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         /* Skip 5 functions to get to the irq/preempt enable function */
 155         __trace_stack(tr, flags, 5, pc);
 156
 157         if (data->critical_sequence != max_sequence)
 158                 goto out_unlock;
 159
 160         data->critical_end = parent_ip;
 161
 162         if (likely(!is_tracing_stopped())) {
 163                 tracing_max_latency = delta;
 164                 update_max_tr_single(tr, current, cpu);
 165         }
 166
 167         max_sequence++;
 168
 169 out_unlock:
 170         spin_unlock_irqrestore(&max_trace_lock, flags);
 171
 172 out:
 173         data->critical_sequence = max_sequence;
 174         data->preempt_timestamp = ftrace_now(cpu);
 175         trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
 176 }
 177
 178 static inline void
 179 start_critical_timing(unsigned long ip, unsigned long parent_ip)
 180 {
 181         int cpu;
 182         struct trace_array *tr = irqsoff_trace;
 183         struct trace_array_cpu *data;
 184         unsigned long flags;
 185
 186         if (likely(!tracer_enabled))
 187                 return;
 188
 189         cpu = raw_smp_processor_id();
 190
 191         if (per_cpu(tracing_cpu, cpu))
 192                 return;
 193
 194         data = tr->data[cpu];
 195
 196         if (unlikely(!data) || atomic_read(&data->disabled))
 197                 return;
 198
 199         atomic_inc(&data->disabled);
 200
 201         data->critical_sequence = max_sequence;
 202         data->preempt_timestamp = ftrace_now(cpu);
 203         data->critical_start = parent_ip ? : ip;
 204
 205         local_save_flags(flags);
 206
 207         trace_function(tr, ip, parent_ip, flags, preempt_count());
 208
 209         per_cpu(tracing_cpu, cpu) = 1;
 210
 211         atomic_dec(&data->disabled);
 212 }
 213
 214 static inline void
 215 stop_critical_timing(unsigned long ip, unsigned long parent_ip)
 216 {
 217         int cpu;
 218         struct trace_array *tr = irqsoff_trace;
 219         struct trace_array_cpu *data;
 220         unsigned long flags;
 221
 222         cpu = raw_smp_processor_id();
 223         /* Always clear the tracing cpu on stopping the trace */
 224         if (unlikely(per_cpu(tracing_cpu, cpu)))
 225                 per_cpu(tracing_cpu, cpu) = 0;
 226         else
 227                 return;
 228
 229         if (!tracer_enabled)
 230                 return;
 231
 232         data = tr->data[cpu];
 233
 234         if (unlikely(!data) ||
 235             !data->critical_start || atomic_read(&data->disabled))
 236                 return;
 237
 238         atomic_inc(&data->disabled);
 239
 240         local_save_flags(flags);
 241         trace_function(tr, ip, parent_ip, flags, preempt_count());
 242         check_critical_timing(tr, data, parent_ip ? : ip, cpu);
 243         data->critical_start = 0;
 244         atomic_dec(&data->disabled);
 245 }
 246
 247 /* start and stop critical timings used to for stoppage (in idle) */
 248 void start_critical_timings(void)
 249 {
 250         if (preempt_trace() || irq_trace())
 251                 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 252 }
 253 EXPORT_SYMBOL_GPL(start_critical_timings);
 254
 255 void stop_critical_timings(void)
 256 {
 257         if (preempt_trace() || irq_trace())
 258                 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 259 }
 260 EXPORT_SYMBOL_GPL(stop_critical_timings);
 261
 262 #ifdef CONFIG_IRQSOFF_TRACER
 263 #ifdef CONFIG_PROVE_LOCKING
 264 void time_hardirqs_on(unsigned long a0, unsigned long a1)
 265 {
 266         if (!preempt_trace() && irq_trace())
 267                 stop_critical_timing(a0, a1);
 268 }
 269
 270 void time_hardirqs_off(unsigned long a0, unsigned long a1)
 271 {
 272         if (!preempt_trace() && irq_trace())
 273                 start_critical_timing(a0, a1);
 274 }
 275
 276 #else /* !CONFIG_PROVE_LOCKING */
 277
 278 /*
 279  * Stubs:
 280  */
 281
 282 void early_boot_irqs_off(void)
 283 {
 284 }
 285
 286 void early_boot_irqs_on(void)
 287 {
 288 }
 289
 290 void trace_softirqs_on(unsigned long ip)
 291 {
 292 }
 293
 294 void trace_softirqs_off(unsigned long ip)
 295 {
 296 }
 297
 298 inline void print_irqtrace_events(struct task_struct *curr)
 299 {
 300 }
 301
 302 /*
 303  * We are only interested in hardirq on/off events:
 304  */
 305 void trace_hardirqs_on(void)
 306 {
 307         if (!preempt_trace() && irq_trace())
 308                 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 309 }
 310 EXPORT_SYMBOL(trace_hardirqs_on);
 311
 312 void trace_hardirqs_off(void)
 313 {
 314         if (!preempt_trace() && irq_trace())
 315                 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 316 }
 317 EXPORT_SYMBOL(trace_hardirqs_off);
 318
 319 void trace_hardirqs_on_caller(unsigned long caller_addr)
 320 {
 321         if (!preempt_trace() && irq_trace())
 322                 stop_critical_timing(CALLER_ADDR0, caller_addr);
 323 }
 324 EXPORT_SYMBOL(trace_hardirqs_on_caller);
 325
 326 void trace_hardirqs_off_caller(unsigned long caller_addr)
 327 {
 328         if (!preempt_trace() && irq_trace())
 329                 start_critical_timing(CALLER_ADDR0, caller_addr);
 330 }
 331 EXPORT_SYMBOL(trace_hardirqs_off_caller);
 332
 333 #endif /* CONFIG_PROVE_LOCKING */
 334 #endif /*  CONFIG_IRQSOFF_TRACER */
 335
 336 #ifdef CONFIG_PREEMPT_TRACER
 337 void trace_preempt_on(unsigned long a0, unsigned long a1)
 338 {
 339         if (preempt_trace())
 340                 stop_critical_timing(a0, a1);
 341 }
 342
 343 void trace_preempt_off(unsigned long a0, unsigned long a1)
 344 {
 345         if (preempt_trace())
 346                 start_critical_timing(a0, a1);
 347 }
 348 #endif /* CONFIG_PREEMPT_TRACER */
 349
 350 static void start_irqsoff_tracer(struct trace_array *tr)
 351 {
 352         register_ftrace_function(&trace_ops);
 353         if (tracing_is_enabled())
 354                 tracer_enabled = 1;
 355         else
 356                 tracer_enabled = 0;
 357 }
 358
 359 static void stop_irqsoff_tracer(struct trace_array *tr)
 360 {
 361         tracer_enabled = 0;
 362         unregister_ftrace_function(&trace_ops);
 363 }
 364
 365 static void __irqsoff_tracer_init(struct trace_array *tr)
 366 {
 367         save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
 368         trace_flags |= TRACE_ITER_LATENCY_FMT;
 369
 370         tracing_max_latency = 0;
 371         irqsoff_trace = tr;
 372         /* make sure that the tracer is visible */
 373         smp_wmb();
 374         tracing_reset_online_cpus(tr);
 375         start_irqsoff_tracer(tr);
 376 }
 377
 378 static void irqsoff_tracer_reset(struct trace_array *tr)
 379 {
 380         stop_irqsoff_tracer(tr);
 381
 382         if (!save_lat_flag)
 383                 trace_flags &= ~TRACE_ITER_LATENCY_FMT;
 384 }
 385
 386 static void irqsoff_tracer_start(struct trace_array *tr)
 387 {
 388         tracer_enabled = 1;
 389 }
 390
 391 static void irqsoff_tracer_stop(struct trace_array *tr)
 392 {
 393         tracer_enabled = 0;
 394 }
 395
 396 #ifdef CONFIG_IRQSOFF_TRACER
 397 static int irqsoff_tracer_init(struct trace_array *tr)
 398 {
 399         trace_type = TRACER_IRQS_OFF;
 400
 401         __irqsoff_tracer_init(tr);
 402         return 0;
 403 }
 404 static struct tracer irqsoff_tracer __read_mostly =
 405 {
 406         .name           = "irqsoff",
 407         .init           = irqsoff_tracer_init,
 408         .reset          = irqsoff_tracer_reset,
 409         .start          = irqsoff_tracer_start,
 410         .stop           = irqsoff_tracer_stop,
 411         .print_max      = 1,
 412 #ifdef CONFIG_FTRACE_SELFTEST
 413         .selftest    = trace_selftest_startup_irqsoff,
 414 #endif
 415 };
 416 # define register_irqsoff(trace) register_tracer(&trace)
 417 #else
 418 # define register_irqsoff(trace) do { } while (0)
 419 #endif
 420
 421 #ifdef CONFIG_PREEMPT_TRACER
 422 static int preemptoff_tracer_init(struct trace_array *tr)
 423 {
 424         trace_type = TRACER_PREEMPT_OFF;
 425
 426         __irqsoff_tracer_init(tr);
 427         return 0;
 428 }
 429
 430 static struct tracer preemptoff_tracer __read_mostly =
 431 {
 432         .name           = "preemptoff",
 433         .init           = preemptoff_tracer_init,
 434         .reset          = irqsoff_tracer_reset,
 435         .start          = irqsoff_tracer_start,
 436         .stop           = irqsoff_tracer_stop,
 437         .print_max      = 1,
 438 #ifdef CONFIG_FTRACE_SELFTEST
 439         .selftest    = trace_selftest_startup_preemptoff,
 440 #endif
 441 };
 442 # define register_preemptoff(trace) register_tracer(&trace)
 443 #else
 444 # define register_preemptoff(trace) do { } while (0)
 445 #endif
 446
 447 #if defined(CONFIG_IRQSOFF_TRACER) && \
 448         defined(CONFIG_PREEMPT_TRACER)
 449
 450 static int preemptirqsoff_tracer_init(struct trace_array *tr)
 451 {
 452         trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
 453
 454         __irqsoff_tracer_init(tr);
 455         return 0;
 456 }
 457
 458 static struct tracer preemptirqsoff_tracer __read_mostly =
 459 {
 460         .name           = "preemptirqsoff",
 461         .init           = preemptirqsoff_tracer_init,
 462         .reset          = irqsoff_tracer_reset,
 463         .start          = irqsoff_tracer_start,
 464         .stop           = irqsoff_tracer_stop,
 465         .print_max      = 1,
 466 #ifdef CONFIG_FTRACE_SELFTEST
 467         .selftest    = trace_selftest_startup_preemptirqsoff,
 468 #endif
 469 };
 470
 471 # define register_preemptirqsoff(trace) register_tracer(&trace)
 472 #else
 473 # define register_preemptirqsoff(trace) do { } while (0)
 474 #endif
 475
 476 __init static int init_irqsoff_tracer(void)
 477 {
 478         register_irqsoff(irqsoff_tracer);
 479         register_preemptoff(preemptoff_tracer);
 480         register_preemptirqsoff(preemptirqsoff_tracer);
 481
 482         return 0;
 483 }
 484 device_initcall(init_irqsoff_tracer);