kernel/trace/trace_irqsoff.c

   1 /*
   2  * trace irqs off critical timings
   3  *
   4  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
   5  * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
   6  *
   7  * From code in 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/kallsyms.h>
  13 #include <linux/debugfs.h>
  14 #include <linux/uaccess.h>
  15 #include <linux/module.h>
  16 #include <linux/ftrace.h>
  17 #include <linux/fs.h>
  18
  19 #include "trace.h"
  20
  21 static struct trace_array               *irqsoff_trace __read_mostly;
  22 static int                              tracer_enabled __read_mostly;
  23
  24 static DEFINE_PER_CPU(int, tracing_cpu);
  25
  26 static DEFINE_RAW_SPINLOCK(max_trace_lock);
  27
  28 enum {
  29         TRACER_IRQS_OFF         = (1 << 1),
  30         TRACER_PREEMPT_OFF      = (1 << 2),
  31 };
  32
  33 static int trace_type __read_mostly;
  34
  35 static int save_lat_flag;
  36
  37 static void stop_irqsoff_tracer(struct trace_array *tr, int graph);
  38 static int start_irqsoff_tracer(struct trace_array *tr, int graph);
  39
  40 #ifdef CONFIG_PREEMPT_TRACER
  41 static inline int
  42 preempt_trace(void)
  43 {
  44         return ((trace_type & TRACER_PREEMPT_OFF) && preempt_count());
  45 }
  46 #else
  47 # define preempt_trace() (0)
  48 #endif
  49
  50 #ifdef CONFIG_IRQSOFF_TRACER
  51 static inline int
  52 irq_trace(void)
  53 {
  54         return ((trace_type & TRACER_IRQS_OFF) &&
  55                 irqs_disabled());
  56 }
  57 #else
  58 # define irq_trace() (0)
  59 #endif
  60
  61 #define TRACE_DISPLAY_GRAPH     1
  62
  63 static struct tracer_opt trace_opts[] = {
  64 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  65         /* display latency trace as call graph */
  66         { TRACER_OPT(display-graph, TRACE_DISPLAY_GRAPH) },
  67 #endif
  68         { } /* Empty entry */
  69 };
  70
  71 static struct tracer_flags tracer_flags = {
  72         .val  = 0,
  73         .opts = trace_opts,
  74 };
  75
  76 #define is_graph() (tracer_flags.val & TRACE_DISPLAY_GRAPH)
  77
  78 /*
  79  * Sequence count - we record it when starting a measurement and
  80  * skip the latency if the sequence has changed - some other section
  81  * did a maximum and could disturb our measurement with serial console
  82  * printouts, etc. Truly coinciding maximum latencies should be rare
  83  * and what happens together happens separately as well, so this doesn't
  84  * decrease the validity of the maximum found:
  85  */
  86 static __cacheline_aligned_in_smp       unsigned long max_sequence;
  87
  88 #ifdef CONFIG_FUNCTION_TRACER
  89 /*
  90  * Prologue for the preempt and irqs off function tracers.
  91  *
  92  * Returns 1 if it is OK to continue, and data->disabled is
  93  *            incremented.
  94  *         0 if the trace is to be ignored, and data->disabled
  95  *            is kept the same.
  96  *
  97  * Note, this function is also used outside this ifdef but
  98  *  inside the #ifdef of the function graph tracer below.
  99  *  This is OK, since the function graph tracer is
 100  *  dependent on the function tracer.
 101  */
 102 static int func_prolog_dec(struct trace_array *tr,
 103                            struct trace_array_cpu **data,
 104                            unsigned long *flags)
 105 {
 106         long disabled;
 107         int cpu;
 108
 109         /*
 110          * Does not matter if we preempt. We test the flags
 111          * afterward, to see if irqs are disabled or not.
 112          * If we preempt and get a false positive, the flags
 113          * test will fail.
 114          */
 115         cpu = raw_smp_processor_id();
 116         if (likely(!per_cpu(tracing_cpu, cpu)))
 117                 return 0;
 118
 119         local_save_flags(*flags);
 120         /* slight chance to get a false positive on tracing_cpu */
 121         if (!irqs_disabled_flags(*flags))
 122                 return 0;
 123
 124         *data = tr->data[cpu];
 125         disabled = atomic_inc_return(&(*data)->disabled);
 126
 127         if (likely(disabled == 1))
 128                 return 1;
 129
 130         atomic_dec(&(*data)->disabled);
 131
 132         return 0;
 133 }
 134
 135 /*
 136  * irqsoff uses its own tracer function to keep the overhead down:
 137  */
 138 static void
 139 irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip)
 140 {
 141         struct trace_array *tr = irqsoff_trace;
 142         struct trace_array_cpu *data;
 143         unsigned long flags;
 144
 145         if (!func_prolog_dec(tr, &data, &flags))
 146                 return;
 147
 148         trace_function(tr, ip, parent_ip, flags, preempt_count());
 149
 150         atomic_dec(&data->disabled);
 151 }
 152
 153 static struct ftrace_ops trace_ops __read_mostly =
 154 {
 155         .func = irqsoff_tracer_call,
 156         .flags = FTRACE_OPS_FL_GLOBAL,
 157 };
 158 #endif /* CONFIG_FUNCTION_TRACER */
 159
 160 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 161 static int irqsoff_set_flag(u32 old_flags, u32 bit, int set)
 162 {
 163         int cpu;
 164
 165         if (!(bit & TRACE_DISPLAY_GRAPH))
 166                 return -EINVAL;
 167
 168         if (!(is_graph() ^ set))
 169                 return 0;
 170
 171         stop_irqsoff_tracer(irqsoff_trace, !set);
 172
 173         for_each_possible_cpu(cpu)
 174                 per_cpu(tracing_cpu, cpu) = 0;
 175
 176         tracing_max_latency = 0;
 177         tracing_reset_online_cpus(irqsoff_trace);
 178
 179         return start_irqsoff_tracer(irqsoff_trace, set);
 180 }
 181
 182 static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
 183 {
 184         struct trace_array *tr = irqsoff_trace;
 185         struct trace_array_cpu *data;
 186         unsigned long flags;
 187         int ret;
 188         int pc;
 189
 190         if (!func_prolog_dec(tr, &data, &flags))
 191                 return 0;
 192
 193         pc = preempt_count();
 194         ret = __trace_graph_entry(tr, trace, flags, pc);
 195         atomic_dec(&data->disabled);
 196
 197         return ret;
 198 }
 199
 200 static void irqsoff_graph_return(struct ftrace_graph_ret *trace)
 201 {
 202         struct trace_array *tr = irqsoff_trace;
 203         struct trace_array_cpu *data;
 204         unsigned long flags;
 205         int pc;
 206
 207         if (!func_prolog_dec(tr, &data, &flags))
 208                 return;
 209
 210         pc = preempt_count();
 211         __trace_graph_return(tr, trace, flags, pc);
 212         atomic_dec(&data->disabled);
 213 }
 214
 215 static void irqsoff_trace_open(struct trace_iterator *iter)
 216 {
 217         if (is_graph())
 218                 graph_trace_open(iter);
 219
 220 }
 221
 222 static void irqsoff_trace_close(struct trace_iterator *iter)
 223 {
 224         if (iter->private)
 225                 graph_trace_close(iter);
 226 }
 227
 228 #define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_CPU | \
 229                             TRACE_GRAPH_PRINT_PROC | \
 230                             TRACE_GRAPH_PRINT_ABS_TIME | \
 231                             TRACE_GRAPH_PRINT_DURATION)
 232
 233 static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
 234 {
 235         /*
 236          * In graph mode call the graph tracer output function,
 237          * otherwise go with the TRACE_FN event handler
 238          */
 239         if (is_graph())
 240                 return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS);
 241
 242         return TRACE_TYPE_UNHANDLED;
 243 }
 244
 245 static void irqsoff_print_header(struct seq_file *s)
 246 {
 247         if (is_graph())
 248                 print_graph_headers_flags(s, GRAPH_TRACER_FLAGS);
 249         else
 250                 trace_default_header(s);
 251 }
 252
 253 static void
 254 __trace_function(struct trace_array *tr,
 255                  unsigned long ip, unsigned long parent_ip,
 256                  unsigned long flags, int pc)
 257 {
 258         if (is_graph())
 259                 trace_graph_function(tr, ip, parent_ip, flags, pc);
 260         else
 261                 trace_function(tr, ip, parent_ip, flags, pc);
 262 }
 263
 264 #else
 265 #define __trace_function trace_function
 266
 267 static int irqsoff_set_flag(u32 old_flags, u32 bit, int set)
 268 {
 269         return -EINVAL;
 270 }
 271
 272 static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
 273 {
 274         return -1;
 275 }
 276
 277 static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
 278 {
 279         return TRACE_TYPE_UNHANDLED;
 280 }
 281
 282 static void irqsoff_graph_return(struct ftrace_graph_ret *trace) { }
 283 static void irqsoff_trace_open(struct trace_iterator *iter) { }
 284 static void irqsoff_trace_close(struct trace_iterator *iter) { }
 285
 286 #ifdef CONFIG_FUNCTION_TRACER
 287 static void irqsoff_print_header(struct seq_file *s)
 288 {
 289         trace_default_header(s);
 290 }
 291 #else
 292 static void irqsoff_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 check_critical_timing(struct trace_array *tr,
 316                       struct trace_array_cpu *data,
 317                       unsigned long parent_ip,
 318                       int cpu)
 319 {
 320         cycle_t T0, T1, delta;
 321         unsigned long flags;
 322         int pc;
 323
 324         T0 = data->preempt_timestamp;
 325         T1 = ftrace_now(cpu);
 326         delta = T1-T0;
 327
 328         local_save_flags(flags);
 329
 330         pc = preempt_count();
 331
 332         if (!report_latency(delta))
 333                 goto out;
 334
 335         raw_spin_lock_irqsave(&max_trace_lock, flags);
 336
 337         /* check if we are still the max latency */
 338         if (!report_latency(delta))
 339                 goto out_unlock;
 340
 341         __trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
 342         /* Skip 5 functions to get to the irq/preempt enable function */
 343         __trace_stack(tr, flags, 5, pc);
 344
 345         if (data->critical_sequence != max_sequence)
 346                 goto out_unlock;
 347
 348         data->critical_end = parent_ip;
 349
 350         if (likely(!is_tracing_stopped())) {
 351                 tracing_max_latency = delta;
 352                 update_max_tr_single(tr, current, cpu);
 353         }
 354
 355         max_sequence++;
 356
 357 out_unlock:
 358         raw_spin_unlock_irqrestore(&max_trace_lock, flags);
 359
 360 out:
 361         data->critical_sequence = max_sequence;
 362         data->preempt_timestamp = ftrace_now(cpu);
 363         __trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
 364 }
 365
 366 static inline void
 367 start_critical_timing(unsigned long ip, unsigned long parent_ip)
 368 {
 369         int cpu;
 370         struct trace_array *tr = irqsoff_trace;
 371         struct trace_array_cpu *data;
 372         unsigned long flags;
 373
 374         if (likely(!tracer_enabled))
 375                 return;
 376
 377         cpu = raw_smp_processor_id();
 378
 379         if (per_cpu(tracing_cpu, cpu))
 380                 return;
 381
 382         data = tr->data[cpu];
 383
 384         if (unlikely(!data) || atomic_read(&data->disabled))
 385                 return;
 386
 387         atomic_inc(&data->disabled);
 388
 389         data->critical_sequence = max_sequence;
 390         data->preempt_timestamp = ftrace_now(cpu);
 391         data->critical_start = parent_ip ? : ip;
 392
 393         local_save_flags(flags);
 394
 395         __trace_function(tr, ip, parent_ip, flags, preempt_count());
 396
 397         per_cpu(tracing_cpu, cpu) = 1;
 398
 399         atomic_dec(&data->disabled);
 400 }
 401
 402 static inline void
 403 stop_critical_timing(unsigned long ip, unsigned long parent_ip)
 404 {
 405         int cpu;
 406         struct trace_array *tr = irqsoff_trace;
 407         struct trace_array_cpu *data;
 408         unsigned long flags;
 409
 410         cpu = raw_smp_processor_id();
 411         /* Always clear the tracing cpu on stopping the trace */
 412         if (unlikely(per_cpu(tracing_cpu, cpu)))
 413                 per_cpu(tracing_cpu, cpu) = 0;
 414         else
 415                 return;
 416
 417         if (!tracer_enabled)
 418                 return;
 419
 420         data = tr->data[cpu];
 421
 422         if (unlikely(!data) ||
 423             !data->critical_start || atomic_read(&data->disabled))
 424                 return;
 425
 426         atomic_inc(&data->disabled);
 427
 428         local_save_flags(flags);
 429         __trace_function(tr, ip, parent_ip, flags, preempt_count());
 430         check_critical_timing(tr, data, parent_ip ? : ip, cpu);
 431         data->critical_start = 0;
 432         atomic_dec(&data->disabled);
 433 }
 434
 435 /* start and stop critical timings used to for stoppage (in idle) */
 436 void start_critical_timings(void)
 437 {
 438         if (preempt_trace() || irq_trace())
 439                 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 440 }
 441 EXPORT_SYMBOL_GPL(start_critical_timings);
 442
 443 void stop_critical_timings(void)
 444 {
 445         if (preempt_trace() || irq_trace())
 446                 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 447 }
 448 EXPORT_SYMBOL_GPL(stop_critical_timings);
 449
 450 #ifdef CONFIG_IRQSOFF_TRACER
 451 #ifdef CONFIG_PROVE_LOCKING
 452 void time_hardirqs_on(unsigned long a0, unsigned long a1)
 453 {
 454         if (!preempt_trace() && irq_trace())
 455                 stop_critical_timing(a0, a1);
 456 }
 457
 458 void time_hardirqs_off(unsigned long a0, unsigned long a1)
 459 {
 460         if (!preempt_trace() && irq_trace())
 461                 start_critical_timing(a0, a1);
 462 }
 463
 464 #else /* !CONFIG_PROVE_LOCKING */
 465
 466 /*
 467  * Stubs:
 468  */
 469
 470 void trace_softirqs_on(unsigned long ip)
 471 {
 472 }
 473
 474 void trace_softirqs_off(unsigned long ip)
 475 {
 476 }
 477
 478 inline void print_irqtrace_events(struct task_struct *curr)
 479 {
 480 }
 481
 482 /*
 483  * We are only interested in hardirq on/off events:
 484  */
 485 void trace_hardirqs_on(void)
 486 {
 487         if (!preempt_trace() && irq_trace())
 488                 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 489 }
 490 EXPORT_SYMBOL(trace_hardirqs_on);
 491
 492 void trace_hardirqs_off(void)
 493 {
 494         if (!preempt_trace() && irq_trace())
 495                 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 496 }
 497 EXPORT_SYMBOL(trace_hardirqs_off);
 498
 499 void trace_hardirqs_on_caller(unsigned long caller_addr)
 500 {
 501         if (!preempt_trace() && irq_trace())
 502                 stop_critical_timing(CALLER_ADDR0, caller_addr);
 503 }
 504 EXPORT_SYMBOL(trace_hardirqs_on_caller);
 505
 506 void trace_hardirqs_off_caller(unsigned long caller_addr)
 507 {
 508         if (!preempt_trace() && irq_trace())
 509                 start_critical_timing(CALLER_ADDR0, caller_addr);
 510 }
 511 EXPORT_SYMBOL(trace_hardirqs_off_caller);
 512
 513 #endif /* CONFIG_PROVE_LOCKING */
 514 #endif /*  CONFIG_IRQSOFF_TRACER */
 515
 516 #ifdef CONFIG_PREEMPT_TRACER
 517 void trace_preempt_on(unsigned long a0, unsigned long a1)
 518 {
 519         if (preempt_trace() && !irq_trace())
 520                 stop_critical_timing(a0, a1);
 521 }
 522
 523 void trace_preempt_off(unsigned long a0, unsigned long a1)
 524 {
 525         if (preempt_trace() && !irq_trace())
 526                 start_critical_timing(a0, a1);
 527 }
 528 #endif /* CONFIG_PREEMPT_TRACER */
 529
 530 static int start_irqsoff_tracer(struct trace_array *tr, int graph)
 531 {
 532         int ret = 0;
 533
 534         if (!graph)
 535                 ret = register_ftrace_function(&trace_ops);
 536         else
 537                 ret = register_ftrace_graph(&irqsoff_graph_return,
 538                                             &irqsoff_graph_entry);
 539
 540         if (!ret && tracing_is_enabled())
 541                 tracer_enabled = 1;
 542         else
 543                 tracer_enabled = 0;
 544
 545         return ret;
 546 }
 547
 548 static void stop_irqsoff_tracer(struct trace_array *tr, int graph)
 549 {
 550         tracer_enabled = 0;
 551
 552         if (!graph)
 553                 unregister_ftrace_function(&trace_ops);
 554         else
 555                 unregister_ftrace_graph();
 556 }
 557
 558 static void __irqsoff_tracer_init(struct trace_array *tr)
 559 {
 560         save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
 561         trace_flags |= TRACE_ITER_LATENCY_FMT;
 562
 563         tracing_max_latency = 0;
 564         irqsoff_trace = tr;
 565         /* make sure that the tracer is visible */
 566         smp_wmb();
 567         tracing_reset_online_cpus(tr);
 568
 569         if (start_irqsoff_tracer(tr, is_graph()))
 570                 printk(KERN_ERR "failed to start irqsoff tracer\n");
 571 }
 572
 573 static void irqsoff_tracer_reset(struct trace_array *tr)
 574 {
 575         stop_irqsoff_tracer(tr, is_graph());
 576
 577         if (!save_lat_flag)
 578                 trace_flags &= ~TRACE_ITER_LATENCY_FMT;
 579 }
 580
 581 static void irqsoff_tracer_start(struct trace_array *tr)
 582 {
 583         tracer_enabled = 1;
 584 }
 585
 586 static void irqsoff_tracer_stop(struct trace_array *tr)
 587 {
 588         tracer_enabled = 0;
 589 }
 590
 591 #ifdef CONFIG_IRQSOFF_TRACER
 592 static int irqsoff_tracer_init(struct trace_array *tr)
 593 {
 594         trace_type = TRACER_IRQS_OFF;
 595
 596         __irqsoff_tracer_init(tr);
 597         return 0;
 598 }
 599 static struct tracer irqsoff_tracer __read_mostly =
 600 {
 601         .name           = "irqsoff",
 602         .init           = irqsoff_tracer_init,
 603         .reset          = irqsoff_tracer_reset,
 604         .start          = irqsoff_tracer_start,
 605         .stop           = irqsoff_tracer_stop,
 606         .print_max      = 1,
 607         .print_header   = irqsoff_print_header,
 608         .print_line     = irqsoff_print_line,
 609         .flags          = &tracer_flags,
 610         .set_flag       = irqsoff_set_flag,
 611 #ifdef CONFIG_FTRACE_SELFTEST
 612         .selftest    = trace_selftest_startup_irqsoff,
 613 #endif
 614         .open           = irqsoff_trace_open,
 615         .close          = irqsoff_trace_close,
 616         .use_max_tr     = 1,
 617 };
 618 # define register_irqsoff(trace) register_tracer(&trace)
 619 #else
 620 # define register_irqsoff(trace) do { } while (0)
 621 #endif
 622
 623 #ifdef CONFIG_PREEMPT_TRACER
 624 static int preemptoff_tracer_init(struct trace_array *tr)
 625 {
 626         trace_type = TRACER_PREEMPT_OFF;
 627
 628         __irqsoff_tracer_init(tr);
 629         return 0;
 630 }
 631
 632 static struct tracer preemptoff_tracer __read_mostly =
 633 {
 634         .name           = "preemptoff",
 635         .init           = preemptoff_tracer_init,
 636         .reset          = irqsoff_tracer_reset,
 637         .start          = irqsoff_tracer_start,
 638         .stop           = irqsoff_tracer_stop,
 639         .print_max      = 1,
 640         .print_header   = irqsoff_print_header,
 641         .print_line     = irqsoff_print_line,
 642         .flags          = &tracer_flags,
 643         .set_flag       = irqsoff_set_flag,
 644 #ifdef CONFIG_FTRACE_SELFTEST
 645         .selftest    = trace_selftest_startup_preemptoff,
 646 #endif
 647         .open           = irqsoff_trace_open,
 648         .close          = irqsoff_trace_close,
 649         .use_max_tr     = 1,
 650 };
 651 # define register_preemptoff(trace) register_tracer(&trace)
 652 #else
 653 # define register_preemptoff(trace) do { } while (0)
 654 #endif
 655
 656 #if defined(CONFIG_IRQSOFF_TRACER) && \
 657         defined(CONFIG_PREEMPT_TRACER)
 658
 659 static int preemptirqsoff_tracer_init(struct trace_array *tr)
 660 {
 661         trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
 662
 663         __irqsoff_tracer_init(tr);
 664         return 0;
 665 }
 666
 667 static struct tracer preemptirqsoff_tracer __read_mostly =
 668 {
 669         .name           = "preemptirqsoff",
 670         .init           = preemptirqsoff_tracer_init,
 671         .reset          = irqsoff_tracer_reset,
 672         .start          = irqsoff_tracer_start,
 673         .stop           = irqsoff_tracer_stop,
 674         .print_max      = 1,
 675         .print_header   = irqsoff_print_header,
 676         .print_line     = irqsoff_print_line,
 677         .flags          = &tracer_flags,
 678         .set_flag       = irqsoff_set_flag,
 679 #ifdef CONFIG_FTRACE_SELFTEST
 680         .selftest    = trace_selftest_startup_preemptirqsoff,
 681 #endif
 682         .open           = irqsoff_trace_open,
 683         .close          = irqsoff_trace_close,
 684         .use_max_tr     = 1,
 685 };
 686
 687 # define register_preemptirqsoff(trace) register_tracer(&trace)
 688 #else
 689 # define register_preemptirqsoff(trace) do { } while (0)
 690 #endif
 691
 692 __init static int init_irqsoff_tracer(void)
 693 {
 694         register_irqsoff(irqsoff_tracer);
 695         register_preemptoff(preemptoff_tracer);
 696         register_preemptirqsoff(preemptirqsoff_tracer);
 697
 698         return 0;
 699 }
 700 device_initcall(init_irqsoff_tracer);