ftrace: cleanups
[linux-2.6] / kernel / trace / trace_sched_wakeup.c
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
30 static void notrace __wakeup_reset(struct trace_array *tr);
31
32 /*
33  * Should this new latency be reported/recorded?
34  */
35 static int notrace report_latency(cycle_t delta)
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
47 void notrace
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
88         ftrace(tr, data, CALLER_ADDR1, CALLER_ADDR2, flags);
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;
95         T1 = now(cpu);
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
109         if (tracing_thresh) {
110                 printk(KERN_INFO "(%16s-%-5d|#%d):"
111                         " %lu us wakeup latency violates %lu us threshold.\n",
112                                 wakeup_task->comm, wakeup_task->pid,
113                                 raw_smp_processor_id(),
114                                 latency, nsecs_to_usecs(tracing_thresh));
115         } else {
116                 printk(KERN_INFO "(%16s-%-5d|#%d):"
117                         " new %lu us maximum wakeup latency.\n",
118                                 wakeup_task->comm, wakeup_task->pid,
119                                 cpu, latency);
120         }
121
122 out_unlock:
123         __wakeup_reset(tr);
124         spin_unlock_irqrestore(&wakeup_lock, flags);
125 out:
126         atomic_dec(&tr->data[cpu]->disabled);
127 }
128
129 static void notrace __wakeup_reset(struct trace_array *tr)
130 {
131         struct trace_array_cpu *data;
132         int cpu;
133
134         assert_spin_locked(&wakeup_lock);
135
136         for_each_possible_cpu(cpu) {
137                 data = tr->data[cpu];
138                 tracing_reset(data);
139         }
140
141         wakeup_cpu = -1;
142         wakeup_prio = -1;
143
144         if (wakeup_task)
145                 put_task_struct(wakeup_task);
146
147         wakeup_task = NULL;
148 }
149
150 static void notrace wakeup_reset(struct trace_array *tr)
151 {
152         unsigned long flags;
153
154         spin_lock_irqsave(&wakeup_lock, flags);
155         __wakeup_reset(tr);
156         spin_unlock_irqrestore(&wakeup_lock, flags);
157 }
158
159 static notrace void
160 wakeup_check_start(struct trace_array *tr, struct task_struct *p,
161                    struct task_struct *curr)
162 {
163         int cpu = smp_processor_id();
164         unsigned long flags;
165         long disabled;
166
167         if (likely(!rt_task(p)) ||
168                         p->prio >= wakeup_prio ||
169                         p->prio >= curr->prio)
170                 return;
171
172         disabled = atomic_inc_return(&tr->data[cpu]->disabled);
173         if (unlikely(disabled != 1))
174                 goto out;
175
176         /* interrupts should be off from try_to_wake_up */
177         spin_lock(&wakeup_lock);
178
179         /* check for races. */
180         if (!tracer_enabled || p->prio >= wakeup_prio)
181                 goto out_locked;
182
183         /* reset the trace */
184         __wakeup_reset(tr);
185
186         wakeup_cpu = task_cpu(p);
187         wakeup_prio = p->prio;
188
189         wakeup_task = p;
190         get_task_struct(wakeup_task);
191
192         local_save_flags(flags);
193
194         tr->data[wakeup_cpu]->preempt_timestamp = now(cpu);
195         ftrace(tr, tr->data[wakeup_cpu], CALLER_ADDR1, CALLER_ADDR2, flags);
196
197 out_locked:
198         spin_unlock(&wakeup_lock);
199 out:
200         atomic_dec(&tr->data[cpu]->disabled);
201 }
202
203 notrace void
204 ftrace_wake_up_task(struct task_struct *wakee, struct task_struct *curr)
205 {
206         if (likely(!tracer_enabled))
207                 return;
208
209         wakeup_check_start(wakeup_trace, wakee, curr);
210 }
211
212 notrace void
213 ftrace_wake_up_new_task(struct task_struct *wakee, struct task_struct *curr)
214 {
215         if (likely(!tracer_enabled))
216                 return;
217
218         wakeup_check_start(wakeup_trace, wakee, curr);
219 }
220
221 static notrace void start_wakeup_tracer(struct trace_array *tr)
222 {
223         wakeup_reset(tr);
224
225         /*
226          * Don't let the tracer_enabled = 1 show up before
227          * the wakeup_task is reset. This may be overkill since
228          * wakeup_reset does a spin_unlock after setting the
229          * wakeup_task to NULL, but I want to be safe.
230          * This is a slow path anyway.
231          */
232         smp_wmb();
233
234         tracer_enabled = 1;
235
236         return;
237 }
238
239 static notrace void stop_wakeup_tracer(struct trace_array *tr)
240 {
241         tracer_enabled = 0;
242 }
243
244 static notrace void wakeup_tracer_init(struct trace_array *tr)
245 {
246         wakeup_trace = tr;
247
248         if (tr->ctrl)
249                 start_wakeup_tracer(tr);
250 }
251
252 static notrace void wakeup_tracer_reset(struct trace_array *tr)
253 {
254         if (tr->ctrl) {
255                 stop_wakeup_tracer(tr);
256                 /* make sure we put back any tasks we are tracing */
257                 wakeup_reset(tr);
258         }
259 }
260
261 static void wakeup_tracer_ctrl_update(struct trace_array *tr)
262 {
263         if (tr->ctrl)
264                 start_wakeup_tracer(tr);
265         else
266                 stop_wakeup_tracer(tr);
267 }
268
269 static void notrace wakeup_tracer_open(struct trace_iterator *iter)
270 {
271         /* stop the trace while dumping */
272         if (iter->tr->ctrl)
273                 stop_wakeup_tracer(iter->tr);
274 }
275
276 static void notrace wakeup_tracer_close(struct trace_iterator *iter)
277 {
278         /* forget about any processes we were recording */
279         if (iter->tr->ctrl)
280                 start_wakeup_tracer(iter->tr);
281 }
282
283 static struct tracer wakeup_tracer __read_mostly =
284 {
285         .name           = "wakeup",
286         .init           = wakeup_tracer_init,
287         .reset          = wakeup_tracer_reset,
288         .open           = wakeup_tracer_open,
289         .close          = wakeup_tracer_close,
290         .ctrl_update    = wakeup_tracer_ctrl_update,
291         .print_max      = 1,
292 #ifdef CONFIG_FTRACE_SELFTEST
293         .selftest    = trace_selftest_startup_wakeup,
294 #endif
295 };
296
297 __init static int init_wakeup_tracer(void)
298 {
299         int ret;
300
301         ret = register_tracer(&wakeup_tracer);
302         if (ret)
303                 return ret;
304
305         return 0;
306 }
307 device_initcall(init_wakeup_tracer);