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