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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/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
  22 static void
  23 probe_sched_switch(struct rq *__rq, struct task_struct *prev,
  24                         struct task_struct *next)
  25 {
  26         struct trace_array_cpu *data;
  27         unsigned long flags;
  28         int cpu;
  29         int pc;
  30
  31         if (!sched_ref)
  32                 return;
  33
  34         tracing_record_cmdline(prev);
  35         tracing_record_cmdline(next);
  36
  37         if (!tracer_enabled)
  38                 return;
  39
  40         pc = preempt_count();
  41         local_irq_save(flags);
  42         cpu = raw_smp_processor_id();
  43         data = ctx_trace->data[cpu];
  44
  45         if (likely(!atomic_read(&data->disabled)))
  46                 tracing_sched_switch_trace(ctx_trace, data, prev, next, flags, pc);
  47
  48         local_irq_restore(flags);
  49 }
  50
  51 static void
  52 probe_sched_wakeup(struct rq *__rq, struct task_struct *wakee, int success)
  53 {
  54         struct trace_array_cpu *data;
  55         unsigned long flags;
  56         int cpu, pc;
  57
  58         if (!likely(tracer_enabled))
  59                 return;
  60
  61         pc = preempt_count();
  62         tracing_record_cmdline(current);
  63
  64         local_irq_save(flags);
  65         cpu = raw_smp_processor_id();
  66         data = ctx_trace->data[cpu];
  67
  68         if (likely(!atomic_read(&data->disabled)))
  69                 tracing_sched_wakeup_trace(ctx_trace, data, wakee, current,
  70                                            flags, pc);
  71
  72         local_irq_restore(flags);
  73 }
  74
  75 static int tracing_sched_register(void)
  76 {
  77         int ret;
  78
  79         ret = register_trace_sched_wakeup(probe_sched_wakeup);
  80         if (ret) {
  81                 pr_info("wakeup trace: Couldn't activate tracepoint"
  82                         " probe to kernel_sched_wakeup\n");
  83                 return ret;
  84         }
  85
  86         ret = register_trace_sched_wakeup_new(probe_sched_wakeup);
  87         if (ret) {
  88                 pr_info("wakeup trace: Couldn't activate tracepoint"
  89                         " probe to kernel_sched_wakeup_new\n");
  90                 goto fail_deprobe;
  91         }
  92
  93         ret = register_trace_sched_switch(probe_sched_switch);
  94         if (ret) {
  95                 pr_info("sched trace: Couldn't activate tracepoint"
  96                         " probe to kernel_sched_schedule\n");
  97                 goto fail_deprobe_wake_new;
  98         }
  99
 100         return ret;
 101 fail_deprobe_wake_new:
 102         unregister_trace_sched_wakeup_new(probe_sched_wakeup);
 103 fail_deprobe:
 104         unregister_trace_sched_wakeup(probe_sched_wakeup);
 105         return ret;
 106 }
 107
 108 static void tracing_sched_unregister(void)
 109 {
 110         unregister_trace_sched_switch(probe_sched_switch);
 111         unregister_trace_sched_wakeup_new(probe_sched_wakeup);
 112         unregister_trace_sched_wakeup(probe_sched_wakeup);
 113 }
 114
 115 static void tracing_start_sched_switch(void)
 116 {
 117         mutex_lock(&sched_register_mutex);
 118         if (!(sched_ref++))
 119                 tracing_sched_register();
 120         mutex_unlock(&sched_register_mutex);
 121 }
 122
 123 static void tracing_stop_sched_switch(void)
 124 {
 125         mutex_lock(&sched_register_mutex);
 126         if (!(--sched_ref))
 127                 tracing_sched_unregister();
 128         mutex_unlock(&sched_register_mutex);
 129 }
 130
 131 void tracing_start_cmdline_record(void)
 132 {
 133         tracing_start_sched_switch();
 134 }
 135
 136 void tracing_stop_cmdline_record(void)
 137 {
 138         tracing_stop_sched_switch();
 139 }
 140
 141 /**
 142  * tracing_start_sched_switch_record - start tracing context switches
 143  *
 144  * Turns on context switch tracing for a tracer.
 145  */
 146 void tracing_start_sched_switch_record(void)
 147 {
 148         if (unlikely(!ctx_trace)) {
 149                 WARN_ON(1);
 150                 return;
 151         }
 152
 153         tracing_start_sched_switch();
 154
 155         mutex_lock(&sched_register_mutex);
 156         tracer_enabled++;
 157         mutex_unlock(&sched_register_mutex);
 158 }
 159
 160 /**
 161  * tracing_stop_sched_switch_record - start tracing context switches
 162  *
 163  * Turns off context switch tracing for a tracer.
 164  */
 165 void tracing_stop_sched_switch_record(void)
 166 {
 167         mutex_lock(&sched_register_mutex);
 168         tracer_enabled--;
 169         WARN_ON(tracer_enabled < 0);
 170         mutex_unlock(&sched_register_mutex);
 171
 172         tracing_stop_sched_switch();
 173 }
 174
 175 /**
 176  * tracing_sched_switch_assign_trace - assign a trace array for ctx switch
 177  * @tr: trace array pointer to assign
 178  *
 179  * Some tracers might want to record the context switches in their
 180  * trace. This function lets those tracers assign the trace array
 181  * to use.
 182  */
 183 void tracing_sched_switch_assign_trace(struct trace_array *tr)
 184 {
 185         ctx_trace = tr;
 186 }
 187
 188 static void start_sched_trace(struct trace_array *tr)
 189 {
 190         tracing_reset_online_cpus(tr);
 191         tracing_start_sched_switch_record();
 192 }
 193
 194 static void stop_sched_trace(struct trace_array *tr)
 195 {
 196         tracing_stop_sched_switch_record();
 197 }
 198
 199 static int sched_switch_trace_init(struct trace_array *tr)
 200 {
 201         ctx_trace = tr;
 202         start_sched_trace(tr);
 203         return 0;
 204 }
 205
 206 static void sched_switch_trace_reset(struct trace_array *tr)
 207 {
 208         if (sched_ref)
 209                 stop_sched_trace(tr);
 210 }
 211
 212 static void sched_switch_trace_start(struct trace_array *tr)
 213 {
 214         tracing_reset_online_cpus(tr);
 215         tracing_start_sched_switch();
 216 }
 217
 218 static void sched_switch_trace_stop(struct trace_array *tr)
 219 {
 220         tracing_stop_sched_switch();
 221 }
 222
 223 static struct tracer sched_switch_trace __read_mostly =
 224 {
 225         .name           = "sched_switch",
 226         .init           = sched_switch_trace_init,
 227         .reset          = sched_switch_trace_reset,
 228         .start          = sched_switch_trace_start,
 229         .stop           = sched_switch_trace_stop,
 230 #ifdef CONFIG_FTRACE_SELFTEST
 231         .selftest    = trace_selftest_startup_sched_switch,
 232 #endif
 233 };
 234
 235 __init static int init_sched_switch_trace(void)
 236 {
 237         return register_tracer(&sched_switch_trace);
 238 }
 239 device_initcall(init_sched_switch_trace);
 240