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Commit db912f96 authored by Avi Kivity's avatar Avi Kivity
Browse files

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: default avatarAvi Kivity <avi@qumranet.com>
parent e495606d

include/linux/notifier.h

+3 −0
Original line number Diff line number Diff line
@@ -196,6 +196,8 @@ extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh, 
#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 @@ extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh, 
#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 */

kernel/cpu.c

+14 −2
Original line number Diff line number Diff line
@@ -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)) {