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 int                      wakeup_current_cpu;
  28 static unsigned                 wakeup_prio = -1;
  29 static int                      wakeup_rt;
  30
  31 static arch_spinlock_t wakeup_lock =
  32         (arch_spinlock_t)__ARCH_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
 102 probe_wakeup_migrate_task(void *ignore, struct task_struct *task, int cpu)
 103 {
 104         if (task != wakeup_task)
 105                 return;
 106
 107         wakeup_current_cpu = cpu;
 108 }
 109
 110 static void notrace
 111 probe_wakeup_sched_switch(void *ignore,
 112                           struct task_struct *prev, struct task_struct *next)
 113 {
 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         arch_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         T0 = data->preempt_timestamp;
 160         T1 = ftrace_now(cpu);
 161         delta = T1-T0;
 162
 163         if (!report_latency(delta))
 164                 goto out_unlock;
 165
 166         if (likely(!is_tracing_stopped())) {
 167                 tracing_max_latency = delta;
 168                 update_max_tr(wakeup_trace, wakeup_task, wakeup_cpu);
 169         }
 170
 171 out_unlock:
 172         __wakeup_reset(wakeup_trace);
 173         arch_spin_unlock(&wakeup_lock);
 174         local_irq_restore(flags);
 175 out:
 176         atomic_dec(&wakeup_trace->data[cpu]->disabled);
 177 }
 178
 179 static void __wakeup_reset(struct trace_array *tr)
 180 {
 181         wakeup_cpu = -1;
 182         wakeup_prio = -1;
 183
 184         if (wakeup_task)
 185                 put_task_struct(wakeup_task);
 186
 187         wakeup_task = NULL;
 188 }
 189
 190 static void wakeup_reset(struct trace_array *tr)
 191 {
 192         unsigned long flags;
 193
 194         tracing_reset_online_cpus(tr);
 195
 196         local_irq_save(flags);
 197         arch_spin_lock(&wakeup_lock);
 198         __wakeup_reset(tr);
 199         arch_spin_unlock(&wakeup_lock);
 200         local_irq_restore(flags);
 201 }
 202
 203 static void
 204 probe_wakeup(void *ignore, struct task_struct *p, int success)
 205 {
 206         struct trace_array_cpu *data;
 207         int cpu = smp_processor_id();
 208         unsigned long flags;
 209         long disabled;
 210         int pc;
 211
 212         if (likely(!tracer_enabled))
 213                 return;
 214
 215         tracing_record_cmdline(p);
 216         tracing_record_cmdline(current);
 217
 218         if ((wakeup_rt && !rt_task(p)) ||
 219                         p->prio >= wakeup_prio ||
 220                         p->prio >= current->prio)
 221                 return;
 222
 223         pc = preempt_count();
 224         disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
 225         if (unlikely(disabled != 1))
 226                 goto out;
 227
 228         /* interrupts should be off from try_to_wake_up */
 229         arch_spin_lock(&wakeup_lock);
 230
 231         /* check for races. */
 232         if (!tracer_enabled || p->prio >= wakeup_prio)
 233                 goto out_locked;
 234
 235         /* reset the trace */
 236         __wakeup_reset(wakeup_trace);
 237
 238         wakeup_cpu = task_cpu(p);
 239         wakeup_current_cpu = wakeup_cpu;
 240         wakeup_prio = p->prio;
 241
 242         wakeup_task = p;
 243         get_task_struct(wakeup_task);
 244
 245         local_save_flags(flags);
 246
 247         data = wakeup_trace->data[wakeup_cpu];
 248         data->preempt_timestamp = ftrace_now(cpu);
 249         tracing_sched_wakeup_trace(wakeup_trace, p, current, flags, pc);
 250
 251         /*
 252          * We must be careful in using CALLER_ADDR2. But since wake_up
 253          * is not called by an assembly function  (where as schedule is)
 254          * it should be safe to use it here.
 255          */
 256         trace_function(wakeup_trace, CALLER_ADDR1, CALLER_ADDR2, flags, pc);
 257
 258 out_locked:
 259         arch_spin_unlock(&wakeup_lock);
 260 out:
 261         atomic_dec(&wakeup_trace->data[cpu]->disabled);
 262 }
 263
 264 static void start_wakeup_tracer(struct trace_array *tr)
 265 {
 266         int ret;
 267
 268         ret = register_trace_sched_wakeup(probe_wakeup, NULL);
 269         if (ret) {
 270                 pr_info("wakeup trace: Couldn't activate tracepoint"
 271                         " probe to kernel_sched_wakeup\n");
 272                 return;
 273         }
 274
 275         ret = register_trace_sched_wakeup_new(probe_wakeup, NULL);
 276         if (ret) {
 277                 pr_info("wakeup trace: Couldn't activate tracepoint"
 278                         " probe to kernel_sched_wakeup_new\n");
 279                 goto fail_deprobe;
 280         }
 281
 282         ret = register_trace_sched_switch(probe_wakeup_sched_switch, NULL);
 283         if (ret) {
 284                 pr_info("sched trace: Couldn't activate tracepoint"
 285                         " probe to kernel_sched_switch\n");
 286                 goto fail_deprobe_wake_new;
 287         }
 288
 289         ret = register_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL);
 290         if (ret) {
 291                 pr_info("wakeup trace: Couldn't activate tracepoint"
 292                         " probe to kernel_sched_migrate_task\n");
 293                 return;
 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, NULL);
 317 fail_deprobe:
 318         unregister_trace_sched_wakeup(probe_wakeup, NULL);
 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, NULL);
 326         unregister_trace_sched_wakeup_new(probe_wakeup, NULL);
 327         unregister_trace_sched_wakeup(probe_wakeup, NULL);
 328         unregister_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL);
 329 }
 330
 331 static int __wakeup_tracer_init(struct trace_array *tr)
 332 {
 333         save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
 334         trace_flags |= TRACE_ITER_LATENCY_FMT;
 335
 336         tracing_max_latency = 0;
 337         wakeup_trace = tr;
 338         start_wakeup_tracer(tr);
 339         return 0;
 340 }
 341
 342 static int wakeup_tracer_init(struct trace_array *tr)
 343 {
 344         wakeup_rt = 0;
 345         return __wakeup_tracer_init(tr);
 346 }
 347
 348 static int wakeup_rt_tracer_init(struct trace_array *tr)
 349 {
 350         wakeup_rt = 1;
 351         return __wakeup_tracer_init(tr);
 352 }
 353
 354 static void wakeup_tracer_reset(struct trace_array *tr)
 355 {
 356         stop_wakeup_tracer(tr);
 357         /* make sure we put back any tasks we are tracing */
 358         wakeup_reset(tr);
 359
 360         if (!save_lat_flag)
 361                 trace_flags &= ~TRACE_ITER_LATENCY_FMT;
 362 }
 363
 364 static void wakeup_tracer_start(struct trace_array *tr)
 365 {
 366         wakeup_reset(tr);
 367         tracer_enabled = 1;
 368 }
 369
 370 static void wakeup_tracer_stop(struct trace_array *tr)
 371 {
 372         tracer_enabled = 0;
 373 }
 374
 375 static struct tracer wakeup_tracer __read_mostly =
 376 {
 377         .name           = "wakeup",
 378         .init           = wakeup_tracer_init,
 379         .reset          = wakeup_tracer_reset,
 380         .start          = wakeup_tracer_start,
 381         .stop           = wakeup_tracer_stop,
 382         .print_max      = 1,
 383 #ifdef CONFIG_FTRACE_SELFTEST
 384         .selftest    = trace_selftest_startup_wakeup,
 385 #endif
 386 };
 387
 388 static struct tracer wakeup_rt_tracer __read_mostly =
 389 {
 390         .name           = "wakeup_rt",
 391         .init           = wakeup_rt_tracer_init,
 392         .reset          = wakeup_tracer_reset,
 393         .start          = wakeup_tracer_start,
 394         .stop           = wakeup_tracer_stop,
 395         .wait_pipe      = poll_wait_pipe,
 396         .print_max      = 1,
 397 #ifdef CONFIG_FTRACE_SELFTEST
 398         .selftest    = trace_selftest_startup_wakeup,
 399 #endif
 400 };
 401
 402 __init static int init_wakeup_tracer(void)
 403 {
 404         int ret;
 405
 406         ret = register_tracer(&wakeup_tracer);
 407         if (ret)
 408                 return ret;
 409
 410         ret = register_tracer(&wakeup_rt_tracer);
 411         if (ret)
 412                 return ret;
 413
 414         return 0;
 415 }
 416 device_initcall(init_wakeup_tracer);