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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 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         trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
 182 }
 183
 184 static inline void
 185 start_critical_timing(unsigned long ip, unsigned long parent_ip)
 186 {
 187         int cpu;
 188         struct trace_array *tr = irqsoff_trace;
 189         struct trace_array_cpu *data;
 190         unsigned long flags;
 191
 192         if (likely(!tracer_enabled))
 193                 return;
 194
 195         cpu = raw_smp_processor_id();
 196
 197         if (per_cpu(tracing_cpu, cpu))
 198                 return;
 199
 200         data = tr->data[cpu];
 201
 202         if (unlikely(!data) || atomic_read(&data->disabled))
 203                 return;
 204
 205         atomic_inc(&data->disabled);
 206
 207         data->critical_sequence = max_sequence;
 208         data->preempt_timestamp = ftrace_now(cpu);
 209         data->critical_start = parent_ip ? : ip;
 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         save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
 374         trace_flags |= TRACE_ITER_LATENCY_FMT;
 375
 376         tracing_max_latency = 0;
 377         irqsoff_trace = tr;
 378         /* make sure that the tracer is visible */
 379         smp_wmb();
 380         tracing_reset_online_cpus(tr);
 381         start_irqsoff_tracer(tr);
 382 }
 383
 384 static void irqsoff_tracer_reset(struct trace_array *tr)
 385 {
 386         stop_irqsoff_tracer(tr);
 387
 388         if (!save_lat_flag)
 389                 trace_flags &= ~TRACE_ITER_LATENCY_FMT;
 390 }
 391
 392 static void irqsoff_tracer_start(struct trace_array *tr)
 393 {
 394         tracer_enabled = 1;
 395 }
 396
 397 static void irqsoff_tracer_stop(struct trace_array *tr)
 398 {
 399         tracer_enabled = 0;
 400 }
 401
 402 #ifdef CONFIG_IRQSOFF_TRACER
 403 static int irqsoff_tracer_init(struct trace_array *tr)
 404 {
 405         trace_type = TRACER_IRQS_OFF;
 406
 407         __irqsoff_tracer_init(tr);
 408         return 0;
 409 }
 410 static struct tracer irqsoff_tracer __read_mostly =
 411 {
 412         .name           = "irqsoff",
 413         .init           = irqsoff_tracer_init,
 414         .reset          = irqsoff_tracer_reset,
 415         .start          = irqsoff_tracer_start,
 416         .stop           = irqsoff_tracer_stop,
 417         .print_max      = 1,
 418 #ifdef CONFIG_FTRACE_SELFTEST
 419         .selftest    = trace_selftest_startup_irqsoff,
 420 #endif
 421 };
 422 # define register_irqsoff(trace) register_tracer(&trace)
 423 #else
 424 # define register_irqsoff(trace) do { } while (0)
 425 #endif
 426
 427 #ifdef CONFIG_PREEMPT_TRACER
 428 static int preemptoff_tracer_init(struct trace_array *tr)
 429 {
 430         trace_type = TRACER_PREEMPT_OFF;
 431
 432         __irqsoff_tracer_init(tr);
 433         return 0;
 434 }
 435
 436 static struct tracer preemptoff_tracer __read_mostly =
 437 {
 438         .name           = "preemptoff",
 439         .init           = preemptoff_tracer_init,
 440         .reset          = irqsoff_tracer_reset,
 441         .start          = irqsoff_tracer_start,
 442         .stop           = irqsoff_tracer_stop,
 443         .print_max      = 1,
 444 #ifdef CONFIG_FTRACE_SELFTEST
 445         .selftest    = trace_selftest_startup_preemptoff,
 446 #endif
 447 };
 448 # define register_preemptoff(trace) register_tracer(&trace)
 449 #else
 450 # define register_preemptoff(trace) do { } while (0)
 451 #endif
 452
 453 #if defined(CONFIG_IRQSOFF_TRACER) && \
 454         defined(CONFIG_PREEMPT_TRACER)
 455
 456 static int preemptirqsoff_tracer_init(struct trace_array *tr)
 457 {
 458         trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
 459
 460         __irqsoff_tracer_init(tr);
 461         return 0;
 462 }
 463
 464 static struct tracer preemptirqsoff_tracer __read_mostly =
 465 {
 466         .name           = "preemptirqsoff",
 467         .init           = preemptirqsoff_tracer_init,
 468         .reset          = irqsoff_tracer_reset,
 469         .start          = irqsoff_tracer_start,
 470         .stop           = irqsoff_tracer_stop,
 471         .print_max      = 1,
 472 #ifdef CONFIG_FTRACE_SELFTEST
 473         .selftest    = trace_selftest_startup_preemptirqsoff,
 474 #endif
 475 };
 476
 477 # define register_preemptirqsoff(trace) register_tracer(&trace)
 478 #else
 479 # define register_preemptirqsoff(trace) do { } while (0)
 480 #endif
 481
 482 __init static int init_irqsoff_tracer(void)
 483 {
 484         register_irqsoff(irqsoff_tracer);
 485         register_preemptoff(preemptoff_tracer);
 486         register_preemptirqsoff(preemptirqsoff_tracer);
 487
 488         return 0;
 489 }
 490 device_initcall(init_irqsoff_tracer);