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352ad25a SR |
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> | |
b07c3f19 | 18 | #include <trace/sched.h> |
352ad25a SR |
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 | ||
e59494f4 SR |
29 | static raw_spinlock_t wakeup_lock = |
30 | (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED; | |
352ad25a | 31 | |
e309b41d | 32 | static void __wakeup_reset(struct trace_array *tr); |
352ad25a | 33 | |
7e18d8e7 SR |
34 | #ifdef CONFIG_FTRACE |
35 | /* | |
36 | * irqsoff uses its own tracer function to keep the overhead down: | |
37 | */ | |
38 | static void | |
39 | wakeup_tracer_call(unsigned long ip, unsigned long parent_ip) | |
40 | { | |
41 | struct trace_array *tr = wakeup_trace; | |
42 | struct trace_array_cpu *data; | |
43 | unsigned long flags; | |
44 | long disabled; | |
45 | int resched; | |
46 | int cpu; | |
47 | ||
48 | if (likely(!wakeup_task)) | |
49 | return; | |
50 | ||
51 | resched = need_resched(); | |
52 | preempt_disable_notrace(); | |
53 | ||
54 | cpu = raw_smp_processor_id(); | |
55 | data = tr->data[cpu]; | |
56 | disabled = atomic_inc_return(&data->disabled); | |
57 | if (unlikely(disabled != 1)) | |
58 | goto out; | |
59 | ||
e59494f4 SR |
60 | local_irq_save(flags); |
61 | __raw_spin_lock(&wakeup_lock); | |
7e18d8e7 SR |
62 | |
63 | if (unlikely(!wakeup_task)) | |
64 | goto unlock; | |
65 | ||
66 | /* | |
67 | * The task can't disappear because it needs to | |
68 | * wake up first, and we have the wakeup_lock. | |
69 | */ | |
70 | if (task_cpu(wakeup_task) != cpu) | |
71 | goto unlock; | |
72 | ||
73 | trace_function(tr, data, ip, parent_ip, flags); | |
74 | ||
75 | unlock: | |
e59494f4 SR |
76 | __raw_spin_unlock(&wakeup_lock); |
77 | local_irq_restore(flags); | |
7e18d8e7 SR |
78 | |
79 | out: | |
80 | atomic_dec(&data->disabled); | |
81 | ||
82 | /* | |
83 | * To prevent recursion from the scheduler, if the | |
84 | * resched flag was set before we entered, then | |
85 | * don't reschedule. | |
86 | */ | |
87 | if (resched) | |
88 | preempt_enable_no_resched_notrace(); | |
89 | else | |
90 | preempt_enable_notrace(); | |
91 | } | |
92 | ||
93 | static struct ftrace_ops trace_ops __read_mostly = | |
94 | { | |
95 | .func = wakeup_tracer_call, | |
96 | }; | |
97 | #endif /* CONFIG_FTRACE */ | |
98 | ||
352ad25a SR |
99 | /* |
100 | * Should this new latency be reported/recorded? | |
101 | */ | |
e309b41d | 102 | static int report_latency(cycle_t delta) |
352ad25a SR |
103 | { |
104 | if (tracing_thresh) { | |
105 | if (delta < tracing_thresh) | |
106 | return 0; | |
107 | } else { | |
108 | if (delta <= tracing_max_latency) | |
109 | return 0; | |
110 | } | |
111 | return 1; | |
112 | } | |
113 | ||
5b82a1b0 | 114 | static void notrace |
b07c3f19 | 115 | probe_wakeup_sched_switch(struct rq *rq, struct task_struct *prev, |
5b82a1b0 | 116 | struct task_struct *next) |
352ad25a SR |
117 | { |
118 | unsigned long latency = 0, t0 = 0, t1 = 0; | |
352ad25a SR |
119 | struct trace_array_cpu *data; |
120 | cycle_t T0, T1, delta; | |
121 | unsigned long flags; | |
122 | long disabled; | |
123 | int cpu; | |
124 | ||
b07c3f19 MD |
125 | tracing_record_cmdline(prev); |
126 | ||
352ad25a SR |
127 | if (unlikely(!tracer_enabled)) |
128 | return; | |
129 | ||
130 | /* | |
131 | * When we start a new trace, we set wakeup_task to NULL | |
132 | * and then set tracer_enabled = 1. We want to make sure | |
133 | * that another CPU does not see the tracer_enabled = 1 | |
134 | * and the wakeup_task with an older task, that might | |
135 | * actually be the same as next. | |
136 | */ | |
137 | smp_rmb(); | |
138 | ||
139 | if (next != wakeup_task) | |
140 | return; | |
141 | ||
7e18d8e7 | 142 | /* The task we are waiting for is waking up */ |
b07c3f19 | 143 | data = wakeup_trace->data[wakeup_cpu]; |
352ad25a SR |
144 | |
145 | /* disable local data, not wakeup_cpu data */ | |
146 | cpu = raw_smp_processor_id(); | |
b07c3f19 | 147 | disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled); |
352ad25a SR |
148 | if (likely(disabled != 1)) |
149 | goto out; | |
150 | ||
e59494f4 SR |
151 | local_irq_save(flags); |
152 | __raw_spin_lock(&wakeup_lock); | |
352ad25a SR |
153 | |
154 | /* We could race with grabbing wakeup_lock */ | |
155 | if (unlikely(!tracer_enabled || next != wakeup_task)) | |
156 | goto out_unlock; | |
157 | ||
b07c3f19 | 158 | trace_function(wakeup_trace, data, CALLER_ADDR1, CALLER_ADDR2, flags); |
352ad25a SR |
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; | |
750ed1a4 | 165 | T1 = ftrace_now(cpu); |
352ad25a SR |
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 | ||
b07c3f19 | 177 | update_max_tr(wakeup_trace, wakeup_task, wakeup_cpu); |
352ad25a | 178 | |
352ad25a | 179 | out_unlock: |
b07c3f19 | 180 | __wakeup_reset(wakeup_trace); |
e59494f4 SR |
181 | __raw_spin_unlock(&wakeup_lock); |
182 | local_irq_restore(flags); | |
352ad25a | 183 | out: |
b07c3f19 | 184 | atomic_dec(&wakeup_trace->data[cpu]->disabled); |
5b82a1b0 MD |
185 | } |
186 | ||
e309b41d | 187 | static void __wakeup_reset(struct trace_array *tr) |
352ad25a SR |
188 | { |
189 | struct trace_array_cpu *data; | |
190 | int cpu; | |
191 | ||
352ad25a SR |
192 | for_each_possible_cpu(cpu) { |
193 | data = tr->data[cpu]; | |
3928a8a2 | 194 | tracing_reset(tr, cpu); |
352ad25a SR |
195 | } |
196 | ||
197 | wakeup_cpu = -1; | |
198 | wakeup_prio = -1; | |
199 | ||
200 | if (wakeup_task) | |
201 | put_task_struct(wakeup_task); | |
202 | ||
203 | wakeup_task = NULL; | |
204 | } | |
205 | ||
e309b41d | 206 | static void wakeup_reset(struct trace_array *tr) |
352ad25a SR |
207 | { |
208 | unsigned long flags; | |
209 | ||
e59494f4 SR |
210 | local_irq_save(flags); |
211 | __raw_spin_lock(&wakeup_lock); | |
352ad25a | 212 | __wakeup_reset(tr); |
e59494f4 SR |
213 | __raw_spin_unlock(&wakeup_lock); |
214 | local_irq_restore(flags); | |
352ad25a SR |
215 | } |
216 | ||
e309b41d | 217 | static void |
b07c3f19 | 218 | probe_wakeup(struct rq *rq, struct task_struct *p) |
352ad25a SR |
219 | { |
220 | int cpu = smp_processor_id(); | |
221 | unsigned long flags; | |
222 | long disabled; | |
223 | ||
b07c3f19 MD |
224 | if (likely(!tracer_enabled)) |
225 | return; | |
226 | ||
227 | tracing_record_cmdline(p); | |
228 | tracing_record_cmdline(current); | |
229 | ||
352ad25a SR |
230 | if (likely(!rt_task(p)) || |
231 | p->prio >= wakeup_prio || | |
b07c3f19 | 232 | p->prio >= current->prio) |
352ad25a SR |
233 | return; |
234 | ||
b07c3f19 | 235 | disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled); |
352ad25a SR |
236 | if (unlikely(disabled != 1)) |
237 | goto out; | |
238 | ||
239 | /* interrupts should be off from try_to_wake_up */ | |
e59494f4 | 240 | __raw_spin_lock(&wakeup_lock); |
352ad25a SR |
241 | |
242 | /* check for races. */ | |
243 | if (!tracer_enabled || p->prio >= wakeup_prio) | |
244 | goto out_locked; | |
245 | ||
246 | /* reset the trace */ | |
b07c3f19 | 247 | __wakeup_reset(wakeup_trace); |
352ad25a SR |
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 | ||
b07c3f19 MD |
257 | wakeup_trace->data[wakeup_cpu]->preempt_timestamp = ftrace_now(cpu); |
258 | trace_function(wakeup_trace, wakeup_trace->data[wakeup_cpu], | |
6fb44b71 | 259 | CALLER_ADDR1, CALLER_ADDR2, flags); |
352ad25a SR |
260 | |
261 | out_locked: | |
e59494f4 | 262 | __raw_spin_unlock(&wakeup_lock); |
352ad25a | 263 | out: |
b07c3f19 | 264 | atomic_dec(&wakeup_trace->data[cpu]->disabled); |
352ad25a SR |
265 | } |
266 | ||
e309b41d | 267 | static void start_wakeup_tracer(struct trace_array *tr) |
352ad25a | 268 | { |
5b82a1b0 MD |
269 | int ret; |
270 | ||
b07c3f19 | 271 | ret = register_trace_sched_wakeup(probe_wakeup); |
5b82a1b0 | 272 | if (ret) { |
b07c3f19 | 273 | pr_info("wakeup trace: Couldn't activate tracepoint" |
5b82a1b0 MD |
274 | " probe to kernel_sched_wakeup\n"); |
275 | return; | |
276 | } | |
277 | ||
b07c3f19 | 278 | ret = register_trace_sched_wakeup_new(probe_wakeup); |
5b82a1b0 | 279 | if (ret) { |
b07c3f19 | 280 | pr_info("wakeup trace: Couldn't activate tracepoint" |
5b82a1b0 MD |
281 | " probe to kernel_sched_wakeup_new\n"); |
282 | goto fail_deprobe; | |
283 | } | |
284 | ||
b07c3f19 | 285 | ret = register_trace_sched_switch(probe_wakeup_sched_switch); |
5b82a1b0 | 286 | if (ret) { |
b07c3f19 | 287 | pr_info("sched trace: Couldn't activate tracepoint" |
5b82a1b0 MD |
288 | " probe to kernel_sched_schedule\n"); |
289 | goto fail_deprobe_wake_new; | |
290 | } | |
291 | ||
352ad25a SR |
292 | wakeup_reset(tr); |
293 | ||
294 | /* | |
295 | * Don't let the tracer_enabled = 1 show up before | |
296 | * the wakeup_task is reset. This may be overkill since | |
297 | * wakeup_reset does a spin_unlock after setting the | |
298 | * wakeup_task to NULL, but I want to be safe. | |
299 | * This is a slow path anyway. | |
300 | */ | |
301 | smp_wmb(); | |
302 | ||
7e18d8e7 | 303 | register_ftrace_function(&trace_ops); |
352ad25a | 304 | |
ad591240 SR |
305 | tracer_enabled = 1; |
306 | ||
352ad25a | 307 | return; |
5b82a1b0 | 308 | fail_deprobe_wake_new: |
b07c3f19 | 309 | unregister_trace_sched_wakeup_new(probe_wakeup); |
5b82a1b0 | 310 | fail_deprobe: |
b07c3f19 | 311 | unregister_trace_sched_wakeup(probe_wakeup); |
352ad25a SR |
312 | } |
313 | ||
e309b41d | 314 | static void stop_wakeup_tracer(struct trace_array *tr) |
352ad25a SR |
315 | { |
316 | tracer_enabled = 0; | |
7e18d8e7 | 317 | unregister_ftrace_function(&trace_ops); |
b07c3f19 MD |
318 | unregister_trace_sched_switch(probe_wakeup_sched_switch); |
319 | unregister_trace_sched_wakeup_new(probe_wakeup); | |
320 | unregister_trace_sched_wakeup(probe_wakeup); | |
352ad25a SR |
321 | } |
322 | ||
e309b41d | 323 | static void wakeup_tracer_init(struct trace_array *tr) |
352ad25a SR |
324 | { |
325 | wakeup_trace = tr; | |
326 | ||
327 | if (tr->ctrl) | |
328 | start_wakeup_tracer(tr); | |
329 | } | |
330 | ||
e309b41d | 331 | static void wakeup_tracer_reset(struct trace_array *tr) |
352ad25a SR |
332 | { |
333 | if (tr->ctrl) { | |
334 | stop_wakeup_tracer(tr); | |
335 | /* make sure we put back any tasks we are tracing */ | |
336 | wakeup_reset(tr); | |
337 | } | |
338 | } | |
339 | ||
340 | static void wakeup_tracer_ctrl_update(struct trace_array *tr) | |
341 | { | |
342 | if (tr->ctrl) | |
343 | start_wakeup_tracer(tr); | |
344 | else | |
345 | stop_wakeup_tracer(tr); | |
346 | } | |
347 | ||
e309b41d | 348 | static void wakeup_tracer_open(struct trace_iterator *iter) |
352ad25a SR |
349 | { |
350 | /* stop the trace while dumping */ | |
351 | if (iter->tr->ctrl) | |
352 | stop_wakeup_tracer(iter->tr); | |
353 | } | |
354 | ||
e309b41d | 355 | static void wakeup_tracer_close(struct trace_iterator *iter) |
352ad25a SR |
356 | { |
357 | /* forget about any processes we were recording */ | |
358 | if (iter->tr->ctrl) | |
359 | start_wakeup_tracer(iter->tr); | |
360 | } | |
361 | ||
362 | static struct tracer wakeup_tracer __read_mostly = | |
363 | { | |
364 | .name = "wakeup", | |
365 | .init = wakeup_tracer_init, | |
366 | .reset = wakeup_tracer_reset, | |
367 | .open = wakeup_tracer_open, | |
368 | .close = wakeup_tracer_close, | |
369 | .ctrl_update = wakeup_tracer_ctrl_update, | |
370 | .print_max = 1, | |
60a11774 SR |
371 | #ifdef CONFIG_FTRACE_SELFTEST |
372 | .selftest = trace_selftest_startup_wakeup, | |
373 | #endif | |
352ad25a SR |
374 | }; |
375 | ||
376 | __init static int init_wakeup_tracer(void) | |
377 | { | |
378 | int ret; | |
379 | ||
380 | ret = register_tracer(&wakeup_tracer); | |
381 | if (ret) | |
382 | return ret; | |
383 | ||
384 | return 0; | |
385 | } | |
386 | device_initcall(init_wakeup_tracer); |