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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> | |
18 | ||
19 | #include "trace.h" | |
20 | ||
21 | static struct trace_array *wakeup_trace; | |
22 | static int __read_mostly tracer_enabled; | |
23 | ||
24 | static struct task_struct *wakeup_task; | |
25 | static int wakeup_cpu; | |
26 | static unsigned wakeup_prio = -1; | |
27 | ||
28 | static DEFINE_SPINLOCK(wakeup_lock); | |
29 | ||
e309b41d | 30 | static void __wakeup_reset(struct trace_array *tr); |
352ad25a SR |
31 | |
32 | /* | |
33 | * Should this new latency be reported/recorded? | |
34 | */ | |
e309b41d | 35 | static int report_latency(cycle_t delta) |
352ad25a SR |
36 | { |
37 | if (tracing_thresh) { | |
38 | if (delta < tracing_thresh) | |
39 | return 0; | |
40 | } else { | |
41 | if (delta <= tracing_max_latency) | |
42 | return 0; | |
43 | } | |
44 | return 1; | |
45 | } | |
46 | ||
e309b41d | 47 | void |
352ad25a SR |
48 | wakeup_sched_switch(struct task_struct *prev, struct task_struct *next) |
49 | { | |
50 | unsigned long latency = 0, t0 = 0, t1 = 0; | |
51 | struct trace_array *tr = wakeup_trace; | |
52 | struct trace_array_cpu *data; | |
53 | cycle_t T0, T1, delta; | |
54 | unsigned long flags; | |
55 | long disabled; | |
56 | int cpu; | |
57 | ||
58 | if (unlikely(!tracer_enabled)) | |
59 | return; | |
60 | ||
61 | /* | |
62 | * When we start a new trace, we set wakeup_task to NULL | |
63 | * and then set tracer_enabled = 1. We want to make sure | |
64 | * that another CPU does not see the tracer_enabled = 1 | |
65 | * and the wakeup_task with an older task, that might | |
66 | * actually be the same as next. | |
67 | */ | |
68 | smp_rmb(); | |
69 | ||
70 | if (next != wakeup_task) | |
71 | return; | |
72 | ||
73 | /* The task we are waitng for is waking up */ | |
74 | data = tr->data[wakeup_cpu]; | |
75 | ||
76 | /* disable local data, not wakeup_cpu data */ | |
77 | cpu = raw_smp_processor_id(); | |
78 | disabled = atomic_inc_return(&tr->data[cpu]->disabled); | |
79 | if (likely(disabled != 1)) | |
80 | goto out; | |
81 | ||
82 | spin_lock_irqsave(&wakeup_lock, flags); | |
83 | ||
84 | /* We could race with grabbing wakeup_lock */ | |
85 | if (unlikely(!tracer_enabled || next != wakeup_task)) | |
86 | goto out_unlock; | |
87 | ||
6fb44b71 | 88 | trace_function(tr, data, CALLER_ADDR1, CALLER_ADDR2, flags); |
352ad25a SR |
89 | |
90 | /* | |
91 | * usecs conversion is slow so we try to delay the conversion | |
92 | * as long as possible: | |
93 | */ | |
94 | T0 = data->preempt_timestamp; | |
750ed1a4 | 95 | T1 = ftrace_now(cpu); |
352ad25a SR |
96 | delta = T1-T0; |
97 | ||
98 | if (!report_latency(delta)) | |
99 | goto out_unlock; | |
100 | ||
101 | latency = nsecs_to_usecs(delta); | |
102 | ||
103 | tracing_max_latency = delta; | |
104 | t0 = nsecs_to_usecs(T0); | |
105 | t1 = nsecs_to_usecs(T1); | |
106 | ||
107 | update_max_tr(tr, wakeup_task, wakeup_cpu); | |
108 | ||
352ad25a SR |
109 | out_unlock: |
110 | __wakeup_reset(tr); | |
111 | spin_unlock_irqrestore(&wakeup_lock, flags); | |
112 | out: | |
113 | atomic_dec(&tr->data[cpu]->disabled); | |
114 | } | |
115 | ||
e309b41d | 116 | static void __wakeup_reset(struct trace_array *tr) |
352ad25a SR |
117 | { |
118 | struct trace_array_cpu *data; | |
119 | int cpu; | |
120 | ||
121 | assert_spin_locked(&wakeup_lock); | |
122 | ||
123 | for_each_possible_cpu(cpu) { | |
124 | data = tr->data[cpu]; | |
125 | tracing_reset(data); | |
126 | } | |
127 | ||
128 | wakeup_cpu = -1; | |
129 | wakeup_prio = -1; | |
130 | ||
131 | if (wakeup_task) | |
132 | put_task_struct(wakeup_task); | |
133 | ||
134 | wakeup_task = NULL; | |
135 | } | |
136 | ||
e309b41d | 137 | static void wakeup_reset(struct trace_array *tr) |
352ad25a SR |
138 | { |
139 | unsigned long flags; | |
140 | ||
141 | spin_lock_irqsave(&wakeup_lock, flags); | |
142 | __wakeup_reset(tr); | |
143 | spin_unlock_irqrestore(&wakeup_lock, flags); | |
144 | } | |
145 | ||
e309b41d | 146 | static void |
352ad25a SR |
147 | wakeup_check_start(struct trace_array *tr, struct task_struct *p, |
148 | struct task_struct *curr) | |
149 | { | |
150 | int cpu = smp_processor_id(); | |
151 | unsigned long flags; | |
152 | long disabled; | |
153 | ||
154 | if (likely(!rt_task(p)) || | |
155 | p->prio >= wakeup_prio || | |
156 | p->prio >= curr->prio) | |
157 | return; | |
158 | ||
159 | disabled = atomic_inc_return(&tr->data[cpu]->disabled); | |
160 | if (unlikely(disabled != 1)) | |
161 | goto out; | |
162 | ||
163 | /* interrupts should be off from try_to_wake_up */ | |
164 | spin_lock(&wakeup_lock); | |
165 | ||
166 | /* check for races. */ | |
167 | if (!tracer_enabled || p->prio >= wakeup_prio) | |
168 | goto out_locked; | |
169 | ||
170 | /* reset the trace */ | |
171 | __wakeup_reset(tr); | |
172 | ||
173 | wakeup_cpu = task_cpu(p); | |
174 | wakeup_prio = p->prio; | |
175 | ||
176 | wakeup_task = p; | |
177 | get_task_struct(wakeup_task); | |
178 | ||
179 | local_save_flags(flags); | |
180 | ||
750ed1a4 | 181 | tr->data[wakeup_cpu]->preempt_timestamp = ftrace_now(cpu); |
6fb44b71 SR |
182 | trace_function(tr, tr->data[wakeup_cpu], |
183 | CALLER_ADDR1, CALLER_ADDR2, flags); | |
352ad25a SR |
184 | |
185 | out_locked: | |
186 | spin_unlock(&wakeup_lock); | |
187 | out: | |
188 | atomic_dec(&tr->data[cpu]->disabled); | |
189 | } | |
190 | ||
8ac0fca4 | 191 | void wakeup_sched_wakeup(struct task_struct *wakee, struct task_struct *curr) |
352ad25a SR |
192 | { |
193 | if (likely(!tracer_enabled)) | |
194 | return; | |
195 | ||
8ac0fca4 IM |
196 | tracing_record_cmdline(curr); |
197 | tracing_record_cmdline(wakee); | |
352ad25a SR |
198 | |
199 | wakeup_check_start(wakeup_trace, wakee, curr); | |
200 | } | |
201 | ||
e309b41d | 202 | static void start_wakeup_tracer(struct trace_array *tr) |
352ad25a SR |
203 | { |
204 | wakeup_reset(tr); | |
205 | ||
206 | /* | |
207 | * Don't let the tracer_enabled = 1 show up before | |
208 | * the wakeup_task is reset. This may be overkill since | |
209 | * wakeup_reset does a spin_unlock after setting the | |
210 | * wakeup_task to NULL, but I want to be safe. | |
211 | * This is a slow path anyway. | |
212 | */ | |
213 | smp_wmb(); | |
214 | ||
215 | tracer_enabled = 1; | |
216 | ||
217 | return; | |
218 | } | |
219 | ||
e309b41d | 220 | static void stop_wakeup_tracer(struct trace_array *tr) |
352ad25a SR |
221 | { |
222 | tracer_enabled = 0; | |
223 | } | |
224 | ||
e309b41d | 225 | static void wakeup_tracer_init(struct trace_array *tr) |
352ad25a SR |
226 | { |
227 | wakeup_trace = tr; | |
228 | ||
229 | if (tr->ctrl) | |
230 | start_wakeup_tracer(tr); | |
231 | } | |
232 | ||
e309b41d | 233 | static void wakeup_tracer_reset(struct trace_array *tr) |
352ad25a SR |
234 | { |
235 | if (tr->ctrl) { | |
236 | stop_wakeup_tracer(tr); | |
237 | /* make sure we put back any tasks we are tracing */ | |
238 | wakeup_reset(tr); | |
239 | } | |
240 | } | |
241 | ||
242 | static void wakeup_tracer_ctrl_update(struct trace_array *tr) | |
243 | { | |
244 | if (tr->ctrl) | |
245 | start_wakeup_tracer(tr); | |
246 | else | |
247 | stop_wakeup_tracer(tr); | |
248 | } | |
249 | ||
e309b41d | 250 | static void wakeup_tracer_open(struct trace_iterator *iter) |
352ad25a SR |
251 | { |
252 | /* stop the trace while dumping */ | |
253 | if (iter->tr->ctrl) | |
254 | stop_wakeup_tracer(iter->tr); | |
255 | } | |
256 | ||
e309b41d | 257 | static void wakeup_tracer_close(struct trace_iterator *iter) |
352ad25a SR |
258 | { |
259 | /* forget about any processes we were recording */ | |
260 | if (iter->tr->ctrl) | |
261 | start_wakeup_tracer(iter->tr); | |
262 | } | |
263 | ||
264 | static struct tracer wakeup_tracer __read_mostly = | |
265 | { | |
266 | .name = "wakeup", | |
267 | .init = wakeup_tracer_init, | |
268 | .reset = wakeup_tracer_reset, | |
269 | .open = wakeup_tracer_open, | |
270 | .close = wakeup_tracer_close, | |
271 | .ctrl_update = wakeup_tracer_ctrl_update, | |
272 | .print_max = 1, | |
60a11774 SR |
273 | #ifdef CONFIG_FTRACE_SELFTEST |
274 | .selftest = trace_selftest_startup_wakeup, | |
275 | #endif | |
352ad25a SR |
276 | }; |
277 | ||
278 | __init static int init_wakeup_tracer(void) | |
279 | { | |
280 | int ret; | |
281 | ||
282 | ret = register_tracer(&wakeup_tracer); | |
283 | if (ret) | |
284 | return ret; | |
285 | ||
286 | return 0; | |
287 | } | |
288 | device_initcall(init_wakeup_tracer); |