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   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 #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_FUNCTION_TRACER
  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, ip, parent_ip, flags, preempt_count());
  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_FUNCTION_TRACER */
 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         int pc;
 134
 135         /*
 136          * usecs conversion is slow so we try to delay the conversion
 137          * as long as possible:
 138          */
 139         T0 = data->preempt_timestamp;
 140         T1 = ftrace_now(cpu);
 141         delta = T1-T0;
 142
 143         local_save_flags(flags);
 144
 145         pc = preempt_count();
 146
 147         if (!report_latency(delta))
 148                 goto out;
 149
 150         spin_lock_irqsave(&max_trace_lock, flags);
 151
 152         /* check if we are still the max latency */
 153         if (!report_latency(delta))
 154                 goto out_unlock;
 155
 156         trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
 157
 158         latency = nsecs_to_usecs(delta);
 159
 160         if (data->critical_sequence != max_sequence)
 161                 goto out_unlock;
 162
 163         tracing_max_latency = delta;
 164         t0 = nsecs_to_usecs(T0);
 165         t1 = nsecs_to_usecs(T1);
 166
 167         data->critical_end = parent_ip;
 168
 169         update_max_tr_single(tr, current, cpu);
 170
 171         max_sequence++;
 172
 173 out_unlock:
 174         spin_unlock_irqrestore(&max_trace_lock, flags);
 175
 176 out:
 177         data->critical_sequence = max_sequence;
 178         data->preempt_timestamp = ftrace_now(cpu);
 179         tracing_reset(tr, cpu);
 180         trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
 181 }
 182
 183 static inline void
 184 start_critical_timing(unsigned long ip, unsigned long parent_ip)
 185 {
 186         int cpu;
 187         struct trace_array *tr = irqsoff_trace;
 188         struct trace_array_cpu *data;
 189         unsigned long flags;
 190
 191         if (likely(!tracer_enabled))
 192                 return;
 193
 194         cpu = raw_smp_processor_id();
 195
 196         if (per_cpu(tracing_cpu, cpu))
 197                 return;
 198
 199         data = tr->data[cpu];
 200
 201         if (unlikely(!data) || atomic_read(&data->disabled))
 202                 return;
 203
 204         atomic_inc(&data->disabled);
 205
 206         data->critical_sequence = max_sequence;
 207         data->preempt_timestamp = ftrace_now(cpu);
 208         data->critical_start = parent_ip ? : ip;
 209         tracing_reset(tr, cpu);
 210
 211         local_save_flags(flags);
 212
 213         trace_function(tr, ip, parent_ip, flags, preempt_count());
 214
 215         per_cpu(tracing_cpu, cpu) = 1;
 216
 217         atomic_dec(&data->disabled);
 218 }
 219
 220 static inline void
 221 stop_critical_timing(unsigned long ip, unsigned long parent_ip)
 222 {
 223         int cpu;
 224         struct trace_array *tr = irqsoff_trace;
 225         struct trace_array_cpu *data;
 226         unsigned long flags;
 227
 228         cpu = raw_smp_processor_id();
 229         /* Always clear the tracing cpu on stopping the trace */
 230         if (unlikely(per_cpu(tracing_cpu, cpu)))
 231                 per_cpu(tracing_cpu, cpu) = 0;
 232         else
 233                 return;
 234
 235         if (!tracer_enabled)
 236                 return;
 237
 238         data = tr->data[cpu];
 239
 240         if (unlikely(!data) ||
 241             !data->critical_start || atomic_read(&data->disabled))
 242                 return;
 243
 244         atomic_inc(&data->disabled);
 245
 246         local_save_flags(flags);
 247         trace_function(tr, ip, parent_ip, flags, preempt_count());
 248         check_critical_timing(tr, data, parent_ip ? : ip, cpu);
 249         data->critical_start = 0;
 250         atomic_dec(&data->disabled);
 251 }
 252
 253 /* start and stop critical timings used to for stoppage (in idle) */
 254 void start_critical_timings(void)
 255 {
 256         if (preempt_trace() || irq_trace())
 257                 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 258 }
 259 EXPORT_SYMBOL_GPL(start_critical_timings);
 260
 261 void stop_critical_timings(void)
 262 {
 263         if (preempt_trace() || irq_trace())
 264                 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 265 }
 266 EXPORT_SYMBOL_GPL(stop_critical_timings);
 267
 268 #ifdef CONFIG_IRQSOFF_TRACER
 269 #ifdef CONFIG_PROVE_LOCKING
 270 void time_hardirqs_on(unsigned long a0, unsigned long a1)
 271 {
 272         if (!preempt_trace() && irq_trace())
 273                 stop_critical_timing(a0, a1);
 274 }
 275
 276 void time_hardirqs_off(unsigned long a0, unsigned long a1)
 277 {
 278         if (!preempt_trace() && irq_trace())
 279                 start_critical_timing(a0, a1);
 280 }
 281
 282 #else /* !CONFIG_PROVE_LOCKING */
 283
 284 /*
 285  * Stubs:
 286  */
 287
 288 void early_boot_irqs_off(void)
 289 {
 290 }
 291
 292 void early_boot_irqs_on(void)
 293 {
 294 }
 295
 296 void trace_softirqs_on(unsigned long ip)
 297 {
 298 }
 299
 300 void trace_softirqs_off(unsigned long ip)
 301 {
 302 }
 303
 304 inline void print_irqtrace_events(struct task_struct *curr)
 305 {
 306 }
 307
 308 /*
 309  * We are only interested in hardirq on/off events:
 310  */
 311 void trace_hardirqs_on(void)
 312 {
 313         if (!preempt_trace() && irq_trace())
 314                 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 315 }
 316 EXPORT_SYMBOL(trace_hardirqs_on);
 317
 318 void trace_hardirqs_off(void)
 319 {
 320         if (!preempt_trace() && irq_trace())
 321                 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 322 }
 323 EXPORT_SYMBOL(trace_hardirqs_off);
 324
 325 void trace_hardirqs_on_caller(unsigned long caller_addr)
 326 {
 327         if (!preempt_trace() && irq_trace())
 328                 stop_critical_timing(CALLER_ADDR0, caller_addr);
 329 }
 330 EXPORT_SYMBOL(trace_hardirqs_on_caller);
 331
 332 void trace_hardirqs_off_caller(unsigned long caller_addr)
 333 {
 334         if (!preempt_trace() && irq_trace())
 335                 start_critical_timing(CALLER_ADDR0, caller_addr);
 336 }
 337 EXPORT_SYMBOL(trace_hardirqs_off_caller);
 338
 339 #endif /* CONFIG_PROVE_LOCKING */
 340 #endif /*  CONFIG_IRQSOFF_TRACER */
 341
 342 #ifdef CONFIG_PREEMPT_TRACER
 343 void trace_preempt_on(unsigned long a0, unsigned long a1)
 344 {
 345         if (preempt_trace())
 346                 stop_critical_timing(a0, a1);
 347 }
 348
 349 void trace_preempt_off(unsigned long a0, unsigned long a1)
 350 {
 351         if (preempt_trace())
 352                 start_critical_timing(a0, a1);
 353 }
 354 #endif /* CONFIG_PREEMPT_TRACER */
 355
 356 static void start_irqsoff_tracer(struct trace_array *tr)
 357 {
 358         register_ftrace_function(&trace_ops);
 359         if (tracing_is_enabled())
 360                 tracer_enabled = 1;
 361         else
 362                 tracer_enabled = 0;
 363 }
 364
 365 static void stop_irqsoff_tracer(struct trace_array *tr)
 366 {
 367         tracer_enabled = 0;
 368         unregister_ftrace_function(&trace_ops);
 369 }
 370
 371 static void __irqsoff_tracer_init(struct trace_array *tr)
 372 {
 373         tracing_max_latency = 0;
 374         irqsoff_trace = tr;
 375         /* make sure that the tracer is visible */
 376         smp_wmb();
 377         start_irqsoff_tracer(tr);
 378 }
 379
 380 static void irqsoff_tracer_reset(struct trace_array *tr)
 381 {
 382         stop_irqsoff_tracer(tr);
 383 }
 384
 385 static void irqsoff_tracer_start(struct trace_array *tr)
 386 {
 387         tracer_enabled = 1;
 388 }
 389
 390 static void irqsoff_tracer_stop(struct trace_array *tr)
 391 {
 392         tracer_enabled = 0;
 393 }
 394
 395 #ifdef CONFIG_IRQSOFF_TRACER
 396 static int irqsoff_tracer_init(struct trace_array *tr)
 397 {
 398         trace_type = TRACER_IRQS_OFF;
 399
 400         __irqsoff_tracer_init(tr);
 401         return 0;
 402 }
 403 static struct tracer irqsoff_tracer __read_mostly =
 404 {
 405         .name           = "irqsoff",
 406         .init           = irqsoff_tracer_init,
 407         .reset          = irqsoff_tracer_reset,
 408         .start          = irqsoff_tracer_start,
 409         .stop           = irqsoff_tracer_stop,
 410         .print_max      = 1,
 411 #ifdef CONFIG_FTRACE_SELFTEST
 412         .selftest    = trace_selftest_startup_irqsoff,
 413 #endif
 414 };
 415 # define register_irqsoff(trace) register_tracer(&trace)
 416 #else
 417 # define register_irqsoff(trace) do { } while (0)
 418 #endif
 419
 420 #ifdef CONFIG_PREEMPT_TRACER
 421 static int preemptoff_tracer_init(struct trace_array *tr)
 422 {
 423         trace_type = TRACER_PREEMPT_OFF;
 424
 425         __irqsoff_tracer_init(tr);
 426         return 0;
 427 }
 428
 429 static struct tracer preemptoff_tracer __read_mostly =
 430 {
 431         .name           = "preemptoff",
 432         .init           = preemptoff_tracer_init,
 433         .reset          = irqsoff_tracer_reset,
 434         .start          = irqsoff_tracer_start,
 435         .stop           = irqsoff_tracer_stop,
 436         .print_max      = 1,
 437 #ifdef CONFIG_FTRACE_SELFTEST
 438         .selftest    = trace_selftest_startup_preemptoff,
 439 #endif
 440 };
 441 # define register_preemptoff(trace) register_tracer(&trace)
 442 #else
 443 # define register_preemptoff(trace) do { } while (0)
 444 #endif
 445
 446 #if defined(CONFIG_IRQSOFF_TRACER) && \
 447         defined(CONFIG_PREEMPT_TRACER)
 448
 449 static int preemptirqsoff_tracer_init(struct trace_array *tr)
 450 {
 451         trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
 452
 453         __irqsoff_tracer_init(tr);
 454         return 0;
 455 }
 456
 457 static struct tracer preemptirqsoff_tracer __read_mostly =
 458 {
 459         .name           = "preemptirqsoff",
 460         .init           = preemptirqsoff_tracer_init,
 461         .reset          = irqsoff_tracer_reset,
 462         .start          = irqsoff_tracer_start,
 463         .stop           = irqsoff_tracer_stop,
 464         .print_max      = 1,
 465 #ifdef CONFIG_FTRACE_SELFTEST
 466         .selftest    = trace_selftest_startup_preemptirqsoff,
 467 #endif
 468 };
 469
 470 # define register_preemptirqsoff(trace) register_tracer(&trace)
 471 #else
 472 # define register_preemptirqsoff(trace) do { } while (0)
 473 #endif
 474
 475 __init static int init_irqsoff_tracer(void)
 476 {
 477         register_irqsoff(irqsoff_tracer);
 478         register_preemptoff(preemptoff_tracer);
 479         register_preemptirqsoff(preemptirqsoff_tracer);
 480
 481         return 0;
 482 }
 483 device_initcall(init_irqsoff_tracer);