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 int                      sched_ref;
  20 static DEFINE_MUTEX(sched_register_mutex);
  21 static int                      sched_stopped;
  22
  23 static void
  24 probe_sched_switch(struct rq *__rq, struct task_struct *prev,
  25                         struct task_struct *next)
  26 {
  27         struct trace_array_cpu *data;
  28         unsigned long flags;
  29         int cpu;
  30         int pc;
  31
  32         if (!sched_ref || sched_stopped)
  33                 return;
  34
  35         tracing_record_cmdline(prev);
  36         tracing_record_cmdline(next);
  37
  38         if (!tracer_enabled)
  39                 return;
  40
  41         pc = preempt_count();
  42         local_irq_save(flags);
  43         cpu = raw_smp_processor_id();
  44         data = ctx_trace->data[cpu];
  45
  46         if (likely(!atomic_read(&data->disabled)))
  47                 tracing_sched_switch_trace(ctx_trace, prev, next, flags, pc);
  48
  49         local_irq_restore(flags);
  50 }
  51
  52 static void
  53 probe_sched_wakeup(struct rq *__rq, struct task_struct *wakee, int success)
  54 {
  55         struct trace_array_cpu *data;
  56         unsigned long flags;
  57         int cpu, pc;
  58
  59         if (!likely(tracer_enabled))
  60                 return;
  61
  62         pc = preempt_count();
  63         tracing_record_cmdline(current);
  64
  65         local_irq_save(flags);
  66         cpu = raw_smp_processor_id();
  67         data = ctx_trace->data[cpu];
  68
  69         if (likely(!atomic_read(&data->disabled)))
  70                 tracing_sched_wakeup_trace(ctx_trace, wakee, current,
  71                                            flags, pc);
  72
  73         local_irq_restore(flags);
  74 }
  75
  76 static int tracing_sched_register(void)
  77 {
  78         int ret;
  79
  80         ret = register_trace_sched_wakeup(probe_sched_wakeup);
  81         if (ret) {
  82                 pr_info("wakeup trace: Couldn't activate tracepoint"
  83                         " probe to kernel_sched_wakeup\n");
  84                 return ret;
  85         }
  86
  87         ret = register_trace_sched_wakeup_new(probe_sched_wakeup);
  88         if (ret) {
  89                 pr_info("wakeup trace: Couldn't activate tracepoint"
  90                         " probe to kernel_sched_wakeup_new\n");
  91                 goto fail_deprobe;
  92         }
  93
  94         ret = register_trace_sched_switch(probe_sched_switch);
  95         if (ret) {
  96                 pr_info("sched trace: Couldn't activate tracepoint"
  97                         " probe to kernel_sched_switch\n");
  98                 goto fail_deprobe_wake_new;
  99         }
 100
 101         return ret;
 102 fail_deprobe_wake_new:
 103         unregister_trace_sched_wakeup_new(probe_sched_wakeup);
 104 fail_deprobe:
 105         unregister_trace_sched_wakeup(probe_sched_wakeup);
 106         return ret;
 107 }
 108
 109 static void tracing_sched_unregister(void)
 110 {
 111         unregister_trace_sched_switch(probe_sched_switch);
 112         unregister_trace_sched_wakeup_new(probe_sched_wakeup);
 113         unregister_trace_sched_wakeup(probe_sched_wakeup);
 114 }
 115
 116 static void tracing_start_sched_switch(void)
 117 {
 118         mutex_lock(&sched_register_mutex);
 119         if (!(sched_ref++))
 120                 tracing_sched_register();
 121         mutex_unlock(&sched_register_mutex);
 122 }
 123
 124 static void tracing_stop_sched_switch(void)
 125 {
 126         mutex_lock(&sched_register_mutex);
 127         if (!(--sched_ref))
 128                 tracing_sched_unregister();
 129         mutex_unlock(&sched_register_mutex);
 130 }
 131
 132 void tracing_start_cmdline_record(void)
 133 {
 134         tracing_start_sched_switch();
 135 }
 136
 137 void tracing_stop_cmdline_record(void)
 138 {
 139         tracing_stop_sched_switch();
 140 }
 141
 142 /**
 143  * tracing_start_sched_switch_record - start tracing context switches
 144  *
 145  * Turns on context switch tracing for a tracer.
 146  */
 147 void tracing_start_sched_switch_record(void)
 148 {
 149         if (unlikely(!ctx_trace)) {
 150                 WARN_ON(1);
 151                 return;
 152         }
 153
 154         tracing_start_sched_switch();
 155
 156         mutex_lock(&sched_register_mutex);
 157         tracer_enabled++;
 158         mutex_unlock(&sched_register_mutex);
 159 }
 160
 161 /**
 162  * tracing_stop_sched_switch_record - start tracing context switches
 163  *
 164  * Turns off context switch tracing for a tracer.
 165  */
 166 void tracing_stop_sched_switch_record(void)
 167 {
 168         mutex_lock(&sched_register_mutex);
 169         tracer_enabled--;
 170         WARN_ON(tracer_enabled < 0);
 171         mutex_unlock(&sched_register_mutex);
 172
 173         tracing_stop_sched_switch();
 174 }
 175
 176 /**
 177  * tracing_sched_switch_assign_trace - assign a trace array for ctx switch
 178  * @tr: trace array pointer to assign
 179  *
 180  * Some tracers might want to record the context switches in their
 181  * trace. This function lets those tracers assign the trace array
 182  * to use.
 183  */
 184 void tracing_sched_switch_assign_trace(struct trace_array *tr)
 185 {
 186         ctx_trace = tr;
 187 }
 188
 189 static void stop_sched_trace(struct trace_array *tr)
 190 {
 191         tracing_stop_sched_switch_record();
 192 }
 193
 194 static int sched_switch_trace_init(struct trace_array *tr)
 195 {
 196         ctx_trace = tr;
 197         tracing_reset_online_cpus(tr);
 198         tracing_start_sched_switch_record();
 199         return 0;
 200 }
 201
 202 static void sched_switch_trace_reset(struct trace_array *tr)
 203 {
 204         if (sched_ref)
 205                 stop_sched_trace(tr);
 206 }
 207
 208 static void sched_switch_trace_start(struct trace_array *tr)
 209 {
 210         sched_stopped = 0;
 211 }
 212
 213 static void sched_switch_trace_stop(struct trace_array *tr)
 214 {
 215         sched_stopped = 1;
 216 }
 217
 218 static struct tracer sched_switch_trace __read_mostly =
 219 {
 220         .name           = "sched_switch",
 221         .init           = sched_switch_trace_init,
 222         .reset          = sched_switch_trace_reset,
 223         .start          = sched_switch_trace_start,
 224         .stop           = sched_switch_trace_stop,
 225         .wait_pipe      = poll_wait_pipe,
 226 #ifdef CONFIG_FTRACE_SELFTEST
 227         .selftest    = trace_selftest_startup_sched_switch,
 228 #endif
 229 };
 230
 231 __init static int init_sched_switch_trace(void)
 232 {
 233         return register_tracer(&sched_switch_trace);
 234 }
 235 device_initcall(init_sched_switch_trace);
 236