Commit 499e5470 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt
Browse files

tracing/ring-buffer: Only have tracing_on disable tracing buffers 



As the ring-buffer code is being used by other facilities in the
kernel, having tracing_on file disable *all* buffers is not a desired
affect. It should only disable the ftrace buffers that are being used.

Move the code into the trace.c file and use the buffer disabling
for tracing_on() and tracing_off(). This way only the ftrace buffers
will be affected by them and other kernel utilities will not be
confused to why their output suddenly stopped.

Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 5500fa51

include/linux/ring_buffer.h

+3 −0
Original line number Diff line number Diff line
@@ -151,6 +151,9 @@ int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu); 


void ring_buffer_record_disable(struct ring_buffer *buffer);

void ring_buffer_record_enable(struct ring_buffer *buffer);

void ring_buffer_record_off(struct ring_buffer *buffer);

void ring_buffer_record_on(struct ring_buffer *buffer);

int ring_buffer_record_is_on(struct ring_buffer *buffer);

void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu);

void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu);

kernel/trace/ring_buffer.c

+60 −97
Original line number Diff line number Diff line
@@ -154,33 +154,10 @@ enum { 


static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON;



#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)



/**

 * tracing_on - enable all tracing buffers

 *

 * This function enables all tracing buffers that may have been

 * disabled with tracing_off.

 */

void tracing_on(void)

{

	set_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags);

}

EXPORT_SYMBOL_GPL(tracing_on);

/* Used for individual buffers (after the counter) */

#define RB_BUFFER_OFF		(1 << 20)



/**

 * tracing_off - turn off all tracing buffers

 *

 * This function stops all tracing buffers from recording data.

 * It does not disable any overhead the tracers themselves may

 * be causing. This function simply causes all recording to

 * the ring buffers to fail.

 */

void tracing_off(void)

{

	clear_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags);

}

EXPORT_SYMBOL_GPL(tracing_off);

#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)



/**

 * tracing_off_permanent - permanently disable ring buffers
@@ -193,15 +170,6 @@ void tracing_off_permanent(void) 
	set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags);

}



/**

 * tracing_is_on - show state of ring buffers enabled

 */

int tracing_is_on(void)

{

	return ring_buffer_flags == RB_BUFFERS_ON;

}

EXPORT_SYMBOL_GPL(tracing_is_on);



#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))

#define RB_ALIGNMENT		4U

#define RB_MAX_SMALL_DATA	(RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
@@ -2618,6 +2586,63 @@ void ring_buffer_record_enable(struct ring_buffer *buffer) 
}

EXPORT_SYMBOL_GPL(ring_buffer_record_enable);



/**

 * ring_buffer_record_off - stop all writes into the buffer

 * @buffer: The ring buffer to stop writes to.

 *

 * This prevents all writes to the buffer. Any attempt to write

 * to the buffer after this will fail and return NULL.

 *

 * This is different than ring_buffer_record_disable() as

 * it works like an on/off switch, where as the disable() verison

 * must be paired with a enable().

 */

void ring_buffer_record_off(struct ring_buffer *buffer)

{

	unsigned int rd;

	unsigned int new_rd;



	do {

		rd = atomic_read(&buffer->record_disabled);

		new_rd = rd | RB_BUFFER_OFF;

	} while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);

}

EXPORT_SYMBOL_GPL(ring_buffer_record_off);



/**

 * ring_buffer_record_on - restart writes into the buffer

 * @buffer: The ring buffer to start writes to.

 *

 * This enables all writes to the buffer that was disabled by

 * ring_buffer_record_off().

 *

 * This is different than ring_buffer_record_enable() as

 * it works like an on/off switch, where as the enable() verison

 * must be paired with a disable().

 */

void ring_buffer_record_on(struct ring_buffer *buffer)

{

	unsigned int rd;

	unsigned int new_rd;



	do {

		rd = atomic_read(&buffer->record_disabled);

		new_rd = rd & ~RB_BUFFER_OFF;

	} while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);

}

EXPORT_SYMBOL_GPL(ring_buffer_record_on);



/**

 * ring_buffer_record_is_on - return true if the ring buffer can write

 * @buffer: The ring buffer to see if write is enabled

 *

 * Returns true if the ring buffer is in a state that it accepts writes.

 */

int ring_buffer_record_is_on(struct ring_buffer *buffer)

{

	return !atomic_read(&buffer->record_disabled);

}



/**

 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer

 * @buffer: The ring buffer to stop writes to.
@@ -4039,68 +4064,6 @@ int ring_buffer_read_page(struct ring_buffer *buffer, 
}

EXPORT_SYMBOL_GPL(ring_buffer_read_page);



#ifdef CONFIG_TRACING

static ssize_t

rb_simple_read(struct file *filp, char __user *ubuf,

	       size_t cnt, loff_t *ppos)

{

	unsigned long *p = filp->private_data;

	char buf[64];

	int r;



	if (test_bit(RB_BUFFERS_DISABLED_BIT, p))

		r = sprintf(buf, "permanently disabled\n");

	else

		r = sprintf(buf, "%d\n", test_bit(RB_BUFFERS_ON_BIT, p));



	return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);

}



static ssize_t

rb_simple_write(struct file *filp, const char __user *ubuf,

		size_t cnt, loff_t *ppos)

{

	unsigned long *p = filp->private_data;

	unsigned long val;

	int ret;



	ret = kstrtoul_from_user(ubuf, cnt, 10, &val);

	if (ret)

		return ret;



	if (val)

		set_bit(RB_BUFFERS_ON_BIT, p);

	else

		clear_bit(RB_BUFFERS_ON_BIT, p);



	(*ppos)++;



	return cnt;

}



static const struct file_operations rb_simple_fops = {

	.open		= tracing_open_generic,

	.read		= rb_simple_read,

	.write		= rb_simple_write,

	.llseek		= default_llseek,

};





static __init int rb_init_debugfs(void)

{

	struct dentry *d_tracer;



	d_tracer = tracing_init_dentry();



	trace_create_file("tracing_on", 0644, d_tracer,

			    &ring_buffer_flags, &rb_simple_fops);



	return 0;

}



fs_initcall(rb_init_debugfs);

#endif



#ifdef CONFIG_HOTPLUG_CPU

static int rb_cpu_notify(struct notifier_block *self,

			 unsigned long action, void *hcpu)

kernel/trace/trace.c

+107 −0
Original line number Diff line number Diff line
@@ -351,6 +351,59 @@ static void wakeup_work_handler(struct work_struct *work) 


static DECLARE_DELAYED_WORK(wakeup_work, wakeup_work_handler);



/**

 * tracing_on - enable tracing buffers

 *

 * This function enables tracing buffers that may have been

 * disabled with tracing_off.

 */

void tracing_on(void)

{

	if (global_trace.buffer)

		ring_buffer_record_on(global_trace.buffer);

	/*

	 * This flag is only looked at when buffers haven't been

	 * allocated yet. We don't really care about the race

	 * between setting this flag and actually turning

	 * on the buffer.

	 */

	global_trace.buffer_disabled = 0;

}

EXPORT_SYMBOL_GPL(tracing_on);



/**

 * tracing_off - turn off tracing buffers

 *

 * This function stops the tracing buffers from recording data.

 * It does not disable any overhead the tracers themselves may

 * be causing. This function simply causes all recording to

 * the ring buffers to fail.

 */

void tracing_off(void)

{

	if (global_trace.buffer)

		ring_buffer_record_on(global_trace.buffer);

	/*

	 * This flag is only looked at when buffers haven't been

	 * allocated yet. We don't really care about the race

	 * between setting this flag and actually turning

	 * on the buffer.

	 */

	global_trace.buffer_disabled = 1;

}

EXPORT_SYMBOL_GPL(tracing_off);



/**

 * tracing_is_on - show state of ring buffers enabled

 */

int tracing_is_on(void)

{

	if (global_trace.buffer)

		return ring_buffer_record_is_on(global_trace.buffer);

	return !global_trace.buffer_disabled;

}

EXPORT_SYMBOL_GPL(tracing_is_on);



/**

 * trace_wake_up - wake up tasks waiting for trace input

 *
@@ -4567,6 +4620,55 @@ static __init void create_trace_options_dir(void) 
		create_trace_option_core_file(trace_options[i], i);

}



static ssize_t

rb_simple_read(struct file *filp, char __user *ubuf,

	       size_t cnt, loff_t *ppos)

{

	struct ring_buffer *buffer = filp->private_data;

	char buf[64];

	int r;



	if (buffer)

		r = ring_buffer_record_is_on(buffer);

	else

		r = 0;



	r = sprintf(buf, "%d\n", r);



	return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);

}



static ssize_t

rb_simple_write(struct file *filp, const char __user *ubuf,

		size_t cnt, loff_t *ppos)

{

	struct ring_buffer *buffer = filp->private_data;

	unsigned long val;

	int ret;



	ret = kstrtoul_from_user(ubuf, cnt, 10, &val);

	if (ret)

		return ret;



	if (buffer) {

		if (val)

			ring_buffer_record_on(buffer);

		else

			ring_buffer_record_off(buffer);

	}



	(*ppos)++;



	return cnt;

}



static const struct file_operations rb_simple_fops = {

	.open		= tracing_open_generic,

	.read		= rb_simple_read,

	.write		= rb_simple_write,

	.llseek		= default_llseek,

};



static __init int tracer_init_debugfs(void)

{

	struct dentry *d_tracer;
@@ -4626,6 +4728,9 @@ static __init int tracer_init_debugfs(void) 
	trace_create_file("trace_clock", 0644, d_tracer, NULL,

			  &trace_clock_fops);



	trace_create_file("tracing_on", 0644, d_tracer,

			    global_trace.buffer, &rb_simple_fops);



#ifdef CONFIG_DYNAMIC_FTRACE

	trace_create_file("dyn_ftrace_total_info", 0444, d_tracer,

			&ftrace_update_tot_cnt, &tracing_dyn_info_fops);
@@ -4863,6 +4968,8 @@ __init static int tracer_alloc_buffers(void) 
		goto out_free_cpumask;

	}

	global_trace.entries = ring_buffer_size(global_trace.buffer);

	if (global_trace.buffer_disabled)

		tracing_off();





#ifdef CONFIG_TRACER_MAX_TRACE

kernel/trace/trace.h

+1 −0
Original line number Diff line number Diff line
@@ -154,6 +154,7 @@ struct trace_array { 
	struct ring_buffer	*buffer;

	unsigned long		entries;

	int			cpu;

	int			buffer_disabled;

	cycle_t			time_start;

	struct task_struct	*waiter;

	struct trace_array_cpu	*data[NR_CPUS];

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