kernel/trace/trace_sched_wakeup.c

   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 unsigned                 wakeup_prio = -1;
  28 static int                      wakeup_rt;
  29
  30 static raw_spinlock_t wakeup_lock =
  31         (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
  32
  33 static void __wakeup_reset(struct trace_array *tr);
  34
  35 static int save_lat_flag;
  36
  37 #ifdef CONFIG_FUNCTION_TRACER
  38 /*
  39  * irqsoff uses its own tracer function to keep the overhead down:
  40  */
  41 static void
  42 wakeup_tracer_call(unsigned long ip, unsigned long parent_ip)
  43 {
  44         struct trace_array *tr = wakeup_trace;
  45         struct trace_array_cpu *data;
  46         unsigned long flags;
  47         long disabled;
  48         int resched;
  49         int cpu;
  50         int pc;
  51
  52         if (likely(!wakeup_task))
  53                 return;
  54
  55         pc = preempt_count();
  56         resched = ftrace_preempt_disable();
  57
  58         cpu = raw_smp_processor_id();
  59         data = tr->data[cpu];
  60         disabled = atomic_inc_return(&data->disabled);
  61         if (unlikely(disabled != 1))
  62                 goto out;
  63
  64         local_irq_save(flags);
  65         __raw_spin_lock(&wakeup_lock);
  66
  67         if (unlikely(!wakeup_task))
  68                 goto unlock;
  69
  70         /*
  71          * The task can't disappear because it needs to
  72          * wake up first, and we have the wakeup_lock.
  73          */
  74         if (task_cpu(wakeup_task) != cpu)
  75                 goto unlock;
  76
  77         trace_function(tr, ip, parent_ip, flags, pc);
  78
  79  unlock:
  80         __raw_spin_unlock(&wakeup_lock);
  81         local_irq_restore(flags);
  82
  83  out:
  84         atomic_dec(&data->disabled);
  85
  86         ftrace_preempt_enable(resched);
  87 }
  88
  89 static struct ftrace_ops trace_ops __read_mostly =
  90 {
  91         .func = wakeup_tracer_call,
  92 };
  93 #endif /* CONFIG_FUNCTION_TRACER */
  94
  95 /*
  96  * Should this new latency be reported/recorded?
  97  */
  98 static int report_latency(cycle_t delta)
  99 {
 100         if (tracing_thresh) {
 101                 if (delta < tracing_thresh)
 102                         return 0;
 103         } else {
 104                 if (delta <= tracing_max_latency)
 105                         return 0;
 106         }
 107         return 1;
 108 }
 109
 110 static void notrace
 111 probe_wakeup_sched_switch(struct rq *rq, struct task_struct *prev,
 112         struct task_struct *next)
 113 {
 114         unsigned long latency = 0, t0 = 0, t1 = 0;
 115         struct trace_array_cpu *data;
 116         cycle_t T0, T1, delta;
 117         unsigned long flags;
 118         long disabled;
 119         int cpu;
 120         int pc;
 121
 122         tracing_record_cmdline(prev);
 123
 124         if (unlikely(!tracer_enabled))
 125                 return;
 126
 127         /*
 128          * When we start a new trace, we set wakeup_task to NULL
 129          * and then set tracer_enabled = 1. We want to make sure
 130          * that another CPU does not see the tracer_enabled = 1
 131          * and the wakeup_task with an older task, that might
 132          * actually be the same as next.
 133          */
 134         smp_rmb();
 135
 136         if (next != wakeup_task)
 137                 return;
 138
 139         pc = preempt_count();
 140
 141         /* disable local data, not wakeup_cpu data */
 142         cpu = raw_smp_processor_id();
 143         disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
 144         if (likely(disabled != 1))
 145                 goto out;
 146
 147         local_irq_save(flags);
 148         __raw_spin_lock(&wakeup_lock);
 149
 150         /* We could race with grabbing wakeup_lock */
 151         if (unlikely(!tracer_enabled || next != wakeup_task))
 152                 goto out_unlock;
 153
 154         /* The task we are waiting for is waking up */
 155         data = wakeup_trace->data[wakeup_cpu];
 156
 157         trace_function(wakeup_trace, CALLER_ADDR0, CALLER_ADDR1, flags, pc);
 158         tracing_sched_switch_trace(wakeup_trace, prev, next, flags, pc);
 159
 160         /*
 161          * usecs conversion is slow so we try to delay the conversion
 162          * as long as possible:
 163          */
 164         T0 = data->preempt_timestamp;
 165         T1 = ftrace_now(cpu);
 166         delta = T1-T0;
 167
 168         if (!report_latency(delta))
 169                 goto out_unlock;
 170
 171         latency = nsecs_to_usecs(delta);
 172
 173         tracing_max_latency = delta;
 174         t0 = nsecs_to_usecs(T0);
 175         t1 = nsecs_to_usecs(T1);
 176
 177         update_max_tr(wakeup_trace, wakeup_task, wakeup_cpu);
 178
 179 out_unlock:
 180         __wakeup_reset(wakeup_trace);
 181         __raw_spin_unlock(&wakeup_lock);
 182         local_irq_restore(flags);
 183 out:
 184         atomic_dec(&wakeup_trace->data[cpu]->disabled);
 185 }
 186
 187 static void __wakeup_reset(struct trace_array *tr)
 188 {
 189         wakeup_cpu = -1;
 190         wakeup_prio = -1;
 191
 192         if (wakeup_task)
 193                 put_task_struct(wakeup_task);
 194
 195         wakeup_task = NULL;
 196 }
 197
 198 static void wakeup_reset(struct trace_array *tr)
 199 {
 200         unsigned long flags;
 201
 202         tracing_reset_online_cpus(tr);
 203
 204         local_irq_save(flags);
 205         __raw_spin_lock(&wakeup_lock);
 206         __wakeup_reset(tr);
 207         __raw_spin_unlock(&wakeup_lock);
 208         local_irq_restore(flags);
 209 }
 210
 211 static void
 212 probe_wakeup(struct rq *rq, struct task_struct *p, int success)
 213 {
 214         struct trace_array_cpu *data;
 215         int cpu = smp_processor_id();
 216         unsigned long flags;
 217         long disabled;
 218         int pc;
 219
 220         if (likely(!tracer_enabled))
 221                 return;
 222
 223         tracing_record_cmdline(p);
 224         tracing_record_cmdline(current);
 225
 226         if ((wakeup_rt && !rt_task(p)) ||
 227                         p->prio >= wakeup_prio ||
 228                         p->prio >= current->prio)
 229                 return;
 230
 231         pc = preempt_count();
 232         disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
 233         if (unlikely(disabled != 1))
 234                 goto out;
 235
 236         /* interrupts should be off from try_to_wake_up */
 237         __raw_spin_lock(&wakeup_lock);
 238
 239         /* check for races. */
 240         if (!tracer_enabled || p->prio >= wakeup_prio)
 241                 goto out_locked;
 242
 243         /* reset the trace */
 244         __wakeup_reset(wakeup_trace);
 245
 246         wakeup_cpu = task_cpu(p);
 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         wakeup_reset(tr);
 297
 298         /*
 299          * Don't let the tracer_enabled = 1 show up before
 300          * the wakeup_task is reset. This may be overkill since
 301          * wakeup_reset does a spin_unlock after setting the
 302          * wakeup_task to NULL, but I want to be safe.
 303          * This is a slow path anyway.
 304          */
 305         smp_wmb();
 306
 307         register_ftrace_function(&trace_ops);
 308
 309         if (tracing_is_enabled())
 310                 tracer_enabled = 1;
 311         else
 312                 tracer_enabled = 0;
 313
 314         return;
 315 fail_deprobe_wake_new:
 316         unregister_trace_sched_wakeup_new(probe_wakeup);
 317 fail_deprobe:
 318         unregister_trace_sched_wakeup(probe_wakeup);
 319 }
 320
 321 static void stop_wakeup_tracer(struct trace_array *tr)
 322 {
 323         tracer_enabled = 0;
 324         unregister_ftrace_function(&trace_ops);
 325         unregister_trace_sched_switch(probe_wakeup_sched_switch);
 326         unregister_trace_sched_wakeup_new(probe_wakeup);
 327         unregister_trace_sched_wakeup(probe_wakeup);
 328 }
 329
 330 static int __wakeup_tracer_init(struct trace_array *tr)
 331 {
 332         save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
 333         trace_flags |= TRACE_ITER_LATENCY_FMT;
 334
 335         tracing_max_latency = 0;
 336         wakeup_trace = tr;
 337         start_wakeup_tracer(tr);
 338         return 0;
 339 }
 340
 341 static int wakeup_tracer_init(struct trace_array *tr)
 342 {
 343         wakeup_rt = 0;
 344         return __wakeup_tracer_init(tr);
 345 }
 346
 347 static int wakeup_rt_tracer_init(struct trace_array *tr)
 348 {
 349         wakeup_rt = 1;
 350         return __wakeup_tracer_init(tr);
 351 }
 352
 353 static void wakeup_tracer_reset(struct trace_array *tr)
 354 {
 355         stop_wakeup_tracer(tr);
 356         /* make sure we put back any tasks we are tracing */
 357         wakeup_reset(tr);
 358
 359         if (!save_lat_flag)
 360                 trace_flags &= ~TRACE_ITER_LATENCY_FMT;
 361 }
 362
 363 static void wakeup_tracer_start(struct trace_array *tr)
 364 {
 365         wakeup_reset(tr);
 366         tracer_enabled = 1;
 367 }
 368
 369 static void wakeup_tracer_stop(struct trace_array *tr)
 370 {
 371         tracer_enabled = 0;
 372 }
 373
 374 static struct tracer wakeup_tracer __read_mostly =
 375 {
 376         .name           = "wakeup",
 377         .init           = wakeup_tracer_init,
 378         .reset          = wakeup_tracer_reset,
 379         .start          = wakeup_tracer_start,
 380         .stop           = wakeup_tracer_stop,
 381         .print_max      = 1,
 382 #ifdef CONFIG_FTRACE_SELFTEST
 383         .selftest    = trace_selftest_startup_wakeup,
 384 #endif
 385 };
 386
 387 static struct tracer wakeup_rt_tracer __read_mostly =
 388 {
 389         .name           = "wakeup_rt",
 390         .init           = wakeup_rt_tracer_init,
 391         .reset          = wakeup_tracer_reset,
 392         .start          = wakeup_tracer_start,
 393         .stop           = wakeup_tracer_stop,
 394         .wait_pipe      = poll_wait_pipe,
 395         .print_max      = 1,
 396 #ifdef CONFIG_FTRACE_SELFTEST
 397         .selftest    = trace_selftest_startup_wakeup,
 398 #endif
 399 };
 400
 401 __init static int init_wakeup_tracer(void)
 402 {
 403         int ret;
 404
 405         ret = register_tracer(&wakeup_tracer);
 406         if (ret)
 407                 return ret;
 408
 409         ret = register_tracer(&wakeup_rt_tracer);
 410         if (ret)
 411                 return ret;
 412
 413         return 0;
 414 }
 415 device_initcall(init_wakeup_tracer);