1 /* 2 * trace task wakeup timings 3 * 4 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com> 5 * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com> 6 * 7 * Based on code from 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/module.h> 13 #include <linux/fs.h> 14 #include <linux/debugfs.h> 15 #include <linux/kallsyms.h> 16 #include <linux/uaccess.h> 17 #include <linux/ftrace.h> 18 #include <trace/events/sched.h> 19 20 #include "trace.h" 21 22 static struct trace_array *wakeup_trace; 23 static int __read_mostly tracer_enabled; 24 25 static struct task_struct *wakeup_task; 26 static int wakeup_cpu; 27 static int wakeup_current_cpu; 28 static unsigned wakeup_prio = -1; 29 static int wakeup_rt; 30 31 static arch_spinlock_t wakeup_lock = 32 (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; 33 34 static void wakeup_reset(struct trace_array *tr); 35 static void __wakeup_reset(struct trace_array *tr); 36 static int wakeup_graph_entry(struct ftrace_graph_ent *trace); 37 static void wakeup_graph_return(struct ftrace_graph_ret *trace); 38 39 static int save_lat_flag; 40 41 #define TRACE_DISPLAY_GRAPH 1 42 43 static struct tracer_opt trace_opts[] = { 44 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 45 /* display latency trace as call graph */ 46 { TRACER_OPT(display-graph, TRACE_DISPLAY_GRAPH) }, 47 #endif 48 { } /* Empty entry */ 49 }; 50 51 static struct tracer_flags tracer_flags = { 52 .val = 0, 53 .opts = trace_opts, 54 }; 55 56 #define is_graph() (tracer_flags.val & TRACE_DISPLAY_GRAPH) 57 58 #ifdef CONFIG_FUNCTION_TRACER 59 60 /* 61 * Prologue for the wakeup function tracers. 62 * 63 * Returns 1 if it is OK to continue, and preemption 64 * is disabled and data->disabled is incremented. 65 * 0 if the trace is to be ignored, and preemption 66 * is not disabled and data->disabled is 67 * kept the same. 68 * 69 * Note, this function is also used outside this ifdef but 70 * inside the #ifdef of the function graph tracer below. 71 * This is OK, since the function graph tracer is 72 * dependent on the function tracer. 73 */ 74 static int 75 func_prolog_preempt_disable(struct trace_array *tr, 76 struct trace_array_cpu **data, 77 int *pc) 78 { 79 long disabled; 80 int cpu; 81 82 if (likely(!wakeup_task)) 83 return 0; 84 85 *pc = preempt_count(); 86 preempt_disable_notrace(); 87 88 cpu = raw_smp_processor_id(); 89 if (cpu != wakeup_current_cpu) 90 goto out_enable; 91 92 *data = tr->data[cpu]; 93 disabled = atomic_inc_return(&(*data)->disabled); 94 if (unlikely(disabled != 1)) 95 goto out; 96 97 return 1; 98 99 out: 100 atomic_dec(&(*data)->disabled); 101 102 out_enable: 103 preempt_enable_notrace(); 104 return 0; 105 } 106 107 /* 108 * wakeup uses its own tracer function to keep the overhead down: 109 */ 110 static void 111 wakeup_tracer_call(unsigned long ip, unsigned long parent_ip) 112 { 113 struct trace_array *tr = wakeup_trace; 114 struct trace_array_cpu *data; 115 unsigned long flags; 116 int pc; 117 118 if (!func_prolog_preempt_disable(tr, &data, &pc)) 119 return; 120 121 local_irq_save(flags); 122 trace_function(tr, ip, parent_ip, flags, pc); 123 local_irq_restore(flags); 124 125 atomic_dec(&data->disabled); 126 preempt_enable_notrace(); 127 } 128 129 static struct ftrace_ops trace_ops __read_mostly = 130 { 131 .func = wakeup_tracer_call, 132 .flags = FTRACE_OPS_FL_GLOBAL, 133 }; 134 #endif /* CONFIG_FUNCTION_TRACER */ 135 136 static int start_func_tracer(int graph) 137 { 138 int ret; 139 140 if (!graph) 141 ret = register_ftrace_function(&trace_ops); 142 else 143 ret = register_ftrace_graph(&wakeup_graph_return, 144 &wakeup_graph_entry); 145 146 if (!ret && tracing_is_enabled()) 147 tracer_enabled = 1; 148 else 149 tracer_enabled = 0; 150 151 return ret; 152 } 153 154 static void stop_func_tracer(int graph) 155 { 156 tracer_enabled = 0; 157 158 if (!graph) 159 unregister_ftrace_function(&trace_ops); 160 else 161 unregister_ftrace_graph(); 162 } 163 164 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 165 static int wakeup_set_flag(u32 old_flags, u32 bit, int set) 166 { 167 168 if (!(bit & TRACE_DISPLAY_GRAPH)) 169 return -EINVAL; 170 171 if (!(is_graph() ^ set)) 172 return 0; 173 174 stop_func_tracer(!set); 175 176 wakeup_reset(wakeup_trace); 177 tracing_max_latency = 0; 178 179 return start_func_tracer(set); 180 } 181 182 static int wakeup_graph_entry(struct ftrace_graph_ent *trace) 183 { 184 struct trace_array *tr = wakeup_trace; 185 struct trace_array_cpu *data; 186 unsigned long flags; 187 int pc, ret = 0; 188 189 if (!func_prolog_preempt_disable(tr, &data, &pc)) 190 return 0; 191 192 local_save_flags(flags); 193 ret = __trace_graph_entry(tr, trace, flags, pc); 194 atomic_dec(&data->disabled); 195 preempt_enable_notrace(); 196 197 return ret; 198 } 199 200 static void wakeup_graph_return(struct ftrace_graph_ret *trace) 201 { 202 struct trace_array *tr = wakeup_trace; 203 struct trace_array_cpu *data; 204 unsigned long flags; 205 int pc; 206 207 if (!func_prolog_preempt_disable(tr, &data, &pc)) 208 return; 209 210 local_save_flags(flags); 211 __trace_graph_return(tr, trace, flags, pc); 212 atomic_dec(&data->disabled); 213 214 preempt_enable_notrace(); 215 return; 216 } 217 218 static void wakeup_trace_open(struct trace_iterator *iter) 219 { 220 if (is_graph()) 221 graph_trace_open(iter); 222 } 223 224 static void wakeup_trace_close(struct trace_iterator *iter) 225 { 226 if (iter->private) 227 graph_trace_close(iter); 228 } 229 230 #define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_PROC | \ 231 TRACE_GRAPH_PRINT_ABS_TIME | \ 232 TRACE_GRAPH_PRINT_DURATION) 233 234 static enum print_line_t wakeup_print_line(struct trace_iterator *iter) 235 { 236 /* 237 * In graph mode call the graph tracer output function, 238 * otherwise go with the TRACE_FN event handler 239 */ 240 if (is_graph()) 241 return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS); 242 243 return TRACE_TYPE_UNHANDLED; 244 } 245 246 static void wakeup_print_header(struct seq_file *s) 247 { 248 if (is_graph()) 249 print_graph_headers_flags(s, GRAPH_TRACER_FLAGS); 250 else 251 trace_default_header(s); 252 } 253 254 static void 255 __trace_function(struct trace_array *tr, 256 unsigned long ip, unsigned long parent_ip, 257 unsigned long flags, int pc) 258 { 259 if (is_graph()) 260 trace_graph_function(tr, ip, parent_ip, flags, pc); 261 else 262 trace_function(tr, ip, parent_ip, flags, pc); 263 } 264 #else 265 #define __trace_function trace_function 266 267 static int wakeup_set_flag(u32 old_flags, u32 bit, int set) 268 { 269 return -EINVAL; 270 } 271 272 static int wakeup_graph_entry(struct ftrace_graph_ent *trace) 273 { 274 return -1; 275 } 276 277 static enum print_line_t wakeup_print_line(struct trace_iterator *iter) 278 { 279 return TRACE_TYPE_UNHANDLED; 280 } 281 282 static void wakeup_graph_return(struct ftrace_graph_ret *trace) { } 283 static void wakeup_print_header(struct seq_file *s) { } 284 static void wakeup_trace_open(struct trace_iterator *iter) { } 285 static void wakeup_trace_close(struct trace_iterator *iter) { } 286 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ 287 288 /* 289 * Should this new latency be reported/recorded? 290 */ 291 static int report_latency(cycle_t delta) 292 { 293 if (tracing_thresh) { 294 if (delta < tracing_thresh) 295 return 0; 296 } else { 297 if (delta <= tracing_max_latency) 298 return 0; 299 } 300 return 1; 301 } 302 303 static void 304 probe_wakeup_migrate_task(void *ignore, struct task_struct *task, int cpu) 305 { 306 if (task != wakeup_task) 307 return; 308 309 wakeup_current_cpu = cpu; 310 } 311 312 static void notrace 313 probe_wakeup_sched_switch(void *ignore, 314 struct task_struct *prev, struct task_struct *next) 315 { 316 struct trace_array_cpu *data; 317 cycle_t T0, T1, delta; 318 unsigned long flags; 319 long disabled; 320 int cpu; 321 int pc; 322 323 tracing_record_cmdline(prev); 324 325 if (unlikely(!tracer_enabled)) 326 return; 327 328 /* 329 * When we start a new trace, we set wakeup_task to NULL 330 * and then set tracer_enabled = 1. We want to make sure 331 * that another CPU does not see the tracer_enabled = 1 332 * and the wakeup_task with an older task, that might 333 * actually be the same as next. 334 */ 335 smp_rmb(); 336 337 if (next != wakeup_task) 338 return; 339 340 pc = preempt_count(); 341 342 /* disable local data, not wakeup_cpu data */ 343 cpu = raw_smp_processor_id(); 344 disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled); 345 if (likely(disabled != 1)) 346 goto out; 347 348 local_irq_save(flags); 349 arch_spin_lock(&wakeup_lock); 350 351 /* We could race with grabbing wakeup_lock */ 352 if (unlikely(!tracer_enabled || next != wakeup_task)) 353 goto out_unlock; 354 355 /* The task we are waiting for is waking up */ 356 data = wakeup_trace->data[wakeup_cpu]; 357 358 __trace_function(wakeup_trace, CALLER_ADDR0, CALLER_ADDR1, flags, pc); 359 tracing_sched_switch_trace(wakeup_trace, prev, next, flags, pc); 360 361 T0 = data->preempt_timestamp; 362 T1 = ftrace_now(cpu); 363 delta = T1-T0; 364 365 if (!report_latency(delta)) 366 goto out_unlock; 367 368 if (likely(!is_tracing_stopped())) { 369 tracing_max_latency = delta; 370 update_max_tr(wakeup_trace, wakeup_task, wakeup_cpu); 371 } 372 373 out_unlock: 374 __wakeup_reset(wakeup_trace); 375 arch_spin_unlock(&wakeup_lock); 376 local_irq_restore(flags); 377 out: 378 atomic_dec(&wakeup_trace->data[cpu]->disabled); 379 } 380 381 static void __wakeup_reset(struct trace_array *tr) 382 { 383 wakeup_cpu = -1; 384 wakeup_prio = -1; 385 386 if (wakeup_task) 387 put_task_struct(wakeup_task); 388 389 wakeup_task = NULL; 390 } 391 392 static void wakeup_reset(struct trace_array *tr) 393 { 394 unsigned long flags; 395 396 tracing_reset_online_cpus(tr); 397 398 local_irq_save(flags); 399 arch_spin_lock(&wakeup_lock); 400 __wakeup_reset(tr); 401 arch_spin_unlock(&wakeup_lock); 402 local_irq_restore(flags); 403 } 404 405 static void 406 probe_wakeup(void *ignore, struct task_struct *p, int success) 407 { 408 struct trace_array_cpu *data; 409 int cpu = smp_processor_id(); 410 unsigned long flags; 411 long disabled; 412 int pc; 413 414 if (likely(!tracer_enabled)) 415 return; 416 417 tracing_record_cmdline(p); 418 tracing_record_cmdline(current); 419 420 if ((wakeup_rt && !rt_task(p)) || 421 p->prio >= wakeup_prio || 422 p->prio >= current->prio) 423 return; 424 425 pc = preempt_count(); 426 disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled); 427 if (unlikely(disabled != 1)) 428 goto out; 429 430 /* interrupts should be off from try_to_wake_up */ 431 arch_spin_lock(&wakeup_lock); 432 433 /* check for races. */ 434 if (!tracer_enabled || p->prio >= wakeup_prio) 435 goto out_locked; 436 437 /* reset the trace */ 438 __wakeup_reset(wakeup_trace); 439 440 wakeup_cpu = task_cpu(p); 441 wakeup_current_cpu = wakeup_cpu; 442 wakeup_prio = p->prio; 443 444 wakeup_task = p; 445 get_task_struct(wakeup_task); 446 447 local_save_flags(flags); 448 449 data = wakeup_trace->data[wakeup_cpu]; 450 data->preempt_timestamp = ftrace_now(cpu); 451 tracing_sched_wakeup_trace(wakeup_trace, p, current, flags, pc); 452 453 /* 454 * We must be careful in using CALLER_ADDR2. But since wake_up 455 * is not called by an assembly function (where as schedule is) 456 * it should be safe to use it here. 457 */ 458 __trace_function(wakeup_trace, CALLER_ADDR1, CALLER_ADDR2, flags, pc); 459 460 out_locked: 461 arch_spin_unlock(&wakeup_lock); 462 out: 463 atomic_dec(&wakeup_trace->data[cpu]->disabled); 464 } 465 466 static void start_wakeup_tracer(struct trace_array *tr) 467 { 468 int ret; 469 470 ret = register_trace_sched_wakeup(probe_wakeup, NULL); 471 if (ret) { 472 pr_info("wakeup trace: Couldn't activate tracepoint" 473 " probe to kernel_sched_wakeup\n"); 474 return; 475 } 476 477 ret = register_trace_sched_wakeup_new(probe_wakeup, NULL); 478 if (ret) { 479 pr_info("wakeup trace: Couldn't activate tracepoint" 480 " probe to kernel_sched_wakeup_new\n"); 481 goto fail_deprobe; 482 } 483 484 ret = register_trace_sched_switch(probe_wakeup_sched_switch, NULL); 485 if (ret) { 486 pr_info("sched trace: Couldn't activate tracepoint" 487 " probe to kernel_sched_switch\n"); 488 goto fail_deprobe_wake_new; 489 } 490 491 ret = register_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL); 492 if (ret) { 493 pr_info("wakeup trace: Couldn't activate tracepoint" 494 " probe to kernel_sched_migrate_task\n"); 495 return; 496 } 497 498 wakeup_reset(tr); 499 500 /* 501 * Don't let the tracer_enabled = 1 show up before 502 * the wakeup_task is reset. This may be overkill since 503 * wakeup_reset does a spin_unlock after setting the 504 * wakeup_task to NULL, but I want to be safe. 505 * This is a slow path anyway. 506 */ 507 smp_wmb(); 508 509 if (start_func_tracer(is_graph())) 510 printk(KERN_ERR "failed to start wakeup tracer\n"); 511 512 return; 513 fail_deprobe_wake_new: 514 unregister_trace_sched_wakeup_new(probe_wakeup, NULL); 515 fail_deprobe: 516 unregister_trace_sched_wakeup(probe_wakeup, NULL); 517 } 518 519 static void stop_wakeup_tracer(struct trace_array *tr) 520 { 521 tracer_enabled = 0; 522 stop_func_tracer(is_graph()); 523 unregister_trace_sched_switch(probe_wakeup_sched_switch, NULL); 524 unregister_trace_sched_wakeup_new(probe_wakeup, NULL); 525 unregister_trace_sched_wakeup(probe_wakeup, NULL); 526 unregister_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL); 527 } 528 529 static int __wakeup_tracer_init(struct trace_array *tr) 530 { 531 save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT; 532 trace_flags |= TRACE_ITER_LATENCY_FMT; 533 534 tracing_max_latency = 0; 535 wakeup_trace = tr; 536 start_wakeup_tracer(tr); 537 return 0; 538 } 539 540 static int wakeup_tracer_init(struct trace_array *tr) 541 { 542 wakeup_rt = 0; 543 return __wakeup_tracer_init(tr); 544 } 545 546 static int wakeup_rt_tracer_init(struct trace_array *tr) 547 { 548 wakeup_rt = 1; 549 return __wakeup_tracer_init(tr); 550 } 551 552 static void wakeup_tracer_reset(struct trace_array *tr) 553 { 554 stop_wakeup_tracer(tr); 555 /* make sure we put back any tasks we are tracing */ 556 wakeup_reset(tr); 557 558 if (!save_lat_flag) 559 trace_flags &= ~TRACE_ITER_LATENCY_FMT; 560 } 561 562 static void wakeup_tracer_start(struct trace_array *tr) 563 { 564 wakeup_reset(tr); 565 tracer_enabled = 1; 566 } 567 568 static void wakeup_tracer_stop(struct trace_array *tr) 569 { 570 tracer_enabled = 0; 571 } 572 573 static struct tracer wakeup_tracer __read_mostly = 574 { 575 .name = "wakeup", 576 .init = wakeup_tracer_init, 577 .reset = wakeup_tracer_reset, 578 .start = wakeup_tracer_start, 579 .stop = wakeup_tracer_stop, 580 .print_max = 1, 581 .print_header = wakeup_print_header, 582 .print_line = wakeup_print_line, 583 .flags = &tracer_flags, 584 .set_flag = wakeup_set_flag, 585 #ifdef CONFIG_FTRACE_SELFTEST 586 .selftest = trace_selftest_startup_wakeup, 587 #endif 588 .open = wakeup_trace_open, 589 .close = wakeup_trace_close, 590 .use_max_tr = 1, 591 }; 592 593 static struct tracer wakeup_rt_tracer __read_mostly = 594 { 595 .name = "wakeup_rt", 596 .init = wakeup_rt_tracer_init, 597 .reset = wakeup_tracer_reset, 598 .start = wakeup_tracer_start, 599 .stop = wakeup_tracer_stop, 600 .wait_pipe = poll_wait_pipe, 601 .print_max = 1, 602 .print_header = wakeup_print_header, 603 .print_line = wakeup_print_line, 604 .flags = &tracer_flags, 605 .set_flag = wakeup_set_flag, 606 #ifdef CONFIG_FTRACE_SELFTEST 607 .selftest = trace_selftest_startup_wakeup, 608 #endif 609 .open = wakeup_trace_open, 610 .close = wakeup_trace_close, 611 .use_max_tr = 1, 612 }; 613 614 __init static int init_wakeup_tracer(void) 615 { 616 int ret; 617 618 ret = register_tracer(&wakeup_tracer); 619 if (ret) 620 return ret; 621 622 ret = register_tracer(&wakeup_rt_tracer); 623 if (ret) 624 return ret; 625 626 return 0; 627 } 628 device_initcall(init_wakeup_tracer); 629