Commit 6ae56b55 authored by Robert Richter's avatar Robert Richter
Browse files

oprofile/x86: protect cpu hotplug sections 



This patch reworks oprofile cpu hotplug code as follows:

Introduce ctr_running variable to check, if counters are running or
not. The state must be known for taking a cpu on or offline and when
switching counters during counter multiplexing.

Protect on_each_cpu() sections with get_online_cpus()/put_online_cpu()
functions. This is necessary if notifiers or states are
modified. Within these sections the cpu mask may not change.

Switch only between counters in nmi_cpu_switch(), if counters are
running. Otherwise the switch may restart a counter though they are
disabled.

Add nmi_cpu_setup() and nmi_cpu_shutdown() to cpu hotplug code. The
function must also be called to avoid uninitialzed counter usage.

Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: default avatarRobert Richter <robert.richter@amd.com>
parent 216f3d9b

arch/x86/oprofile/nmi_int.c

+46 −6
Original line number Diff line number Diff line
@@ -31,8 +31,9 @@ static struct op_x86_model_spec *model; 
static DEFINE_PER_CPU(struct op_msrs, cpu_msrs);

static DEFINE_PER_CPU(unsigned long, saved_lvtpc);



/* 0 == registered but off, 1 == registered and on */

static int nmi_enabled = 0;

/* must be protected with get_online_cpus()/put_online_cpus(): */

static int nmi_enabled;

static int ctr_running;



struct op_counter_config counter_config[OP_MAX_COUNTER];
@@ -103,7 +104,10 @@ static void nmi_cpu_start(void *dummy) 


static int nmi_start(void)

{

	get_online_cpus();

	on_each_cpu(nmi_cpu_start, NULL, 1);

	ctr_running = 1;

	put_online_cpus();

	return 0;

}
@@ -118,7 +122,10 @@ static void nmi_cpu_stop(void *dummy) 


static void nmi_stop(void)

{

	get_online_cpus();

	on_each_cpu(nmi_cpu_stop, NULL, 1);

	ctr_running = 0;

	put_online_cpus();

}



#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
@@ -258,7 +265,10 @@ static int nmi_switch_event(void) 
	if (nmi_multiplex_on() < 0)

		return -EINVAL;		/* not necessary */



	get_online_cpus();

	if (ctr_running)

		on_each_cpu(nmi_cpu_switch, NULL, 1);

	put_online_cpus();



	return 0;

}
@@ -386,8 +396,11 @@ static int nmi_setup(void) 
	if (err)

		goto fail;



	get_online_cpus();

	on_each_cpu(nmi_cpu_setup, NULL, 1);

	nmi_enabled = 1;

	put_online_cpus();



	return 0;

fail:

	free_msrs();
@@ -433,8 +446,11 @@ static void nmi_shutdown(void) 
{

	struct op_msrs *msrs;



	nmi_enabled = 0;

	get_online_cpus();

	on_each_cpu(nmi_cpu_shutdown, NULL, 1);

	nmi_enabled = 0;

	ctr_running = 0;

	put_online_cpus();

	unregister_die_notifier(&profile_exceptions_nb);

	msrs = &get_cpu_var(cpu_msrs);

	model->shutdown(msrs);
@@ -442,6 +458,22 @@ static void nmi_shutdown(void) 
	put_cpu_var(cpu_msrs);

}



static void nmi_cpu_up(void *dummy)

{

	if (nmi_enabled)

		nmi_cpu_setup(dummy);

	if (ctr_running)

		nmi_cpu_start(dummy);

}



static void nmi_cpu_down(void *dummy)

{

	if (ctr_running)

		nmi_cpu_stop(dummy);

	if (nmi_enabled)

		nmi_cpu_shutdown(dummy);

}



static int nmi_create_files(struct super_block *sb, struct dentry *root)

{

	unsigned int i;
@@ -478,10 +510,10 @@ static int oprofile_cpu_notifier(struct notifier_block *b, unsigned long action, 
	switch (action) {

	case CPU_DOWN_FAILED:

	case CPU_ONLINE:

		smp_call_function_single(cpu, nmi_cpu_start, NULL, 0);

		smp_call_function_single(cpu, nmi_cpu_up, NULL, 0);

		break;

	case CPU_DOWN_PREPARE:

		smp_call_function_single(cpu, nmi_cpu_stop, NULL, 1);

		smp_call_function_single(cpu, nmi_cpu_down, NULL, 1);

		break;

	}

	return NOTIFY_DONE;
@@ -699,7 +731,11 @@ int __init op_nmi_init(struct oprofile_operations *ops) 
		return -ENODEV;

	}



	get_online_cpus();

	register_cpu_notifier(&oprofile_cpu_nb);

	nmi_enabled = 0;

	ctr_running = 0;

	put_online_cpus();



	/* default values, can be overwritten by model */

	ops->create_files	= nmi_create_files;
@@ -729,7 +765,11 @@ void op_nmi_exit(void) 
{

	if (using_nmi) {

		exit_sysfs();

		get_online_cpus();

		unregister_cpu_notifier(&oprofile_cpu_nb);

		nmi_enabled = 0;

		ctr_running = 0;

		put_online_cpus();

	}

	if (model->exit)

		model->exit();

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