Commit 036f2137 authored by Rusty Russell's avatar Rusty Russell Committed by Linus Torvalds

[PATCH] Hotplug CPUs: cpu_down()

Implement cpu_down(): uses stop_machine to freeze the machine, then
uses (arch-specific) __cpu_disable() and migrate_all_tasks().

Whole thing under CONFIG_HOTPLUG_CPU, so doesn't break archs which
don't define that.
parent c884a1a3
...@@ -63,6 +63,7 @@ extern struct semaphore cpucontrol; ...@@ -63,6 +63,7 @@ extern struct semaphore cpucontrol;
static struct notifier_block fn##_nb = { fn, pri }; \ static struct notifier_block fn##_nb = { fn, pri }; \
register_cpu_notifier(&fn##_nb); \ register_cpu_notifier(&fn##_nb); \
} }
int cpu_down(unsigned int cpu);
#define cpu_is_offline(cpu) unlikely(!cpu_online(cpu)) #define cpu_is_offline(cpu) unlikely(!cpu_online(cpu))
#else #else
#define lock_cpu_hotplug() do { } while (0) #define lock_cpu_hotplug() do { } while (0)
......
/* CPU control. /* CPU control.
* (C) 2001 Rusty Russell * (C) 2001, 2002, 2003, 2004 Rusty Russell
*
* This code is licenced under the GPL. * This code is licenced under the GPL.
*/ */
#include <linux/proc_fs.h> #include <linux/proc_fs.h>
...@@ -10,6 +11,9 @@ ...@@ -10,6 +11,9 @@
#include <linux/unistd.h> #include <linux/unistd.h>
#include <linux/cpu.h> #include <linux/cpu.h>
#include <linux/module.h> #include <linux/module.h>
#include <linux/kmod.h> /* for hotplug_path */
#include <linux/kthread.h>
#include <linux/stop_machine.h>
#include <asm/semaphore.h> #include <asm/semaphore.h>
/* This protects CPUs going up and down... */ /* This protects CPUs going up and down... */
...@@ -38,6 +42,125 @@ void unregister_cpu_notifier(struct notifier_block *nb) ...@@ -38,6 +42,125 @@ void unregister_cpu_notifier(struct notifier_block *nb)
} }
EXPORT_SYMBOL(unregister_cpu_notifier); EXPORT_SYMBOL(unregister_cpu_notifier);
#ifdef CONFIG_HOTPLUG_CPU
static inline void check_for_tasks(int cpu, struct task_struct *k)
{
struct task_struct *p;
write_lock_irq(&tasklist_lock);
for_each_process(p) {
if (task_cpu(p) == cpu && p != k)
printk(KERN_WARNING "Task %s is on cpu %d\n",
p->comm, cpu);
}
write_unlock_irq(&tasklist_lock);
}
/* Notify userspace when a cpu event occurs, by running '/sbin/hotplug
* cpu' with certain environment variables set. */
static int cpu_run_sbin_hotplug(unsigned int cpu, const char *action)
{
char *argv[3], *envp[5], cpu_str[12], action_str[32];
int i;
sprintf(cpu_str, "CPU=%d", cpu);
sprintf(action_str, "ACTION=%s", action);
/* FIXME: Add DEVPATH. --RR */
i = 0;
argv[i++] = hotplug_path;
argv[i++] = "cpu";
argv[i] = NULL;
i = 0;
/* minimal command environment */
envp[i++] = "HOME=/";
envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
envp[i++] = cpu_str;
envp[i++] = action_str;
envp[i] = NULL;
return call_usermodehelper(argv[0], argv, envp, 0);
}
/* Take this CPU down. */
static int take_cpu_down(void *unused)
{
int err;
/* Take offline: makes arch_cpu_down somewhat easier. */
cpu_clear(smp_processor_id(), cpu_online_map);
/* Ensure this CPU doesn't handle any more interrupts. */
err = __cpu_disable();
if (err < 0)
cpu_set(smp_processor_id(), cpu_online_map);
else
/* Everyone else gets kicked off. */
migrate_all_tasks();
return err;
}
int cpu_down(unsigned int cpu)
{
int err;
struct task_struct *p;
if ((err = lock_cpu_hotplug_interruptible()) != 0)
return err;
if (num_online_cpus() == 1) {
err = -EBUSY;
goto out;
}
if (!cpu_online(cpu)) {
err = -EINVAL;
goto out;
}
p = __stop_machine_run(take_cpu_down, NULL, cpu);
if (IS_ERR(p)) {
err = PTR_ERR(p);
goto out;
}
if (cpu_online(cpu))
goto out_thread;
check_for_tasks(cpu, p);
/* Wait for it to sleep (leaving idle task). */
while (!idle_cpu(cpu))
yield();
/* This actually kills the CPU. */
__cpu_die(cpu);
/* Move it here so it can run. */
kthread_bind(p, smp_processor_id());
/* CPU is completely dead: tell everyone. Too late to complain. */
if (notifier_call_chain(&cpu_chain, CPU_DEAD, (void *)(long)cpu)
== NOTIFY_BAD)
BUG();
cpu_run_sbin_hotplug(cpu, "offline");
out_thread:
err = kthread_stop(p);
out:
unlock_cpu_hotplug();
return err;
}
#else
static inline int cpu_run_sbin_hotplug(unsigned int cpu, const char *action)
{
return 0;
}
#endif /*CONFIG_HOTPLUG_CPU*/
int __devinit cpu_up(unsigned int cpu) int __devinit cpu_up(unsigned int cpu)
{ {
int ret; int ret;
......
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