Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 0f048701 authored by Steven Rostedt's avatar Steven Rostedt Committed by Ingo Molnar
Browse files

ftrace: soft tracing stop and start 



Impact: add way to quickly start stop tracing from the kernel

This patch adds a soft stop and start to the trace. This simply
disables function tracing via the ftrace_disabled flag, and
disables the trace buffers to prevent recording. The tracing
code may still be executed, but the trace will not be recorded.

Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 60a7ecf4

include/linux/ftrace.h

+5 −0
Original line number Diff line number Diff line
@@ -216,6 +216,9 @@ static inline void __ftrace_enabled_restore(int enabled) 
#ifdef CONFIG_TRACING

extern int ftrace_dump_on_oops;



extern void tracing_start(void);

extern void tracing_stop(void);



extern void

ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3);
@@ -246,6 +249,8 @@ ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3) { } 
static inline int

ftrace_printk(const char *fmt, ...) __attribute__ ((format (printf, 1, 0)));



static inline void tracing_start(void) { }

static inline void tracing_stop(void) { }

static inline int

ftrace_printk(const char *fmt, ...)

{

kernel/trace/trace.c

+79 −2
Original line number Diff line number Diff line
@@ -43,6 +43,15 @@ 
unsigned long __read_mostly	tracing_max_latency = (cycle_t)ULONG_MAX;

unsigned long __read_mostly	tracing_thresh;





/*

 * Kill all tracing for good (never come back).

 * It is initialized to 1 but will turn to zero if the initialization

 * of the tracer is successful. But that is the only place that sets

 * this back to zero.

 */

int tracing_disabled = 1;



static DEFINE_PER_CPU(local_t, ftrace_cpu_disabled);



static inline void ftrace_disable_cpu(void)
@@ -62,8 +71,6 @@ static cpumask_t __read_mostly tracing_buffer_mask; 
#define for_each_tracing_cpu(cpu)	\

	for_each_cpu_mask(cpu, tracing_buffer_mask)



static int tracing_disabled = 1;



/*

 * ftrace_dump_on_oops - variable to dump ftrace buffer on oops

 *
@@ -613,6 +620,76 @@ static void trace_init_cmdlines(void) 
	cmdline_idx = 0;

}



static int trace_stop_count;

static DEFINE_SPINLOCK(tracing_start_lock);



/**

 * tracing_start - quick start of the tracer

 *

 * If tracing is enabled but was stopped by tracing_stop,

 * this will start the tracer back up.

 */

void tracing_start(void)

{

	struct ring_buffer *buffer;

	unsigned long flags;



	if (tracing_disabled)

		return;



	spin_lock_irqsave(&tracing_start_lock, flags);

	if (--trace_stop_count)

		goto out;



	if (trace_stop_count < 0) {

		/* Someone screwed up their debugging */

		WARN_ON_ONCE(1);

		trace_stop_count = 0;

		goto out;

	}





	buffer = global_trace.buffer;

	if (buffer)

		ring_buffer_record_enable(buffer);



	buffer = max_tr.buffer;

	if (buffer)

		ring_buffer_record_enable(buffer);



	ftrace_start();

 out:

	spin_unlock_irqrestore(&tracing_start_lock, flags);

}



/**

 * tracing_stop - quick stop of the tracer

 *

 * Light weight way to stop tracing. Use in conjunction with

 * tracing_start.

 */

void tracing_stop(void)

{

	struct ring_buffer *buffer;

	unsigned long flags;



	ftrace_stop();

	spin_lock_irqsave(&tracing_start_lock, flags);

	if (trace_stop_count++)

		goto out;



	buffer = global_trace.buffer;

	if (buffer)

		ring_buffer_record_disable(buffer);



	buffer = max_tr.buffer;

	if (buffer)

		ring_buffer_record_disable(buffer);



 out:

	spin_unlock_irqrestore(&tracing_start_lock, flags);

}



void trace_stop_cmdline_recording(void);



static void trace_save_cmdline(struct task_struct *tsk)