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   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/events/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 (unlikely(!sched_ref))
  33                 return;
  34
  35         tracing_record_cmdline(prev);
  36         tracing_record_cmdline(next);
  37
  38         if (!tracer_enabled || sched_stopped)
  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 (unlikely(!sched_ref))
  60                 return;
  61
  62         tracing_record_cmdline(current);
  63
  64         if (!tracer_enabled || sched_stopped)
  65                 return;
  66
  67         pc = preempt_count();
  68         local_irq_save(flags);
  69         cpu = raw_smp_processor_id();
  70         data = ctx_trace->data[cpu];
  71
  72         if (likely(!atomic_read(&data->disabled)))
  73                 tracing_sched_wakeup_trace(ctx_trace, wakee, current,
  74                                            flags, pc);
  75
  76         local_irq_restore(flags);
  77 }
  78
  79 static int tracing_sched_register(void)
  80 {
  81         int ret;
  82
  83         ret = register_trace_sched_wakeup(probe_sched_wakeup);
  84         if (ret) {
  85                 pr_info("wakeup trace: Couldn't activate tracepoint"
  86                         " probe to kernel_sched_wakeup\n");
  87                 return ret;
  88         }
  89
  90         ret = register_trace_sched_wakeup_new(probe_sched_wakeup);
  91         if (ret) {
  92                 pr_info("wakeup trace: Couldn't activate tracepoint"
  93                         " probe to kernel_sched_wakeup_new\n");
  94                 goto fail_deprobe;
  95         }
  96
  97         ret = register_trace_sched_switch(probe_sched_switch);
  98         if (ret) {
  99                 pr_info("sched trace: Couldn't activate tracepoint"
 100                         " probe to kernel_sched_switch\n");
 101                 goto fail_deprobe_wake_new;
 102         }
 103
 104         return ret;
 105 fail_deprobe_wake_new:
 106         unregister_trace_sched_wakeup_new(probe_sched_wakeup);
 107 fail_deprobe:
 108         unregister_trace_sched_wakeup(probe_sched_wakeup);
 109         return ret;
 110 }
 111
 112 static void tracing_sched_unregister(void)
 113 {
 114         unregister_trace_sched_switch(probe_sched_switch);
 115         unregister_trace_sched_wakeup_new(probe_sched_wakeup);
 116         unregister_trace_sched_wakeup(probe_sched_wakeup);
 117 }
 118
 119 static void tracing_start_sched_switch(void)
 120 {
 121         mutex_lock(&sched_register_mutex);
 122         if (!(sched_ref++))
 123                 tracing_sched_register();
 124         mutex_unlock(&sched_register_mutex);
 125 }
 126
 127 static void tracing_stop_sched_switch(void)
 128 {
 129         mutex_lock(&sched_register_mutex);
 130         if (!(--sched_ref))
 131                 tracing_sched_unregister();
 132         mutex_unlock(&sched_register_mutex);
 133 }
 134
 135 void tracing_start_cmdline_record(void)
 136 {
 137         tracing_start_sched_switch();
 138 }
 139
 140 void tracing_stop_cmdline_record(void)
 141 {
 142         tracing_stop_sched_switch();
 143 }
 144
 145 /**
 146  * tracing_start_sched_switch_record - start tracing context switches
 147  *
 148  * Turns on context switch tracing for a tracer.
 149  */
 150 void tracing_start_sched_switch_record(void)
 151 {
 152         if (unlikely(!ctx_trace)) {
 153                 WARN_ON(1);
 154                 return;
 155         }
 156
 157         tracing_start_sched_switch();
 158
 159         mutex_lock(&sched_register_mutex);
 160         tracer_enabled++;
 161         mutex_unlock(&sched_register_mutex);
 162 }
 163
 164 /**
 165  * tracing_stop_sched_switch_record - start tracing context switches
 166  *
 167  * Turns off context switch tracing for a tracer.
 168  */
 169 void tracing_stop_sched_switch_record(void)
 170 {
 171         mutex_lock(&sched_register_mutex);
 172         tracer_enabled--;
 173         WARN_ON(tracer_enabled < 0);
 174         mutex_unlock(&sched_register_mutex);
 175
 176         tracing_stop_sched_switch();
 177 }
 178
 179 /**
 180  * tracing_sched_switch_assign_trace - assign a trace array for ctx switch
 181  * @tr: trace array pointer to assign
 182  *
 183  * Some tracers might want to record the context switches in their
 184  * trace. This function lets those tracers assign the trace array
 185  * to use.
 186  */
 187 void tracing_sched_switch_assign_trace(struct trace_array *tr)
 188 {
 189         ctx_trace = tr;
 190 }
 191
 192 static void stop_sched_trace(struct trace_array *tr)
 193 {
 194         tracing_stop_sched_switch_record();
 195 }
 196
 197 static int sched_switch_trace_init(struct trace_array *tr)
 198 {
 199         ctx_trace = tr;
 200         tracing_reset_online_cpus(tr);
 201         tracing_start_sched_switch_record();
 202         return 0;
 203 }
 204
 205 static void sched_switch_trace_reset(struct trace_array *tr)
 206 {
 207         if (sched_ref)
 208                 stop_sched_trace(tr);
 209 }
 210
 211 static void sched_switch_trace_start(struct trace_array *tr)
 212 {
 213         sched_stopped = 0;
 214 }
 215
 216 static void sched_switch_trace_stop(struct trace_array *tr)
 217 {
 218         sched_stopped = 1;
 219 }
 220
 221 static struct tracer sched_switch_trace __read_mostly =
 222 {
 223         .name           = "sched_switch",
 224         .init           = sched_switch_trace_init,
 225         .reset          = sched_switch_trace_reset,
 226         .start          = sched_switch_trace_start,
 227         .stop           = sched_switch_trace_stop,
 228         .wait_pipe      = poll_wait_pipe,
 229 #ifdef CONFIG_FTRACE_SELFTEST
 230         .selftest    = trace_selftest_startup_sched_switch,
 231 #endif
 232 };
 233
 234 __init static int init_sched_switch_trace(void)
 235 {
 236         return register_tracer(&sched_switch_trace);
 237 }
 238 device_initcall(init_sched_switch_trace);
 239