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   1 /*
   2  * trace irqs off criticall 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 #ifdef CONFIG_PREEMPT_TRACER
  36 static inline int
  37 preempt_trace(void)
  38 {
  39         return ((trace_type & TRACER_PREEMPT_OFF) && preempt_count());
  40 }
  41 #else
  42 # define preempt_trace() (0)
  43 #endif
  44
  45 #ifdef CONFIG_IRQSOFF_TRACER
  46 static inline int
  47 irq_trace(void)
  48 {
  49         return ((trace_type & TRACER_IRQS_OFF) &&
  50                 irqs_disabled());
  51 }
  52 #else
  53 # define irq_trace() (0)
  54 #endif
  55
  56 /*
  57  * Sequence count - we record it when starting a measurement and
  58  * skip the latency if the sequence has changed - some other section
  59  * did a maximum and could disturb our measurement with serial console
  60  * printouts, etc. Truly coinciding maximum latencies should be rare
  61  * and what happens together happens separately as well, so this doesnt
  62  * decrease the validity of the maximum found:
  63  */
  64 static __cacheline_aligned_in_smp       unsigned long max_sequence;
  65
  66 #ifdef CONFIG_FTRACE
  67 /*
  68  * irqsoff uses its own tracer function to keep the overhead down:
  69  */
  70 static void
  71 irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip)
  72 {
  73         struct trace_array *tr = irqsoff_trace;
  74         struct trace_array_cpu *data;
  75         unsigned long flags;
  76         long disabled;
  77         int cpu;
  78
  79         /*
  80          * Does not matter if we preempt. We test the flags
  81          * afterward, to see if irqs are disabled or not.
  82          * If we preempt and get a false positive, the flags
  83          * test will fail.
  84          */
  85         cpu = raw_smp_processor_id();
  86         if (likely(!per_cpu(tracing_cpu, cpu)))
  87                 return;
  88
  89         local_save_flags(flags);
  90         /* slight chance to get a false positive on tracing_cpu */
  91         if (!irqs_disabled_flags(flags))
  92                 return;
  93
  94         data = tr->data[cpu];
  95         disabled = atomic_inc_return(&data->disabled);
  96
  97         if (likely(disabled == 1))
  98                 trace_function(tr, data, ip, parent_ip, flags);
  99
 100         atomic_dec(&data->disabled);
 101 }
 102
 103 static struct ftrace_ops trace_ops __read_mostly =
 104 {
 105         .func = irqsoff_tracer_call,
 106 };
 107 #endif /* CONFIG_FTRACE */
 108
 109 /*
 110  * Should this new latency be reported/recorded?
 111  */
 112 static int report_latency(cycle_t delta)
 113 {
 114         if (tracing_thresh) {
 115                 if (delta < tracing_thresh)
 116                         return 0;
 117         } else {
 118                 if (delta <= tracing_max_latency)
 119                         return 0;
 120         }
 121         return 1;
 122 }
 123
 124 static void
 125 check_critical_timing(struct trace_array *tr,
 126                       struct trace_array_cpu *data,
 127                       unsigned long parent_ip,
 128                       int cpu)
 129 {
 130         unsigned long latency, t0, t1;
 131         cycle_t T0, T1, delta;
 132         unsigned long flags;
 133
 134         /*
 135          * usecs conversion is slow so we try to delay the conversion
 136          * as long as possible:
 137          */
 138         T0 = data->preempt_timestamp;
 139         T1 = ftrace_now(cpu);
 140         delta = T1-T0;
 141
 142         local_save_flags(flags);
 143
 144         if (!report_latency(delta))
 145                 goto out;
 146
 147         spin_lock_irqsave(&max_trace_lock, flags);
 148
 149         /* check if we are still the max latency */
 150         if (!report_latency(delta))
 151                 goto out_unlock;
 152
 153         trace_function(tr, data, CALLER_ADDR0, parent_ip, flags);
 154
 155         latency = nsecs_to_usecs(delta);
 156
 157         if (data->critical_sequence != max_sequence)
 158                 goto out_unlock;
 159
 160         tracing_max_latency = delta;
 161         t0 = nsecs_to_usecs(T0);
 162         t1 = nsecs_to_usecs(T1);
 163
 164         data->critical_end = parent_ip;
 165
 166         update_max_tr_single(tr, current, cpu);
 167
 168         if (!runqueue_is_locked()) {
 169                 if (tracing_thresh) {
 170                         printk(KERN_INFO "(%16s-%-5d|#%d): %lu us critical"
 171                                " section violates %lu us threshold.\n",
 172                                current->comm, current->pid,
 173                                raw_smp_processor_id(),
 174                                latency, nsecs_to_usecs(tracing_thresh));
 175                 } else {
 176                         printk(KERN_INFO "(%16s-%-5d|#%d): new %lu us"
 177                                " maximum-latency critical section.\n",
 178                                current->comm, current->pid,
 179                                raw_smp_processor_id(),
 180                                latency);
 181                 }
 182         }
 183
 184         max_sequence++;
 185
 186 out_unlock:
 187         spin_unlock_irqrestore(&max_trace_lock, flags);
 188
 189 out:
 190         data->critical_sequence = max_sequence;
 191         data->preempt_timestamp = ftrace_now(cpu);
 192         tracing_reset(data);
 193         trace_function(tr, data, CALLER_ADDR0, parent_ip, flags);
 194 }
 195
 196 static inline void
 197 start_critical_timing(unsigned long ip, unsigned long parent_ip)
 198 {
 199         int cpu;
 200         struct trace_array *tr = irqsoff_trace;
 201         struct trace_array_cpu *data;
 202         unsigned long flags;
 203
 204         if (likely(!tracer_enabled))
 205                 return;
 206
 207         if (__get_cpu_var(tracing_cpu))
 208                 return;
 209
 210         cpu = raw_smp_processor_id();
 211         data = tr->data[cpu];
 212
 213         if (unlikely(!data) || unlikely(!head_page(data)) ||
 214             atomic_read(&data->disabled))
 215                 return;
 216
 217         atomic_inc(&data->disabled);
 218
 219         data->critical_sequence = max_sequence;
 220         data->preempt_timestamp = ftrace_now(cpu);
 221         data->critical_start = parent_ip ? : ip;
 222         tracing_reset(data);
 223
 224         local_save_flags(flags);
 225
 226         trace_function(tr, data, ip, parent_ip, flags);
 227
 228         __get_cpu_var(tracing_cpu) = 1;
 229
 230         atomic_dec(&data->disabled);
 231 }
 232
 233 static inline void
 234 stop_critical_timing(unsigned long ip, unsigned long parent_ip)
 235 {
 236         int cpu;
 237         struct trace_array *tr = irqsoff_trace;
 238         struct trace_array_cpu *data;
 239         unsigned long flags;
 240
 241         /* Always clear the tracing cpu on stopping the trace */
 242         if (unlikely(__get_cpu_var(tracing_cpu)))
 243                 __get_cpu_var(tracing_cpu) = 0;
 244         else
 245                 return;
 246
 247         if (!tracer_enabled)
 248                 return;
 249
 250         cpu = raw_smp_processor_id();
 251         data = tr->data[cpu];
 252
 253         if (unlikely(!data) || unlikely(!head_page(data)) ||
 254             !data->critical_start || atomic_read(&data->disabled))
 255                 return;
 256
 257         atomic_inc(&data->disabled);
 258         local_save_flags(flags);
 259         trace_function(tr, data, ip, parent_ip, flags);
 260         check_critical_timing(tr, data, parent_ip ? : ip, cpu);
 261         data->critical_start = 0;
 262         atomic_dec(&data->disabled);
 263 }
 264
 265 /* start and stop critical timings used to for stoppage (in idle) */
 266 void start_critical_timings(void)
 267 {
 268         if (preempt_trace() || irq_trace())
 269                 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 270 }
 271
 272 void stop_critical_timings(void)
 273 {
 274         if (preempt_trace() || irq_trace())
 275                 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 276 }
 277
 278 #ifdef CONFIG_IRQSOFF_TRACER
 279 #ifdef CONFIG_PROVE_LOCKING
 280 void time_hardirqs_on(unsigned long a0, unsigned long a1)
 281 {
 282         if (!preempt_trace() && irq_trace())
 283                 stop_critical_timing(a0, a1);
 284 }
 285
 286 void time_hardirqs_off(unsigned long a0, unsigned long a1)
 287 {
 288         if (!preempt_trace() && irq_trace())
 289                 start_critical_timing(a0, a1);
 290 }
 291
 292 #else /* !CONFIG_PROVE_LOCKING */
 293
 294 /*
 295  * Stubs:
 296  */
 297
 298 void early_boot_irqs_off(void)
 299 {
 300 }
 301
 302 void early_boot_irqs_on(void)
 303 {
 304 }
 305
 306 void trace_softirqs_on(unsigned long ip)
 307 {
 308 }
 309
 310 void trace_softirqs_off(unsigned long ip)
 311 {
 312 }
 313
 314 inline void print_irqtrace_events(struct task_struct *curr)
 315 {
 316 }
 317
 318 /*
 319  * We are only interested in hardirq on/off events:
 320  */
 321 void trace_hardirqs_on(void)
 322 {
 323         if (!preempt_trace() && irq_trace())
 324                 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 325 }
 326 EXPORT_SYMBOL(trace_hardirqs_on);
 327
 328 void trace_hardirqs_off(void)
 329 {
 330         if (!preempt_trace() && irq_trace())
 331                 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 332 }
 333 EXPORT_SYMBOL(trace_hardirqs_off);
 334
 335 void trace_hardirqs_on_caller(unsigned long caller_addr)
 336 {
 337         if (!preempt_trace() && irq_trace())
 338                 stop_critical_timing(CALLER_ADDR0, caller_addr);
 339 }
 340 EXPORT_SYMBOL(trace_hardirqs_on_caller);
 341
 342 void trace_hardirqs_off_caller(unsigned long caller_addr)
 343 {
 344         if (!preempt_trace() && irq_trace())
 345                 start_critical_timing(CALLER_ADDR0, caller_addr);
 346 }
 347 EXPORT_SYMBOL(trace_hardirqs_off_caller);
 348
 349 #endif /* CONFIG_PROVE_LOCKING */
 350 #endif /*  CONFIG_IRQSOFF_TRACER */
 351
 352 #ifdef CONFIG_PREEMPT_TRACER
 353 void trace_preempt_on(unsigned long a0, unsigned long a1)
 354 {
 355         stop_critical_timing(a0, a1);
 356 }
 357
 358 void trace_preempt_off(unsigned long a0, unsigned long a1)
 359 {
 360         start_critical_timing(a0, a1);
 361 }
 362 #endif /* CONFIG_PREEMPT_TRACER */
 363
 364 static void start_irqsoff_tracer(struct trace_array *tr)
 365 {
 366         register_ftrace_function(&trace_ops);
 367         tracer_enabled = 1;
 368 }
 369
 370 static void stop_irqsoff_tracer(struct trace_array *tr)
 371 {
 372         tracer_enabled = 0;
 373         unregister_ftrace_function(&trace_ops);
 374 }
 375
 376 static void __irqsoff_tracer_init(struct trace_array *tr)
 377 {
 378         irqsoff_trace = tr;
 379         /* make sure that the tracer is visibel */
 380         smp_wmb();
 381
 382         if (tr->ctrl)
 383                 start_irqsoff_tracer(tr);
 384 }
 385
 386 static void irqsoff_tracer_reset(struct trace_array *tr)
 387 {
 388         if (tr->ctrl)
 389                 stop_irqsoff_tracer(tr);
 390 }
 391
 392 static void irqsoff_tracer_ctrl_update(struct trace_array *tr)
 393 {
 394         if (tr->ctrl)
 395                 start_irqsoff_tracer(tr);
 396         else
 397                 stop_irqsoff_tracer(tr);
 398 }
 399
 400 static void irqsoff_tracer_open(struct trace_iterator *iter)
 401 {
 402         /* stop the trace while dumping */
 403         if (iter->tr->ctrl)
 404                 stop_irqsoff_tracer(iter->tr);
 405 }
 406
 407 static void irqsoff_tracer_close(struct trace_iterator *iter)
 408 {
 409         if (iter->tr->ctrl)
 410                 start_irqsoff_tracer(iter->tr);
 411 }
 412
 413 #ifdef CONFIG_IRQSOFF_TRACER
 414 static void irqsoff_tracer_init(struct trace_array *tr)
 415 {
 416         trace_type = TRACER_IRQS_OFF;
 417
 418         __irqsoff_tracer_init(tr);
 419 }
 420 static struct tracer irqsoff_tracer __read_mostly =
 421 {
 422         .name           = "irqsoff",
 423         .init           = irqsoff_tracer_init,
 424         .reset          = irqsoff_tracer_reset,
 425         .open           = irqsoff_tracer_open,
 426         .close          = irqsoff_tracer_close,
 427         .ctrl_update    = irqsoff_tracer_ctrl_update,
 428         .print_max      = 1,
 429 #ifdef CONFIG_FTRACE_SELFTEST
 430         .selftest    = trace_selftest_startup_irqsoff,
 431 #endif
 432 };
 433 # define register_irqsoff(trace) register_tracer(&trace)
 434 #else
 435 # define register_irqsoff(trace) do { } while (0)
 436 #endif
 437
 438 #ifdef CONFIG_PREEMPT_TRACER
 439 static void preemptoff_tracer_init(struct trace_array *tr)
 440 {
 441         trace_type = TRACER_PREEMPT_OFF;
 442
 443         __irqsoff_tracer_init(tr);
 444 }
 445
 446 static struct tracer preemptoff_tracer __read_mostly =
 447 {
 448         .name           = "preemptoff",
 449         .init           = preemptoff_tracer_init,
 450         .reset          = irqsoff_tracer_reset,
 451         .open           = irqsoff_tracer_open,
 452         .close          = irqsoff_tracer_close,
 453         .ctrl_update    = irqsoff_tracer_ctrl_update,
 454         .print_max      = 1,
 455 #ifdef CONFIG_FTRACE_SELFTEST
 456         .selftest    = trace_selftest_startup_preemptoff,
 457 #endif
 458 };
 459 # define register_preemptoff(trace) register_tracer(&trace)
 460 #else
 461 # define register_preemptoff(trace) do { } while (0)
 462 #endif
 463
 464 #if defined(CONFIG_IRQSOFF_TRACER) && \
 465         defined(CONFIG_PREEMPT_TRACER)
 466
 467 static void preemptirqsoff_tracer_init(struct trace_array *tr)
 468 {
 469         trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
 470
 471         __irqsoff_tracer_init(tr);
 472 }
 473
 474 static struct tracer preemptirqsoff_tracer __read_mostly =
 475 {
 476         .name           = "preemptirqsoff",
 477         .init           = preemptirqsoff_tracer_init,
 478         .reset          = irqsoff_tracer_reset,
 479         .open           = irqsoff_tracer_open,
 480         .close          = irqsoff_tracer_close,
 481         .ctrl_update    = irqsoff_tracer_ctrl_update,
 482         .print_max      = 1,
 483 #ifdef CONFIG_FTRACE_SELFTEST
 484         .selftest    = trace_selftest_startup_preemptirqsoff,
 485 #endif
 486 };
 487
 488 # define register_preemptirqsoff(trace) register_tracer(&trace)
 489 #else
 490 # define register_preemptirqsoff(trace) do { } while (0)
 491 #endif
 492
 493 __init static int init_irqsoff_tracer(void)
 494 {
 495         register_irqsoff(irqsoff_tracer);
 496         register_preemptoff(preemptoff_tracer);
 497         register_preemptirqsoff(preemptirqsoff_tracer);
 498
 499         return 0;
 500 }
 501 device_initcall(init_irqsoff_tracer);