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Commit d5915816 authored by Joel Fernandes's avatar Joel Fernandes Committed by Steven Rostedt (VMware)
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tracing: Add support for preempt and irq enable/disable events 

Preempt and irq trace events can be used for tracing the start and
end of an atomic section which can be used by a trace viewer like
systrace to graphically view the start and end of an atomic section and
correlate them with latencies and scheduling issues.

This also serves as a prelude to using synthetic events or probes to
rewrite the preempt and irqsoff tracers, along with numerous benefits of
using trace events features for these events.
Link: http://lkml.kernel.org/r/20171006005432.14244-3-joelaf@google.com
Link: http://lkml.kernel.org/r/20171010225137.17370-1-joelaf@google.com



Cc: Peter Zilstra <peterz@infradead.org>
Cc: kernel-team@android.com
Signed-off-by: default avatarJoel Fernandes <joelaf@google.com>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent aaecaa0b

include/linux/ftrace.h

+2 −1
Original line number Diff line number Diff line
@@ -769,7 +769,8 @@ static inline unsigned long get_lock_parent_ip(void) 
  static inline void time_hardirqs_off(unsigned long a0, unsigned long a1) { }

#endif



#ifdef CONFIG_PREEMPT_TRACER

#if defined(CONFIG_PREEMPT_TRACER) || \

	(defined(CONFIG_DEBUG_PREEMPT) && defined(CONFIG_PREEMPTIRQ_EVENTS))

  extern void trace_preempt_on(unsigned long a0, unsigned long a1);

  extern void trace_preempt_off(unsigned long a0, unsigned long a1);

#else

include/trace/events/preemptirq.h

0 → 100644
+70 −0
Original line number Diff line number Diff line 
#ifdef CONFIG_PREEMPTIRQ_EVENTS



#undef TRACE_SYSTEM

#define TRACE_SYSTEM preemptirq



#if !defined(_TRACE_PREEMPTIRQ_H) || defined(TRACE_HEADER_MULTI_READ)

#define _TRACE_PREEMPTIRQ_H



#include <linux/ktime.h>

#include <linux/tracepoint.h>

#include <linux/string.h>

#include <asm/sections.h>



DECLARE_EVENT_CLASS(preemptirq_template,



	TP_PROTO(unsigned long ip, unsigned long parent_ip),



	TP_ARGS(ip, parent_ip),



	TP_STRUCT__entry(

		__field(u32, caller_offs)

		__field(u32, parent_offs)

	),



	TP_fast_assign(

		__entry->caller_offs = (u32)(ip - (unsigned long)_stext);

		__entry->parent_offs = (u32)(parent_ip - (unsigned long)_stext);

	),



	TP_printk("caller=%pF parent=%pF",

		  (void *)((unsigned long)(_stext) + __entry->caller_offs),

		  (void *)((unsigned long)(_stext) + __entry->parent_offs))

);



#ifndef CONFIG_PROVE_LOCKING

DEFINE_EVENT(preemptirq_template, irq_disable,

	     TP_PROTO(unsigned long ip, unsigned long parent_ip),

	     TP_ARGS(ip, parent_ip));



DEFINE_EVENT(preemptirq_template, irq_enable,

	     TP_PROTO(unsigned long ip, unsigned long parent_ip),

	     TP_ARGS(ip, parent_ip));

#endif



#ifdef CONFIG_DEBUG_PREEMPT

DEFINE_EVENT(preemptirq_template, preempt_disable,

	     TP_PROTO(unsigned long ip, unsigned long parent_ip),

	     TP_ARGS(ip, parent_ip));



DEFINE_EVENT(preemptirq_template, preempt_enable,

	     TP_PROTO(unsigned long ip, unsigned long parent_ip),

	     TP_ARGS(ip, parent_ip));

#endif



#endif /* _TRACE_PREEMPTIRQ_H */



#include <trace/define_trace.h>



#else /* !CONFIG_PREEMPTIRQ_EVENTS */



#define trace_irq_enable(...)

#define trace_irq_disable(...)

#define trace_preempt_enable(...)

#define trace_preempt_disable(...)

#define trace_irq_enable_rcuidle(...)

#define trace_irq_disable_rcuidle(...)

#define trace_preempt_enable_rcuidle(...)

#define trace_preempt_disable_rcuidle(...)



#endif

kernel/trace/Kconfig

+11 −0
Original line number Diff line number Diff line
@@ -160,6 +160,17 @@ config FUNCTION_GRAPH_TRACER 
	  address on the current task structure into a stack of calls.





config PREEMPTIRQ_EVENTS

	bool "Enable trace events for preempt and irq disable/enable"

	select TRACE_IRQFLAGS

	depends on DEBUG_PREEMPT || !PROVE_LOCKING

	default n

	help

	  Enable tracing of disable and enable events for preemption and irqs.

	  For tracing preempt disable/enable events, DEBUG_PREEMPT must be

	  enabled. For tracing irq disable/enable events, PROVE_LOCKING must

	  be disabled.



config IRQSOFF_TRACER

	bool "Interrupts-off Latency Tracer"

	default n

kernel/trace/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ obj-$(CONFIG_TRACING) += trace_printk.o 
obj-$(CONFIG_TRACING_MAP) += tracing_map.o

obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o

obj-$(CONFIG_FUNCTION_TRACER) += trace_functions.o

obj-$(CONFIG_PREEMPTIRQ_EVENTS) += trace_irqsoff.o

obj-$(CONFIG_IRQSOFF_TRACER) += trace_irqsoff.o

obj-$(CONFIG_PREEMPT_TRACER) += trace_irqsoff.o

obj-$(CONFIG_SCHED_TRACER) += trace_sched_wakeup.o

kernel/trace/trace_irqsoff.c

+34 −1
Original line number Diff line number Diff line
@@ -16,6 +16,9 @@ 


#include "trace.h"



#define CREATE_TRACE_POINTS

#include <trace/events/preemptirq.h>



#if defined(CONFIG_IRQSOFF_TRACER) || defined(CONFIG_PREEMPT_TRACER)

static struct trace_array		*irqsoff_trace __read_mostly;

static int				tracer_enabled __read_mostly;
@@ -777,26 +780,53 @@ static inline void tracer_preempt_off(unsigned long a0, unsigned long a1) { } 
#endif



#if defined(CONFIG_TRACE_IRQFLAGS) && !defined(CONFIG_PROVE_LOCKING)

/* Per-cpu variable to prevent redundant calls when IRQs already off */

static DEFINE_PER_CPU(int, tracing_irq_cpu);



void trace_hardirqs_on(void)

{

	if (!this_cpu_read(tracing_irq_cpu))

		return;



	trace_irq_enable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);

	tracer_hardirqs_on();



	this_cpu_write(tracing_irq_cpu, 0);

}

EXPORT_SYMBOL(trace_hardirqs_on);



void trace_hardirqs_off(void)

{

	if (this_cpu_read(tracing_irq_cpu))

		return;



	this_cpu_write(tracing_irq_cpu, 1);



	trace_irq_disable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);

	tracer_hardirqs_off();

}

EXPORT_SYMBOL(trace_hardirqs_off);



__visible void trace_hardirqs_on_caller(unsigned long caller_addr)

{

	if (!this_cpu_read(tracing_irq_cpu))

		return;



	trace_irq_enable_rcuidle(CALLER_ADDR0, caller_addr);

	tracer_hardirqs_on_caller(caller_addr);



	this_cpu_write(tracing_irq_cpu, 0);

}

EXPORT_SYMBOL(trace_hardirqs_on_caller);



__visible void trace_hardirqs_off_caller(unsigned long caller_addr)

{

	if (this_cpu_read(tracing_irq_cpu))

		return;



	this_cpu_write(tracing_irq_cpu, 1);



	trace_irq_disable_rcuidle(CALLER_ADDR0, caller_addr);

	tracer_hardirqs_off_caller(caller_addr);

}

EXPORT_SYMBOL(trace_hardirqs_off_caller);
@@ -818,14 +848,17 @@ inline void print_irqtrace_events(struct task_struct *curr) 
}

#endif



#ifdef CONFIG_PREEMPT_TRACER

#if defined(CONFIG_PREEMPT_TRACER) || \

	(defined(CONFIG_DEBUG_PREEMPT) && defined(CONFIG_PREEMPTIRQ_EVENTS))

void trace_preempt_on(unsigned long a0, unsigned long a1)

{

	trace_preempt_enable_rcuidle(a0, a1);

	tracer_preempt_on(a0, a1);

}



void trace_preempt_off(unsigned long a0, unsigned long a1)

{

	trace_preempt_disable_rcuidle(a0, a1);

	tracer_preempt_off(a0, a1);

}

#endif