HOTPLUG: Add CPU_DYING notifier
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>
diff --git a/include/linux/notifier.h b/include/linux/notifier.h
index 9431101..576f2bb 100644
--- a/include/linux/notifier.h
+++ b/include/linux/notifier.h
@@ -196,6 +196,8 @@
#define CPU_DEAD 0x0007 /* CPU (unsigned)v dead */
#define CPU_LOCK_ACQUIRE 0x0008 /* Acquire all hotcpu locks */
#define CPU_LOCK_RELEASE 0x0009 /* Release all hotcpu locks */
+#define CPU_DYING 0x000A /* CPU (unsigned)v not running any task,
+ * not handling interrupts, soon dead */
/* Used for CPU hotplug events occuring while tasks are frozen due to a suspend
* operation in progress
@@ -208,6 +210,7 @@
#define CPU_DOWN_PREPARE_FROZEN (CPU_DOWN_PREPARE | CPU_TASKS_FROZEN)
#define CPU_DOWN_FAILED_FROZEN (CPU_DOWN_FAILED | CPU_TASKS_FROZEN)
#define CPU_DEAD_FROZEN (CPU_DEAD | CPU_TASKS_FROZEN)
+#define CPU_DYING_FROZEN (CPU_DYING | CPU_TASKS_FROZEN)
#endif /* __KERNEL__ */
#endif /* _LINUX_NOTIFIER_H */
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 208cf34..181ae70 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -103,11 +103,19 @@
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 @@
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 @@
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)) {
