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
......@@ -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,
......
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