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Commit fb1b6d8b authored by Steven Noonan's avatar Steven Noonan Committed by Ingo Molnar
Browse files

ftrace: add nop tracer 



A no-op tracer which can serve two purposes:

 1. A template for development of a new tracer.
 2. A convenient way to see ftrace_printk() calls without
    an irrelevant trace making the output messy.

[ mingo@elte.hu: resolved conflicts ]
Signed-off-by: default avatarSteven Noonan <steven@uplinklabs.net>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 5bf9a1ee

kernel/trace/Kconfig

+10 −0
Original line number Original line Diff line number Diff line
@@ -101,6 +101,16 @@ config SCHED_TRACER 
	  This tracer tracks the latency of the highest priority task

	  This tracer tracks the latency of the highest priority task

	  to be scheduled in, starting from the point it has woken up.

	  to be scheduled in, starting from the point it has woken up.





config NOP_TRACER

	bool "NOP Tracer"

	depends on HAVE_FTRACE

	depends on DEBUG_KERNEL

	select TRACING

	help

	  This tracer does nothing. The primary purpose for it is to

	  politely print the output of ftrace_printk() calls without

	  the overhead of an irrelevant trace taking place.



config CONTEXT_SWITCH_TRACER

config CONTEXT_SWITCH_TRACER

	bool "Trace process context switches"

	bool "Trace process context switches"

	depends on HAVE_FTRACE

	depends on HAVE_FTRACE

kernel/trace/Makefile

+1 −0
Original line number Original line Diff line number Diff line
@@ -19,6 +19,7 @@ obj-$(CONFIG_FTRACE) += trace_functions.o 
obj-$(CONFIG_IRQSOFF_TRACER) += trace_irqsoff.o

obj-$(CONFIG_IRQSOFF_TRACER) += trace_irqsoff.o

obj-$(CONFIG_PREEMPT_TRACER) += trace_irqsoff.o

obj-$(CONFIG_PREEMPT_TRACER) += trace_irqsoff.o

obj-$(CONFIG_SCHED_TRACER) += trace_sched_wakeup.o

obj-$(CONFIG_SCHED_TRACER) += trace_sched_wakeup.o

obj-$(CONFIG_NOP_TRACER) += trace_nop.o

obj-$(CONFIG_STACK_TRACER) += trace_stack.o

obj-$(CONFIG_STACK_TRACER) += trace_stack.o

obj-$(CONFIG_MMIOTRACE) += trace_mmiotrace.o

obj-$(CONFIG_MMIOTRACE) += trace_mmiotrace.o

kernel/trace/trace.h

+4 −0
Original line number Original line Diff line number Diff line
@@ -339,6 +339,10 @@ extern int trace_selftest_startup_preemptirqsoff(struct tracer *trace, 
extern int trace_selftest_startup_wakeup(struct tracer *trace,

extern int trace_selftest_startup_wakeup(struct tracer *trace,

					 struct trace_array *tr);

					 struct trace_array *tr);

#endif

#endif

#ifdef CONFIG_NOP_TRACER

extern int trace_selftest_startup_nop(struct tracer *trace,

					 struct trace_array *tr);

#endif

#ifdef CONFIG_CONTEXT_SWITCH_TRACER

#ifdef CONFIG_CONTEXT_SWITCH_TRACER

extern int trace_selftest_startup_sched_switch(struct tracer *trace,

extern int trace_selftest_startup_sched_switch(struct tracer *trace,

					       struct trace_array *tr);

					       struct trace_array *tr);

kernel/trace/trace_nop.c

0 → 100644
+65 −0
Original line number Original line Diff line number Diff line 
/*

 * nop tracer

 *

 * Copyright (C) 2008 Steven Noonan <steven@uplinklabs.net>

 *

 */



#include <linux/module.h>

#include <linux/fs.h>

#include <linux/debugfs.h>

#include <linux/ftrace.h>



#include "trace.h"



static struct trace_array	*ctx_trace;



static void start_nop_trace(struct trace_array *tr)

{

	/* Nothing to do! */

}



static void stop_nop_trace(struct trace_array *tr)

{

	/* Nothing to do! */

}



static void nop_trace_init(struct trace_array *tr)

{

	ctx_trace = tr;



	if (tr->ctrl)

		start_nop_trace(tr);

}



static void nop_trace_reset(struct trace_array *tr)

{

	if (tr->ctrl)

		stop_nop_trace(tr);

}



static void nop_trace_ctrl_update(struct trace_array *tr)

{

	/* When starting a new trace, reset the buffers */

	if (tr->ctrl)

		start_nop_trace(tr);

	else

		stop_nop_trace(tr);

}



static struct tracer nop_trace __read_mostly =

{

	.name		= "nop",

	.init		= nop_trace_init,

	.reset		= nop_trace_reset,

	.ctrl_update	= nop_trace_ctrl_update,

#ifdef CONFIG_FTRACE_SELFTEST

	.selftest	= trace_selftest_startup_nop,

#endif

};



__init static int init_nop_trace(void)

{

	return register_tracer(&nop_trace);

}

device_initcall(init_nop_trace);

kernel/trace/trace_selftest.c

+9 −0
Original line number Original line Diff line number Diff line
@@ -418,6 +418,15 @@ trace_selftest_startup_preemptirqsoff(struct tracer *trace, struct trace_array * 
}

}

#endif /* CONFIG_IRQSOFF_TRACER && CONFIG_PREEMPT_TRACER */

#endif /* CONFIG_IRQSOFF_TRACER && CONFIG_PREEMPT_TRACER */





#ifdef CONFIG_NOP_TRACER

int

trace_selftest_startup_nop(struct tracer *trace, struct trace_array *tr)

{

	/* What could possibly go wrong? */

	return 0;

}

#endif



#ifdef CONFIG_SCHED_TRACER

#ifdef CONFIG_SCHED_TRACER

static int trace_wakeup_test_thread(void *data)

static int trace_wakeup_test_thread(void *data)

{

{