kernel/trace/trace_irqsoff.c - maze/linux - Git at Google

 /*
  * trace irqs off criticall timings
  *
  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
  * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
  *
  * From code in the latency_tracer, that is:
  *
  *  Copyright (C) 2004-2006 Ingo Molnar
  *  Copyright (C) 2004 William Lee Irwin III
  */
 #include <linux/kallsyms.h>
 #include <linux/debugfs.h>
 #include <linux/uaccess.h>
 #include <linux/module.h>
 #include <linux/ftrace.h>
 #include <linux/fs.h>

 #include "trace.h"

 static struct trace_array		*irqsoff_trace __read_mostly;
 static int				tracer_enabled __read_mostly;

 static DEFINE_PER_CPU(int, tracing_cpu);

 static DEFINE_SPINLOCK(max_trace_lock);

 enum {
 	TRACER_IRQS_OFF		= (1 << 1),
 	TRACER_PREEMPT_OFF	= (1 << 2),
 };

 static int trace_type __read_mostly;

 #ifdef CONFIG_PREEMPT_TRACER
 static inline int
 preempt_trace(void)
 {
 	return ((trace_type & TRACER_PREEMPT_OFF) && preempt_count());
 }
 #else
 # define preempt_trace() (0)
 #endif

 #ifdef CONFIG_IRQSOFF_TRACER
 static inline int
 irq_trace(void)
 {
 	return ((trace_type & TRACER_IRQS_OFF) &&
 		irqs_disabled());
 }
 #else
 # define irq_trace() (0)
 #endif

 /*
  * Sequence count - we record it when starting a measurement and
  * skip the latency if the sequence has changed - some other section
  * did a maximum and could disturb our measurement with serial console
  * printouts, etc. Truly coinciding maximum latencies should be rare
  * and what happens together happens separately as well, so this doesnt
  * decrease the validity of the maximum found:
  */
 static __cacheline_aligned_in_smp	unsigned long max_sequence;

 #ifdef CONFIG_FTRACE
 /*
  * irqsoff uses its own tracer function to keep the overhead down:
  */
 static void
 irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip)
 {
 	struct trace_array *tr = irqsoff_trace;
 	struct trace_array_cpu *data;
 	unsigned long flags;
 	long disabled;
 	int cpu;

 	/*
 	 * Does not matter if we preempt. We test the flags
 	 * afterward, to see if irqs are disabled or not.
 	 * If we preempt and get a false positive, the flags
 	 * test will fail.
 	 */
 	cpu = raw_smp_processor_id();
 	if (likely(!per_cpu(tracing_cpu, cpu)))
 		return;

 	local_save_flags(flags);
 	/* slight chance to get a false positive on tracing_cpu */
 	if (!irqs_disabled_flags(flags))
 		return;

 	data = tr->data[cpu];
 	disabled = atomic_inc_return(&data->disabled);

 	if (likely(disabled == 1))
 		trace_function(tr, data, ip, parent_ip, flags, preempt_count());

 	atomic_dec(&data->disabled);
 }

 static struct ftrace_ops trace_ops __read_mostly =
 {
 	.func = irqsoff_tracer_call,
 };
 #endif /* CONFIG_FTRACE */

 /*
  * Should this new latency be reported/recorded?
  */
 static int report_latency(cycle_t delta)
 {
 	if (tracing_thresh) {
 		if (delta < tracing_thresh)
 			return 0;
 	} else {
 		if (delta <= tracing_max_latency)
 			return 0;
 	}
 	return 1;
 }

 static void
 check_critical_timing(struct trace_array *tr,
 		      struct trace_array_cpu *data,
 		      unsigned long parent_ip,
 		      int cpu)
 {
 	unsigned long latency, t0, t1;
 	cycle_t T0, T1, delta;
 	unsigned long flags;
 	int pc;

 	/*
 	 * usecs conversion is slow so we try to delay the conversion
 	 * as long as possible:
 	 */
 	T0 = data->preempt_timestamp;
 	T1 = ftrace_now(cpu);
 	delta = T1-T0;

 	local_save_flags(flags);

 	pc = preempt_count();

 	if (!report_latency(delta))
 		goto out;

 	spin_lock_irqsave(&max_trace_lock, flags);

 	/* check if we are still the max latency */
 	if (!report_latency(delta))
 		goto out_unlock;

 	trace_function(tr, data, CALLER_ADDR0, parent_ip, flags, pc);

 	latency = nsecs_to_usecs(delta);

 	if (data->critical_sequence != max_sequence)
 		goto out_unlock;

 	tracing_max_latency = delta;
 	t0 = nsecs_to_usecs(T0);
 	t1 = nsecs_to_usecs(T1);

 	data->critical_end = parent_ip;

 	update_max_tr_single(tr, current, cpu);

 	max_sequence++;

 out_unlock:
 	spin_unlock_irqrestore(&max_trace_lock, flags);

 out:
 	data->critical_sequence = max_sequence;
 	data->preempt_timestamp = ftrace_now(cpu);
 	tracing_reset(tr, cpu);
 	trace_function(tr, data, CALLER_ADDR0, parent_ip, flags, pc);
 }

 static inline void
 start_critical_timing(unsigned long ip, unsigned long parent_ip)
 {
 	int cpu;
 	struct trace_array *tr = irqsoff_trace;
 	struct trace_array_cpu *data;
 	unsigned long flags;

 	if (likely(!tracer_enabled))
 		return;

 	cpu = raw_smp_processor_id();

 	if (per_cpu(tracing_cpu, cpu))
 		return;

 	data = tr->data[cpu];

 	if (unlikely(!data) || atomic_read(&data->disabled))
 		return;

 	atomic_inc(&data->disabled);

 	data->critical_sequence = max_sequence;
 	data->preempt_timestamp = ftrace_now(cpu);
 	data->critical_start = parent_ip ? : ip;
 	tracing_reset(tr, cpu);

 	local_save_flags(flags);

 	trace_function(tr, data, ip, parent_ip, flags, preempt_count());

 	per_cpu(tracing_cpu, cpu) = 1;

 	atomic_dec(&data->disabled);
 }

 static inline void
 stop_critical_timing(unsigned long ip, unsigned long parent_ip)
 {
 	int cpu;
 	struct trace_array *tr = irqsoff_trace;
 	struct trace_array_cpu *data;
 	unsigned long flags;

 	cpu = raw_smp_processor_id();
 	/* Always clear the tracing cpu on stopping the trace */
 	if (unlikely(per_cpu(tracing_cpu, cpu)))
 		per_cpu(tracing_cpu, cpu) = 0;
 	else
 		return;

 	if (!tracer_enabled)
 		return;

 	data = tr->data[cpu];

 	if (unlikely(!data) ||
 	    !data->critical_start || atomic_read(&data->disabled))
 		return;

 	atomic_inc(&data->disabled);

 	local_save_flags(flags);
 	trace_function(tr, data, ip, parent_ip, flags, preempt_count());
 	check_critical_timing(tr, data, parent_ip ? : ip, cpu);
 	data->critical_start = 0;
 	atomic_dec(&data->disabled);
 }

 /* start and stop critical timings used to for stoppage (in idle) */
 void start_critical_timings(void)
 {
 	if (preempt_trace() || irq_trace())
 		start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 }
 EXPORT_SYMBOL_GPL(start_critical_timings);

 void stop_critical_timings(void)
 {
 	if (preempt_trace() || irq_trace())
 		stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 }
 EXPORT_SYMBOL_GPL(stop_critical_timings);

 #ifdef CONFIG_IRQSOFF_TRACER
 #ifdef CONFIG_PROVE_LOCKING
 void time_hardirqs_on(unsigned long a0, unsigned long a1)
 {
 	if (!preempt_trace() && irq_trace())
 		stop_critical_timing(a0, a1);
 }

 void time_hardirqs_off(unsigned long a0, unsigned long a1)
 {
 	if (!preempt_trace() && irq_trace())
 		start_critical_timing(a0, a1);
 }

 #else /* !CONFIG_PROVE_LOCKING */

 /*
  * Stubs:
  */

 void early_boot_irqs_off(void)
 {
 }

 void early_boot_irqs_on(void)
 {
 }

 void trace_softirqs_on(unsigned long ip)
 {
 }

 void trace_softirqs_off(unsigned long ip)
 {
 }

 inline void print_irqtrace_events(struct task_struct *curr)
 {
 }

 /*
  * We are only interested in hardirq on/off events:
  */
 void trace_hardirqs_on(void)
 {
 	if (!preempt_trace() && irq_trace())
 		stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 }
 EXPORT_SYMBOL(trace_hardirqs_on);

 void trace_hardirqs_off(void)
 {
 	if (!preempt_trace() && irq_trace())
 		start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 }
 EXPORT_SYMBOL(trace_hardirqs_off);

 void trace_hardirqs_on_caller(unsigned long caller_addr)
 {
 	if (!preempt_trace() && irq_trace())
 		stop_critical_timing(CALLER_ADDR0, caller_addr);
 }
 EXPORT_SYMBOL(trace_hardirqs_on_caller);

 void trace_hardirqs_off_caller(unsigned long caller_addr)
 {
 	if (!preempt_trace() && irq_trace())
 		start_critical_timing(CALLER_ADDR0, caller_addr);
 }
 EXPORT_SYMBOL(trace_hardirqs_off_caller);

 #endif /* CONFIG_PROVE_LOCKING */
 #endif /*  CONFIG_IRQSOFF_TRACER */

 #ifdef CONFIG_PREEMPT_TRACER
 void trace_preempt_on(unsigned long a0, unsigned long a1)
 {
 	if (preempt_trace())
 		stop_critical_timing(a0, a1);
 }

 void trace_preempt_off(unsigned long a0, unsigned long a1)
 {
 	if (preempt_trace())
 		start_critical_timing(a0, a1);
 }
 #endif /* CONFIG_PREEMPT_TRACER */

 static void start_irqsoff_tracer(struct trace_array *tr)
 {
 	register_ftrace_function(&trace_ops);
 	tracer_enabled = 1;
 }

 static void stop_irqsoff_tracer(struct trace_array *tr)
 {
 	tracer_enabled = 0;
 	unregister_ftrace_function(&trace_ops);
 }

 static void __irqsoff_tracer_init(struct trace_array *tr)
 {
 	irqsoff_trace = tr;
 	/* make sure that the tracer is visible */
 	smp_wmb();

 	if (tr->ctrl)
 		start_irqsoff_tracer(tr);
 }

 static void irqsoff_tracer_reset(struct trace_array *tr)
 {
 	if (tr->ctrl)
 		stop_irqsoff_tracer(tr);
 }

 static void irqsoff_tracer_ctrl_update(struct trace_array *tr)
 {
 	if (tr->ctrl)
 		start_irqsoff_tracer(tr);
 	else
 		stop_irqsoff_tracer(tr);
 }

 static void irqsoff_tracer_open(struct trace_iterator *iter)
 {
 	/* stop the trace while dumping */
 	if (iter->tr->ctrl)
 		stop_irqsoff_tracer(iter->tr);
 }

 static void irqsoff_tracer_close(struct trace_iterator *iter)
 {
 	if (iter->tr->ctrl)
 		start_irqsoff_tracer(iter->tr);
 }

 #ifdef CONFIG_IRQSOFF_TRACER
 static void irqsoff_tracer_init(struct trace_array *tr)
 {
 	trace_type = TRACER_IRQS_OFF;

 	__irqsoff_tracer_init(tr);
 }
 static struct tracer irqsoff_tracer __read_mostly =
 {
 	.name		= "irqsoff",
 	.init		= irqsoff_tracer_init,
 	.reset		= irqsoff_tracer_reset,
 	.open		= irqsoff_tracer_open,
 	.close		= irqsoff_tracer_close,
 	.ctrl_update	= irqsoff_tracer_ctrl_update,
 	.print_max	= 1,
 #ifdef CONFIG_FTRACE_SELFTEST
 	.selftest    = trace_selftest_startup_irqsoff,
 #endif
 };
 # define register_irqsoff(trace) register_tracer(&trace)
 #else
 # define register_irqsoff(trace) do { } while (0)
 #endif

 #ifdef CONFIG_PREEMPT_TRACER
 static void preemptoff_tracer_init(struct trace_array *tr)
 {
 	trace_type = TRACER_PREEMPT_OFF;

 	__irqsoff_tracer_init(tr);
 }

 static struct tracer preemptoff_tracer __read_mostly =
 {
 	.name		= "preemptoff",
 	.init		= preemptoff_tracer_init,
 	.reset		= irqsoff_tracer_reset,
 	.open		= irqsoff_tracer_open,
 	.close		= irqsoff_tracer_close,
 	.ctrl_update	= irqsoff_tracer_ctrl_update,
 	.print_max	= 1,
 #ifdef CONFIG_FTRACE_SELFTEST
 	.selftest    = trace_selftest_startup_preemptoff,
 #endif
 };
 # define register_preemptoff(trace) register_tracer(&trace)
 #else
 # define register_preemptoff(trace) do { } while (0)
 #endif

 #if defined(CONFIG_IRQSOFF_TRACER) && \
 	defined(CONFIG_PREEMPT_TRACER)

 static void preemptirqsoff_tracer_init(struct trace_array *tr)
 {
 	trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;

 	__irqsoff_tracer_init(tr);
 }

 static struct tracer preemptirqsoff_tracer __read_mostly =
 {
 	.name		= "preemptirqsoff",
 	.init		= preemptirqsoff_tracer_init,
 	.reset		= irqsoff_tracer_reset,
 	.open		= irqsoff_tracer_open,
 	.close		= irqsoff_tracer_close,
 	.ctrl_update	= irqsoff_tracer_ctrl_update,
 	.print_max	= 1,
 #ifdef CONFIG_FTRACE_SELFTEST
 	.selftest    = trace_selftest_startup_preemptirqsoff,
 #endif
 };

 # define register_preemptirqsoff(trace) register_tracer(&trace)
 #else
 # define register_preemptirqsoff(trace) do { } while (0)
 #endif

 __init static int init_irqsoff_tracer(void)
 {
 	register_irqsoff(irqsoff_tracer);
 	register_preemptoff(preemptoff_tracer);
 	register_preemptirqsoff(preemptirqsoff_tracer);

 	return 0;
 }
 device_initcall(init_irqsoff_tracer);
	/*
	* trace irqs off criticall timings
	*
	* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
	* Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
	*
	* From code in the latency_tracer, that is:
	*
	* Copyright (C) 2004-2006 Ingo Molnar
	* Copyright (C) 2004 William Lee Irwin III
	*/
	#include <linux/kallsyms.h>
	#include <linux/debugfs.h>
	#include <linux/uaccess.h>
	#include <linux/module.h>
	#include <linux/ftrace.h>
	#include <linux/fs.h>

	#include "trace.h"

	static struct trace_array *irqsoff_trace __read_mostly;
	static int tracer_enabled __read_mostly;

	static DEFINE_PER_CPU(int, tracing_cpu);

	static DEFINE_SPINLOCK(max_trace_lock);

	enum {
	TRACER_IRQS_OFF = (1 << 1),
	TRACER_PREEMPT_OFF = (1 << 2),
	};

	static int trace_type __read_mostly;

	#ifdef CONFIG_PREEMPT_TRACER
	static inline int
	preempt_trace(void)
	{
	return ((trace_type & TRACER_PREEMPT_OFF) && preempt_count());
	}
	#else
	# define preempt_trace() (0)
	#endif

	#ifdef CONFIG_IRQSOFF_TRACER
	static inline int
	irq_trace(void)
	{
	return ((trace_type & TRACER_IRQS_OFF) &&
	irqs_disabled());
	}
	#else
	# define irq_trace() (0)
	#endif

	/*
	* Sequence count - we record it when starting a measurement and
	* skip the latency if the sequence has changed - some other section
	* did a maximum and could disturb our measurement with serial console
	* printouts, etc. Truly coinciding maximum latencies should be rare
	* and what happens together happens separately as well, so this doesnt
	* decrease the validity of the maximum found:
	*/
	static __cacheline_aligned_in_smp unsigned long max_sequence;

	#ifdef CONFIG_FTRACE
	/*
	* irqsoff uses its own tracer function to keep the overhead down:
	*/
	static void
	irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip)
	{
	struct trace_array *tr = irqsoff_trace;
	struct trace_array_cpu *data;
	unsigned long flags;
	long disabled;
	int cpu;

	/*
	* Does not matter if we preempt. We test the flags
	* afterward, to see if irqs are disabled or not.
	* If we preempt and get a false positive, the flags
	* test will fail.
	*/
	cpu = raw_smp_processor_id();
	if (likely(!per_cpu(tracing_cpu, cpu)))
	return;

	local_save_flags(flags);
	/* slight chance to get a false positive on tracing_cpu */
	if (!irqs_disabled_flags(flags))
	return;

	data = tr->data[cpu];
	disabled = atomic_inc_return(&data->disabled);

	if (likely(disabled == 1))
	trace_function(tr, data, ip, parent_ip, flags, preempt_count());

	atomic_dec(&data->disabled);
	}

	static struct ftrace_ops trace_ops __read_mostly =
	{
	.func = irqsoff_tracer_call,
	};
	#endif /* CONFIG_FTRACE */

	/*
	* Should this new latency be reported/recorded?
	*/
	static int report_latency(cycle_t delta)
	{
	if (tracing_thresh) {
	if (delta < tracing_thresh)
	return 0;
	} else {
	if (delta <= tracing_max_latency)
	return 0;
	}
	return 1;
	}

	static void
	check_critical_timing(struct trace_array *tr,
	struct trace_array_cpu *data,
	unsigned long parent_ip,
	int cpu)
	{
	unsigned long latency, t0, t1;
	cycle_t T0, T1, delta;
	unsigned long flags;
	int pc;

	/*
	* usecs conversion is slow so we try to delay the conversion
	* as long as possible:
	*/
	T0 = data->preempt_timestamp;
	T1 = ftrace_now(cpu);
	delta = T1-T0;

	local_save_flags(flags);

	pc = preempt_count();

	if (!report_latency(delta))
	goto out;

	spin_lock_irqsave(&max_trace_lock, flags);

	/* check if we are still the max latency */
	if (!report_latency(delta))
	goto out_unlock;

	trace_function(tr, data, CALLER_ADDR0, parent_ip, flags, pc);

	latency = nsecs_to_usecs(delta);

	if (data->critical_sequence != max_sequence)
	goto out_unlock;

	tracing_max_latency = delta;
	t0 = nsecs_to_usecs(T0);
	t1 = nsecs_to_usecs(T1);

	data->critical_end = parent_ip;

	update_max_tr_single(tr, current, cpu);

	max_sequence++;

	out_unlock:
	spin_unlock_irqrestore(&max_trace_lock, flags);

	out:
	data->critical_sequence = max_sequence;
	data->preempt_timestamp = ftrace_now(cpu);
	tracing_reset(tr, cpu);
	trace_function(tr, data, CALLER_ADDR0, parent_ip, flags, pc);
	}

	static inline void
	start_critical_timing(unsigned long ip, unsigned long parent_ip)
	{
	int cpu;
	struct trace_array *tr = irqsoff_trace;
	struct trace_array_cpu *data;
	unsigned long flags;

	if (likely(!tracer_enabled))
	return;

	cpu = raw_smp_processor_id();

	if (per_cpu(tracing_cpu, cpu))
	return;

	data = tr->data[cpu];

	if (unlikely(!data) \|\| atomic_read(&data->disabled))
	return;

	atomic_inc(&data->disabled);

	data->critical_sequence = max_sequence;
	data->preempt_timestamp = ftrace_now(cpu);
	data->critical_start = parent_ip ? : ip;
	tracing_reset(tr, cpu);

	local_save_flags(flags);

	trace_function(tr, data, ip, parent_ip, flags, preempt_count());

	per_cpu(tracing_cpu, cpu) = 1;

	atomic_dec(&data->disabled);
	}

	static inline void
	stop_critical_timing(unsigned long ip, unsigned long parent_ip)
	{
	int cpu;
	struct trace_array *tr = irqsoff_trace;
	struct trace_array_cpu *data;
	unsigned long flags;

	cpu = raw_smp_processor_id();
	/* Always clear the tracing cpu on stopping the trace */
	if (unlikely(per_cpu(tracing_cpu, cpu)))
	per_cpu(tracing_cpu, cpu) = 0;
	else
	return;

	if (!tracer_enabled)
	return;

	data = tr->data[cpu];

	if (unlikely(!data) \|\|
	!data->critical_start \|\| atomic_read(&data->disabled))
	return;

	atomic_inc(&data->disabled);

	local_save_flags(flags);
	trace_function(tr, data, ip, parent_ip, flags, preempt_count());
	check_critical_timing(tr, data, parent_ip ? : ip, cpu);
	data->critical_start = 0;
	atomic_dec(&data->disabled);
	}

	/* start and stop critical timings used to for stoppage (in idle) */
	void start_critical_timings(void)
	{
	if (preempt_trace() \|\| irq_trace())
	start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
	}
	EXPORT_SYMBOL_GPL(start_critical_timings);

	void stop_critical_timings(void)
	{
	if (preempt_trace() \|\| irq_trace())
	stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
	}
	EXPORT_SYMBOL_GPL(stop_critical_timings);

	#ifdef CONFIG_IRQSOFF_TRACER
	#ifdef CONFIG_PROVE_LOCKING
	void time_hardirqs_on(unsigned long a0, unsigned long a1)
	{
	if (!preempt_trace() && irq_trace())
	stop_critical_timing(a0, a1);
	}

	void time_hardirqs_off(unsigned long a0, unsigned long a1)
	{
	if (!preempt_trace() && irq_trace())
	start_critical_timing(a0, a1);
	}

	#else /* !CONFIG_PROVE_LOCKING */

	/*
	* Stubs:
	*/

	void early_boot_irqs_off(void)
	{
	}

	void early_boot_irqs_on(void)
	{
	}

	void trace_softirqs_on(unsigned long ip)
	{
	}

	void trace_softirqs_off(unsigned long ip)
	{
	}

	inline void print_irqtrace_events(struct task_struct *curr)
	{
	}

	/*
	* We are only interested in hardirq on/off events:
	*/
	void trace_hardirqs_on(void)
	{
	if (!preempt_trace() && irq_trace())
	stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
	}
	EXPORT_SYMBOL(trace_hardirqs_on);

	void trace_hardirqs_off(void)
	{
	if (!preempt_trace() && irq_trace())
	start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
	}
	EXPORT_SYMBOL(trace_hardirqs_off);

	void trace_hardirqs_on_caller(unsigned long caller_addr)
	{
	if (!preempt_trace() && irq_trace())
	stop_critical_timing(CALLER_ADDR0, caller_addr);
	}
	EXPORT_SYMBOL(trace_hardirqs_on_caller);

	void trace_hardirqs_off_caller(unsigned long caller_addr)
	{
	if (!preempt_trace() && irq_trace())
	start_critical_timing(CALLER_ADDR0, caller_addr);
	}
	EXPORT_SYMBOL(trace_hardirqs_off_caller);

	#endif /* CONFIG_PROVE_LOCKING */
	#endif /* CONFIG_IRQSOFF_TRACER */

	#ifdef CONFIG_PREEMPT_TRACER
	void trace_preempt_on(unsigned long a0, unsigned long a1)
	{
	if (preempt_trace())
	stop_critical_timing(a0, a1);
	}

	void trace_preempt_off(unsigned long a0, unsigned long a1)
	{
	if (preempt_trace())
	start_critical_timing(a0, a1);
	}
	#endif /* CONFIG_PREEMPT_TRACER */

	static void start_irqsoff_tracer(struct trace_array *tr)
	{
	register_ftrace_function(&trace_ops);
	tracer_enabled = 1;
	}

	static void stop_irqsoff_tracer(struct trace_array *tr)
	{
	tracer_enabled = 0;
	unregister_ftrace_function(&trace_ops);
	}

	static void __irqsoff_tracer_init(struct trace_array *tr)
	{
	irqsoff_trace = tr;
	/* make sure that the tracer is visible */
	smp_wmb();

	if (tr->ctrl)
	start_irqsoff_tracer(tr);
	}

	static void irqsoff_tracer_reset(struct trace_array *tr)
	{
	if (tr->ctrl)
	stop_irqsoff_tracer(tr);
	}

	static void irqsoff_tracer_ctrl_update(struct trace_array *tr)
	{
	if (tr->ctrl)
	start_irqsoff_tracer(tr);
	else
	stop_irqsoff_tracer(tr);
	}

	static void irqsoff_tracer_open(struct trace_iterator *iter)
	{
	/* stop the trace while dumping */
	if (iter->tr->ctrl)
	stop_irqsoff_tracer(iter->tr);
	}

	static void irqsoff_tracer_close(struct trace_iterator *iter)
	{
	if (iter->tr->ctrl)
	start_irqsoff_tracer(iter->tr);
	}

	#ifdef CONFIG_IRQSOFF_TRACER
	static void irqsoff_tracer_init(struct trace_array *tr)
	{
	trace_type = TRACER_IRQS_OFF;

	__irqsoff_tracer_init(tr);
	}
	static struct tracer irqsoff_tracer __read_mostly =
	{
	.name = "irqsoff",
	.init = irqsoff_tracer_init,
	.reset = irqsoff_tracer_reset,
	.open = irqsoff_tracer_open,
	.close = irqsoff_tracer_close,
	.ctrl_update = irqsoff_tracer_ctrl_update,
	.print_max = 1,
	#ifdef CONFIG_FTRACE_SELFTEST
	.selftest = trace_selftest_startup_irqsoff,
	#endif
	};
	# define register_irqsoff(trace) register_tracer(&trace)
	#else
	# define register_irqsoff(trace) do { } while (0)
	#endif

	#ifdef CONFIG_PREEMPT_TRACER
	static void preemptoff_tracer_init(struct trace_array *tr)
	{
	trace_type = TRACER_PREEMPT_OFF;

	__irqsoff_tracer_init(tr);
	}

	static struct tracer preemptoff_tracer __read_mostly =
	{
	.name = "preemptoff",
	.init = preemptoff_tracer_init,
	.reset = irqsoff_tracer_reset,
	.open = irqsoff_tracer_open,
	.close = irqsoff_tracer_close,
	.ctrl_update = irqsoff_tracer_ctrl_update,
	.print_max = 1,
	#ifdef CONFIG_FTRACE_SELFTEST
	.selftest = trace_selftest_startup_preemptoff,
	#endif
	};
	# define register_preemptoff(trace) register_tracer(&trace)
	#else
	# define register_preemptoff(trace) do { } while (0)
	#endif

	#if defined(CONFIG_IRQSOFF_TRACER) && \
	defined(CONFIG_PREEMPT_TRACER)

	static void preemptirqsoff_tracer_init(struct trace_array *tr)
	{
	trace_type = TRACER_IRQS_OFF \| TRACER_PREEMPT_OFF;

	__irqsoff_tracer_init(tr);
	}

	static struct tracer preemptirqsoff_tracer __read_mostly =
	{
	.name = "preemptirqsoff",
	.init = preemptirqsoff_tracer_init,
	.reset = irqsoff_tracer_reset,
	.open = irqsoff_tracer_open,
	.close = irqsoff_tracer_close,
	.ctrl_update = irqsoff_tracer_ctrl_update,
	.print_max = 1,
	#ifdef CONFIG_FTRACE_SELFTEST
	.selftest = trace_selftest_startup_preemptirqsoff,
	#endif
	};

	# define register_preemptirqsoff(trace) register_tracer(&trace)
	#else
	# define register_preemptirqsoff(trace) do { } while (0)
	#endif

	__init static int init_irqsoff_tracer(void)
	{
	register_irqsoff(irqsoff_tracer);
	register_preemptoff(preemptoff_tracer);
	register_preemptirqsoff(preemptirqsoff_tracer);

	return 0;
	}
	device_initcall(init_irqsoff_tracer);