ftrace: add README
make it easier for newbies to find their way around.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 61d2f02..c736dd2 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -995,6 +995,7 @@
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 @@
entry->ctx.next_prio);
break;
}
- seq_printf(m, "\n");
}
static int trace_empty(struct trace_iterator *iter)
@@ -1332,6 +1332,39 @@
.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 @@
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,
