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Commit 020e5f85 authored by Li Zefan's avatar Li Zefan Committed by Ingo Molnar
Browse files

tracing/events: Add trace_event boot option 



We already have ftrace= boot option, and this adds a similar
boot option for trace events, so allow trace events to be
enabled at boot, for boot debugging purpose.

Signed-off-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A4ACE29.3010407@cn.fujitsu.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent c5cb5a2d

Documentation/kernel-parameters.txt

+5 −0
Original line number Diff line number Diff line
@@ -2478,6 +2478,11 @@ and is between 256 and 4096 characters. It is defined in the file 
	trace_buf_size=nn[KMG]

			[FTRACE] will set tracing buffer size.



	trace_event=[event-list]

			[FTRACE] Set and start specified trace events in order

			to facilitate early boot debugging.

			See also Documentation/trace/events.txt



	trix=		[HW,OSS] MediaTrix AudioTrix Pro

			Format:

			<io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>

Documentation/trace/events.txt

+9 −0
Original line number Diff line number Diff line
@@ -83,6 +83,15 @@ When reading one of these enable files, there are four results: 
 X - there is a mixture of events enabled and disabled

 ? - this file does not affect any event



2.3 Boot option

---------------



In order to facilitate early boot debugging, use boot option:



	trace_event=[event-list]



The format of this boot option is the same as described in section 2.1.



3. Defining an event-enabled tracepoint

=======================================

kernel/trace/trace.c

+2 −2
Original line number Diff line number Diff line
@@ -49,7 +49,7 @@ unsigned long __read_mostly tracing_thresh; 
 * On boot up, the ring buffer is set to the minimum size, so that

 * we do not waste memory on systems that are not using tracing.

 */

static int ring_buffer_expanded;

int ring_buffer_expanded;



/*

 * We need to change this state when a selftest is running.
@@ -63,7 +63,7 @@ static bool __read_mostly tracing_selftest_running; 
/*

 * If a tracer is running, we do not want to run SELFTEST.

 */

static bool __read_mostly tracing_selftest_disabled;

bool __read_mostly tracing_selftest_disabled;



/* For tracers that don't implement custom flags */

static struct tracer_opt dummy_tracer_opt[] = {

kernel/trace/trace.h

+3 −0
Original line number Diff line number Diff line
@@ -517,6 +517,9 @@ extern unsigned long ftrace_update_tot_cnt; 
extern int DYN_FTRACE_TEST_NAME(void);

#endif



extern int ring_buffer_expanded;

extern bool tracing_selftest_disabled;



#ifdef CONFIG_FTRACE_STARTUP_TEST

extern int trace_selftest_startup_function(struct tracer *trace,

					   struct trace_array *tr);

kernel/trace/trace_events.c

+33 −4
Original line number Diff line number Diff line
@@ -17,6 +17,8 @@ 
#include <linux/ctype.h>

#include <linux/delay.h>



#include <asm/setup.h>



#include "trace_output.h"



#define TRACE_SYSTEM "TRACE_SYSTEM"
@@ -1133,6 +1135,18 @@ struct notifier_block trace_module_nb = { 
extern struct ftrace_event_call __start_ftrace_events[];

extern struct ftrace_event_call __stop_ftrace_events[];



static char bootup_event_buf[COMMAND_LINE_SIZE] __initdata;



static __init int setup_trace_event(char *str)

{

	strlcpy(bootup_event_buf, str, COMMAND_LINE_SIZE);

	ring_buffer_expanded = 1;

	tracing_selftest_disabled = 1;



	return 1;

}

__setup("trace_event=", setup_trace_event);



static __init int event_trace_init(void)

{

	struct ftrace_event_call *call;
@@ -1140,6 +1154,8 @@ static __init int event_trace_init(void) 
	struct dentry *entry;

	struct dentry *d_events;

	int ret;

	char *buf = bootup_event_buf;

	char *token;



	d_tracer = tracing_init_dentry();

	if (!d_tracer)
@@ -1185,6 +1201,19 @@ static __init int event_trace_init(void) 
				 &ftrace_event_format_fops);

	}



	while (true) {

		token = strsep(&buf, ",");



		if (!token)

			break;

		if (!*token)

			continue;



		ret = ftrace_set_clr_event(token, 1);

		if (ret)

			pr_warning("Failed to enable trace event: %s\n", token);

	}



	ret = register_module_notifier(&trace_module_nb);

	if (ret)

		pr_warning("Failed to register trace events module notifier\n");
@@ -1392,10 +1421,10 @@ static __init void event_trace_self_test_with_function(void) 


static __init int event_trace_self_tests_init(void)

{



	if (!tracing_selftest_disabled) {

		event_trace_self_tests();



		event_trace_self_test_with_function();

	}



	return 0;

}