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 unsigned wakeup_prio = -1; 28 static int wakeup_rt; 29 30 static raw_spinlock_t wakeup_lock = 31 (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED; 32 33 static void __wakeup_reset(struct trace_array *tr); 34 35 static int save_lat_flag; 36 37 #ifdef CONFIG_FUNCTION_TRACER 38 /* 39 * irqsoff uses its own tracer function to keep the overhead down: 40 */ 41 static void 42 wakeup_tracer_call(unsigned long ip, unsigned long parent_ip) 43 { 44 struct trace_array *tr = wakeup_trace; 45 struct trace_array_cpu *data; 46 unsigned long flags; 47 long disabled; 48 int resched; 49 int cpu; 50 int pc; 51 52 if (likely(!wakeup_task)) 53 return; 54 55 pc = preempt_count(); 56 resched = ftrace_preempt_disable(); 57 58 cpu = raw_smp_processor_id(); 59 data = tr->data[cpu]; 60 disabled = atomic_inc_return(&data->disabled); 61 if (unlikely(disabled != 1)) 62 goto out; 63 64 local_irq_save(flags); 65 __raw_spin_lock(&wakeup_lock); 66 67 if (unlikely(!wakeup_task)) 68 goto unlock; 69 70 /* 71 * The task can't disappear because it needs to 72 * wake up first, and we have the wakeup_lock. 73 */ 74 if (task_cpu(wakeup_task) != cpu) 75 goto unlock; 76 77 trace_function(tr, ip, parent_ip, flags, pc); 78 79 unlock: 80 __raw_spin_unlock(&wakeup_lock); 81 local_irq_restore(flags); 82 83 out: 84 atomic_dec(&data->disabled); 85 86 ftrace_preempt_enable(resched); 87 } 88 89 static struct ftrace_ops trace_ops __read_mostly = 90 { 91 .func = wakeup_tracer_call, 92 }; 93 #endif /* CONFIG_FUNCTION_TRACER */ 94 95 /* 96 * Should this new latency be reported/recorded? 97 */ 98 static int report_latency(cycle_t delta) 99 { 100 if (tracing_thresh) { 101 if (delta < tracing_thresh) 102 return 0; 103 } else { 104 if (delta <= tracing_max_latency) 105 return 0; 106 } 107 return 1; 108 } 109 110 static void notrace 111 probe_wakeup_sched_switch(struct rq *rq, struct task_struct *prev, 112 struct task_struct *next) 113 { 114 unsigned long latency = 0, t0 = 0, t1 = 0; 115 struct trace_array_cpu *data; 116 cycle_t T0, T1, delta; 117 unsigned long flags; 118 long disabled; 119 int cpu; 120 int pc; 121 122 tracing_record_cmdline(prev); 123 124 if (unlikely(!tracer_enabled)) 125 return; 126 127 /* 128 * When we start a new trace, we set wakeup_task to NULL 129 * and then set tracer_enabled = 1. We want to make sure 130 * that another CPU does not see the tracer_enabled = 1 131 * and the wakeup_task with an older task, that might 132 * actually be the same as next. 133 */ 134 smp_rmb(); 135 136 if (next != wakeup_task) 137 return; 138 139 pc = preempt_count(); 140 141 /* disable local data, not wakeup_cpu data */ 142 cpu = raw_smp_processor_id(); 143 disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled); 144 if (likely(disabled != 1)) 145 goto out; 146 147 local_irq_save(flags); 148 __raw_spin_lock(&wakeup_lock); 149 150 /* We could race with grabbing wakeup_lock */ 151 if (unlikely(!tracer_enabled || next != wakeup_task)) 152 goto out_unlock; 153 154 /* The task we are waiting for is waking up */ 155 data = wakeup_trace->data[wakeup_cpu]; 156 157 trace_function(wakeup_trace, CALLER_ADDR0, CALLER_ADDR1, flags, pc); 158 tracing_sched_switch_trace(wakeup_trace, prev, next, flags, pc); 159 160 /* 161 * usecs conversion is slow so we try to delay the conversion 162 * as long as possible: 163 */ 164 T0 = data->preempt_timestamp; 165 T1 = ftrace_now(cpu); 166 delta = T1-T0; 167 168 if (!report_latency(delta)) 169 goto out_unlock; 170 171 latency = nsecs_to_usecs(delta); 172 173 tracing_max_latency = delta; 174 t0 = nsecs_to_usecs(T0); 175 t1 = nsecs_to_usecs(T1); 176 177 update_max_tr(wakeup_trace, wakeup_task, wakeup_cpu); 178 179 out_unlock: 180 __wakeup_reset(wakeup_trace); 181 __raw_spin_unlock(&wakeup_lock); 182 local_irq_restore(flags); 183 out: 184 atomic_dec(&wakeup_trace->data[cpu]->disabled); 185 } 186 187 static void __wakeup_reset(struct trace_array *tr) 188 { 189 int cpu; 190 191 for_each_possible_cpu(cpu) 192 tracing_reset(tr, cpu); 193 194 wakeup_cpu = -1; 195 wakeup_prio = -1; 196 197 if (wakeup_task) 198 put_task_struct(wakeup_task); 199 200 wakeup_task = NULL; 201 } 202 203 static void wakeup_reset(struct trace_array *tr) 204 { 205 unsigned long flags; 206 207 local_irq_save(flags); 208 __raw_spin_lock(&wakeup_lock); 209 __wakeup_reset(tr); 210 __raw_spin_unlock(&wakeup_lock); 211 local_irq_restore(flags); 212 } 213 214 static void 215 probe_wakeup(struct rq *rq, struct task_struct *p, int success) 216 { 217 struct trace_array_cpu *data; 218 int cpu = smp_processor_id(); 219 unsigned long flags; 220 long disabled; 221 int pc; 222 223 if (likely(!tracer_enabled)) 224 return; 225 226 tracing_record_cmdline(p); 227 tracing_record_cmdline(current); 228 229 if ((wakeup_rt && !rt_task(p)) || 230 p->prio >= wakeup_prio || 231 p->prio >= current->prio) 232 return; 233 234 pc = preempt_count(); 235 disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled); 236 if (unlikely(disabled != 1)) 237 goto out; 238 239 /* interrupts should be off from try_to_wake_up */ 240 __raw_spin_lock(&wakeup_lock); 241 242 /* check for races. */ 243 if (!tracer_enabled || p->prio >= wakeup_prio) 244 goto out_locked; 245 246 /* reset the trace */ 247 __wakeup_reset(wakeup_trace); 248 249 wakeup_cpu = task_cpu(p); 250 wakeup_prio = p->prio; 251 252 wakeup_task = p; 253 get_task_struct(wakeup_task); 254 255 local_save_flags(flags); 256 257 data = wakeup_trace->data[wakeup_cpu]; 258 data->preempt_timestamp = ftrace_now(cpu); 259 tracing_sched_wakeup_trace(wakeup_trace, p, current, flags, pc); 260 261 /* 262 * We must be careful in using CALLER_ADDR2. But since wake_up 263 * is not called by an assembly function (where as schedule is) 264 * it should be safe to use it here. 265 */ 266 trace_function(wakeup_trace, CALLER_ADDR1, CALLER_ADDR2, flags, pc); 267 268 out_locked: 269 __raw_spin_unlock(&wakeup_lock); 270 out: 271 atomic_dec(&wakeup_trace->data[cpu]->disabled); 272 } 273 274 static void start_wakeup_tracer(struct trace_array *tr) 275 { 276 int ret; 277 278 ret = register_trace_sched_wakeup(probe_wakeup); 279 if (ret) { 280 pr_info("wakeup trace: Couldn't activate tracepoint" 281 " probe to kernel_sched_wakeup\n"); 282 return; 283 } 284 285 ret = register_trace_sched_wakeup_new(probe_wakeup); 286 if (ret) { 287 pr_info("wakeup trace: Couldn't activate tracepoint" 288 " probe to kernel_sched_wakeup_new\n"); 289 goto fail_deprobe; 290 } 291 292 ret = register_trace_sched_switch(probe_wakeup_sched_switch); 293 if (ret) { 294 pr_info("sched trace: Couldn't activate tracepoint" 295 " probe to kernel_sched_switch\n"); 296 goto fail_deprobe_wake_new; 297 } 298 299 wakeup_reset(tr); 300 301 /* 302 * Don't let the tracer_enabled = 1 show up before 303 * the wakeup_task is reset. This may be overkill since 304 * wakeup_reset does a spin_unlock after setting the 305 * wakeup_task to NULL, but I want to be safe. 306 * This is a slow path anyway. 307 */ 308 smp_wmb(); 309 310 register_ftrace_function(&trace_ops); 311 312 if (tracing_is_enabled()) 313 tracer_enabled = 1; 314 else 315 tracer_enabled = 0; 316 317 return; 318 fail_deprobe_wake_new: 319 unregister_trace_sched_wakeup_new(probe_wakeup); 320 fail_deprobe: 321 unregister_trace_sched_wakeup(probe_wakeup); 322 } 323 324 static void stop_wakeup_tracer(struct trace_array *tr) 325 { 326 tracer_enabled = 0; 327 unregister_ftrace_function(&trace_ops); 328 unregister_trace_sched_switch(probe_wakeup_sched_switch); 329 unregister_trace_sched_wakeup_new(probe_wakeup); 330 unregister_trace_sched_wakeup(probe_wakeup); 331 } 332 333 static int __wakeup_tracer_init(struct trace_array *tr) 334 { 335 save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT; 336 trace_flags |= TRACE_ITER_LATENCY_FMT; 337 338 tracing_max_latency = 0; 339 wakeup_trace = tr; 340 start_wakeup_tracer(tr); 341 return 0; 342 } 343 344 static int wakeup_tracer_init(struct trace_array *tr) 345 { 346 wakeup_rt = 0; 347 return __wakeup_tracer_init(tr); 348 } 349 350 static int wakeup_rt_tracer_init(struct trace_array *tr) 351 { 352 wakeup_rt = 1; 353 return __wakeup_tracer_init(tr); 354 } 355 356 static void wakeup_tracer_reset(struct trace_array *tr) 357 { 358 stop_wakeup_tracer(tr); 359 /* make sure we put back any tasks we are tracing */ 360 wakeup_reset(tr); 361 362 if (!save_lat_flag) 363 trace_flags &= ~TRACE_ITER_LATENCY_FMT; 364 } 365 366 static void wakeup_tracer_start(struct trace_array *tr) 367 { 368 wakeup_reset(tr); 369 tracer_enabled = 1; 370 } 371 372 static void wakeup_tracer_stop(struct trace_array *tr) 373 { 374 tracer_enabled = 0; 375 } 376 377 static struct tracer wakeup_tracer __read_mostly = 378 { 379 .name = "wakeup", 380 .init = wakeup_tracer_init, 381 .reset = wakeup_tracer_reset, 382 .start = wakeup_tracer_start, 383 .stop = wakeup_tracer_stop, 384 .print_max = 1, 385 #ifdef CONFIG_FTRACE_SELFTEST 386 .selftest = trace_selftest_startup_wakeup, 387 #endif 388 }; 389 390 static struct tracer wakeup_rt_tracer __read_mostly = 391 { 392 .name = "wakeup_rt", 393 .init = wakeup_rt_tracer_init, 394 .reset = wakeup_tracer_reset, 395 .start = wakeup_tracer_start, 396 .stop = wakeup_tracer_stop, 397 .wait_pipe = poll_wait_pipe, 398 .print_max = 1, 399 #ifdef CONFIG_FTRACE_SELFTEST 400 .selftest = trace_selftest_startup_wakeup, 401 #endif 402 }; 403 404 __init static int init_wakeup_tracer(void) 405 { 406 int ret; 407 408 ret = register_tracer(&wakeup_tracer); 409 if (ret) 410 return ret; 411 412 ret = register_tracer(&wakeup_rt_tracer); 413 if (ret) 414 return ret; 415 416 return 0; 417 } 418 device_initcall(init_wakeup_tracer); 419