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         cycle_t T0, T1, delta;
 133         unsigned long flags;
 134         int pc;
 135
 136         T0 = data->preempt_timestamp;
 137         T1 = ftrace_now(cpu);
 138         delta = T1-T0;
 139
 140         local_save_flags(flags);
 141
 142         pc = preempt_count();
 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, CALLER_ADDR0, parent_ip, flags, pc);
 154
 155         if (data->critical_sequence != max_sequence)
 156                 goto out_unlock;
 157
 158         data->critical_end = parent_ip;
 159
 160         if (likely(!is_tracing_stopped())) {
 161                 tracing_max_latency = delta;
 162                 update_max_tr_single(tr, current, cpu);
 163         }
 164
 165         max_sequence++;
 166
 167 out_unlock:
 168         spin_unlock_irqrestore(&max_trace_lock, flags);
 169
 170 out:
 171         data->critical_sequence = max_sequence;
 172         data->preempt_timestamp = ftrace_now(cpu);
 173         trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
 174 }
 175
 176 static inline void
 177 start_critical_timing(unsigned long ip, unsigned long parent_ip)
 178 {
 179         int cpu;
 180         struct trace_array *tr = irqsoff_trace;
 181         struct trace_array_cpu *data;
 182         unsigned long flags;
 183
 184         if (likely(!tracer_enabled))
 185                 return;
 186
 187         cpu = raw_smp_processor_id();
 188
 189         if (per_cpu(tracing_cpu, cpu))
 190                 return;
 191
 192         data = tr->data[cpu];
 193
 194         if (unlikely(!data) || atomic_read(&data->disabled))
 195                 return;
 196
 197         atomic_inc(&data->disabled);
 198
 199         data->critical_sequence = max_sequence;
 200         data->preempt_timestamp = ftrace_now(cpu);
 201         data->critical_start = parent_ip ? : ip;
 202
 203         local_save_flags(flags);
 204
 205         trace_function(tr, ip, parent_ip, flags, preempt_count());
 206
 207         per_cpu(tracing_cpu, cpu) = 1;
 208
 209         atomic_dec(&data->disabled);
 210 }
 211
 212 static inline void
 213 stop_critical_timing(unsigned long ip, unsigned long parent_ip)
 214 {
 215         int cpu;
 216         struct trace_array *tr = irqsoff_trace;
 217         struct trace_array_cpu *data;
 218         unsigned long flags;
 219
 220         cpu = raw_smp_processor_id();
 221         /* Always clear the tracing cpu on stopping the trace */
 222         if (unlikely(per_cpu(tracing_cpu, cpu)))
 223                 per_cpu(tracing_cpu, cpu) = 0;
 224         else
 225                 return;
 226
 227         if (!tracer_enabled)
 228                 return;
 229
 230         data = tr->data[cpu];
 231
 232         if (unlikely(!data) ||
 233             !data->critical_start || atomic_read(&data->disabled))
 234                 return;
 235
 236         atomic_inc(&data->disabled);
 237
 238         local_save_flags(flags);
 239         trace_function(tr, ip, parent_ip, flags, preempt_count());
 240         check_critical_timing(tr, data, parent_ip ? : ip, cpu);
 241         data->critical_start = 0;
 242         atomic_dec(&data->disabled);
 243 }
 244
 245 /* start and stop critical timings used to for stoppage (in idle) */
 246 void start_critical_timings(void)
 247 {
 248         if (preempt_trace() || irq_trace())
 249                 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 250 }
 251 EXPORT_SYMBOL_GPL(start_critical_timings);
 252
 253 void stop_critical_timings(void)
 254 {
 255         if (preempt_trace() || irq_trace())
 256                 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 257 }
 258 EXPORT_SYMBOL_GPL(stop_critical_timings);
 259
 260 #ifdef CONFIG_IRQSOFF_TRACER
 261 #ifdef CONFIG_PROVE_LOCKING
 262 void time_hardirqs_on(unsigned long a0, unsigned long a1)
 263 {
 264         if (!preempt_trace() && irq_trace())
 265                 stop_critical_timing(a0, a1);
 266 }
 267
 268 void time_hardirqs_off(unsigned long a0, unsigned long a1)
 269 {
 270         if (!preempt_trace() && irq_trace())
 271                 start_critical_timing(a0, a1);
 272 }
 273
 274 #else /* !CONFIG_PROVE_LOCKING */
 275
 276 /*
 277  * Stubs:
 278  */
 279
 280 void early_boot_irqs_off(void)
 281 {
 282 }
 283
 284 void early_boot_irqs_on(void)
 285 {
 286 }
 287
 288 void trace_softirqs_on(unsigned long ip)
 289 {
 290 }
 291
 292 void trace_softirqs_off(unsigned long ip)
 293 {
 294 }
 295
 296 inline void print_irqtrace_events(struct task_struct *curr)
 297 {
 298 }
 299
 300 /*
 301  * We are only interested in hardirq on/off events:
 302  */
 303 void trace_hardirqs_on(void)
 304 {
 305         if (!preempt_trace() && irq_trace())
 306                 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 307 }
 308 EXPORT_SYMBOL(trace_hardirqs_on);
 309
 310 void trace_hardirqs_off(void)
 311 {
 312         if (!preempt_trace() && irq_trace())
 313                 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 314 }
 315 EXPORT_SYMBOL(trace_hardirqs_off);
 316
 317 void trace_hardirqs_on_caller(unsigned long caller_addr)
 318 {
 319         if (!preempt_trace() && irq_trace())
 320                 stop_critical_timing(CALLER_ADDR0, caller_addr);
 321 }
 322 EXPORT_SYMBOL(trace_hardirqs_on_caller);
 323
 324 void trace_hardirqs_off_caller(unsigned long caller_addr)
 325 {
 326         if (!preempt_trace() && irq_trace())
 327                 start_critical_timing(CALLER_ADDR0, caller_addr);
 328 }
 329 EXPORT_SYMBOL(trace_hardirqs_off_caller);
 330
 331 #endif /* CONFIG_PROVE_LOCKING */
 332 #endif /*  CONFIG_IRQSOFF_TRACER */
 333
 334 #ifdef CONFIG_PREEMPT_TRACER
 335 void trace_preempt_on(unsigned long a0, unsigned long a1)
 336 {
 337         if (preempt_trace())
 338                 stop_critical_timing(a0, a1);
 339 }
 340
 341 void trace_preempt_off(unsigned long a0, unsigned long a1)
 342 {
 343         if (preempt_trace())
 344                 start_critical_timing(a0, a1);
 345 }
 346 #endif /* CONFIG_PREEMPT_TRACER */
 347
 348 static void start_irqsoff_tracer(struct trace_array *tr)
 349 {
 350         register_ftrace_function(&trace_ops);
 351         if (tracing_is_enabled())
 352                 tracer_enabled = 1;
 353         else
 354                 tracer_enabled = 0;
 355 }
 356
 357 static void stop_irqsoff_tracer(struct trace_array *tr)
 358 {
 359         tracer_enabled = 0;
 360         unregister_ftrace_function(&trace_ops);
 361 }
 362
 363 static void __irqsoff_tracer_init(struct trace_array *tr)
 364 {
 365         save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
 366         trace_flags |= TRACE_ITER_LATENCY_FMT;
 367
 368         tracing_max_latency = 0;
 369         irqsoff_trace = tr;
 370         /* make sure that the tracer is visible */
 371         smp_wmb();
 372         tracing_reset_online_cpus(tr);
 373         start_irqsoff_tracer(tr);
 374 }
 375
 376 static void irqsoff_tracer_reset(struct trace_array *tr)
 377 {
 378         stop_irqsoff_tracer(tr);
 379
 380         if (!save_lat_flag)
 381                 trace_flags &= ~TRACE_ITER_LATENCY_FMT;
 382 }
 383
 384 static void irqsoff_tracer_start(struct trace_array *tr)
 385 {
 386         tracer_enabled = 1;
 387 }
 388
 389 static void irqsoff_tracer_stop(struct trace_array *tr)
 390 {
 391         tracer_enabled = 0;
 392 }
 393
 394 #ifdef CONFIG_IRQSOFF_TRACER
 395 static int irqsoff_tracer_init(struct trace_array *tr)
 396 {
 397         trace_type = TRACER_IRQS_OFF;
 398
 399         __irqsoff_tracer_init(tr);
 400         return 0;
 401 }
 402 static struct tracer irqsoff_tracer __read_mostly =
 403 {
 404         .name           = "irqsoff",
 405         .init           = irqsoff_tracer_init,
 406         .reset          = irqsoff_tracer_reset,
 407         .start          = irqsoff_tracer_start,
 408         .stop           = irqsoff_tracer_stop,
 409         .print_max      = 1,
 410 #ifdef CONFIG_FTRACE_SELFTEST
 411         .selftest    = trace_selftest_startup_irqsoff,
 412 #endif
 413 };
 414 # define register_irqsoff(trace) register_tracer(&trace)
 415 #else
 416 # define register_irqsoff(trace) do { } while (0)
 417 #endif
 418
 419 #ifdef CONFIG_PREEMPT_TRACER
 420 static int preemptoff_tracer_init(struct trace_array *tr)
 421 {
 422         trace_type = TRACER_PREEMPT_OFF;
 423
 424         __irqsoff_tracer_init(tr);
 425         return 0;
 426 }
 427
 428 static struct tracer preemptoff_tracer __read_mostly =
 429 {
 430         .name           = "preemptoff",
 431         .init           = preemptoff_tracer_init,
 432         .reset          = irqsoff_tracer_reset,
 433         .start          = irqsoff_tracer_start,
 434         .stop           = irqsoff_tracer_stop,
 435         .print_max      = 1,
 436 #ifdef CONFIG_FTRACE_SELFTEST
 437         .selftest    = trace_selftest_startup_preemptoff,
 438 #endif
 439 };
 440 # define register_preemptoff(trace) register_tracer(&trace)
 441 #else
 442 # define register_preemptoff(trace) do { } while (0)
 443 #endif
 444
 445 #if defined(CONFIG_IRQSOFF_TRACER) && \
 446         defined(CONFIG_PREEMPT_TRACER)
 447
 448 static int preemptirqsoff_tracer_init(struct trace_array *tr)
 449 {
 450         trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
 451
 452         __irqsoff_tracer_init(tr);
 453         return 0;
 454 }
 455
 456 static struct tracer preemptirqsoff_tracer __read_mostly =
 457 {
 458         .name           = "preemptirqsoff",
 459         .init           = preemptirqsoff_tracer_init,
 460         .reset          = irqsoff_tracer_reset,
 461         .start          = irqsoff_tracer_start,
 462         .stop           = irqsoff_tracer_stop,
 463         .print_max      = 1,
 464 #ifdef CONFIG_FTRACE_SELFTEST
 465         .selftest    = trace_selftest_startup_preemptirqsoff,
 466 #endif
 467 };
 468
 469 # define register_preemptirqsoff(trace) register_tracer(&trace)
 470 #else
 471 # define register_preemptirqsoff(trace) do { } while (0)
 472 #endif
 473
 474 __init static int init_irqsoff_tracer(void)
 475 {
 476         register_irqsoff(irqsoff_tracer);
 477         register_preemptoff(preemptoff_tracer);
 478         register_preemptirqsoff(preemptirqsoff_tracer);
 479
 480         return 0;
 481 }
 482 device_initcall(init_irqsoff_tracer);