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HOTPLUG: Add CPU_DYING notifier

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KVM wants a notification when a cpu is about to die, so it can disable
hardware extensions, but at a time when user processes cannot be scheduled
on the cpu, so it doesn't try to use virtualization extensions after they
have been disabled.

This adds a CPU_DYING notification.  The notification is called in atomic
context on the doomed cpu.

Signed-off-by: Avi Kivity <avi@qumranet.com>
This commit is contained in:
Avi Kivity
2007-05-24 12:23:10 +03:00
parent e495606dd0
commit db912f9639
2 changed files with 17 additions and 2 deletions
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16
kernel/cpu.c
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@@ -103,11 +103,19 @@ static inline void check_for_tasks(int cpu)
write_unlock_irq(&tasklist_lock);
}
struct take_cpu_down_param {
unsigned long mod;
void *hcpu;
};
/* Take this CPU down. */
static int take_cpu_down(void *unused)
static int take_cpu_down(void *_param)
{
struct take_cpu_down_param *param = _param;
int err;
raw_notifier_call_chain(&cpu_chain, CPU_DYING | param->mod,
param->hcpu);
/* Ensure this CPU doesn't handle any more interrupts. */
err = __cpu_disable();
if (err < 0)
@@ -127,6 +135,10 @@ static int _cpu_down(unsigned int cpu, int tasks_frozen)
cpumask_t old_allowed, tmp;
void *hcpu = (void *)(long)cpu;
unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
struct take_cpu_down_param tcd_param = {
.mod = mod,
.hcpu = hcpu,
};
if (num_online_cpus() == 1)
return -EBUSY;
@@ -153,7 +165,7 @@ static int _cpu_down(unsigned int cpu, int tasks_frozen)
set_cpus_allowed(current, tmp);
mutex_lock(&cpu_bitmask_lock);
p = __stop_machine_run(take_cpu_down, NULL, cpu);
p = __stop_machine_run(take_cpu_down, &tcd_param, cpu);
mutex_unlock(&cpu_bitmask_lock);
if (IS_ERR(p) || cpu_online(cpu)) {