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
  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)
  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 void sched_switch_reset(struct trace_array *tr)
  76 {
  77         int cpu;
  78
  79         tr->time_start = ftrace_now(tr->cpu);
  80
  81         for_each_online_cpu(cpu)
  82                 tracing_reset(tr, cpu);
  83 }
  84
  85 static int tracing_sched_register(void)
  86 {
  87         int ret;
  88
  89         ret = register_trace_sched_wakeup(probe_sched_wakeup);
  90         if (ret) {
  91                 pr_info("wakeup trace: Couldn't activate tracepoint"
  92                         " probe to kernel_sched_wakeup\n");
  93                 return ret;
  94         }
  95
  96         ret = register_trace_sched_wakeup_new(probe_sched_wakeup);
  97         if (ret) {
  98                 pr_info("wakeup trace: Couldn't activate tracepoint"
  99                         " probe to kernel_sched_wakeup_new\n");
 100                 goto fail_deprobe;
 101         }
 102
 103         ret = register_trace_sched_switch(probe_sched_switch);
 104         if (ret) {
 105                 pr_info("sched trace: Couldn't activate tracepoint"
 106                         " probe to kernel_sched_schedule\n");
 107                 goto fail_deprobe_wake_new;
 108         }
 109
 110         return ret;
 111 fail_deprobe_wake_new:
 112         unregister_trace_sched_wakeup_new(probe_sched_wakeup);
 113 fail_deprobe:
 114         unregister_trace_sched_wakeup(probe_sched_wakeup);
 115         return ret;
 116 }
 117
 118 static void tracing_sched_unregister(void)
 119 {
 120         unregister_trace_sched_switch(probe_sched_switch);
 121         unregister_trace_sched_wakeup_new(probe_sched_wakeup);
 122         unregister_trace_sched_wakeup(probe_sched_wakeup);
 123 }
 124
 125 static void tracing_start_sched_switch(void)
 126 {
 127         mutex_lock(&sched_register_mutex);
 128         if (!(sched_ref++)) {
 129                 tracer_enabled = 1;
 130                 tracing_sched_register();
 131         }
 132         mutex_unlock(&sched_register_mutex);
 133 }
 134
 135 static void tracing_stop_sched_switch(void)
 136 {
 137         mutex_lock(&sched_register_mutex);
 138         if (!(--sched_ref)) {
 139                 tracing_sched_unregister();
 140                 tracer_enabled = 0;
 141         }
 142         mutex_unlock(&sched_register_mutex);
 143 }
 144
 145 void tracing_start_cmdline_record(void)
 146 {
 147         tracing_start_sched_switch();
 148 }
 149
 150 void tracing_stop_cmdline_record(void)
 151 {
 152         tracing_stop_sched_switch();
 153 }
 154
 155 /**
 156  * tracing_cmdline_assign_trace - assign a trace array for ctx switch
 157  * @tr: trace array pointer to assign
 158  *
 159  * Some tracers might want to record the context switches in their
 160  * trace. This function lets those tracers assign the trace array
 161  * to use.
 162  */
 163 void tracing_cmdline_assign_trace(struct trace_array *tr)
 164 {
 165         ctx_trace = tr;
 166 }
 167
 168 static void start_sched_trace(struct trace_array *tr)
 169 {
 170         sched_switch_reset(tr);
 171         tracing_start_cmdline_record();
 172 }
 173
 174 static void stop_sched_trace(struct trace_array *tr)
 175 {
 176         tracing_stop_cmdline_record();
 177 }
 178
 179 static void sched_switch_trace_init(struct trace_array *tr)
 180 {
 181         ctx_trace = tr;
 182
 183         if (tr->ctrl)
 184                 start_sched_trace(tr);
 185 }
 186
 187 static void sched_switch_trace_reset(struct trace_array *tr)
 188 {
 189         if (tr->ctrl && sched_ref)
 190                 stop_sched_trace(tr);
 191 }
 192
 193 static void sched_switch_trace_ctrl_update(struct trace_array *tr)
 194 {
 195         /* When starting a new trace, reset the buffers */
 196         if (tr->ctrl)
 197                 start_sched_trace(tr);
 198         else
 199                 stop_sched_trace(tr);
 200 }
 201
 202 static void sched_switch_trace_start(struct trace_array *tr)
 203 {
 204         sched_switch_reset(tr);
 205         tracing_start_sched_switch();
 206 }
 207
 208 static void sched_switch_trace_stop(struct trace_array *tr)
 209 {
 210         tracing_stop_sched_switch();
 211 }
 212
 213 static struct tracer sched_switch_trace __read_mostly =
 214 {
 215         .name           = "sched_switch",
 216         .init           = sched_switch_trace_init,
 217         .reset          = sched_switch_trace_reset,
 218         .start          = sched_switch_trace_start,
 219         .stop           = sched_switch_trace_stop,
 220         .ctrl_update    = sched_switch_trace_ctrl_update,
 221 #ifdef CONFIG_FTRACE_SELFTEST
 222         .selftest    = trace_selftest_startup_sched_switch,
 223 #endif
 224 };
 225
 226 __init static int init_sched_switch_trace(void)
 227 {
 228         return register_tracer(&sched_switch_trace);
 229 }
 230 device_initcall(init_sched_switch_trace);