kernel/trace/trace_sched_switch.c

   1 /*
   2  * trace context switch
   3  *
   4  * Copyright (C) 2007 Steven Rostedt <srostedt@redhat.com>
   5  *
   6  */
   7 #include <linux/module.h>
   8 #include <linux/fs.h>
   9 #include <linux/debugfs.h>
  10 #include <linux/kallsyms.h>
  11 #include <linux/uaccess.h>
  12 #include <linux/ftrace.h>
  13 #include <trace/sched.h>
  14
  15 #include "trace.h"
  16
  17 static struct trace_array       *ctx_trace;
  18 static int __read_mostly        tracer_enabled;
  19 static atomic_t                 sched_ref;
  20
  21 static void
  22 probe_sched_switch(struct rq *__rq, struct task_struct *prev,
  23                         struct task_struct *next)
  24 {
  25         struct trace_array_cpu *data;
  26         unsigned long flags;
  27         int cpu;
  28         int pc;
  29
  30         if (!atomic_read(&sched_ref))
  31                 return;
  32
  33         tracing_record_cmdline(prev);
  34         tracing_record_cmdline(next);
  35
  36         if (!tracer_enabled)
  37                 return;
  38
  39         pc = preempt_count();
  40         local_irq_save(flags);
  41         cpu = raw_smp_processor_id();
  42         data = ctx_trace->data[cpu];
  43
  44         if (likely(!atomic_read(&data->disabled)))
  45                 tracing_sched_switch_trace(ctx_trace, data, prev, next, flags, pc);
  46
  47         local_irq_restore(flags);
  48 }
  49
  50 static void
  51 probe_sched_wakeup(struct rq *__rq, struct task_struct *wakee)
  52 {
  53         struct trace_array_cpu *data;
  54         unsigned long flags;
  55         int cpu, pc;
  56
  57         if (!likely(tracer_enabled))
  58                 return;
  59
  60         pc = preempt_count();
  61         tracing_record_cmdline(current);
  62
  63         local_irq_save(flags);
  64         cpu = raw_smp_processor_id();
  65         data = ctx_trace->data[cpu];
  66
  67         if (likely(!atomic_read(&data->disabled)))
  68                 tracing_sched_wakeup_trace(ctx_trace, data, wakee, current,
  69                                            flags, pc);
  70
  71         local_irq_restore(flags);
  72 }
  73
  74 static void sched_switch_reset(struct trace_array *tr)
  75 {
  76         int cpu;
  77
  78         tr->time_start = ftrace_now(tr->cpu);
  79
  80         for_each_online_cpu(cpu)
  81                 tracing_reset(tr, cpu);
  82 }
  83
  84 static int tracing_sched_register(void)
  85 {
  86         int ret;
  87
  88         ret = register_trace_sched_wakeup(probe_sched_wakeup);
  89         if (ret) {
  90                 pr_info("wakeup trace: Couldn't activate tracepoint"
  91                         " probe to kernel_sched_wakeup\n");
  92                 return ret;
  93         }
  94
  95         ret = register_trace_sched_wakeup_new(probe_sched_wakeup);
  96         if (ret) {
  97                 pr_info("wakeup trace: Couldn't activate tracepoint"
  98                         " probe to kernel_sched_wakeup_new\n");
  99                 goto fail_deprobe;
 100         }
 101
 102         ret = register_trace_sched_switch(probe_sched_switch);
 103         if (ret) {
 104                 pr_info("sched trace: Couldn't activate tracepoint"
 105                         " probe to kernel_sched_schedule\n");
 106                 goto fail_deprobe_wake_new;
 107         }
 108
 109         return ret;
 110 fail_deprobe_wake_new:
 111         unregister_trace_sched_wakeup_new(probe_sched_wakeup);
 112 fail_deprobe:
 113         unregister_trace_sched_wakeup(probe_sched_wakeup);
 114         return ret;
 115 }
 116
 117 static void tracing_sched_unregister(void)
 118 {
 119         unregister_trace_sched_switch(probe_sched_switch);
 120         unregister_trace_sched_wakeup_new(probe_sched_wakeup);
 121         unregister_trace_sched_wakeup(probe_sched_wakeup);
 122 }
 123
 124 static void tracing_start_sched_switch(void)
 125 {
 126         long ref;
 127
 128         ref = atomic_inc_return(&sched_ref);
 129         if (ref == 1)
 130                 tracing_sched_register();
 131 }
 132
 133 static void tracing_stop_sched_switch(void)
 134 {
 135         long ref;
 136
 137         ref = atomic_dec_and_test(&sched_ref);
 138         if (ref)
 139                 tracing_sched_unregister();
 140 }
 141
 142 void tracing_start_cmdline_record(void)
 143 {
 144         tracing_start_sched_switch();
 145 }
 146
 147 void tracing_stop_cmdline_record(void)
 148 {
 149         tracing_stop_sched_switch();
 150 }
 151
 152 static void start_sched_trace(struct trace_array *tr)
 153 {
 154         sched_switch_reset(tr);
 155         tracing_start_cmdline_record();
 156         tracer_enabled = 1;
 157 }
 158
 159 static void stop_sched_trace(struct trace_array *tr)
 160 {
 161         tracer_enabled = 0;
 162         tracing_stop_cmdline_record();
 163 }
 164
 165 static void sched_switch_trace_init(struct trace_array *tr)
 166 {
 167         ctx_trace = tr;
 168
 169         if (tr->ctrl)
 170                 start_sched_trace(tr);
 171 }
 172
 173 static void sched_switch_trace_reset(struct trace_array *tr)
 174 {
 175         if (tr->ctrl)
 176                 stop_sched_trace(tr);
 177 }
 178
 179 static void sched_switch_trace_ctrl_update(struct trace_array *tr)
 180 {
 181         /* When starting a new trace, reset the buffers */
 182         if (tr->ctrl)
 183                 start_sched_trace(tr);
 184         else
 185                 stop_sched_trace(tr);
 186 }
 187
 188 static struct tracer sched_switch_trace __read_mostly =
 189 {
 190         .name           = "sched_switch",
 191         .init           = sched_switch_trace_init,
 192         .reset          = sched_switch_trace_reset,
 193         .ctrl_update    = sched_switch_trace_ctrl_update,
 194 #ifdef CONFIG_FTRACE_SELFTEST
 195         .selftest    = trace_selftest_startup_sched_switch,
 196 #endif
 197 };
 198
 199 __init static int init_sched_switch_trace(void)
 200 {
 201         int ret = 0;
 202
 203         if (atomic_read(&sched_ref))
 204                 ret = tracing_sched_register();
 205         if (ret) {
 206                 pr_info("error registering scheduler trace\n");
 207                 return ret;
 208         }
 209         return register_tracer(&sched_switch_trace);
 210 }
 211 device_initcall(init_sched_switch_trace);