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