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 <linux/marker.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
  29 static DEFINE_SPINLOCK(wakeup_lock);
  30
  31 static void __wakeup_reset(struct trace_array *tr);
  32
  33 /*
  34  * Should this new latency be reported/recorded?
  35  */
  36 static int report_latency(cycle_t delta)
  37 {
  38         if (tracing_thresh) {
  39                 if (delta < tracing_thresh)
  40                         return 0;
  41         } else {
  42                 if (delta <= tracing_max_latency)
  43                         return 0;
  44         }
  45         return 1;
  46 }
  47
  48 static void notrace
  49 wakeup_sched_switch(void *private, void *rq, struct task_struct *prev,
  50         struct task_struct *next)
  51 {
  52         unsigned long latency = 0, t0 = 0, t1 = 0;
  53         struct trace_array **ptr = private;
  54         struct trace_array *tr = *ptr;
  55         struct trace_array_cpu *data;
  56         cycle_t T0, T1, delta;
  57         unsigned long flags;
  58         long disabled;
  59         int cpu;
  60
  61         if (unlikely(!tracer_enabled))
  62                 return;
  63
  64         /*
  65          * When we start a new trace, we set wakeup_task to NULL
  66          * and then set tracer_enabled = 1. We want to make sure
  67          * that another CPU does not see the tracer_enabled = 1
  68          * and the wakeup_task with an older task, that might
  69          * actually be the same as next.
  70          */
  71         smp_rmb();
  72
  73         if (next != wakeup_task)
  74                 return;
  75
  76         /* The task we are waitng for is waking up */
  77         data = tr->data[wakeup_cpu];
  78
  79         /* disable local data, not wakeup_cpu data */
  80         cpu = raw_smp_processor_id();
  81         disabled = atomic_inc_return(&tr->data[cpu]->disabled);
  82         if (likely(disabled != 1))
  83                 goto out;
  84
  85         spin_lock_irqsave(&wakeup_lock, flags);
  86
  87         /* We could race with grabbing wakeup_lock */
  88         if (unlikely(!tracer_enabled || next != wakeup_task))
  89                 goto out_unlock;
  90
  91         trace_function(tr, data, CALLER_ADDR1, CALLER_ADDR2, flags);
  92
  93         /*
  94          * usecs conversion is slow so we try to delay the conversion
  95          * as long as possible:
  96          */
  97         T0 = data->preempt_timestamp;
  98         T1 = ftrace_now(cpu);
  99         delta = T1-T0;
 100
 101         if (!report_latency(delta))
 102                 goto out_unlock;
 103
 104         latency = nsecs_to_usecs(delta);
 105
 106         tracing_max_latency = delta;
 107         t0 = nsecs_to_usecs(T0);
 108         t1 = nsecs_to_usecs(T1);
 109
 110         update_max_tr(tr, wakeup_task, wakeup_cpu);
 111
 112 out_unlock:
 113         __wakeup_reset(tr);
 114         spin_unlock_irqrestore(&wakeup_lock, flags);
 115 out:
 116         atomic_dec(&tr->data[cpu]->disabled);
 117 }
 118
 119 static notrace void
 120 sched_switch_callback(void *probe_data, void *call_data,
 121                       const char *format, va_list *args)
 122 {
 123         struct task_struct *prev;
 124         struct task_struct *next;
 125         struct rq *__rq;
 126
 127         /* skip prev_pid %d next_pid %d prev_state %ld */
 128         (void)va_arg(*args, int);
 129         (void)va_arg(*args, int);
 130         (void)va_arg(*args, long);
 131         __rq = va_arg(*args, typeof(__rq));
 132         prev = va_arg(*args, typeof(prev));
 133         next = va_arg(*args, typeof(next));
 134
 135         tracing_record_cmdline(prev);
 136
 137         /*
 138          * If tracer_switch_func only points to the local
 139          * switch func, it still needs the ptr passed to it.
 140          */
 141         wakeup_sched_switch(probe_data, __rq, prev, next);
 142 }
 143
 144 static void __wakeup_reset(struct trace_array *tr)
 145 {
 146         struct trace_array_cpu *data;
 147         int cpu;
 148
 149         assert_spin_locked(&wakeup_lock);
 150
 151         for_each_possible_cpu(cpu) {
 152                 data = tr->data[cpu];
 153                 tracing_reset(data);
 154         }
 155
 156         wakeup_cpu = -1;
 157         wakeup_prio = -1;
 158
 159         if (wakeup_task)
 160                 put_task_struct(wakeup_task);
 161
 162         wakeup_task = NULL;
 163 }
 164
 165 static void wakeup_reset(struct trace_array *tr)
 166 {
 167         unsigned long flags;
 168
 169         spin_lock_irqsave(&wakeup_lock, flags);
 170         __wakeup_reset(tr);
 171         spin_unlock_irqrestore(&wakeup_lock, flags);
 172 }
 173
 174 static void
 175 wakeup_check_start(struct trace_array *tr, struct task_struct *p,
 176                    struct task_struct *curr)
 177 {
 178         int cpu = smp_processor_id();
 179         unsigned long flags;
 180         long disabled;
 181
 182         if (likely(!rt_task(p)) ||
 183                         p->prio >= wakeup_prio ||
 184                         p->prio >= curr->prio)
 185                 return;
 186
 187         disabled = atomic_inc_return(&tr->data[cpu]->disabled);
 188         if (unlikely(disabled != 1))
 189                 goto out;
 190
 191         /* interrupts should be off from try_to_wake_up */
 192         spin_lock(&wakeup_lock);
 193
 194         /* check for races. */
 195         if (!tracer_enabled || p->prio >= wakeup_prio)
 196                 goto out_locked;
 197
 198         /* reset the trace */
 199         __wakeup_reset(tr);
 200
 201         wakeup_cpu = task_cpu(p);
 202         wakeup_prio = p->prio;
 203
 204         wakeup_task = p;
 205         get_task_struct(wakeup_task);
 206
 207         local_save_flags(flags);
 208
 209         tr->data[wakeup_cpu]->preempt_timestamp = ftrace_now(cpu);
 210         trace_function(tr, tr->data[wakeup_cpu],
 211                        CALLER_ADDR1, CALLER_ADDR2, flags);
 212
 213 out_locked:
 214         spin_unlock(&wakeup_lock);
 215 out:
 216         atomic_dec(&tr->data[cpu]->disabled);
 217 }
 218
 219 static notrace void
 220 wake_up_callback(void *probe_data, void *call_data,
 221                  const char *format, va_list *args)
 222 {
 223         struct trace_array **ptr = probe_data;
 224         struct trace_array *tr = *ptr;
 225         struct task_struct *curr;
 226         struct task_struct *task;
 227         struct rq *__rq;
 228
 229         if (likely(!tracer_enabled))
 230                 return;
 231
 232         /* Skip pid %d state %ld */
 233         (void)va_arg(*args, int);
 234         (void)va_arg(*args, long);
 235         /* now get the meat: "rq %p task %p rq->curr %p" */
 236         __rq = va_arg(*args, typeof(__rq));
 237         task = va_arg(*args, typeof(task));
 238         curr = va_arg(*args, typeof(curr));
 239
 240         tracing_record_cmdline(task);
 241         tracing_record_cmdline(curr);
 242
 243         wakeup_check_start(tr, task, curr);
 244 }
 245
 246 static void start_wakeup_tracer(struct trace_array *tr)
 247 {
 248         int ret;
 249
 250         ret = marker_probe_register("kernel_sched_wakeup",
 251                         "pid %d state %ld ## rq %p task %p rq->curr %p",
 252                         wake_up_callback,
 253                         &wakeup_trace);
 254         if (ret) {
 255                 pr_info("wakeup trace: Couldn't add marker"
 256                         " probe to kernel_sched_wakeup\n");
 257                 return;
 258         }
 259
 260         ret = marker_probe_register("kernel_sched_wakeup_new",
 261                         "pid %d state %ld ## rq %p task %p rq->curr %p",
 262                         wake_up_callback,
 263                         &wakeup_trace);
 264         if (ret) {
 265                 pr_info("wakeup trace: Couldn't add marker"
 266                         " probe to kernel_sched_wakeup_new\n");
 267                 goto fail_deprobe;
 268         }
 269
 270         ret = marker_probe_register("kernel_sched_schedule",
 271                 "prev_pid %d next_pid %d prev_state %ld "
 272                 "## rq %p prev %p next %p",
 273                 sched_switch_callback,
 274                 &wakeup_trace);
 275         if (ret) {
 276                 pr_info("sched trace: Couldn't add marker"
 277                         " probe to kernel_sched_schedule\n");
 278                 goto fail_deprobe_wake_new;
 279         }
 280
 281         wakeup_reset(tr);
 282
 283         /*
 284          * Don't let the tracer_enabled = 1 show up before
 285          * the wakeup_task is reset. This may be overkill since
 286          * wakeup_reset does a spin_unlock after setting the
 287          * wakeup_task to NULL, but I want to be safe.
 288          * This is a slow path anyway.
 289          */
 290         smp_wmb();
 291
 292         tracer_enabled = 1;
 293
 294         return;
 295 fail_deprobe_wake_new:
 296         marker_probe_unregister("kernel_sched_wakeup_new",
 297                                 wake_up_callback,
 298                                 &wakeup_trace);
 299 fail_deprobe:
 300         marker_probe_unregister("kernel_sched_wakeup",
 301                                 wake_up_callback,
 302                                 &wakeup_trace);
 303 }
 304
 305 static void stop_wakeup_tracer(struct trace_array *tr)
 306 {
 307         tracer_enabled = 0;
 308         marker_probe_unregister("kernel_sched_schedule",
 309                                 sched_switch_callback,
 310                                 &wakeup_trace);
 311         marker_probe_unregister("kernel_sched_wakeup_new",
 312                                 wake_up_callback,
 313                                 &wakeup_trace);
 314         marker_probe_unregister("kernel_sched_wakeup",
 315                                 wake_up_callback,
 316                                 &wakeup_trace);
 317 }
 318
 319 static void wakeup_tracer_init(struct trace_array *tr)
 320 {
 321         wakeup_trace = tr;
 322
 323         if (tr->ctrl)
 324                 start_wakeup_tracer(tr);
 325 }
 326
 327 static void wakeup_tracer_reset(struct trace_array *tr)
 328 {
 329         if (tr->ctrl) {
 330                 stop_wakeup_tracer(tr);
 331                 /* make sure we put back any tasks we are tracing */
 332                 wakeup_reset(tr);
 333         }
 334 }
 335
 336 static void wakeup_tracer_ctrl_update(struct trace_array *tr)
 337 {
 338         if (tr->ctrl)
 339                 start_wakeup_tracer(tr);
 340         else
 341                 stop_wakeup_tracer(tr);
 342 }
 343
 344 static void wakeup_tracer_open(struct trace_iterator *iter)
 345 {
 346         /* stop the trace while dumping */
 347         if (iter->tr->ctrl)
 348                 stop_wakeup_tracer(iter->tr);
 349 }
 350
 351 static void wakeup_tracer_close(struct trace_iterator *iter)
 352 {
 353         /* forget about any processes we were recording */
 354         if (iter->tr->ctrl)
 355                 start_wakeup_tracer(iter->tr);
 356 }
 357
 358 static struct tracer wakeup_tracer __read_mostly =
 359 {
 360         .name           = "wakeup",
 361         .init           = wakeup_tracer_init,
 362         .reset          = wakeup_tracer_reset,
 363         .open           = wakeup_tracer_open,
 364         .close          = wakeup_tracer_close,
 365         .ctrl_update    = wakeup_tracer_ctrl_update,
 366         .print_max      = 1,
 367 #ifdef CONFIG_FTRACE_SELFTEST
 368         .selftest    = trace_selftest_startup_wakeup,
 369 #endif
 370 };
 371
 372 __init static int init_wakeup_tracer(void)
 373 {
 374         int ret;
 375
 376         ret = register_tracer(&wakeup_tracer);
 377         if (ret)
 378                 return ret;
 379
 380         return 0;
 381 }
 382 device_initcall(init_wakeup_tracer);