kernel/trace/trace_irqsoff.c - kernel/msm-4.9 - Gitiles

 /*
  * trace irqs off critical 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 Nadia Yvette Chambers
  */
 #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_RAW_SPINLOCK(max_trace_lock);

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

 static int trace_type __read_mostly;

 static int save_lat_flag;

 static void stop_irqsoff_tracer(struct trace_array *tr, int graph);
 static int start_irqsoff_tracer(struct trace_array *tr, int graph);

 #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

 #define TRACE_DISPLAY_GRAPH	1

 static struct tracer_opt trace_opts[] = {
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 	/* display latency trace as call graph */
 	{ TRACER_OPT(display-graph, TRACE_DISPLAY_GRAPH) },
 #endif
 	{ } /* Empty entry */
 };

 static struct tracer_flags tracer_flags = {
 	.val  = 0,
 	.opts = trace_opts,
 };

 #define is_graph() (tracer_flags.val & TRACE_DISPLAY_GRAPH)

 /*
  * 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 doesn't
  * decrease the validity of the maximum found:
  */
 static __cacheline_aligned_in_smp	unsigned long max_sequence;

 #ifdef CONFIG_FUNCTION_TRACER
 /*
  * Prologue for the preempt and irqs off function tracers.
  *
  * Returns 1 if it is OK to continue, and data->disabled is
  *            incremented.
  *         0 if the trace is to be ignored, and data->disabled
  *            is kept the same.
  *
  * Note, this function is also used outside this ifdef but
  *  inside the #ifdef of the function graph tracer below.
  *  This is OK, since the function graph tracer is
  *  dependent on the function tracer.
  */
 static int func_prolog_dec(struct trace_array *tr,
 			   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 0;

 	local_save_flags(*flags);
 	/* slight chance to get a false positive on tracing_cpu */
 	if (!irqs_disabled_flags(*flags))
 		return 0;

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

 	if (likely(disabled == 1))
 		return 1;

 	atomic_dec(&(*data)->disabled);

 	return 0;
 }

 /*
  * irqsoff uses its own tracer function to keep the overhead down:
  */
 static void
 irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip,
 		    struct ftrace_ops *op, struct pt_regs *pt_regs)
 {
 	struct trace_array *tr = irqsoff_trace;
 	struct trace_array_cpu *data;
 	unsigned long flags;

 	if (!func_prolog_dec(tr, &data, &flags))
 		return;

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

 	atomic_dec(&data->disabled);
 }

 static struct ftrace_ops trace_ops __read_mostly =
 {
 	.func = irqsoff_tracer_call,
 	.flags = FTRACE_OPS_FL_GLOBAL | FTRACE_OPS_FL_RECURSION_SAFE,
 };
 #endif /* CONFIG_FUNCTION_TRACER */

 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 static int irqsoff_set_flag(u32 old_flags, u32 bit, int set)
 {
 	int cpu;

 	if (!(bit & TRACE_DISPLAY_GRAPH))
 		return -EINVAL;

 	if (!(is_graph() ^ set))
 		return 0;

 	stop_irqsoff_tracer(irqsoff_trace, !set);

 	for_each_possible_cpu(cpu)
 		per_cpu(tracing_cpu, cpu) = 0;

 	tracing_max_latency = 0;
 	tracing_reset_online_cpus(irqsoff_trace);

 	return start_irqsoff_tracer(irqsoff_trace, set);
 }

 static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
 {
 	struct trace_array *tr = irqsoff_trace;
 	struct trace_array_cpu *data;
 	unsigned long flags;
 	int ret;
 	int pc;

 	if (!func_prolog_dec(tr, &data, &flags))
 		return 0;

 	pc = preempt_count();
 	ret = __trace_graph_entry(tr, trace, flags, pc);
 	atomic_dec(&data->disabled);

 	return ret;
 }

 static void irqsoff_graph_return(struct ftrace_graph_ret *trace)
 {
 	struct trace_array *tr = irqsoff_trace;
 	struct trace_array_cpu *data;
 	unsigned long flags;
 	int pc;

 	if (!func_prolog_dec(tr, &data, &flags))
 		return;

 	pc = preempt_count();
 	__trace_graph_return(tr, trace, flags, pc);
 	atomic_dec(&data->disabled);
 }

 static void irqsoff_trace_open(struct trace_iterator *iter)
 {
 	if (is_graph())
 		graph_trace_open(iter);

 }

 static void irqsoff_trace_close(struct trace_iterator *iter)
 {
 	if (iter->private)
 		graph_trace_close(iter);
 }

 #define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_CPU | \
 			    TRACE_GRAPH_PRINT_PROC | \
 			    TRACE_GRAPH_PRINT_ABS_TIME | \
 			    TRACE_GRAPH_PRINT_DURATION)

 static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
 {
 	/*
 	 * In graph mode call the graph tracer output function,
 	 * otherwise go with the TRACE_FN event handler
 	 */
 	if (is_graph())
 		return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS);

 	return TRACE_TYPE_UNHANDLED;
 }

 static void irqsoff_print_header(struct seq_file *s)
 {
 	if (is_graph())
 		print_graph_headers_flags(s, GRAPH_TRACER_FLAGS);
 	else
 		trace_default_header(s);
 }

 static void
 __trace_function(struct trace_array *tr,
 		 unsigned long ip, unsigned long parent_ip,
 		 unsigned long flags, int pc)
 {
 	if (is_graph())
 		trace_graph_function(tr, ip, parent_ip, flags, pc);
 	else
 		trace_function(tr, ip, parent_ip, flags, pc);
 }

 #else
 #define __trace_function trace_function

 static int irqsoff_set_flag(u32 old_flags, u32 bit, int set)
 {
 	return -EINVAL;
 }

 static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
 {
 	return -1;
 }

 static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
 {
 	return TRACE_TYPE_UNHANDLED;
 }

 static void irqsoff_graph_return(struct ftrace_graph_ret *trace) { }
 static void irqsoff_trace_open(struct trace_iterator *iter) { }
 static void irqsoff_trace_close(struct trace_iterator *iter) { }

 #ifdef CONFIG_FUNCTION_TRACER
 static void irqsoff_print_header(struct seq_file *s)
 {
 	trace_default_header(s);
 }
 #else
 static void irqsoff_print_header(struct seq_file *s)
 {
 	trace_latency_header(s);
 }
 #endif /* CONFIG_FUNCTION_TRACER */
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */

 /*
  * 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)
 {
 	cycle_t T0, T1, delta;
 	unsigned long flags;
 	int pc;

 	T0 = data->preempt_timestamp;
 	T1 = ftrace_now(cpu);
 	delta = T1-T0;

 	local_save_flags(flags);

 	pc = preempt_count();

 	if (!report_latency(delta))
 		goto out;

 	raw_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, CALLER_ADDR0, parent_ip, flags, pc);
 	/* Skip 5 functions to get to the irq/preempt enable function */
 	__trace_stack(tr, flags, 5, pc);

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

 	data->critical_end = parent_ip;

 	if (likely(!is_tracing_stopped())) {
 		tracing_max_latency = delta;
 		update_max_tr_single(tr, current, cpu);
 	}

 	max_sequence++;

 out_unlock:
 	raw_spin_unlock_irqrestore(&max_trace_lock, flags);

 out:
 	data->critical_sequence = max_sequence;
 	data->preempt_timestamp = ftrace_now(cpu);
 	__trace_function(tr, 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;

 	local_save_flags(flags);

 	__trace_function(tr, 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, 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 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() && !irq_trace())
 		stop_critical_timing(a0, a1);
 }

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

 static int start_irqsoff_tracer(struct trace_array *tr, int graph)
 {
 	int ret = 0;

 	if (!graph)
 		ret = register_ftrace_function(&trace_ops);
 	else
 		ret = register_ftrace_graph(&irqsoff_graph_return,
 					    &irqsoff_graph_entry);

 	if (!ret && tracing_is_enabled())
 		tracer_enabled = 1;
 	else
 		tracer_enabled = 0;

 	return ret;
 }

 static void stop_irqsoff_tracer(struct trace_array *tr, int graph)
 {
 	tracer_enabled = 0;

 	if (!graph)
 		unregister_ftrace_function(&trace_ops);
 	else
 		unregister_ftrace_graph();
 }

 static void __irqsoff_tracer_init(struct trace_array *tr)
 {
 	save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
 	trace_flags |= TRACE_ITER_LATENCY_FMT;

 	tracing_max_latency = 0;
 	irqsoff_trace = tr;
 	/* make sure that the tracer is visible */
 	smp_wmb();
 	tracing_reset_online_cpus(tr);

 	if (start_irqsoff_tracer(tr, is_graph()))
 		printk(KERN_ERR "failed to start irqsoff tracer\n");
 }

 static void irqsoff_tracer_reset(struct trace_array *tr)
 {
 	stop_irqsoff_tracer(tr, is_graph());

 	if (!save_lat_flag)
 		trace_flags &= ~TRACE_ITER_LATENCY_FMT;
 }

 static void irqsoff_tracer_start(struct trace_array *tr)
 {
 	tracer_enabled = 1;
 }

 static void irqsoff_tracer_stop(struct trace_array *tr)
 {
 	tracer_enabled = 0;
 }

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

 	__irqsoff_tracer_init(tr);
 	return 0;
 }
 static struct tracer irqsoff_tracer __read_mostly =
 {
 	.name		= "irqsoff",
 	.init		= irqsoff_tracer_init,
 	.reset		= irqsoff_tracer_reset,
 	.start		= irqsoff_tracer_start,
 	.stop		= irqsoff_tracer_stop,
 	.print_max	= true,
 	.print_header   = irqsoff_print_header,
 	.print_line     = irqsoff_print_line,
 	.flags		= &tracer_flags,
 	.set_flag	= irqsoff_set_flag,
 #ifdef CONFIG_FTRACE_SELFTEST
 	.selftest    = trace_selftest_startup_irqsoff,
 #endif
 	.open           = irqsoff_trace_open,
 	.close          = irqsoff_trace_close,
 	.use_max_tr	= true,
 };
 # define register_irqsoff(trace) register_tracer(&trace)
 #else
 # define register_irqsoff(trace) do { } while (0)
 #endif

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

 	__irqsoff_tracer_init(tr);
 	return 0;
 }

 static struct tracer preemptoff_tracer __read_mostly =
 {
 	.name		= "preemptoff",
 	.init		= preemptoff_tracer_init,
 	.reset		= irqsoff_tracer_reset,
 	.start		= irqsoff_tracer_start,
 	.stop		= irqsoff_tracer_stop,
 	.print_max	= true,
 	.print_header   = irqsoff_print_header,
 	.print_line     = irqsoff_print_line,
 	.flags		= &tracer_flags,
 	.set_flag	= irqsoff_set_flag,
 #ifdef CONFIG_FTRACE_SELFTEST
 	.selftest    = trace_selftest_startup_preemptoff,
 #endif
 	.open		= irqsoff_trace_open,
 	.close		= irqsoff_trace_close,
 	.use_max_tr	= true,
 };
 # 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 int preemptirqsoff_tracer_init(struct trace_array *tr)
 {
 	trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;

 	__irqsoff_tracer_init(tr);
 	return 0;
 }

 static struct tracer preemptirqsoff_tracer __read_mostly =
 {
 	.name		= "preemptirqsoff",
 	.init		= preemptirqsoff_tracer_init,
 	.reset		= irqsoff_tracer_reset,
 	.start		= irqsoff_tracer_start,
 	.stop		= irqsoff_tracer_stop,
 	.print_max	= true,
 	.print_header   = irqsoff_print_header,
 	.print_line     = irqsoff_print_line,
 	.flags		= &tracer_flags,
 	.set_flag	= irqsoff_set_flag,
 #ifdef CONFIG_FTRACE_SELFTEST
 	.selftest    = trace_selftest_startup_preemptirqsoff,
 #endif
 	.open		= irqsoff_trace_open,
 	.close		= irqsoff_trace_close,
 	.use_max_tr	= true,
 };

 # 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;
 }
 core_initcall(init_irqsoff_tracer);
	/*
	* trace irqs off critical 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 Nadia Yvette Chambers
	*/
	#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_RAW_SPINLOCK(max_trace_lock);

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

	static int trace_type __read_mostly;

	static int save_lat_flag;

	static void stop_irqsoff_tracer(struct trace_array *tr, int graph);
	static int start_irqsoff_tracer(struct trace_array *tr, int graph);

	#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

	#define TRACE_DISPLAY_GRAPH 1

	static struct tracer_opt trace_opts[] = {
	#ifdef CONFIG_FUNCTION_GRAPH_TRACER
	/* display latency trace as call graph */
	{ TRACER_OPT(display-graph, TRACE_DISPLAY_GRAPH) },
	#endif
	{ } /* Empty entry */
	};

	static struct tracer_flags tracer_flags = {
	.val = 0,
	.opts = trace_opts,
	};

	#define is_graph() (tracer_flags.val & TRACE_DISPLAY_GRAPH)

	/*
	* 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 doesn't
	* decrease the validity of the maximum found:
	*/
	static __cacheline_aligned_in_smp unsigned long max_sequence;

	#ifdef CONFIG_FUNCTION_TRACER
	/*
	* Prologue for the preempt and irqs off function tracers.
	*
	* Returns 1 if it is OK to continue, and data->disabled is
	* incremented.
	* 0 if the trace is to be ignored, and data->disabled
	* is kept the same.
	*
	* Note, this function is also used outside this ifdef but
	* inside the #ifdef of the function graph tracer below.
	* This is OK, since the function graph tracer is
	* dependent on the function tracer.
	*/
	static int func_prolog_dec(struct trace_array *tr,
	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 0;

	local_save_flags(*flags);
	/* slight chance to get a false positive on tracing_cpu */
	if (!irqs_disabled_flags(*flags))
	return 0;

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

	if (likely(disabled == 1))
	return 1;

	atomic_dec(&(*data)->disabled);

	return 0;
	}

	/*
	* irqsoff uses its own tracer function to keep the overhead down:
	*/
	static void
	irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip,
	struct ftrace_ops op, struct pt_regs pt_regs)
	{
	struct trace_array *tr = irqsoff_trace;
	struct trace_array_cpu *data;
	unsigned long flags;

	if (!func_prolog_dec(tr, &data, &flags))
	return;

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

	atomic_dec(&data->disabled);
	}

	static struct ftrace_ops trace_ops __read_mostly =
	{
	.func = irqsoff_tracer_call,
	.flags = FTRACE_OPS_FL_GLOBAL \| FTRACE_OPS_FL_RECURSION_SAFE,
	};
	#endif /* CONFIG_FUNCTION_TRACER */

	#ifdef CONFIG_FUNCTION_GRAPH_TRACER
	static int irqsoff_set_flag(u32 old_flags, u32 bit, int set)
	{
	int cpu;

	if (!(bit & TRACE_DISPLAY_GRAPH))
	return -EINVAL;

	if (!(is_graph() ^ set))
	return 0;

	stop_irqsoff_tracer(irqsoff_trace, !set);

	for_each_possible_cpu(cpu)
	per_cpu(tracing_cpu, cpu) = 0;

	tracing_max_latency = 0;
	tracing_reset_online_cpus(irqsoff_trace);

	return start_irqsoff_tracer(irqsoff_trace, set);
	}

	static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
	{
	struct trace_array *tr = irqsoff_trace;
	struct trace_array_cpu *data;
	unsigned long flags;
	int ret;
	int pc;

	if (!func_prolog_dec(tr, &data, &flags))
	return 0;

	pc = preempt_count();
	ret = __trace_graph_entry(tr, trace, flags, pc);
	atomic_dec(&data->disabled);

	return ret;
	}

	static void irqsoff_graph_return(struct ftrace_graph_ret *trace)
	{
	struct trace_array *tr = irqsoff_trace;
	struct trace_array_cpu *data;
	unsigned long flags;
	int pc;

	if (!func_prolog_dec(tr, &data, &flags))
	return;

	pc = preempt_count();
	__trace_graph_return(tr, trace, flags, pc);
	atomic_dec(&data->disabled);
	}

	static void irqsoff_trace_open(struct trace_iterator *iter)
	{
	if (is_graph())
	graph_trace_open(iter);

	}

	static void irqsoff_trace_close(struct trace_iterator *iter)
	{
	if (iter->private)
	graph_trace_close(iter);
	}

	#define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_CPU \| \
	TRACE_GRAPH_PRINT_PROC \| \
	TRACE_GRAPH_PRINT_ABS_TIME \| \
	TRACE_GRAPH_PRINT_DURATION)

	static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
	{
	/*
	* In graph mode call the graph tracer output function,
	* otherwise go with the TRACE_FN event handler
	*/
	if (is_graph())
	return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS);

	return TRACE_TYPE_UNHANDLED;
	}

	static void irqsoff_print_header(struct seq_file *s)
	{
	if (is_graph())
	print_graph_headers_flags(s, GRAPH_TRACER_FLAGS);
	else
	trace_default_header(s);
	}

	static void
	__trace_function(struct trace_array *tr,
	unsigned long ip, unsigned long parent_ip,
	unsigned long flags, int pc)
	{
	if (is_graph())
	trace_graph_function(tr, ip, parent_ip, flags, pc);
	else
	trace_function(tr, ip, parent_ip, flags, pc);
	}

	#else
	#define __trace_function trace_function

	static int irqsoff_set_flag(u32 old_flags, u32 bit, int set)
	{
	return -EINVAL;
	}

	static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
	{
	return -1;
	}

	static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
	{
	return TRACE_TYPE_UNHANDLED;
	}

	static void irqsoff_graph_return(struct ftrace_graph_ret *trace) { }
	static void irqsoff_trace_open(struct trace_iterator *iter) { }
	static void irqsoff_trace_close(struct trace_iterator *iter) { }

	#ifdef CONFIG_FUNCTION_TRACER
	static void irqsoff_print_header(struct seq_file *s)
	{
	trace_default_header(s);
	}
	#else
	static void irqsoff_print_header(struct seq_file *s)
	{
	trace_latency_header(s);
	}
	#endif /* CONFIG_FUNCTION_TRACER */
	#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

	/*
	* 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)
	{
	cycle_t T0, T1, delta;
	unsigned long flags;
	int pc;

	T0 = data->preempt_timestamp;
	T1 = ftrace_now(cpu);
	delta = T1-T0;

	local_save_flags(flags);

	pc = preempt_count();

	if (!report_latency(delta))
	goto out;

	raw_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, CALLER_ADDR0, parent_ip, flags, pc);
	/* Skip 5 functions to get to the irq/preempt enable function */
	__trace_stack(tr, flags, 5, pc);

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

	data->critical_end = parent_ip;

	if (likely(!is_tracing_stopped())) {
	tracing_max_latency = delta;
	update_max_tr_single(tr, current, cpu);
	}

	max_sequence++;

	out_unlock:
	raw_spin_unlock_irqrestore(&max_trace_lock, flags);

	out:
	data->critical_sequence = max_sequence;
	data->preempt_timestamp = ftrace_now(cpu);
	__trace_function(tr, 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;

	local_save_flags(flags);

	__trace_function(tr, 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, 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 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() && !irq_trace())
	stop_critical_timing(a0, a1);
	}

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

	static int start_irqsoff_tracer(struct trace_array *tr, int graph)
	{
	int ret = 0;

	if (!graph)
	ret = register_ftrace_function(&trace_ops);
	else
	ret = register_ftrace_graph(&irqsoff_graph_return,
	&irqsoff_graph_entry);

	if (!ret && tracing_is_enabled())
	tracer_enabled = 1;
	else
	tracer_enabled = 0;

	return ret;
	}

	static void stop_irqsoff_tracer(struct trace_array *tr, int graph)
	{
	tracer_enabled = 0;

	if (!graph)
	unregister_ftrace_function(&trace_ops);
	else
	unregister_ftrace_graph();
	}

	static void __irqsoff_tracer_init(struct trace_array *tr)
	{
	save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
	trace_flags \|= TRACE_ITER_LATENCY_FMT;

	tracing_max_latency = 0;
	irqsoff_trace = tr;
	/* make sure that the tracer is visible */
	smp_wmb();
	tracing_reset_online_cpus(tr);

	if (start_irqsoff_tracer(tr, is_graph()))
	printk(KERN_ERR "failed to start irqsoff tracer\n");
	}

	static void irqsoff_tracer_reset(struct trace_array *tr)
	{
	stop_irqsoff_tracer(tr, is_graph());

	if (!save_lat_flag)
	trace_flags &= ~TRACE_ITER_LATENCY_FMT;
	}

	static void irqsoff_tracer_start(struct trace_array *tr)
	{
	tracer_enabled = 1;
	}

	static void irqsoff_tracer_stop(struct trace_array *tr)
	{
	tracer_enabled = 0;
	}

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

	__irqsoff_tracer_init(tr);
	return 0;
	}
	static struct tracer irqsoff_tracer __read_mostly =
	{
	.name = "irqsoff",
	.init = irqsoff_tracer_init,
	.reset = irqsoff_tracer_reset,
	.start = irqsoff_tracer_start,
	.stop = irqsoff_tracer_stop,
	.print_max = true,
	.print_header = irqsoff_print_header,
	.print_line = irqsoff_print_line,
	.flags = &tracer_flags,
	.set_flag = irqsoff_set_flag,
	#ifdef CONFIG_FTRACE_SELFTEST
	.selftest = trace_selftest_startup_irqsoff,
	#endif
	.open = irqsoff_trace_open,
	.close = irqsoff_trace_close,
	.use_max_tr = true,
	};
	# define register_irqsoff(trace) register_tracer(&trace)
	#else
	# define register_irqsoff(trace) do { } while (0)
	#endif

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

	__irqsoff_tracer_init(tr);
	return 0;
	}

	static struct tracer preemptoff_tracer __read_mostly =
	{
	.name = "preemptoff",
	.init = preemptoff_tracer_init,
	.reset = irqsoff_tracer_reset,
	.start = irqsoff_tracer_start,
	.stop = irqsoff_tracer_stop,
	.print_max = true,
	.print_header = irqsoff_print_header,
	.print_line = irqsoff_print_line,
	.flags = &tracer_flags,
	.set_flag = irqsoff_set_flag,
	#ifdef CONFIG_FTRACE_SELFTEST
	.selftest = trace_selftest_startup_preemptoff,
	#endif
	.open = irqsoff_trace_open,
	.close = irqsoff_trace_close,
	.use_max_tr = true,
	};
	# 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 int preemptirqsoff_tracer_init(struct trace_array *tr)
	{
	trace_type = TRACER_IRQS_OFF \| TRACER_PREEMPT_OFF;

	__irqsoff_tracer_init(tr);
	return 0;
	}

	static struct tracer preemptirqsoff_tracer __read_mostly =
	{
	.name = "preemptirqsoff",
	.init = preemptirqsoff_tracer_init,
	.reset = irqsoff_tracer_reset,
	.start = irqsoff_tracer_start,
	.stop = irqsoff_tracer_stop,
	.print_max = true,
	.print_header = irqsoff_print_header,
	.print_line = irqsoff_print_line,
	.flags = &tracer_flags,
	.set_flag = irqsoff_set_flag,
	#ifdef CONFIG_FTRACE_SELFTEST
	.selftest = trace_selftest_startup_preemptirqsoff,
	#endif
	.open = irqsoff_trace_open,
	.close = irqsoff_trace_close,
	.use_max_tr = true,
	};

	# 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;
	}
	core_initcall(init_irqsoff_tracer);