Commit 7bd2f24c authored by Ingo Molnar's avatar Ingo Molnar Committed by Thomas Gleixner
Browse files

ftrace: add README 



make it easier for newbies to find their way around.

Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent c7aafc54

kernel/trace/trace.c

+39 −1
Original line number Diff line number Diff line
@@ -995,6 +995,7 @@ print_trace_fmt(struct seq_file *m, struct trace_iterator *iter) 
			seq_printf(m, " <-");

			seq_print_ip_sym(m, entry->fn.parent_ip, sym_flags);

		}

		seq_printf(m, "\n");

		break;

	case TRACE_CTX:

		S = entry->ctx.prev_state < sizeof(state_to_char) ?
@@ -1007,7 +1008,6 @@ print_trace_fmt(struct seq_file *m, struct trace_iterator *iter) 
			   entry->ctx.next_prio);

		break;

	}

	seq_printf(m, "\n");

}



static int trace_empty(struct trace_iterator *iter)
@@ -1332,6 +1332,39 @@ static struct file_operations tracing_iter_fops = { 
	.write = tracing_iter_ctrl_write,

};



static const char readme_msg[] =

	"tracing mini-HOWTO:\n\n"

	"# mkdir /debug\n"

	"# mount -t debugfs nodev /debug\n\n"

	"# cat /debug/tracing/available_tracers\n"

	"wakeup preemptirqsoff preemptoff irqsoff ftrace sched_switch none\n\n"

	"# cat /debug/tracing/current_tracer\n"

	"none\n"

	"# echo sched_switch > /debug/tracing/current_tracer\n"

	"# cat /debug/tracing/current_tracer\n"

	"sched_switch\n"

	"# cat /debug/tracing/iter_ctrl\n"

	"noprint-parent nosym-offset nosym-addr noverbose\n"

	"# echo print-parent > /debug/tracing/iter_ctrl\n"

	"# echo 1 > /debug/tracing/tracing_enabled\n"

	"# cat /debug/tracing/trace > /tmp/trace.txt\n"

	"echo 0 > /debug/tracing/tracing_enabled\n"

;



static ssize_t

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

		       size_t cnt, loff_t *ppos)

{

	return simple_read_from_buffer(ubuf, cnt, ppos,

					readme_msg, strlen(readme_msg));

}



static struct file_operations tracing_readme_fops = {

	.open = tracing_open_generic,

	.read = tracing_readme_read,

};





static ssize_t

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

		  size_t cnt, loff_t *ppos)
@@ -1598,6 +1631,11 @@ static __init void tracer_init_debugfs(void) 
	if (!entry)

		pr_warning("Could not create debugfs "

			   "'tracing_threash' entry\n");

	entry = debugfs_create_file("README", 0644, d_tracer,

				    NULL, &tracing_readme_fops);

	if (!entry)

		pr_warning("Could not create debugfs 'README' entry\n");





#ifdef CONFIG_DYNAMIC_FTRACE

	entry = debugfs_create_file("dyn_ftrace_total_info", 0444, d_tracer,