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   1 /*
   2  * trace irqs off criticall 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_FTRACE
  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, data, ip, parent_ip, flags);
  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_FTRACE */
 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
 134         /*
 135          * usecs conversion is slow so we try to delay the conversion
 136          * as long as possible:
 137          */
 138         T0 = data->preempt_timestamp;
 139         T1 = ftrace_now(cpu);
 140         delta = T1-T0;
 141
 142         local_save_flags(flags);
 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, data, CALLER_ADDR0, parent_ip, flags);
 154
 155         latency = nsecs_to_usecs(delta);
 156
 157         if (data->critical_sequence != max_sequence)
 158                 goto out_unlock;
 159
 160         tracing_max_latency = delta;
 161         t0 = nsecs_to_usecs(T0);
 162         t1 = nsecs_to_usecs(T1);
 163
 164         data->critical_end = parent_ip;
 165
 166         update_max_tr_single(tr, current, cpu);
 167
 168         max_sequence++;
 169
 170 out_unlock:
 171         spin_unlock_irqrestore(&max_trace_lock, flags);
 172
 173 out:
 174         data->critical_sequence = max_sequence;
 175         data->preempt_timestamp = ftrace_now(cpu);
 176         tracing_reset(data);
 177         trace_function(tr, data, CALLER_ADDR0, parent_ip, flags);
 178 }
 179
 180 static inline void
 181 start_critical_timing(unsigned long ip, unsigned long parent_ip)
 182 {
 183         int cpu;
 184         struct trace_array *tr = irqsoff_trace;
 185         struct trace_array_cpu *data;
 186         unsigned long flags;
 187
 188         if (likely(!tracer_enabled))
 189                 return;
 190
 191         cpu = raw_smp_processor_id();
 192
 193         if (per_cpu(tracing_cpu, cpu))
 194                 return;
 195
 196         data = tr->data[cpu];
 197
 198         if (unlikely(!data) || atomic_read(&data->disabled))
 199                 return;
 200
 201         atomic_inc(&data->disabled);
 202
 203         data->critical_sequence = max_sequence;
 204         data->preempt_timestamp = ftrace_now(cpu);
 205         data->critical_start = parent_ip ? : ip;
 206         tracing_reset(data);
 207
 208         local_save_flags(flags);
 209
 210         trace_function(tr, data, ip, parent_ip, flags);
 211
 212         per_cpu(tracing_cpu, cpu) = 1;
 213
 214         atomic_dec(&data->disabled);
 215 }
 216
 217 static inline void
 218 stop_critical_timing(unsigned long ip, unsigned long parent_ip)
 219 {
 220         int cpu;
 221         struct trace_array *tr = irqsoff_trace;
 222         struct trace_array_cpu *data;
 223         unsigned long flags;
 224
 225         cpu = raw_smp_processor_id();
 226         /* Always clear the tracing cpu on stopping the trace */
 227         if (unlikely(per_cpu(tracing_cpu, cpu)))
 228                 per_cpu(tracing_cpu, cpu) = 0;
 229         else
 230                 return;
 231
 232         if (!tracer_enabled)
 233                 return;
 234
 235         data = tr->data[cpu];
 236
 237         if (unlikely(!data) || unlikely(!head_page(data)) ||
 238             !data->critical_start || atomic_read(&data->disabled))
 239                 return;
 240
 241         atomic_inc(&data->disabled);
 242
 243         local_save_flags(flags);
 244         trace_function(tr, data, ip, parent_ip, flags);
 245         check_critical_timing(tr, data, parent_ip ? : ip, cpu);
 246         data->critical_start = 0;
 247         atomic_dec(&data->disabled);
 248 }
 249
 250 /* start and stop critical timings used to for stoppage (in idle) */
 251 void start_critical_timings(void)
 252 {
 253         if (preempt_trace() || irq_trace())
 254                 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 255 }
 256
 257 void stop_critical_timings(void)
 258 {
 259         if (preempt_trace() || irq_trace())
 260                 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 261 }
 262
 263 #ifdef CONFIG_IRQSOFF_TRACER
 264 #ifdef CONFIG_PROVE_LOCKING
 265 void time_hardirqs_on(unsigned long a0, unsigned long a1)
 266 {
 267         if (!preempt_trace() && irq_trace())
 268                 stop_critical_timing(a0, a1);
 269 }
 270
 271 void time_hardirqs_off(unsigned long a0, unsigned long a1)
 272 {
 273         if (!preempt_trace() && irq_trace())
 274                 start_critical_timing(a0, a1);
 275 }
 276
 277 #else /* !CONFIG_PROVE_LOCKING */
 278
 279 /*
 280  * Stubs:
 281  */
 282
 283 void early_boot_irqs_off(void)
 284 {
 285 }
 286
 287 void early_boot_irqs_on(void)
 288 {
 289 }
 290
 291 void trace_softirqs_on(unsigned long ip)
 292 {
 293 }
 294
 295 void trace_softirqs_off(unsigned long ip)
 296 {
 297 }
 298
 299 inline void print_irqtrace_events(struct task_struct *curr)
 300 {
 301 }
 302
 303 /*
 304  * We are only interested in hardirq on/off events:
 305  */
 306 void trace_hardirqs_on(void)
 307 {
 308         if (!preempt_trace() && irq_trace())
 309                 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 310 }
 311 EXPORT_SYMBOL(trace_hardirqs_on);
 312
 313 void trace_hardirqs_off(void)
 314 {
 315         if (!preempt_trace() && irq_trace())
 316                 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 317 }
 318 EXPORT_SYMBOL(trace_hardirqs_off);
 319
 320 void trace_hardirqs_on_caller(unsigned long caller_addr)
 321 {
 322         if (!preempt_trace() && irq_trace())
 323                 stop_critical_timing(CALLER_ADDR0, caller_addr);
 324 }
 325 EXPORT_SYMBOL(trace_hardirqs_on_caller);
 326
 327 void trace_hardirqs_off_caller(unsigned long caller_addr)
 328 {
 329         if (!preempt_trace() && irq_trace())
 330                 start_critical_timing(CALLER_ADDR0, caller_addr);
 331 }
 332 EXPORT_SYMBOL(trace_hardirqs_off_caller);
 333
 334 #endif /* CONFIG_PROVE_LOCKING */
 335 #endif /*  CONFIG_IRQSOFF_TRACER */
 336
 337 #ifdef CONFIG_PREEMPT_TRACER
 338 void trace_preempt_on(unsigned long a0, unsigned long a1)
 339 {
 340         if (preempt_trace())
 341                 stop_critical_timing(a0, a1);
 342 }
 343
 344 void trace_preempt_off(unsigned long a0, unsigned long a1)
 345 {
 346         if (preempt_trace())
 347                 start_critical_timing(a0, a1);
 348 }
 349 #endif /* CONFIG_PREEMPT_TRACER */
 350
 351 static void start_irqsoff_tracer(struct trace_array *tr)
 352 {
 353         register_ftrace_function(&trace_ops);
 354         tracer_enabled = 1;
 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         irqsoff_trace = tr;
 366         /* make sure that the tracer is visible */
 367         smp_wmb();
 368
 369         if (tr->ctrl)
 370                 start_irqsoff_tracer(tr);
 371 }
 372
 373 static void irqsoff_tracer_reset(struct trace_array *tr)
 374 {
 375         if (tr->ctrl)
 376                 stop_irqsoff_tracer(tr);
 377 }
 378
 379 static void irqsoff_tracer_ctrl_update(struct trace_array *tr)
 380 {
 381         if (tr->ctrl)
 382                 start_irqsoff_tracer(tr);
 383         else
 384                 stop_irqsoff_tracer(tr);
 385 }
 386
 387 static void irqsoff_tracer_open(struct trace_iterator *iter)
 388 {
 389         /* stop the trace while dumping */
 390         if (iter->tr->ctrl)
 391                 stop_irqsoff_tracer(iter->tr);
 392 }
 393
 394 static void irqsoff_tracer_close(struct trace_iterator *iter)
 395 {
 396         if (iter->tr->ctrl)
 397                 start_irqsoff_tracer(iter->tr);
 398 }
 399
 400 #ifdef CONFIG_IRQSOFF_TRACER
 401 static void irqsoff_tracer_init(struct trace_array *tr)
 402 {
 403         trace_type = TRACER_IRQS_OFF;
 404
 405         __irqsoff_tracer_init(tr);
 406 }
 407 static struct tracer irqsoff_tracer __read_mostly =
 408 {
 409         .name           = "irqsoff",
 410         .init           = irqsoff_tracer_init,
 411         .reset          = irqsoff_tracer_reset,
 412         .open           = irqsoff_tracer_open,
 413         .close          = irqsoff_tracer_close,
 414         .ctrl_update    = irqsoff_tracer_ctrl_update,
 415         .print_max      = 1,
 416 #ifdef CONFIG_FTRACE_SELFTEST
 417         .selftest    = trace_selftest_startup_irqsoff,
 418 #endif
 419 };
 420 # define register_irqsoff(trace) register_tracer(&trace)
 421 #else
 422 # define register_irqsoff(trace) do { } while (0)
 423 #endif
 424
 425 #ifdef CONFIG_PREEMPT_TRACER
 426 static void preemptoff_tracer_init(struct trace_array *tr)
 427 {
 428         trace_type = TRACER_PREEMPT_OFF;
 429
 430         __irqsoff_tracer_init(tr);
 431 }
 432
 433 static struct tracer preemptoff_tracer __read_mostly =
 434 {
 435         .name           = "preemptoff",
 436         .init           = preemptoff_tracer_init,
 437         .reset          = irqsoff_tracer_reset,
 438         .open           = irqsoff_tracer_open,
 439         .close          = irqsoff_tracer_close,
 440         .ctrl_update    = irqsoff_tracer_ctrl_update,
 441         .print_max      = 1,
 442 #ifdef CONFIG_FTRACE_SELFTEST
 443         .selftest    = trace_selftest_startup_preemptoff,
 444 #endif
 445 };
 446 # define register_preemptoff(trace) register_tracer(&trace)
 447 #else
 448 # define register_preemptoff(trace) do { } while (0)
 449 #endif
 450
 451 #if defined(CONFIG_IRQSOFF_TRACER) && \
 452         defined(CONFIG_PREEMPT_TRACER)
 453
 454 static void preemptirqsoff_tracer_init(struct trace_array *tr)
 455 {
 456         trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
 457
 458         __irqsoff_tracer_init(tr);
 459 }
 460
 461 static struct tracer preemptirqsoff_tracer __read_mostly =
 462 {
 463         .name           = "preemptirqsoff",
 464         .init           = preemptirqsoff_tracer_init,
 465         .reset          = irqsoff_tracer_reset,
 466         .open           = irqsoff_tracer_open,
 467         .close          = irqsoff_tracer_close,
 468         .ctrl_update    = irqsoff_tracer_ctrl_update,
 469         .print_max      = 1,
 470 #ifdef CONFIG_FTRACE_SELFTEST
 471         .selftest    = trace_selftest_startup_preemptirqsoff,
 472 #endif
 473 };
 474
 475 # define register_preemptirqsoff(trace) register_tracer(&trace)
 476 #else
 477 # define register_preemptirqsoff(trace) do { } while (0)
 478 #endif
 479
 480 __init static int init_irqsoff_tracer(void)
 481 {
 482         register_irqsoff(irqsoff_tracer);
 483         register_preemptoff(preemptoff_tracer);
 484         register_preemptirqsoff(preemptirqsoff_tracer);
 485
 486         return 0;
 487 }
 488 device_initcall(init_irqsoff_tracer);