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/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         /* The task we are waiting for is waking up */
 142         data = wakeup_trace->data[wakeup_cpu];
 143
 144         /* disable local data, not wakeup_cpu data */
 145         cpu = raw_smp_processor_id();
 146         disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
 147         if (likely(disabled != 1))
 148                 goto out;
 149
 150         local_irq_save(flags);
 151         __raw_spin_lock(&wakeup_lock);
 152
 153         /* We could race with grabbing wakeup_lock */
 154         if (unlikely(!tracer_enabled || next != wakeup_task))
 155                 goto out_unlock;
 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         int cpu;
 190
 191         for_each_possible_cpu(cpu)
 192                 tracing_reset(tr, cpu);
 193
 194         wakeup_cpu = -1;
 195         wakeup_prio = -1;
 196
 197         if (wakeup_task)
 198                 put_task_struct(wakeup_task);
 199
 200         wakeup_task = NULL;
 201 }
 202
 203 static void wakeup_reset(struct trace_array *tr)
 204 {
 205         unsigned long flags;
 206
 207         local_irq_save(flags);
 208         __raw_spin_lock(&wakeup_lock);
 209         __wakeup_reset(tr);
 210         __raw_spin_unlock(&wakeup_lock);
 211         local_irq_restore(flags);
 212 }
 213
 214 static void
 215 probe_wakeup(struct rq *rq, struct task_struct *p, int success)
 216 {
 217         struct trace_array_cpu *data;
 218         int cpu = smp_processor_id();
 219         unsigned long flags;
 220         long disabled;
 221         int pc;
 222
 223         if (likely(!tracer_enabled))
 224                 return;
 225
 226         tracing_record_cmdline(p);
 227         tracing_record_cmdline(current);
 228
 229         if ((wakeup_rt && !rt_task(p)) ||
 230                         p->prio >= wakeup_prio ||
 231                         p->prio >= current->prio)
 232                 return;
 233
 234         pc = preempt_count();
 235         disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
 236         if (unlikely(disabled != 1))
 237                 goto out;
 238
 239         /* interrupts should be off from try_to_wake_up */
 240         __raw_spin_lock(&wakeup_lock);
 241
 242         /* check for races. */
 243         if (!tracer_enabled || p->prio >= wakeup_prio)
 244                 goto out_locked;
 245
 246         /* reset the trace */
 247         __wakeup_reset(wakeup_trace);
 248
 249         wakeup_cpu = task_cpu(p);
 250         wakeup_prio = p->prio;
 251
 252         wakeup_task = p;
 253         get_task_struct(wakeup_task);
 254
 255         local_save_flags(flags);
 256
 257         data = wakeup_trace->data[wakeup_cpu];
 258         data->preempt_timestamp = ftrace_now(cpu);
 259         tracing_sched_wakeup_trace(wakeup_trace, p, current, flags, pc);
 260
 261         /*
 262          * We must be careful in using CALLER_ADDR2. But since wake_up
 263          * is not called by an assembly function  (where as schedule is)
 264          * it should be safe to use it here.
 265          */
 266         trace_function(wakeup_trace, CALLER_ADDR1, CALLER_ADDR2, flags, pc);
 267
 268 out_locked:
 269         __raw_spin_unlock(&wakeup_lock);
 270 out:
 271         atomic_dec(&wakeup_trace->data[cpu]->disabled);
 272 }
 273
 274 static void start_wakeup_tracer(struct trace_array *tr)
 275 {
 276         int ret;
 277
 278         ret = register_trace_sched_wakeup(probe_wakeup);
 279         if (ret) {
 280                 pr_info("wakeup trace: Couldn't activate tracepoint"
 281                         " probe to kernel_sched_wakeup\n");
 282                 return;
 283         }
 284
 285         ret = register_trace_sched_wakeup_new(probe_wakeup);
 286         if (ret) {
 287                 pr_info("wakeup trace: Couldn't activate tracepoint"
 288                         " probe to kernel_sched_wakeup_new\n");
 289                 goto fail_deprobe;
 290         }
 291
 292         ret = register_trace_sched_switch(probe_wakeup_sched_switch);
 293         if (ret) {
 294                 pr_info("sched trace: Couldn't activate tracepoint"
 295                         " probe to kernel_sched_switch\n");
 296                 goto fail_deprobe_wake_new;
 297         }
 298
 299         wakeup_reset(tr);
 300
 301         /*
 302          * Don't let the tracer_enabled = 1 show up before
 303          * the wakeup_task is reset. This may be overkill since
 304          * wakeup_reset does a spin_unlock after setting the
 305          * wakeup_task to NULL, but I want to be safe.
 306          * This is a slow path anyway.
 307          */
 308         smp_wmb();
 309
 310         register_ftrace_function(&trace_ops);
 311
 312         if (tracing_is_enabled())
 313                 tracer_enabled = 1;
 314         else
 315                 tracer_enabled = 0;
 316
 317         return;
 318 fail_deprobe_wake_new:
 319         unregister_trace_sched_wakeup_new(probe_wakeup);
 320 fail_deprobe:
 321         unregister_trace_sched_wakeup(probe_wakeup);
 322 }
 323
 324 static void stop_wakeup_tracer(struct trace_array *tr)
 325 {
 326         tracer_enabled = 0;
 327         unregister_ftrace_function(&trace_ops);
 328         unregister_trace_sched_switch(probe_wakeup_sched_switch);
 329         unregister_trace_sched_wakeup_new(probe_wakeup);
 330         unregister_trace_sched_wakeup(probe_wakeup);
 331 }
 332
 333 static int __wakeup_tracer_init(struct trace_array *tr)
 334 {
 335         save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
 336         trace_flags |= TRACE_ITER_LATENCY_FMT;
 337
 338         tracing_max_latency = 0;
 339         wakeup_trace = tr;
 340         start_wakeup_tracer(tr);
 341         return 0;
 342 }
 343
 344 static int wakeup_tracer_init(struct trace_array *tr)
 345 {
 346         wakeup_rt = 0;
 347         return __wakeup_tracer_init(tr);
 348 }
 349
 350 static int wakeup_rt_tracer_init(struct trace_array *tr)
 351 {
 352         wakeup_rt = 1;
 353         return __wakeup_tracer_init(tr);
 354 }
 355
 356 static void wakeup_tracer_reset(struct trace_array *tr)
 357 {
 358         stop_wakeup_tracer(tr);
 359         /* make sure we put back any tasks we are tracing */
 360         wakeup_reset(tr);
 361
 362         if (!save_lat_flag)
 363                 trace_flags &= ~TRACE_ITER_LATENCY_FMT;
 364 }
 365
 366 static void wakeup_tracer_start(struct trace_array *tr)
 367 {
 368         wakeup_reset(tr);
 369         tracer_enabled = 1;
 370 }
 371
 372 static void wakeup_tracer_stop(struct trace_array *tr)
 373 {
 374         tracer_enabled = 0;
 375 }
 376
 377 static struct tracer wakeup_tracer __read_mostly =
 378 {
 379         .name           = "wakeup",
 380         .init           = wakeup_tracer_init,
 381         .reset          = wakeup_tracer_reset,
 382         .start          = wakeup_tracer_start,
 383         .stop           = wakeup_tracer_stop,
 384         .print_max      = 1,
 385 #ifdef CONFIG_FTRACE_SELFTEST
 386         .selftest    = trace_selftest_startup_wakeup,
 387 #endif
 388 };
 389
 390 static struct tracer wakeup_rt_tracer __read_mostly =
 391 {
 392         .name           = "wakeup_rt",
 393         .init           = wakeup_rt_tracer_init,
 394         .reset          = wakeup_tracer_reset,
 395         .start          = wakeup_tracer_start,
 396         .stop           = wakeup_tracer_stop,
 397         .wait_pipe      = poll_wait_pipe,
 398         .print_max      = 1,
 399 #ifdef CONFIG_FTRACE_SELFTEST
 400         .selftest    = trace_selftest_startup_wakeup,
 401 #endif
 402 };
 403
 404 __init static int init_wakeup_tracer(void)
 405 {
 406         int ret;
 407
 408         ret = register_tracer(&wakeup_tracer);
 409         if (ret)
 410                 return ret;
 411
 412         ret = register_tracer(&wakeup_rt_tracer);
 413         if (ret)
 414                 return ret;
 415
 416         return 0;
 417 }
 418 device_initcall(init_wakeup_tracer);