kernel/trace/trace_functions.c

   1 /*
   2  * ring buffer based function tracer
   3  *
   4  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
   5  * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
   6  *
   7  * Based on code from the latency_tracer, that is:
   8  *
   9  *  Copyright (C) 2004-2006 Ingo Molnar
  10  *  Copyright (C) 2004 William Lee Irwin III
  11  */
  12 #include <linux/debugfs.h>
  13 #include <linux/uaccess.h>
  14 #include <linux/ftrace.h>
  15 #include <linux/fs.h>
  16
  17 #include "trace.h"
  18
  19 static void function_reset(struct trace_array *tr)
  20 {
  21         int cpu;
  22
  23         tr->time_start = ftrace_now(tr->cpu);
  24
  25         for_each_online_cpu(cpu)
  26                 tracing_reset(tr->data[cpu]);
  27 }
  28
  29 static void start_function_trace(struct trace_array *tr)
  30 {
  31         tr->cpu = get_cpu();
  32         function_reset(tr);
  33         put_cpu();
  34
  35         tracing_start_cmdline_record();
  36         tracing_start_function_trace();
  37 }
  38
  39 static void stop_function_trace(struct trace_array *tr)
  40 {
  41         tracing_stop_function_trace();
  42         tracing_stop_cmdline_record();
  43 }
  44
  45 static void function_trace_init(struct trace_array *tr)
  46 {
  47         if (tr->ctrl)
  48                 start_function_trace(tr);
  49 }
  50
  51 static void function_trace_reset(struct trace_array *tr)
  52 {
  53         if (tr->ctrl)
  54                 stop_function_trace(tr);
  55 }
  56
  57 static void function_trace_ctrl_update(struct trace_array *tr)
  58 {
  59         if (tr->ctrl)
  60                 start_function_trace(tr);
  61         else
  62                 stop_function_trace(tr);
  63 }
  64
  65 static struct tracer function_trace __read_mostly =
  66 {
  67         .name        = "ftrace",
  68         .init        = function_trace_init,
  69         .reset       = function_trace_reset,
  70         .ctrl_update = function_trace_ctrl_update,
  71 #ifdef CONFIG_FTRACE_SELFTEST
  72         .selftest    = trace_selftest_startup_function,
  73 #endif
  74 };
  75
  76 static __init int init_function_trace(void)
  77 {
  78         return register_tracer(&function_trace);
  79 }
  80
  81 device_initcall(init_function_trace);