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

	  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

	bool "Trace process context switches"

	depends on HAVE_FTRACE

kernel/trace/Makefile

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

obj-$(CONFIG_PREEMPT_TRACER) += trace_irqsoff.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_MMIOTRACE) += trace_mmiotrace.o

kernel/trace/trace.h

+4 −0
Original line number 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,

					 struct trace_array *tr);

#endif

#ifdef CONFIG_NOP_TRACER

extern int trace_selftest_startup_nop(struct tracer *trace,

					 struct trace_array *tr);

#endif

#ifdef CONFIG_CONTEXT_SWITCH_TRACER

extern int trace_selftest_startup_sched_switch(struct tracer *trace,

					       struct trace_array *tr);

kernel/trace/trace_nop.c

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



#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

static int trace_wakeup_test_thread(void *data)

{