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
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