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   1 /*
   2  * trace task wakeup timings
   3  *
   4  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
   5  * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
   6  *
   7  * Based on code from the latency_tracer, that is:
   8  *
   9  *  Copyright (C) 2004-2006 Ingo Molnar
  10  *  Copyright (C) 2004 William Lee Irwin III
  11  */
  12 #include <linux/module.h>
  13 #include <linux/fs.h>
  14 #include <linux/debugfs.h>
  15 #include <linux/kallsyms.h>
  16 #include <linux/uaccess.h>
  17 #include <linux/ftrace.h>
  18 #include <trace/events/sched.h>
  19
  20 #include "trace.h"
  21
  22 static struct trace_array       *wakeup_trace;
  23 static int __read_mostly        tracer_enabled;
  24
  25 static struct task_struct       *wakeup_task;
  26 static int                      wakeup_cpu;
  27 static int                      wakeup_current_cpu;
  28 static unsigned                 wakeup_prio = -1;
  29 static int                      wakeup_rt;
  30
  31 static raw_spinlock_t wakeup_lock =
  32         (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
  33
  34 static void __wakeup_reset(struct trace_array *tr);
  35
  36 static int save_lat_flag;
  37
  38 #ifdef CONFIG_FUNCTION_TRACER
  39 /*
  40  * irqsoff uses its own tracer function to keep the overhead down:
  41  */
  42 static void
  43 wakeup_tracer_call(unsigned long ip, unsigned long parent_ip)
  44 {
  45         struct trace_array *tr = wakeup_trace;
  46         struct trace_array_cpu *data;
  47         unsigned long flags;
  48         long disabled;
  49         int resched;
  50         int cpu;
  51         int pc;
  52
  53         if (likely(!wakeup_task))
  54                 return;
  55
  56         pc = preempt_count();
  57         resched = ftrace_preempt_disable();
  58
  59         cpu = raw_smp_processor_id();
  60         if (cpu != wakeup_current_cpu)
  61                 goto out_enable;
  62
  63         data = tr->data[cpu];
  64         disabled = atomic_inc_return(&data->disabled);
  65         if (unlikely(disabled != 1))
  66                 goto out;
  67
  68         local_irq_save(flags);
  69
  70         trace_function(tr, ip, parent_ip, flags, pc);
  71
  72         local_irq_restore(flags);
  73
  74  out:
  75         atomic_dec(&data->disabled);
  76  out_enable:
  77         ftrace_preempt_enable(resched);
  78 }
  79
  80 static struct ftrace_ops trace_ops __read_mostly =
  81 {
  82         .func = wakeup_tracer_call,
  83 };
  84 #endif /* CONFIG_FUNCTION_TRACER */
  85
  86 /*
  87  * Should this new latency be reported/recorded?
  88  */
  89 static int report_latency(cycle_t delta)
  90 {
  91         if (tracing_thresh) {
  92                 if (delta < tracing_thresh)
  93                         return 0;
  94         } else {
  95                 if (delta <= tracing_max_latency)
  96                         return 0;
  97         }
  98         return 1;
  99 }
 100
 101 static void probe_wakeup_migrate_task(struct task_struct *task, int cpu)
 102 {
 103         if (task != wakeup_task)
 104                 return;
 105
 106         wakeup_current_cpu = cpu;
 107 }
 108
 109 static void notrace
 110 probe_wakeup_sched_switch(struct rq *rq, struct task_struct *prev,
 111         struct task_struct *next)
 112 {
 113         unsigned long latency = 0, t0 = 0, t1 = 0;
 114         struct trace_array_cpu *data;
 115         cycle_t T0, T1, delta;
 116         unsigned long flags;
 117         long disabled;
 118         int cpu;
 119         int pc;
 120
 121         tracing_record_cmdline(prev);
 122
 123         if (unlikely(!tracer_enabled))
 124                 return;
 125
 126         /*
 127          * When we start a new trace, we set wakeup_task to NULL
 128          * and then set tracer_enabled = 1. We want to make sure
 129          * that another CPU does not see the tracer_enabled = 1
 130          * and the wakeup_task with an older task, that might
 131          * actually be the same as next.
 132          */
 133         smp_rmb();
 134
 135         if (next != wakeup_task)
 136                 return;
 137
 138         pc = preempt_count();
 139
 140         /* disable local data, not wakeup_cpu data */
 141         cpu = raw_smp_processor_id();
 142         disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
 143         if (likely(disabled != 1))
 144                 goto out;
 145
 146         local_irq_save(flags);
 147         __raw_spin_lock(&wakeup_lock);
 148
 149         /* We could race with grabbing wakeup_lock */
 150         if (unlikely(!tracer_enabled || next != wakeup_task))
 151                 goto out_unlock;
 152
 153         /* The task we are waiting for is waking up */
 154         data = wakeup_trace->data[wakeup_cpu];
 155
 156         trace_function(wakeup_trace, CALLER_ADDR0, CALLER_ADDR1, flags, pc);
 157         tracing_sched_switch_trace(wakeup_trace, prev, next, flags, pc);
 158
 159         /*
 160          * usecs conversion is slow so we try to delay the conversion
 161          * as long as possible:
 162          */
 163         T0 = data->preempt_timestamp;
 164         T1 = ftrace_now(cpu);
 165         delta = T1-T0;
 166
 167         if (!report_latency(delta))
 168                 goto out_unlock;
 169
 170         latency = nsecs_to_usecs(delta);
 171
 172         tracing_max_latency = delta;
 173         t0 = nsecs_to_usecs(T0);
 174         t1 = nsecs_to_usecs(T1);
 175
 176         update_max_tr(wakeup_trace, wakeup_task, wakeup_cpu);
 177
 178 out_unlock:
 179         __wakeup_reset(wakeup_trace);
 180         __raw_spin_unlock(&wakeup_lock);
 181         local_irq_restore(flags);
 182 out:
 183         atomic_dec(&wakeup_trace->data[cpu]->disabled);
 184 }
 185
 186 static void __wakeup_reset(struct trace_array *tr)
 187 {
 188         wakeup_cpu = -1;
 189         wakeup_prio = -1;
 190
 191         if (wakeup_task)
 192                 put_task_struct(wakeup_task);
 193
 194         wakeup_task = NULL;
 195 }
 196
 197 static void wakeup_reset(struct trace_array *tr)
 198 {
 199         unsigned long flags;
 200
 201         tracing_reset_online_cpus(tr);
 202
 203         local_irq_save(flags);
 204         __raw_spin_lock(&wakeup_lock);
 205         __wakeup_reset(tr);
 206         __raw_spin_unlock(&wakeup_lock);
 207         local_irq_restore(flags);
 208 }
 209
 210 static void
 211 probe_wakeup(struct rq *rq, struct task_struct *p, int success)
 212 {
 213         struct trace_array_cpu *data;
 214         int cpu = smp_processor_id();
 215         unsigned long flags;
 216         long disabled;
 217         int pc;
 218
 219         if (likely(!tracer_enabled))
 220                 return;
 221
 222         tracing_record_cmdline(p);
 223         tracing_record_cmdline(current);
 224
 225         if ((wakeup_rt && !rt_task(p)) ||
 226                         p->prio >= wakeup_prio ||
 227                         p->prio >= current->prio)
 228                 return;
 229
 230         pc = preempt_count();
 231         disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
 232         if (unlikely(disabled != 1))
 233                 goto out;
 234
 235         /* interrupts should be off from try_to_wake_up */
 236         __raw_spin_lock(&wakeup_lock);
 237
 238         /* check for races. */
 239         if (!tracer_enabled || p->prio >= wakeup_prio)
 240                 goto out_locked;
 241
 242         /* reset the trace */
 243         __wakeup_reset(wakeup_trace);
 244
 245         wakeup_cpu = task_cpu(p);
 246         wakeup_current_cpu = wakeup_cpu;
 247         wakeup_prio = p->prio;
 248
 249         wakeup_task = p;
 250         get_task_struct(wakeup_task);
 251
 252         local_save_flags(flags);
 253
 254         data = wakeup_trace->data[wakeup_cpu];
 255         data->preempt_timestamp = ftrace_now(cpu);
 256         tracing_sched_wakeup_trace(wakeup_trace, p, current, flags, pc);
 257
 258         /*
 259          * We must be careful in using CALLER_ADDR2. But since wake_up
 260          * is not called by an assembly function  (where as schedule is)
 261          * it should be safe to use it here.
 262          */
 263         trace_function(wakeup_trace, CALLER_ADDR1, CALLER_ADDR2, flags, pc);
 264
 265 out_locked:
 266         __raw_spin_unlock(&wakeup_lock);
 267 out:
 268         atomic_dec(&wakeup_trace->data[cpu]->disabled);
 269 }
 270
 271 static void start_wakeup_tracer(struct trace_array *tr)
 272 {
 273         int ret;
 274
 275         ret = register_trace_sched_wakeup(probe_wakeup);
 276         if (ret) {
 277                 pr_info("wakeup trace: Couldn't activate tracepoint"
 278                         " probe to kernel_sched_wakeup\n");
 279                 return;
 280         }
 281
 282         ret = register_trace_sched_wakeup_new(probe_wakeup);
 283         if (ret) {
 284                 pr_info("wakeup trace: Couldn't activate tracepoint"
 285                         " probe to kernel_sched_wakeup_new\n");
 286                 goto fail_deprobe;
 287         }
 288
 289         ret = register_trace_sched_switch(probe_wakeup_sched_switch);
 290         if (ret) {
 291                 pr_info("sched trace: Couldn't activate tracepoint"
 292                         " probe to kernel_sched_switch\n");
 293                 goto fail_deprobe_wake_new;
 294         }
 295
 296         ret = register_trace_sched_migrate_task(probe_wakeup_migrate_task);
 297         if (ret) {
 298                 pr_info("wakeup trace: Couldn't activate tracepoint"
 299                         " probe to kernel_sched_migrate_task\n");
 300                 return;
 301         }
 302
 303         wakeup_reset(tr);
 304
 305         /*
 306          * Don't let the tracer_enabled = 1 show up before
 307          * the wakeup_task is reset. This may be overkill since
 308          * wakeup_reset does a spin_unlock after setting the
 309          * wakeup_task to NULL, but I want to be safe.
 310          * This is a slow path anyway.
 311          */
 312         smp_wmb();
 313
 314         register_ftrace_function(&trace_ops);
 315
 316         if (tracing_is_enabled())
 317                 tracer_enabled = 1;
 318         else
 319                 tracer_enabled = 0;
 320
 321         return;
 322 fail_deprobe_wake_new:
 323         unregister_trace_sched_wakeup_new(probe_wakeup);
 324 fail_deprobe:
 325         unregister_trace_sched_wakeup(probe_wakeup);
 326 }
 327
 328 static void stop_wakeup_tracer(struct trace_array *tr)
 329 {
 330         tracer_enabled = 0;
 331         unregister_ftrace_function(&trace_ops);
 332         unregister_trace_sched_switch(probe_wakeup_sched_switch);
 333         unregister_trace_sched_wakeup_new(probe_wakeup);
 334         unregister_trace_sched_wakeup(probe_wakeup);
 335         unregister_trace_sched_migrate_task(probe_wakeup_migrate_task);
 336 }
 337
 338 static int __wakeup_tracer_init(struct trace_array *tr)
 339 {
 340         save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
 341         trace_flags |= TRACE_ITER_LATENCY_FMT;
 342
 343         tracing_max_latency = 0;
 344         wakeup_trace = tr;
 345         start_wakeup_tracer(tr);
 346         return 0;
 347 }
 348
 349 static int wakeup_tracer_init(struct trace_array *tr)
 350 {
 351         wakeup_rt = 0;
 352         return __wakeup_tracer_init(tr);
 353 }
 354
 355 static int wakeup_rt_tracer_init(struct trace_array *tr)
 356 {
 357         wakeup_rt = 1;
 358         return __wakeup_tracer_init(tr);
 359 }
 360
 361 static void wakeup_tracer_reset(struct trace_array *tr)
 362 {
 363         stop_wakeup_tracer(tr);
 364         /* make sure we put back any tasks we are tracing */
 365         wakeup_reset(tr);
 366
 367         if (!save_lat_flag)
 368                 trace_flags &= ~TRACE_ITER_LATENCY_FMT;
 369 }
 370
 371 static void wakeup_tracer_start(struct trace_array *tr)
 372 {
 373         wakeup_reset(tr);
 374         tracer_enabled = 1;
 375 }
 376
 377 static void wakeup_tracer_stop(struct trace_array *tr)
 378 {
 379         tracer_enabled = 0;
 380 }
 381
 382 static struct tracer wakeup_tracer __read_mostly =
 383 {
 384         .name           = "wakeup",
 385         .init           = wakeup_tracer_init,
 386         .reset          = wakeup_tracer_reset,
 387         .start          = wakeup_tracer_start,
 388         .stop           = wakeup_tracer_stop,
 389         .print_max      = 1,
 390 #ifdef CONFIG_FTRACE_SELFTEST
 391         .selftest    = trace_selftest_startup_wakeup,
 392 #endif
 393 };
 394
 395 static struct tracer wakeup_rt_tracer __read_mostly =
 396 {
 397         .name           = "wakeup_rt",
 398         .init           = wakeup_rt_tracer_init,
 399         .reset          = wakeup_tracer_reset,
 400         .start          = wakeup_tracer_start,
 401         .stop           = wakeup_tracer_stop,
 402         .wait_pipe      = poll_wait_pipe,
 403         .print_max      = 1,
 404 #ifdef CONFIG_FTRACE_SELFTEST
 405         .selftest    = trace_selftest_startup_wakeup,
 406 #endif
 407 };
 408
 409 __init static int init_wakeup_tracer(void)
 410 {
 411         int ret;
 412
 413         ret = register_tracer(&wakeup_tracer);
 414         if (ret)
 415                 return ret;
 416
 417         ret = register_tracer(&wakeup_rt_tracer);
 418         if (ret)
 419                 return ret;
 420
 421         return 0;
 422 }
 423 device_initcall(init_wakeup_tracer);