Commit b179d48b authored by Daniel Bristot de Oliveira's avatar Daniel Bristot de Oliveira Committed by Steven Rostedt (Google)
Browse files

tracing/osnoise: Add osnoise/options file 

Add the tracing/osnoise/options file to control
osnoise/timerlat tracer features. It is a single
file to contain multiple features, similar to
the sched/features file.

Reading the file displays a list of options. Writing
the OPTION_NAME enables it, writing NO_OPTION_NAME disables
it.

The DEAFULTS is a particular option that resets the options
to the default ones.

It uses a bitmask to keep track of the status of the option. When
needed, we can add a list of static keys, but for now
it does not justify the memory increase.

Link: https://lkml.kernel.org/r/f8d34aefdb225d2603fcb4c02a120832a0cd3339.1668692096.git.bristot@kernel.org



Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: default avatarDaniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 04aabc32

kernel/trace/trace_osnoise.c

+170 −0
Original line number Diff line number Diff line
@@ -48,6 +48,19 @@ 
#define DEFAULT_TIMERLAT_PERIOD	1000			/* 1ms */

#define DEFAULT_TIMERLAT_PRIO	95			/* FIFO 95 */



/*

 * osnoise/options entries.

 */

enum osnoise_options_index {

	OSN_DEFAULTS = 0,

	OSN_MAX

};



static const char * const osnoise_options_str[OSN_MAX] = { "DEFAULTS" };



#define OSN_DEFAULT_OPTIONS	0

unsigned long osnoise_options	= OSN_DEFAULT_OPTIONS;



/*

 * trace_array of the enabled osnoise/timerlat instances.

 */
@@ -1860,6 +1873,150 @@ static void osnoise_init_hotplug_support(void) 
}

#endif /* CONFIG_HOTPLUG_CPU */



/*

 * seq file functions for the osnoise/options file.

 */

static void *s_options_start(struct seq_file *s, loff_t *pos)

{

	int option = *pos;



	mutex_lock(&interface_lock);



	if (option >= OSN_MAX)

		return NULL;



	return pos;

}



static void *s_options_next(struct seq_file *s, void *v, loff_t *pos)

{

	int option = ++(*pos);



	if (option >= OSN_MAX)

		return NULL;



	return pos;

}



static int s_options_show(struct seq_file *s, void *v)

{

	loff_t *pos = v;

	int option = *pos;



	if (option == OSN_DEFAULTS) {

		if (osnoise_options == OSN_DEFAULT_OPTIONS)

			seq_printf(s, "%s", osnoise_options_str[option]);

		else

			seq_printf(s, "NO_%s", osnoise_options_str[option]);

		goto out;

	}



	if (test_bit(option, &osnoise_options))

		seq_printf(s, "%s", osnoise_options_str[option]);

	else

		seq_printf(s, "NO_%s", osnoise_options_str[option]);



out:

	if (option != OSN_MAX)

		seq_puts(s, " ");



	return 0;

}



static void s_options_stop(struct seq_file *s, void *v)

{

	seq_puts(s, "\n");

	mutex_unlock(&interface_lock);

}



static const struct seq_operations osnoise_options_seq_ops = {

	.start		= s_options_start,

	.next		= s_options_next,

	.show		= s_options_show,

	.stop		= s_options_stop

};



static int osnoise_options_open(struct inode *inode, struct file *file)

{

	return seq_open(file, &osnoise_options_seq_ops);

};



/**

 * osnoise_options_write - Write function for "options" entry

 * @filp: The active open file structure

 * @ubuf: The user buffer that contains the value to write

 * @cnt: The maximum number of bytes to write to "file"

 * @ppos: The current position in @file

 *

 * Writing the option name sets the option, writing the "NO_"

 * prefix in front of the option name disables it.

 *

 * Writing "DEFAULTS" resets the option values to the default ones.

 */

static ssize_t osnoise_options_write(struct file *filp, const char __user *ubuf,

				     size_t cnt, loff_t *ppos)

{

	int running, option, enable, retval;

	char buf[256], *option_str;



	if (cnt >= 256)

		return -EINVAL;



	if (copy_from_user(buf, ubuf, cnt))

		return -EFAULT;



	buf[cnt] = 0;



	if (strncmp(buf, "NO_", 3)) {

		option_str = strstrip(buf);

		enable = true;

	} else {

		option_str = strstrip(&buf[3]);

		enable = false;

	}



	option = match_string(osnoise_options_str, OSN_MAX, option_str);

	if (option < 0)

		return -EINVAL;



	/*

	 * trace_types_lock is taken to avoid concurrency on start/stop.

	 */

	mutex_lock(&trace_types_lock);

	running = osnoise_has_registered_instances();

	if (running)

		stop_per_cpu_kthreads();



	mutex_lock(&interface_lock);

	/*

	 * avoid CPU hotplug operations that might read options.

	 */

	cpus_read_lock();



	retval = cnt;



	if (enable) {

		if (option == OSN_DEFAULTS)

			osnoise_options = OSN_DEFAULT_OPTIONS;

		else

			set_bit(option, &osnoise_options);

	} else {

		if (option == OSN_DEFAULTS)

			retval = -EINVAL;

		else

			clear_bit(option, &osnoise_options);

	}



	cpus_read_unlock();

	mutex_unlock(&interface_lock);



	if (running)

		start_per_cpu_kthreads();

	mutex_unlock(&trace_types_lock);



	return retval;

}



/*

 * osnoise_cpus_read - Read function for reading the "cpus" file

 * @filp: The active open file structure
@@ -2042,6 +2199,14 @@ static const struct file_operations cpus_fops = { 
	.llseek		= generic_file_llseek,

};



static const struct file_operations osnoise_options_fops = {

	.open		= osnoise_options_open,

	.read		= seq_read,

	.llseek		= seq_lseek,

	.release	= seq_release,

	.write		= osnoise_options_write

};



#ifdef CONFIG_TIMERLAT_TRACER

#ifdef CONFIG_STACKTRACE

static int init_timerlat_stack_tracefs(struct dentry *top_dir)
@@ -2128,6 +2293,11 @@ static int init_tracefs(void) 
	if (!tmp)

		goto err;



	tmp = trace_create_file("options", TRACE_MODE_WRITE, top_dir, NULL,

				&osnoise_options_fops);

	if (!tmp)

		goto err;



	ret = init_timerlat_tracefs(top_dir);

	if (ret)

		goto err;