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_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 };
 157 #endif /* CONFIG_FUNCTION_TRACER */
 158
 159 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 160 static int irqsoff_set_flag(u32 old_flags, u32 bit, int set)
 161 {
 162         int cpu;
 163
 164         if (!(bit & TRACE_DISPLAY_GRAPH))
 165                 return -EINVAL;
 166
 167         if (!(is_graph() ^ set))
 168                 return 0;
 169
 170         stop_irqsoff_tracer(irqsoff_trace, !set);
 171
 172         for_each_possible_cpu(cpu)
 173                 per_cpu(tracing_cpu, cpu) = 0;
 174
 175         tracing_max_latency = 0;
 176         tracing_reset_online_cpus(irqsoff_trace);
 177
 178         return start_irqsoff_tracer(irqsoff_trace, set);
 179 }
 180
 181 static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
 182 {
 183         struct trace_array *tr = irqsoff_trace;
 184         struct trace_array_cpu *data;
 185         unsigned long flags;
 186         int ret;
 187         int pc;
 188
 189         if (!func_prolog_dec(tr, &data, &flags))
 190                 return 0;
 191
 192         pc = preempt_count();
 193         ret = __trace_graph_entry(tr, trace, flags, pc);
 194         atomic_dec(&data->disabled);
 195
 196         return ret;
 197 }
 198
 199 static void irqsoff_graph_return(struct ftrace_graph_ret *trace)
 200 {
 201         struct trace_array *tr = irqsoff_trace;
 202         struct trace_array_cpu *data;
 203         unsigned long flags;
 204         int pc;
 205
 206         if (!func_prolog_dec(tr, &data, &flags))
 207                 return;
 208
 209         pc = preempt_count();
 210         __trace_graph_return(tr, trace, flags, pc);
 211         atomic_dec(&data->disabled);
 212 }
 213
 214 static void irqsoff_trace_open(struct trace_iterator *iter)
 215 {
 216         if (is_graph())
 217                 graph_trace_open(iter);
 218
 219 }
 220
 221 static void irqsoff_trace_close(struct trace_iterator *iter)
 222 {
 223         if (iter->private)
 224                 graph_trace_close(iter);
 225 }
 226
 227 #define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_CPU | \
 228                             TRACE_GRAPH_PRINT_PROC)
 229
 230 static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
 231 {
 232         /*
 233          * In graph mode call the graph tracer output function,
 234          * otherwise go with the TRACE_FN event handler
 235          */
 236         if (is_graph())
 237                 return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS);
 238
 239         return TRACE_TYPE_UNHANDLED;
 240 }
 241
 242 static void irqsoff_print_header(struct seq_file *s)
 243 {
 244         if (is_graph())
 245                 print_graph_headers_flags(s, GRAPH_TRACER_FLAGS);
 246         else
 247                 trace_default_header(s);
 248 }
 249
 250 static void
 251 __trace_function(struct trace_array *tr,
 252                  unsigned long ip, unsigned long parent_ip,
 253                  unsigned long flags, int pc)
 254 {
 255         if (is_graph())
 256                 trace_graph_function(tr, ip, parent_ip, flags, pc);
 257         else
 258                 trace_function(tr, ip, parent_ip, flags, pc);
 259 }
 260
 261 #else
 262 #define __trace_function trace_function
 263
 264 static int irqsoff_set_flag(u32 old_flags, u32 bit, int set)
 265 {
 266         return -EINVAL;
 267 }
 268
 269 static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
 270 {
 271         return -1;
 272 }
 273
 274 static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
 275 {
 276         return TRACE_TYPE_UNHANDLED;
 277 }
 278
 279 static void irqsoff_graph_return(struct ftrace_graph_ret *trace) { }
 280 static void irqsoff_print_header(struct seq_file *s) { }
 281 static void irqsoff_trace_open(struct trace_iterator *iter) { }
 282 static void irqsoff_trace_close(struct trace_iterator *iter) { }
 283 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 284
 285 /*
 286  * Should this new latency be reported/recorded?
 287  */
 288 static int report_latency(cycle_t delta)
 289 {
 290         if (tracing_thresh) {
 291                 if (delta < tracing_thresh)
 292                         return 0;
 293         } else {
 294                 if (delta <= tracing_max_latency)
 295                         return 0;
 296         }
 297         return 1;
 298 }
 299
 300 static void
 301 check_critical_timing(struct trace_array *tr,
 302                       struct trace_array_cpu *data,
 303                       unsigned long parent_ip,
 304                       int cpu)
 305 {
 306         cycle_t T0, T1, delta;
 307         unsigned long flags;
 308         int pc;
 309
 310         T0 = data->preempt_timestamp;
 311         T1 = ftrace_now(cpu);
 312         delta = T1-T0;
 313
 314         local_save_flags(flags);
 315
 316         pc = preempt_count();
 317
 318         if (!report_latency(delta))
 319                 goto out;
 320
 321         spin_lock_irqsave(&max_trace_lock, flags);
 322
 323         /* check if we are still the max latency */
 324         if (!report_latency(delta))
 325                 goto out_unlock;
 326
 327         __trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
 328         /* Skip 5 functions to get to the irq/preempt enable function */
 329         __trace_stack(tr, flags, 5, pc);
 330
 331         if (data->critical_sequence != max_sequence)
 332                 goto out_unlock;
 333
 334         data->critical_end = parent_ip;
 335
 336         if (likely(!is_tracing_stopped())) {
 337                 tracing_max_latency = delta;
 338                 update_max_tr_single(tr, current, cpu);
 339         }
 340
 341         max_sequence++;
 342
 343 out_unlock:
 344         spin_unlock_irqrestore(&max_trace_lock, flags);
 345
 346 out:
 347         data->critical_sequence = max_sequence;
 348         data->preempt_timestamp = ftrace_now(cpu);
 349         __trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
 350 }
 351
 352 static inline void
 353 start_critical_timing(unsigned long ip, unsigned long parent_ip)
 354 {
 355         int cpu;
 356         struct trace_array *tr = irqsoff_trace;
 357         struct trace_array_cpu *data;
 358         unsigned long flags;
 359
 360         if (likely(!tracer_enabled))
 361                 return;
 362
 363         cpu = raw_smp_processor_id();
 364
 365         if (per_cpu(tracing_cpu, cpu))
 366                 return;
 367
 368         data = tr->data[cpu];
 369
 370         if (unlikely(!data) || atomic_read(&data->disabled))
 371                 return;
 372
 373         atomic_inc(&data->disabled);
 374
 375         data->critical_sequence = max_sequence;
 376         data->preempt_timestamp = ftrace_now(cpu);
 377         data->critical_start = parent_ip ? : ip;
 378
 379         local_save_flags(flags);
 380
 381         __trace_function(tr, ip, parent_ip, flags, preempt_count());
 382
 383         per_cpu(tracing_cpu, cpu) = 1;
 384
 385         atomic_dec(&data->disabled);
 386 }
 387
 388 static inline void
 389 stop_critical_timing(unsigned long ip, unsigned long parent_ip)
 390 {
 391         int cpu;
 392         struct trace_array *tr = irqsoff_trace;
 393         struct trace_array_cpu *data;
 394         unsigned long flags;
 395
 396         cpu = raw_smp_processor_id();
 397         /* Always clear the tracing cpu on stopping the trace */
 398         if (unlikely(per_cpu(tracing_cpu, cpu)))
 399                 per_cpu(tracing_cpu, cpu) = 0;
 400         else
 401                 return;
 402
 403         if (!tracer_enabled)
 404                 return;
 405
 406         data = tr->data[cpu];
 407
 408         if (unlikely(!data) ||
 409             !data->critical_start || atomic_read(&data->disabled))
 410                 return;
 411
 412         atomic_inc(&data->disabled);
 413
 414         local_save_flags(flags);
 415         __trace_function(tr, ip, parent_ip, flags, preempt_count());
 416         check_critical_timing(tr, data, parent_ip ? : ip, cpu);
 417         data->critical_start = 0;
 418         atomic_dec(&data->disabled);
 419 }
 420
 421 /* start and stop critical timings used to for stoppage (in idle) */
 422 void start_critical_timings(void)
 423 {
 424         if (preempt_trace() || irq_trace())
 425                 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 426 }
 427 EXPORT_SYMBOL_GPL(start_critical_timings);
 428
 429 void stop_critical_timings(void)
 430 {
 431         if (preempt_trace() || irq_trace())
 432                 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 433 }
 434 EXPORT_SYMBOL_GPL(stop_critical_timings);
 435
 436 #ifdef CONFIG_IRQSOFF_TRACER
 437 #ifdef CONFIG_PROVE_LOCKING
 438 void time_hardirqs_on(unsigned long a0, unsigned long a1)
 439 {
 440         if (!preempt_trace() && irq_trace())
 441                 stop_critical_timing(a0, a1);
 442 }
 443
 444 void time_hardirqs_off(unsigned long a0, unsigned long a1)
 445 {
 446         if (!preempt_trace() && irq_trace())
 447                 start_critical_timing(a0, a1);
 448 }
 449
 450 #else /* !CONFIG_PROVE_LOCKING */
 451
 452 /*
 453  * Stubs:
 454  */
 455
 456 void trace_softirqs_on(unsigned long ip)
 457 {
 458 }
 459
 460 void trace_softirqs_off(unsigned long ip)
 461 {
 462 }
 463
 464 inline void print_irqtrace_events(struct task_struct *curr)
 465 {
 466 }
 467
 468 /*
 469  * We are only interested in hardirq on/off events:
 470  */
 471 void trace_hardirqs_on(void)
 472 {
 473         if (!preempt_trace() && irq_trace())
 474                 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 475 }
 476 EXPORT_SYMBOL(trace_hardirqs_on);
 477
 478 void trace_hardirqs_off(void)
 479 {
 480         if (!preempt_trace() && irq_trace())
 481                 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 482 }
 483 EXPORT_SYMBOL(trace_hardirqs_off);
 484
 485 void trace_hardirqs_on_caller(unsigned long caller_addr)
 486 {
 487         if (!preempt_trace() && irq_trace())
 488                 stop_critical_timing(CALLER_ADDR0, caller_addr);
 489 }
 490 EXPORT_SYMBOL(trace_hardirqs_on_caller);
 491
 492 void trace_hardirqs_off_caller(unsigned long caller_addr)
 493 {
 494         if (!preempt_trace() && irq_trace())
 495                 start_critical_timing(CALLER_ADDR0, caller_addr);
 496 }
 497 EXPORT_SYMBOL(trace_hardirqs_off_caller);
 498
 499 #endif /* CONFIG_PROVE_LOCKING */
 500 #endif /*  CONFIG_IRQSOFF_TRACER */
 501
 502 #ifdef CONFIG_PREEMPT_TRACER
 503 void trace_preempt_on(unsigned long a0, unsigned long a1)
 504 {
 505         if (preempt_trace())
 506                 stop_critical_timing(a0, a1);
 507 }
 508
 509 void trace_preempt_off(unsigned long a0, unsigned long a1)
 510 {
 511         if (preempt_trace())
 512                 start_critical_timing(a0, a1);
 513 }
 514 #endif /* CONFIG_PREEMPT_TRACER */
 515
 516 static int start_irqsoff_tracer(struct trace_array *tr, int graph)
 517 {
 518         int ret = 0;
 519
 520         if (!graph)
 521                 ret = register_ftrace_function(&trace_ops);
 522         else
 523                 ret = register_ftrace_graph(&irqsoff_graph_return,
 524                                             &irqsoff_graph_entry);
 525
 526         if (!ret && tracing_is_enabled())
 527                 tracer_enabled = 1;
 528         else
 529                 tracer_enabled = 0;
 530
 531         return ret;
 532 }
 533
 534 static void stop_irqsoff_tracer(struct trace_array *tr, int graph)
 535 {
 536         tracer_enabled = 0;
 537
 538         if (!graph)
 539                 unregister_ftrace_function(&trace_ops);
 540         else
 541                 unregister_ftrace_graph();
 542 }
 543
 544 static void __irqsoff_tracer_init(struct trace_array *tr)
 545 {
 546         save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
 547         trace_flags |= TRACE_ITER_LATENCY_FMT;
 548
 549         tracing_max_latency = 0;
 550         irqsoff_trace = tr;
 551         /* make sure that the tracer is visible */
 552         smp_wmb();
 553         tracing_reset_online_cpus(tr);
 554
 555         if (start_irqsoff_tracer(tr, is_graph()))
 556                 printk(KERN_ERR "failed to start irqsoff tracer\n");
 557 }
 558
 559 static void irqsoff_tracer_reset(struct trace_array *tr)
 560 {
 561         stop_irqsoff_tracer(tr, is_graph());
 562
 563         if (!save_lat_flag)
 564                 trace_flags &= ~TRACE_ITER_LATENCY_FMT;
 565 }
 566
 567 static void irqsoff_tracer_start(struct trace_array *tr)
 568 {
 569         tracer_enabled = 1;
 570 }
 571
 572 static void irqsoff_tracer_stop(struct trace_array *tr)
 573 {
 574         tracer_enabled = 0;
 575 }
 576
 577 #ifdef CONFIG_IRQSOFF_TRACER
 578 static int irqsoff_tracer_init(struct trace_array *tr)
 579 {
 580         trace_type = TRACER_IRQS_OFF;
 581
 582         __irqsoff_tracer_init(tr);
 583         return 0;
 584 }
 585 static struct tracer irqsoff_tracer __read_mostly =
 586 {
 587         .name           = "irqsoff",
 588         .init           = irqsoff_tracer_init,
 589         .reset          = irqsoff_tracer_reset,
 590         .start          = irqsoff_tracer_start,
 591         .stop           = irqsoff_tracer_stop,
 592         .print_max      = 1,
 593         .print_header   = irqsoff_print_header,
 594         .print_line     = irqsoff_print_line,
 595         .flags          = &tracer_flags,
 596         .set_flag       = irqsoff_set_flag,
 597 #ifdef CONFIG_FTRACE_SELFTEST
 598         .selftest    = trace_selftest_startup_irqsoff,
 599 #endif
 600         .open           = irqsoff_trace_open,
 601         .close          = irqsoff_trace_close,
 602         .use_max_tr     = 1,
 603 };
 604 # define register_irqsoff(trace) register_tracer(&trace)
 605 #else
 606 # define register_irqsoff(trace) do { } while (0)
 607 #endif
 608
 609 #ifdef CONFIG_PREEMPT_TRACER
 610 static int preemptoff_tracer_init(struct trace_array *tr)
 611 {
 612         trace_type = TRACER_PREEMPT_OFF;
 613
 614         __irqsoff_tracer_init(tr);
 615         return 0;
 616 }
 617
 618 static struct tracer preemptoff_tracer __read_mostly =
 619 {
 620         .name           = "preemptoff",
 621         .init           = preemptoff_tracer_init,
 622         .reset          = irqsoff_tracer_reset,
 623         .start          = irqsoff_tracer_start,
 624         .stop           = irqsoff_tracer_stop,
 625         .print_max      = 1,
 626         .print_header   = irqsoff_print_header,
 627         .print_line     = irqsoff_print_line,
 628         .flags          = &tracer_flags,
 629         .set_flag       = irqsoff_set_flag,
 630 #ifdef CONFIG_FTRACE_SELFTEST
 631         .selftest    = trace_selftest_startup_preemptoff,
 632 #endif
 633         .open           = irqsoff_trace_open,
 634         .close          = irqsoff_trace_close,
 635         .use_max_tr     = 1,
 636 };
 637 # define register_preemptoff(trace) register_tracer(&trace)
 638 #else
 639 # define register_preemptoff(trace) do { } while (0)
 640 #endif
 641
 642 #if defined(CONFIG_IRQSOFF_TRACER) && \
 643         defined(CONFIG_PREEMPT_TRACER)
 644
 645 static int preemptirqsoff_tracer_init(struct trace_array *tr)
 646 {
 647         trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
 648
 649         __irqsoff_tracer_init(tr);
 650         return 0;
 651 }
 652
 653 static struct tracer preemptirqsoff_tracer __read_mostly =
 654 {
 655         .name           = "preemptirqsoff",
 656         .init           = preemptirqsoff_tracer_init,
 657         .reset          = irqsoff_tracer_reset,
 658         .start          = irqsoff_tracer_start,
 659         .stop           = irqsoff_tracer_stop,
 660         .print_max      = 1,
 661         .print_header   = irqsoff_print_header,
 662         .print_line     = irqsoff_print_line,
 663         .flags          = &tracer_flags,
 664         .set_flag       = irqsoff_set_flag,
 665 #ifdef CONFIG_FTRACE_SELFTEST
 666         .selftest    = trace_selftest_startup_preemptirqsoff,
 667 #endif
 668         .open           = irqsoff_trace_open,
 669         .close          = irqsoff_trace_close,
 670         .use_max_tr     = 1,
 671 };
 672
 673 # define register_preemptirqsoff(trace) register_tracer(&trace)
 674 #else
 675 # define register_preemptirqsoff(trace) do { } while (0)
 676 #endif
 677
 678 __init static int init_irqsoff_tracer(void)
 679 {
 680         register_irqsoff(irqsoff_tracer);
 681         register_preemptoff(preemptoff_tracer);
 682         register_preemptirqsoff(preemptirqsoff_tracer);
 683
 684         return 0;
 685 }
 686 device_initcall(init_irqsoff_tracer);