linux/kernel/cpu.c
Zwane Mwaikambo f370513640 [PATCH] i386 CPU hotplug
(The i386 CPU hotplug patch provides infrastructure for some work which Pavel
is doing as well as for ACPI S3 (suspend-to-RAM) work which Li Shaohua
<shaohua.li@intel.com> is doing)

The following provides i386 architecture support for safely unregistering and
registering processors during runtime, updated for the current -mm tree.  In
order to avoid dumping cpu hotplug code into kernel/irq/* i dropped the
cpu_online check in do_IRQ() by modifying fixup_irqs().  The difference being
that on cpu offline, fixup_irqs() is called before we clear the cpu from
cpu_online_map and a long delay in order to ensure that we never have any
queued external interrupts on the APICs.  There are additional changes to s390
and ppc64 to account for this change.

1) Add CONFIG_HOTPLUG_CPU
2) disable local APIC timer on dead cpus.
3) Disable preempt around irq balancing to prevent CPUs going down.
4) Print irq stats for all possible cpus.
5) Debugging check for interrupts on offline cpus.
6) Hacky fixup_irqs() to redirect irqs when cpus go off/online.
7) play_dead() for offline cpus to spin inside.
8) Handle offline cpus set in flush_tlb_others().
9) Grab lock earlier in smp_call_function() to prevent CPUs going down.
10) Implement __cpu_disable() and __cpu_die().
11) Enable local interrupts in cpu_enable() after fixup_irqs()
12) Don't fiddle with NMI on dead cpu, but leave intact on other cpus.
13) Program IRQ affinity whilst cpu is still in cpu_online_map on offline.

Signed-off-by: Zwane Mwaikambo <zwane@linuxpower.ca>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-25 16:24:29 -07:00

189 lines
4 KiB
C

/* CPU control.
* (C) 2001, 2002, 2003, 2004 Rusty Russell
*
* This code is licenced under the GPL.
*/
#include <linux/proc_fs.h>
#include <linux/smp.h>
#include <linux/init.h>
#include <linux/notifier.h>
#include <linux/sched.h>
#include <linux/unistd.h>
#include <linux/cpu.h>
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/stop_machine.h>
#include <asm/semaphore.h>
/* This protects CPUs going up and down... */
DECLARE_MUTEX(cpucontrol);
static struct notifier_block *cpu_chain;
/* Need to know about CPUs going up/down? */
int register_cpu_notifier(struct notifier_block *nb)
{
int ret;
if ((ret = down_interruptible(&cpucontrol)) != 0)
return ret;
ret = notifier_chain_register(&cpu_chain, nb);
up(&cpucontrol);
return ret;
}
EXPORT_SYMBOL(register_cpu_notifier);
void unregister_cpu_notifier(struct notifier_block *nb)
{
down(&cpucontrol);
notifier_chain_unregister(&cpu_chain, nb);
up(&cpucontrol);
}
EXPORT_SYMBOL(unregister_cpu_notifier);
#ifdef CONFIG_HOTPLUG_CPU
static inline void check_for_tasks(int cpu)
{
struct task_struct *p;
write_lock_irq(&tasklist_lock);
for_each_process(p) {
if (task_cpu(p) == cpu &&
(!cputime_eq(p->utime, cputime_zero) ||
!cputime_eq(p->stime, cputime_zero)))
printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\
(state = %ld, flags = %lx) \n",
p->comm, p->pid, cpu, p->state, p->flags);
}
write_unlock_irq(&tasklist_lock);
}
/* Take this CPU down. */
static int take_cpu_down(void *unused)
{
int err;
/* Ensure this CPU doesn't handle any more interrupts. */
err = __cpu_disable();
if (err < 0)
return err;
/* Force idle task to run as soon as we yield: it should
immediately notice cpu is offline and die quickly. */
sched_idle_next();
return 0;
}
int cpu_down(unsigned int cpu)
{
int err;
struct task_struct *p;
cpumask_t old_allowed, tmp;
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;
}
err = notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
(void *)(long)cpu);
if (err == NOTIFY_BAD) {
printk("%s: attempt to take down CPU %u failed\n",
__FUNCTION__, cpu);
err = -EINVAL;
goto out;
}
/* Ensure that we are not runnable on dying cpu */
old_allowed = current->cpus_allowed;
tmp = CPU_MASK_ALL;
cpu_clear(cpu, tmp);
set_cpus_allowed(current, tmp);
p = __stop_machine_run(take_cpu_down, NULL, cpu);
if (IS_ERR(p)) {
/* CPU didn't die: tell everyone. Can't complain. */
if (notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED,
(void *)(long)cpu) == NOTIFY_BAD)
BUG();
err = PTR_ERR(p);
goto out_allowed;
}
if (cpu_online(cpu))
goto out_thread;
/* 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, get_cpu());
put_cpu();
/* CPU is completely dead: tell everyone. Too late to complain. */
if (notifier_call_chain(&cpu_chain, CPU_DEAD, (void *)(long)cpu)
== NOTIFY_BAD)
BUG();
check_for_tasks(cpu);
out_thread:
err = kthread_stop(p);
out_allowed:
set_cpus_allowed(current, old_allowed);
out:
unlock_cpu_hotplug();
return err;
}
#endif /*CONFIG_HOTPLUG_CPU*/
int __devinit cpu_up(unsigned int cpu)
{
int ret;
void *hcpu = (void *)(long)cpu;
if ((ret = down_interruptible(&cpucontrol)) != 0)
return ret;
if (cpu_online(cpu) || !cpu_present(cpu)) {
ret = -EINVAL;
goto out;
}
ret = notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);
if (ret == NOTIFY_BAD) {
printk("%s: attempt to bring up CPU %u failed\n",
__FUNCTION__, cpu);
ret = -EINVAL;
goto out_notify;
}
/* Arch-specific enabling code. */
ret = __cpu_up(cpu);
if (ret != 0)
goto out_notify;
if (!cpu_online(cpu))
BUG();
/* Now call notifier in preparation. */
notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu);
out_notify:
if (ret != 0)
notifier_call_chain(&cpu_chain, CPU_UP_CANCELED, hcpu);
out:
up(&cpucontrol);
return ret;
}