Commit e447e1df authored by Steven Rostedt's avatar Steven Rostedt

tracing: explain why stack tracer is empty

If the stack tracing is disabled (by default) the stack_trace file
will only contain the header:

 # cat /debug/tracing/stack_trace
        Depth    Size      Location    (0 entries)
        -----    ----      --------

This can be frustrating to a developer that does not realize that the
stack tracer is disabled. This patch adds the following text:

  # cat /debug/tracing/stack_trace
        Depth    Size      Location    (0 entries)
        -----    ----      --------
 #
 #  Stack tracer disabled
 #
 # To enable the stack tracer, either add 'stacktrace' to the
 # kernel command line
 # or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'
 #
Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
parent 2da03ece
......@@ -245,6 +245,17 @@ static int trace_lookup_stack(struct seq_file *m, long i)
#endif
}
static void print_disabled(struct seq_file *m)
{
seq_puts(m, "#\n"
"# Stack tracer disabled\n"
"#\n"
"# To enable the stack tracer, either add 'stacktrace' to the\n"
"# kernel command line\n"
"# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
"#\n");
}
static int t_show(struct seq_file *m, void *v)
{
long i;
......@@ -255,6 +266,10 @@ static int t_show(struct seq_file *m, void *v)
" (%d entries)\n"
" ----- ---- --------\n",
max_stack_trace.nr_entries);
if (!stack_tracer_enabled && !max_stack_size)
print_disabled(m);
return 0;
}
......
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