ftrace: add self-tests
[linux-2.6.git] / 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): %lu us wakeup latency "
111                        "violates %lu us threshold.\n"
112                        " => started at timestamp %lu: ",
113                                 wakeup_task->comm, wakeup_task->pid,
114                                 raw_smp_processor_id(),
115                                 latency, nsecs_to_usecs(tracing_thresh), t0);
116         } else {
117                 printk(KERN_INFO "(%16s-%-5d|#%d): new %lu us maximum "
118                        "wakeup latency.\n => started at timestamp %lu: ",
119                                 wakeup_task->comm, wakeup_task->pid,
120                                 cpu, latency, t0);
121         }
122
123         printk(KERN_CONT "   ended at timestamp %lu: ", t1);
124         dump_stack();
125         t1 = nsecs_to_usecs(now(cpu));
126         printk(KERN_CONT "   dump-end timestamp %lu\n\n", t1);
127
128 out_unlock:
129         __wakeup_reset(tr);
130         spin_unlock_irqrestore(&wakeup_lock, flags);
131 out:
132         atomic_dec(&tr->data[cpu]->disabled);
133 }
134
135 static void notrace __wakeup_reset(struct trace_array *tr)
136 {
137         struct trace_array_cpu *data;
138         int cpu;
139
140         assert_spin_locked(&wakeup_lock);
141
142         for_each_possible_cpu(cpu) {
143                 data = tr->data[cpu];
144                 tracing_reset(data);
145         }
146
147         wakeup_cpu = -1;
148         wakeup_prio = -1;
149
150         if (wakeup_task)
151                 put_task_struct(wakeup_task);
152
153         wakeup_task = NULL;
154 }
155
156 static void notrace wakeup_reset(struct trace_array *tr)
157 {
158         unsigned long flags;
159
160         spin_lock_irqsave(&wakeup_lock, flags);
161         __wakeup_reset(tr);
162         spin_unlock_irqrestore(&wakeup_lock, flags);
163 }
164
165 static notrace void
166 wakeup_check_start(struct trace_array *tr, struct task_struct *p,
167                    struct task_struct *curr)
168 {
169         int cpu = smp_processor_id();
170         unsigned long flags;
171         long disabled;
172
173         if (likely(!rt_task(p)) ||
174                         p->prio >= wakeup_prio ||
175                         p->prio >= curr->prio)
176                 return;
177
178         disabled = atomic_inc_return(&tr->data[cpu]->disabled);
179         if (unlikely(disabled != 1))
180                 goto out;
181
182         /* interrupts should be off from try_to_wake_up */
183         spin_lock(&wakeup_lock);
184
185         /* check for races. */
186         if (!tracer_enabled || p->prio >= wakeup_prio)
187                 goto out_locked;
188
189         /* reset the trace */
190         __wakeup_reset(tr);
191
192         wakeup_cpu = task_cpu(p);
193         wakeup_prio = p->prio;
194
195         wakeup_task = p;
196         get_task_struct(wakeup_task);
197
198         local_save_flags(flags);
199
200         tr->data[wakeup_cpu]->preempt_timestamp = now(cpu);
201         ftrace(tr, tr->data[wakeup_cpu], CALLER_ADDR1, CALLER_ADDR2, flags);
202
203 out_locked:
204         spin_unlock(&wakeup_lock);
205 out:
206         atomic_dec(&tr->data[cpu]->disabled);
207 }
208
209 notrace void
210 ftrace_wake_up_task(struct task_struct *wakee, struct task_struct *curr)
211 {
212         if (likely(!tracer_enabled))
213                 return;
214
215         wakeup_check_start(wakeup_trace, wakee, curr);
216 }
217
218 notrace void
219 ftrace_wake_up_new_task(struct task_struct *wakee, struct task_struct *curr)
220 {
221         if (likely(!tracer_enabled))
222                 return;
223
224         wakeup_check_start(wakeup_trace, wakee, curr);
225 }
226
227 static notrace void start_wakeup_tracer(struct trace_array *tr)
228 {
229         wakeup_reset(tr);
230
231         /*
232          * Don't let the tracer_enabled = 1 show up before
233          * the wakeup_task is reset. This may be overkill since
234          * wakeup_reset does a spin_unlock after setting the
235          * wakeup_task to NULL, but I want to be safe.
236          * This is a slow path anyway.
237          */
238         smp_wmb();
239
240         tracer_enabled = 1;
241
242         return;
243 }
244
245 static notrace void stop_wakeup_tracer(struct trace_array *tr)
246 {
247         tracer_enabled = 0;
248 }
249
250 static notrace void wakeup_tracer_init(struct trace_array *tr)
251 {
252         wakeup_trace = tr;
253
254         if (tr->ctrl)
255                 start_wakeup_tracer(tr);
256 }
257
258 static notrace void wakeup_tracer_reset(struct trace_array *tr)
259 {
260         if (tr->ctrl) {
261                 stop_wakeup_tracer(tr);
262                 /* make sure we put back any tasks we are tracing */
263                 wakeup_reset(tr);
264         }
265 }
266
267 static void wakeup_tracer_ctrl_update(struct trace_array *tr)
268 {
269         if (tr->ctrl)
270                 start_wakeup_tracer(tr);
271         else
272                 stop_wakeup_tracer(tr);
273 }
274
275 static void notrace wakeup_tracer_open(struct trace_iterator *iter)
276 {
277         /* stop the trace while dumping */
278         if (iter->tr->ctrl)
279                 stop_wakeup_tracer(iter->tr);
280 }
281
282 static void notrace wakeup_tracer_close(struct trace_iterator *iter)
283 {
284         /* forget about any processes we were recording */
285         if (iter->tr->ctrl)
286                 start_wakeup_tracer(iter->tr);
287 }
288
289 static struct tracer wakeup_tracer __read_mostly =
290 {
291         .name           = "wakeup",
292         .init           = wakeup_tracer_init,
293         .reset          = wakeup_tracer_reset,
294         .open           = wakeup_tracer_open,
295         .close          = wakeup_tracer_close,
296         .ctrl_update    = wakeup_tracer_ctrl_update,
297         .print_max      = 1,
298 #ifdef CONFIG_FTRACE_SELFTEST
299         .selftest    = trace_selftest_startup_wakeup,
300 #endif
301 };
302
303 __init static int init_wakeup_tracer(void)
304 {
305         int ret;
306
307         ret = register_tracer(&wakeup_tracer);
308         if (ret)
309                 return ret;
310
311         return 0;
312 }
313 device_initcall(init_wakeup_tracer);