unsigned int cpu);
#endif
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