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 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 task_struct *prev, struct task_struct *next)
 111 {
 112         struct trace_array_cpu *data;
 113         cycle_t T0, T1, delta;
 114         unsigned long flags;
 115         long disabled;
 116         int cpu;
 117         int pc;
 118
 119         tracing_record_cmdline(prev);
 120
 121         if (unlikely(!tracer_enabled))
 122                 return;
 123
 124         /*
 125          * When we start a new trace, we set wakeup_task to NULL
 126          * and then set tracer_enabled = 1. We want to make sure
 127          * that another CPU does not see the tracer_enabled = 1
 128          * and the wakeup_task with an older task, that might
 129          * actually be the same as next.
 130          */
 131         smp_rmb();
 132
 133         if (next != wakeup_task)
 134                 return;
 135
 136         pc = preempt_count();
 137
 138         /* disable local data, not wakeup_cpu data */
 139         cpu = raw_smp_processor_id();
 140         disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
 141         if (likely(disabled != 1))
 142                 goto out;
 143
 144         local_irq_save(flags);
 145         arch_spin_lock(&wakeup_lock);
 146
 147         /* We could race with grabbing wakeup_lock */
 148         if (unlikely(!tracer_enabled || next != wakeup_task))
 149                 goto out_unlock;
 150
 151         /* The task we are waiting for is waking up */
 152         data = wakeup_trace->data[wakeup_cpu];
 153
 154         trace_function(wakeup_trace, CALLER_ADDR0, CALLER_ADDR1, flags, pc);
 155         tracing_sched_switch_trace(wakeup_trace, prev, next, flags, pc);
 156
 157         T0 = data->preempt_timestamp;
 158         T1 = ftrace_now(cpu);
 159         delta = T1-T0;
 160
 161         if (!report_latency(delta))
 162                 goto out_unlock;
 163
 164         if (likely(!is_tracing_stopped())) {
 165                 tracing_max_latency = delta;
 166                 update_max_tr(wakeup_trace, wakeup_task, wakeup_cpu);
 167         }
 168
 169 out_unlock:
 170         __wakeup_reset(wakeup_trace);
 171         arch_spin_unlock(&wakeup_lock);
 172         local_irq_restore(flags);
 173 out:
 174         atomic_dec(&wakeup_trace->data[cpu]->disabled);
 175 }
 176
 177 static void __wakeup_reset(struct trace_array *tr)
 178 {
 179         wakeup_cpu = -1;
 180         wakeup_prio = -1;
 181
 182         if (wakeup_task)
 183                 put_task_struct(wakeup_task);
 184
 185         wakeup_task = NULL;
 186 }
 187
 188 static void wakeup_reset(struct trace_array *tr)
 189 {
 190         unsigned long flags;
 191
 192         tracing_reset_online_cpus(tr);
 193
 194         local_irq_save(flags);
 195         arch_spin_lock(&wakeup_lock);
 196         __wakeup_reset(tr);
 197         arch_spin_unlock(&wakeup_lock);
 198         local_irq_restore(flags);
 199 }
 200
 201 static void
 202 probe_wakeup(struct task_struct *p, int success)
 203 {
 204         struct trace_array_cpu *data;
 205         int cpu = smp_processor_id();
 206         unsigned long flags;
 207         long disabled;
 208         int pc;
 209
 210         if (likely(!tracer_enabled))
 211                 return;
 212
 213         tracing_record_cmdline(p);
 214         tracing_record_cmdline(current);
 215
 216         if ((wakeup_rt && !rt_task(p)) ||
 217                         p->prio >= wakeup_prio ||
 218                         p->prio >= current->prio)
 219                 return;
 220
 221         pc = preempt_count();
 222         disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
 223         if (unlikely(disabled != 1))
 224                 goto out;
 225
 226         /* interrupts should be off from try_to_wake_up */
 227         arch_spin_lock(&wakeup_lock);
 228
 229         /* check for races. */
 230         if (!tracer_enabled || p->prio >= wakeup_prio)
 231                 goto out_locked;
 232
 233         /* reset the trace */
 234         __wakeup_reset(wakeup_trace);
 235
 236         wakeup_cpu = task_cpu(p);
 237         wakeup_current_cpu = wakeup_cpu;
 238         wakeup_prio = p->prio;
 239
 240         wakeup_task = p;
 241         get_task_struct(wakeup_task);
 242
 243         local_save_flags(flags);
 244
 245         data = wakeup_trace->data[wakeup_cpu];
 246         data->preempt_timestamp = ftrace_now(cpu);
 247         tracing_sched_wakeup_trace(wakeup_trace, p, current, flags, pc);
 248
 249         /*
 250          * We must be careful in using CALLER_ADDR2. But since wake_up
 251          * is not called by an assembly function  (where as schedule is)
 252          * it should be safe to use it here.
 253          */
 254         trace_function(wakeup_trace, CALLER_ADDR1, CALLER_ADDR2, flags, pc);
 255
 256 out_locked:
 257         arch_spin_unlock(&wakeup_lock);
 258 out:
 259         atomic_dec(&wakeup_trace->data[cpu]->disabled);
 260 }
 261
 262 static void start_wakeup_tracer(struct trace_array *tr)
 263 {
 264         int ret;
 265
 266         ret = register_trace_sched_wakeup(probe_wakeup);
 267         if (ret) {
 268                 pr_info("wakeup trace: Couldn't activate tracepoint"
 269                         " probe to kernel_sched_wakeup\n");
 270                 return;
 271         }
 272
 273         ret = register_trace_sched_wakeup_new(probe_wakeup);
 274         if (ret) {
 275                 pr_info("wakeup trace: Couldn't activate tracepoint"
 276                         " probe to kernel_sched_wakeup_new\n");
 277                 goto fail_deprobe;
 278         }
 279
 280         ret = register_trace_sched_switch(probe_wakeup_sched_switch);
 281         if (ret) {
 282                 pr_info("sched trace: Couldn't activate tracepoint"
 283                         " probe to kernel_sched_switch\n");
 284                 goto fail_deprobe_wake_new;
 285         }
 286
 287         ret = register_trace_sched_migrate_task(probe_wakeup_migrate_task);
 288         if (ret) {
 289                 pr_info("wakeup trace: Couldn't activate tracepoint"
 290                         " probe to kernel_sched_migrate_task\n");
 291                 return;
 292         }
 293
 294         wakeup_reset(tr);
 295
 296         /*
 297          * Don't let the tracer_enabled = 1 show up before
 298          * the wakeup_task is reset. This may be overkill since
 299          * wakeup_reset does a spin_unlock after setting the
 300          * wakeup_task to NULL, but I want to be safe.
 301          * This is a slow path anyway.
 302          */
 303         smp_wmb();
 304
 305         register_ftrace_function(&trace_ops);
 306
 307         if (tracing_is_enabled())
 308                 tracer_enabled = 1;
 309         else
 310                 tracer_enabled = 0;
 311
 312         return;
 313 fail_deprobe_wake_new:
 314         unregister_trace_sched_wakeup_new(probe_wakeup);
 315 fail_deprobe:
 316         unregister_trace_sched_wakeup(probe_wakeup);
 317 }
 318
 319 static void stop_wakeup_tracer(struct trace_array *tr)
 320 {
 321         tracer_enabled = 0;
 322         unregister_ftrace_function(&trace_ops);
 323         unregister_trace_sched_switch(probe_wakeup_sched_switch);
 324         unregister_trace_sched_wakeup_new(probe_wakeup);
 325         unregister_trace_sched_wakeup(probe_wakeup);
 326         unregister_trace_sched_migrate_task(probe_wakeup_migrate_task);
 327 }
 328
 329 static int __wakeup_tracer_init(struct trace_array *tr)
 330 {
 331         save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
 332         trace_flags |= TRACE_ITER_LATENCY_FMT;
 333
 334         tracing_max_latency = 0;
 335         wakeup_trace = tr;
 336         start_wakeup_tracer(tr);
 337         return 0;
 338 }
 339
 340 static int wakeup_tracer_init(struct trace_array *tr)
 341 {
 342         wakeup_rt = 0;
 343         return __wakeup_tracer_init(tr);
 344 }
 345
 346 static int wakeup_rt_tracer_init(struct trace_array *tr)
 347 {
 348         wakeup_rt = 1;
 349         return __wakeup_tracer_init(tr);
 350 }
 351
 352 static void wakeup_tracer_reset(struct trace_array *tr)
 353 {
 354         stop_wakeup_tracer(tr);
 355         /* make sure we put back any tasks we are tracing */
 356         wakeup_reset(tr);
 357
 358         if (!save_lat_flag)
 359                 trace_flags &= ~TRACE_ITER_LATENCY_FMT;
 360 }
 361
 362 static void wakeup_tracer_start(struct trace_array *tr)
 363 {
 364         wakeup_reset(tr);
 365         tracer_enabled = 1;
 366 }
 367
 368 static void wakeup_tracer_stop(struct trace_array *tr)
 369 {
 370         tracer_enabled = 0;
 371 }
 372
 373 static struct tracer wakeup_tracer __read_mostly =
 374 {
 375         .name           = "wakeup",
 376         .init           = wakeup_tracer_init,
 377         .reset          = wakeup_tracer_reset,
 378         .start          = wakeup_tracer_start,
 379         .stop           = wakeup_tracer_stop,
 380         .print_max      = 1,
 381 #ifdef CONFIG_FTRACE_SELFTEST
 382         .selftest    = trace_selftest_startup_wakeup,
 383 #endif
 384 };
 385
 386 static struct tracer wakeup_rt_tracer __read_mostly =
 387 {
 388         .name           = "wakeup_rt",
 389         .init           = wakeup_rt_tracer_init,
 390         .reset          = wakeup_tracer_reset,
 391         .start          = wakeup_tracer_start,
 392         .stop           = wakeup_tracer_stop,
 393         .wait_pipe      = poll_wait_pipe,
 394         .print_max      = 1,
 395 #ifdef CONFIG_FTRACE_SELFTEST
 396         .selftest    = trace_selftest_startup_wakeup,
 397 #endif
 398 };
 399
 400 __init static int init_wakeup_tracer(void)
 401 {
 402         int ret;
 403
 404         ret = register_tracer(&wakeup_tracer);
 405         if (ret)
 406                 return ret;
 407
 408         ret = register_tracer(&wakeup_rt_tracer);
 409         if (ret)
 410                 return ret;
 411
 412         return 0;
 413 }
 414 device_initcall(init_wakeup_tracer);