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