Commit 71566a0d authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Ingo Molnar
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tracing/fastboot: Enable boot tracing only during initcalls 



Impact: modify boot tracer

We used to disable the initcall tracing at a specified time (IE: end
of builtin initcalls). But we don't need it anymore. It will be
stopped when initcalls are finished.

However we want two things:

_Start this tracing only after pre-smp initcalls are finished.

_Since we are planning to trace sched_switches at the same time, we
want to enable them only during the initcall execution.

For this purpose, this patch introduce two functions to enable/disable
the sched_switch tracing during boot.

Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 7a895f53

include/linux/ftrace.h

+22 −2
Original line number Diff line number Diff line
@@ -234,6 +234,11 @@ ftrace_init_module(unsigned long *start, unsigned long *end) { } 
#endif





/*

 * Structure which defines the trace of an initcall.

 * You don't have to fill the func field since it is

 * only used internally by the tracer.

 */

struct boot_trace {

	pid_t			caller;

	char			func[KSYM_NAME_LEN];
@@ -244,13 +249,28 @@ struct boot_trace { 
};



#ifdef CONFIG_BOOT_TRACER

/* Append the trace on the ring-buffer */

extern void trace_boot(struct boot_trace *it, initcall_t fn);



/* Tells the tracer that smp_pre_initcall is finished.

 * So we can start the tracing

 */

extern void start_boot_trace(void);

extern void stop_boot_trace(void);



/* Resume the tracing of other necessary events

 * such as sched switches

 */

extern void enable_boot_trace(void);



/* Suspend this tracing. Actually, only sched_switches tracing have

 * to be suspended. Initcalls doesn't need it.)

 */

extern void disable_boot_trace(void);

#else

static inline void trace_boot(struct boot_trace *it, initcall_t fn) { }

static inline void start_boot_trace(void) { }

static inline void stop_boot_trace(void) { }

static inline void enable_boot_trace(void) { }

static inline void disable_boot_trace(void) { }

#endif

init/main.c

+3 −1
Original line number Diff line number Diff line
@@ -711,6 +711,7 @@ int do_one_initcall(initcall_t fn) 
		it.caller = task_pid_nr(current);

		printk("calling  %pF @ %i\n", fn, it.caller);

		it.calltime = ktime_get();

		enable_boot_trace();

	}



	it.result = fn();
@@ -722,6 +723,7 @@ int do_one_initcall(initcall_t fn) 
		printk("initcall %pF returned %d after %Ld usecs\n", fn,

			it.result, it.duration);

		trace_boot(&it, fn);

		disable_boot_trace();

	}



	msgbuf[0] = 0;
@@ -882,7 +884,7 @@ static int __init kernel_init(void * unused) 
	 * we're essentially up and running. Get rid of the

	 * initmem segments and start the user-mode stuff..

	 */

	stop_boot_trace();



	init_post();

	return 0;

}

kernel/trace/trace_boot.c

+16 −12
Original line number Diff line number Diff line
@@ -13,23 +13,29 @@ 
#include "trace.h"



static struct trace_array *boot_trace;

static int trace_boot_enabled;

static bool pre_initcalls_finished;





/* Should be started after do_pre_smp_initcalls() in init/main.c */

/* Tells the boot tracer that the pre_smp_initcalls are finished.

 * So we are ready .

 * It doesn't enable sched events tracing however.

 * You have to call enable_boot_trace to do so.

 */

void start_boot_trace(void)

{

	trace_boot_enabled = 1;

	pre_initcalls_finished = true;

}



void enable_boot_trace(void)

{

}



void stop_boot_trace(void)

void disable_boot_trace(void)

{

	trace_boot_enabled = 0;

}



void reset_boot_trace(struct trace_array *tr)

{

	stop_boot_trace();

	disable_boot_trace();

}



static void boot_trace_init(struct trace_array *tr)
@@ -37,8 +43,6 @@ static void boot_trace_init(struct trace_array *tr) 
	int cpu;

	boot_trace = tr;



	trace_boot_enabled = 0;



	for_each_cpu_mask(cpu, cpu_possible_map)

		tracing_reset(tr, cpu);

}
@@ -46,9 +50,9 @@ static void boot_trace_init(struct trace_array *tr) 
static void boot_trace_ctrl_update(struct trace_array *tr)

{

	if (tr->ctrl)

		start_boot_trace();

		enable_boot_trace();

	else

		stop_boot_trace();

		disable_boot_trace();

}



static enum print_line_t initcall_print_line(struct trace_iterator *iter)
@@ -99,7 +103,7 @@ void trace_boot(struct boot_trace *it, initcall_t fn) 
	unsigned long irq_flags;

	struct trace_array *tr = boot_trace;



	if (!trace_boot_enabled)

	if (!pre_initcalls_finished)

		return;



	/* Get its name now since this function could

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