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 static void __wakeup_reset(struct trace_array *tr);
  36 static int wakeup_graph_entry(struct ftrace_graph_ent *trace);
  37 static void wakeup_graph_return(struct ftrace_graph_ret *trace);
  38
  39 static int save_lat_flag;
  40
  41 #define TRACE_DISPLAY_GRAPH     1
  42
  43 static struct tracer_opt trace_opts[] = {
  44 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  45         /* display latency trace as call graph */
  46         { TRACER_OPT(display-graph, TRACE_DISPLAY_GRAPH) },
  47 #endif
  48         { } /* Empty entry */
  49 };
  50
  51 static struct tracer_flags tracer_flags = {
  52         .val  = 0,
  53         .opts = trace_opts,
  54 };
  55
  56 #define is_graph() (tracer_flags.val & TRACE_DISPLAY_GRAPH)
  57
  58 #ifdef CONFIG_FUNCTION_TRACER
  59
  60 /*
  61  * Prologue for the wakeup function tracers.
  62  *
  63  * Returns 1 if it is OK to continue, and preemption
  64  *            is disabled and data->disabled is incremented.
  65  *         0 if the trace is to be ignored, and preemption
  66  *            is not disabled and data->disabled is
  67  *            kept the same.
  68  *
  69  * Note, this function is also used outside this ifdef but
  70  *  inside the #ifdef of the function graph tracer below.
  71  *  This is OK, since the function graph tracer is
  72  *  dependent on the function tracer.
  73  */
  74 static int
  75 func_prolog_preempt_disable(struct trace_array *tr,
  76                             struct trace_array_cpu **data,
  77                             int *pc)
  78 {
  79         long disabled;
  80         int cpu;
  81
  82         if (likely(!wakeup_task))
  83                 return 0;
  84
  85         *pc = preempt_count();
  86         preempt_disable_notrace();
  87
  88         cpu = raw_smp_processor_id();
  89         if (cpu != wakeup_current_cpu)
  90                 goto out_enable;
  91
  92         *data = tr->data[cpu];
  93         disabled = atomic_inc_return(&(*data)->disabled);
  94         if (unlikely(disabled != 1))
  95                 goto out;
  96
  97         return 1;
  98
  99 out:
 100         atomic_dec(&(*data)->disabled);
 101
 102 out_enable:
 103         preempt_enable_notrace();
 104         return 0;
 105 }
 106
 107 /*
 108  * wakeup uses its own tracer function to keep the overhead down:
 109  */
 110 static void
 111 wakeup_tracer_call(unsigned long ip, unsigned long parent_ip, struct ftrace_ops *op)
 112 {
 113         struct trace_array *tr = wakeup_trace;
 114         struct trace_array_cpu *data;
 115         unsigned long flags;
 116         int pc;
 117
 118         if (!func_prolog_preempt_disable(tr, &data, &pc))
 119                 return;
 120
 121         local_irq_save(flags);
 122         trace_function(tr, ip, parent_ip, flags, pc);
 123         local_irq_restore(flags);
 124
 125         atomic_dec(&data->disabled);
 126         preempt_enable_notrace();
 127 }
 128
 129 static struct ftrace_ops trace_ops __read_mostly =
 130 {
 131         .func = wakeup_tracer_call,
 132         .flags = FTRACE_OPS_FL_GLOBAL,
 133 };
 134 #endif /* CONFIG_FUNCTION_TRACER */
 135
 136 static int start_func_tracer(int graph)
 137 {
 138         int ret;
 139
 140         if (!graph)
 141                 ret = register_ftrace_function(&trace_ops);
 142         else
 143                 ret = register_ftrace_graph(&wakeup_graph_return,
 144                                             &wakeup_graph_entry);
 145
 146         if (!ret && tracing_is_enabled())
 147                 tracer_enabled = 1;
 148         else
 149                 tracer_enabled = 0;
 150
 151         return ret;
 152 }
 153
 154 static void stop_func_tracer(int graph)
 155 {
 156         tracer_enabled = 0;
 157
 158         if (!graph)
 159                 unregister_ftrace_function(&trace_ops);
 160         else
 161                 unregister_ftrace_graph();
 162 }
 163
 164 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 165 static int wakeup_set_flag(u32 old_flags, u32 bit, int set)
 166 {
 167
 168         if (!(bit & TRACE_DISPLAY_GRAPH))
 169                 return -EINVAL;
 170
 171         if (!(is_graph() ^ set))
 172                 return 0;
 173
 174         stop_func_tracer(!set);
 175
 176         wakeup_reset(wakeup_trace);
 177         tracing_max_latency = 0;
 178
 179         return start_func_tracer(set);
 180 }
 181
 182 static int wakeup_graph_entry(struct ftrace_graph_ent *trace)
 183 {
 184         struct trace_array *tr = wakeup_trace;
 185         struct trace_array_cpu *data;
 186         unsigned long flags;
 187         int pc, ret = 0;
 188
 189         if (!func_prolog_preempt_disable(tr, &data, &pc))
 190                 return 0;
 191
 192         local_save_flags(flags);
 193         ret = __trace_graph_entry(tr, trace, flags, pc);
 194         atomic_dec(&data->disabled);
 195         preempt_enable_notrace();
 196
 197         return ret;
 198 }
 199
 200 static void wakeup_graph_return(struct ftrace_graph_ret *trace)
 201 {
 202         struct trace_array *tr = wakeup_trace;
 203         struct trace_array_cpu *data;
 204         unsigned long flags;
 205         int pc;
 206
 207         if (!func_prolog_preempt_disable(tr, &data, &pc))
 208                 return;
 209
 210         local_save_flags(flags);
 211         __trace_graph_return(tr, trace, flags, pc);
 212         atomic_dec(&data->disabled);
 213
 214         preempt_enable_notrace();
 215         return;
 216 }
 217
 218 static void wakeup_trace_open(struct trace_iterator *iter)
 219 {
 220         if (is_graph())
 221                 graph_trace_open(iter);
 222 }
 223
 224 static void wakeup_trace_close(struct trace_iterator *iter)
 225 {
 226         if (iter->private)
 227                 graph_trace_close(iter);
 228 }
 229
 230 #define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_PROC | \
 231                             TRACE_GRAPH_PRINT_ABS_TIME | \
 232                             TRACE_GRAPH_PRINT_DURATION)
 233
 234 static enum print_line_t wakeup_print_line(struct trace_iterator *iter)
 235 {
 236         /*
 237          * In graph mode call the graph tracer output function,
 238          * otherwise go with the TRACE_FN event handler
 239          */
 240         if (is_graph())
 241                 return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS);
 242
 243         return TRACE_TYPE_UNHANDLED;
 244 }
 245
 246 static void wakeup_print_header(struct seq_file *s)
 247 {
 248         if (is_graph())
 249                 print_graph_headers_flags(s, GRAPH_TRACER_FLAGS);
 250         else
 251                 trace_default_header(s);
 252 }
 253
 254 static void
 255 __trace_function(struct trace_array *tr,
 256                  unsigned long ip, unsigned long parent_ip,
 257                  unsigned long flags, int pc)
 258 {
 259         if (is_graph())
 260                 trace_graph_function(tr, ip, parent_ip, flags, pc);
 261         else
 262                 trace_function(tr, ip, parent_ip, flags, pc);
 263 }
 264 #else
 265 #define __trace_function trace_function
 266
 267 static int wakeup_set_flag(u32 old_flags, u32 bit, int set)
 268 {
 269         return -EINVAL;
 270 }
 271
 272 static int wakeup_graph_entry(struct ftrace_graph_ent *trace)
 273 {
 274         return -1;
 275 }
 276
 277 static enum print_line_t wakeup_print_line(struct trace_iterator *iter)
 278 {
 279         return TRACE_TYPE_UNHANDLED;
 280 }
 281
 282 static void wakeup_graph_return(struct ftrace_graph_ret *trace) { }
 283 static void wakeup_trace_open(struct trace_iterator *iter) { }
 284 static void wakeup_trace_close(struct trace_iterator *iter) { }
 285
 286 #ifdef CONFIG_FUNCTION_TRACER
 287 static void wakeup_print_header(struct seq_file *s)
 288 {
 289         trace_default_header(s);
 290 }
 291 #else
 292 static void wakeup_print_header(struct seq_file *s)
 293 {
 294         trace_latency_header(s);
 295 }
 296 #endif /* CONFIG_FUNCTION_TRACER */
 297 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 298
 299 /*
 300  * Should this new latency be reported/recorded?
 301  */
 302 static int report_latency(cycle_t delta)
 303 {
 304         if (tracing_thresh) {
 305                 if (delta < tracing_thresh)
 306                         return 0;
 307         } else {
 308                 if (delta <= tracing_max_latency)
 309                         return 0;
 310         }
 311         return 1;
 312 }
 313
 314 static void
 315 probe_wakeup_migrate_task(void *ignore, struct task_struct *task, int cpu)
 316 {
 317         if (task != wakeup_task)
 318                 return;
 319
 320         wakeup_current_cpu = cpu;
 321 }
 322
 323 static void notrace
 324 probe_wakeup_sched_switch(void *ignore,
 325                           struct task_struct *prev, struct task_struct *next)
 326 {
 327         struct trace_array_cpu *data;
 328         cycle_t T0, T1, delta;
 329         unsigned long flags;
 330         long disabled;
 331         int cpu;
 332         int pc;
 333
 334         tracing_record_cmdline(prev);
 335
 336         if (unlikely(!tracer_enabled))
 337                 return;
 338
 339         /*
 340          * When we start a new trace, we set wakeup_task to NULL
 341          * and then set tracer_enabled = 1. We want to make sure
 342          * that another CPU does not see the tracer_enabled = 1
 343          * and the wakeup_task with an older task, that might
 344          * actually be the same as next.
 345          */
 346         smp_rmb();
 347
 348         if (next != wakeup_task)
 349                 return;
 350
 351         pc = preempt_count();
 352
 353         /* disable local data, not wakeup_cpu data */
 354         cpu = raw_smp_processor_id();
 355         disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
 356         if (likely(disabled != 1))
 357                 goto out;
 358
 359         local_irq_save(flags);
 360         arch_spin_lock(&wakeup_lock);
 361
 362         /* We could race with grabbing wakeup_lock */
 363         if (unlikely(!tracer_enabled || next != wakeup_task))
 364                 goto out_unlock;
 365
 366         /* The task we are waiting for is waking up */
 367         data = wakeup_trace->data[wakeup_cpu];
 368
 369         __trace_function(wakeup_trace, CALLER_ADDR0, CALLER_ADDR1, flags, pc);
 370         tracing_sched_switch_trace(wakeup_trace, prev, next, flags, pc);
 371
 372         T0 = data->preempt_timestamp;
 373         T1 = ftrace_now(cpu);
 374         delta = T1-T0;
 375
 376         if (!report_latency(delta))
 377                 goto out_unlock;
 378
 379         if (likely(!is_tracing_stopped())) {
 380                 tracing_max_latency = delta;
 381                 update_max_tr(wakeup_trace, wakeup_task, wakeup_cpu);
 382         }
 383
 384 out_unlock:
 385         __wakeup_reset(wakeup_trace);
 386         arch_spin_unlock(&wakeup_lock);
 387         local_irq_restore(flags);
 388 out:
 389         atomic_dec(&wakeup_trace->data[cpu]->disabled);
 390 }
 391
 392 static void __wakeup_reset(struct trace_array *tr)
 393 {
 394         wakeup_cpu = -1;
 395         wakeup_prio = -1;
 396
 397         if (wakeup_task)
 398                 put_task_struct(wakeup_task);
 399
 400         wakeup_task = NULL;
 401 }
 402
 403 static void wakeup_reset(struct trace_array *tr)
 404 {
 405         unsigned long flags;
 406
 407         tracing_reset_online_cpus(tr);
 408
 409         local_irq_save(flags);
 410         arch_spin_lock(&wakeup_lock);
 411         __wakeup_reset(tr);
 412         arch_spin_unlock(&wakeup_lock);
 413         local_irq_restore(flags);
 414 }
 415
 416 static void
 417 probe_wakeup(void *ignore, struct task_struct *p, int success)
 418 {
 419         struct trace_array_cpu *data;
 420         int cpu = smp_processor_id();
 421         unsigned long flags;
 422         long disabled;
 423         int pc;
 424
 425         if (likely(!tracer_enabled))
 426                 return;
 427
 428         tracing_record_cmdline(p);
 429         tracing_record_cmdline(current);
 430
 431         if ((wakeup_rt && !rt_task(p)) ||
 432                         p->prio >= wakeup_prio ||
 433                         p->prio >= current->prio)
 434                 return;
 435
 436         pc = preempt_count();
 437         disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
 438         if (unlikely(disabled != 1))
 439                 goto out;
 440
 441         /* interrupts should be off from try_to_wake_up */
 442         arch_spin_lock(&wakeup_lock);
 443
 444         /* check for races. */
 445         if (!tracer_enabled || p->prio >= wakeup_prio)
 446                 goto out_locked;
 447
 448         /* reset the trace */
 449         __wakeup_reset(wakeup_trace);
 450
 451         wakeup_cpu = task_cpu(p);
 452         wakeup_current_cpu = wakeup_cpu;
 453         wakeup_prio = p->prio;
 454
 455         wakeup_task = p;
 456         get_task_struct(wakeup_task);
 457
 458         local_save_flags(flags);
 459
 460         data = wakeup_trace->data[wakeup_cpu];
 461         data->preempt_timestamp = ftrace_now(cpu);
 462         tracing_sched_wakeup_trace(wakeup_trace, p, current, flags, pc);
 463
 464         /*
 465          * We must be careful in using CALLER_ADDR2. But since wake_up
 466          * is not called by an assembly function  (where as schedule is)
 467          * it should be safe to use it here.
 468          */
 469         __trace_function(wakeup_trace, CALLER_ADDR1, CALLER_ADDR2, flags, pc);
 470
 471 out_locked:
 472         arch_spin_unlock(&wakeup_lock);
 473 out:
 474         atomic_dec(&wakeup_trace->data[cpu]->disabled);
 475 }
 476
 477 static void start_wakeup_tracer(struct trace_array *tr)
 478 {
 479         int ret;
 480
 481         ret = register_trace_sched_wakeup(probe_wakeup, NULL);
 482         if (ret) {
 483                 pr_info("wakeup trace: Couldn't activate tracepoint"
 484                         " probe to kernel_sched_wakeup\n");
 485                 return;
 486         }
 487
 488         ret = register_trace_sched_wakeup_new(probe_wakeup, NULL);
 489         if (ret) {
 490                 pr_info("wakeup trace: Couldn't activate tracepoint"
 491                         " probe to kernel_sched_wakeup_new\n");
 492                 goto fail_deprobe;
 493         }
 494
 495         ret = register_trace_sched_switch(probe_wakeup_sched_switch, NULL);
 496         if (ret) {
 497                 pr_info("sched trace: Couldn't activate tracepoint"
 498                         " probe to kernel_sched_switch\n");
 499                 goto fail_deprobe_wake_new;
 500         }
 501
 502         ret = register_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL);
 503         if (ret) {
 504                 pr_info("wakeup trace: Couldn't activate tracepoint"
 505                         " probe to kernel_sched_migrate_task\n");
 506                 return;
 507         }
 508
 509         wakeup_reset(tr);
 510
 511         /*
 512          * Don't let the tracer_enabled = 1 show up before
 513          * the wakeup_task is reset. This may be overkill since
 514          * wakeup_reset does a spin_unlock after setting the
 515          * wakeup_task to NULL, but I want to be safe.
 516          * This is a slow path anyway.
 517          */
 518         smp_wmb();
 519
 520         if (start_func_tracer(is_graph()))
 521                 printk(KERN_ERR "failed to start wakeup tracer\n");
 522
 523         return;
 524 fail_deprobe_wake_new:
 525         unregister_trace_sched_wakeup_new(probe_wakeup, NULL);
 526 fail_deprobe:
 527         unregister_trace_sched_wakeup(probe_wakeup, NULL);
 528 }
 529
 530 static void stop_wakeup_tracer(struct trace_array *tr)
 531 {
 532         tracer_enabled = 0;
 533         stop_func_tracer(is_graph());
 534         unregister_trace_sched_switch(probe_wakeup_sched_switch, NULL);
 535         unregister_trace_sched_wakeup_new(probe_wakeup, NULL);
 536         unregister_trace_sched_wakeup(probe_wakeup, NULL);
 537         unregister_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL);
 538 }
 539
 540 static int __wakeup_tracer_init(struct trace_array *tr)
 541 {
 542         save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
 543         trace_flags |= TRACE_ITER_LATENCY_FMT;
 544
 545         tracing_max_latency = 0;
 546         wakeup_trace = tr;
 547         start_wakeup_tracer(tr);
 548         return 0;
 549 }
 550
 551 static int wakeup_tracer_init(struct trace_array *tr)
 552 {
 553         wakeup_rt = 0;
 554         return __wakeup_tracer_init(tr);
 555 }
 556
 557 static int wakeup_rt_tracer_init(struct trace_array *tr)
 558 {
 559         wakeup_rt = 1;
 560         return __wakeup_tracer_init(tr);
 561 }
 562
 563 static void wakeup_tracer_reset(struct trace_array *tr)
 564 {
 565         stop_wakeup_tracer(tr);
 566         /* make sure we put back any tasks we are tracing */
 567         wakeup_reset(tr);
 568
 569         if (!save_lat_flag)
 570                 trace_flags &= ~TRACE_ITER_LATENCY_FMT;
 571 }
 572
 573 static void wakeup_tracer_start(struct trace_array *tr)
 574 {
 575         wakeup_reset(tr);
 576         tracer_enabled = 1;
 577 }
 578
 579 static void wakeup_tracer_stop(struct trace_array *tr)
 580 {
 581         tracer_enabled = 0;
 582 }
 583
 584 static struct tracer wakeup_tracer __read_mostly =
 585 {
 586         .name           = "wakeup",
 587         .init           = wakeup_tracer_init,
 588         .reset          = wakeup_tracer_reset,
 589         .start          = wakeup_tracer_start,
 590         .stop           = wakeup_tracer_stop,
 591         .print_max      = 1,
 592         .print_header   = wakeup_print_header,
 593         .print_line     = wakeup_print_line,
 594         .flags          = &tracer_flags,
 595         .set_flag       = wakeup_set_flag,
 596 #ifdef CONFIG_FTRACE_SELFTEST
 597         .selftest    = trace_selftest_startup_wakeup,
 598 #endif
 599         .open           = wakeup_trace_open,
 600         .close          = wakeup_trace_close,
 601         .use_max_tr     = 1,
 602 };
 603
 604 static struct tracer wakeup_rt_tracer __read_mostly =
 605 {
 606         .name           = "wakeup_rt",
 607         .init           = wakeup_rt_tracer_init,
 608         .reset          = wakeup_tracer_reset,
 609         .start          = wakeup_tracer_start,
 610         .stop           = wakeup_tracer_stop,
 611         .wait_pipe      = poll_wait_pipe,
 612         .print_max      = 1,
 613         .print_header   = wakeup_print_header,
 614         .print_line     = wakeup_print_line,
 615         .flags          = &tracer_flags,
 616         .set_flag       = wakeup_set_flag,
 617 #ifdef CONFIG_FTRACE_SELFTEST
 618         .selftest    = trace_selftest_startup_wakeup,
 619 #endif
 620         .open           = wakeup_trace_open,
 621         .close          = wakeup_trace_close,
 622         .use_max_tr     = 1,
 623 };
 624
 625 __init static int init_wakeup_tracer(void)
 626 {
 627         int ret;
 628
 629         ret = register_tracer(&wakeup_tracer);
 630         if (ret)
 631                 return ret;
 632
 633         ret = register_tracer(&wakeup_rt_tracer);
 634         if (ret)
 635                 return ret;
 636
 637         return 0;
 638 }
 639 device_initcall(init_wakeup_tracer);