kernel/trace/trace_nop.c

   1 /*
   2  * nop tracer
   3  *
   4  * Copyright (C) 2008 Steven Noonan <steven@uplinklabs.net>
   5  *
   6  */
   7
   8 #include <linux/module.h>
   9 #include <linux/fs.h>
  10 #include <linux/debugfs.h>
  11 #include <linux/ftrace.h>
  12
  13 #include "trace.h"
  14
  15 static struct trace_array       *ctx_trace;
  16
  17 static void start_nop_trace(struct trace_array *tr)
  18 {
  19         /* Nothing to do! */
  20 }
  21
  22 static void stop_nop_trace(struct trace_array *tr)
  23 {
  24         /* Nothing to do! */
  25 }
  26
  27 static void nop_trace_init(struct trace_array *tr)
  28 {
  29         int cpu;
  30         ctx_trace = tr;
  31
  32         for_each_online_cpu(cpu)
  33                 tracing_reset(tr, cpu);
  34
  35         if (tr->ctrl)
  36                 start_nop_trace(tr);
  37 }
  38
  39 static void nop_trace_reset(struct trace_array *tr)
  40 {
  41         if (tr->ctrl)
  42                 stop_nop_trace(tr);
  43 }
  44
  45 static void nop_trace_ctrl_update(struct trace_array *tr)
  46 {
  47         /* When starting a new trace, reset the buffers */
  48         if (tr->ctrl)
  49                 start_nop_trace(tr);
  50         else
  51                 stop_nop_trace(tr);
  52 }
  53
  54 struct tracer nop_trace __read_mostly =
  55 {
  56         .name           = "nop",
  57         .init           = nop_trace_init,
  58         .reset          = nop_trace_reset,
  59         .ctrl_update    = nop_trace_ctrl_update,
  60 #ifdef CONFIG_FTRACE_SELFTEST
  61         .selftest       = trace_selftest_startup_nop,
  62 #endif
  63 };
  64