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