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