ftrace: make work with new ring buffer
[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 #include <trace/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
29 static raw_spinlock_t wakeup_lock =
30         (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
31
32 static void __wakeup_reset(struct trace_array *tr);
33
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
60         local_irq_save(flags);
61         __raw_spin_lock(&wakeup_lock);
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:
76         __raw_spin_unlock(&wakeup_lock);
77         local_irq_restore(flags);
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
99 /*
100  * Should this new latency be reported/recorded?
101  */
102 static int report_latency(cycle_t delta)
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
114 static void notrace
115 probe_wakeup_sched_switch(struct rq *rq, struct task_struct *prev,
116         struct task_struct *next)
117 {
118         unsigned long latency = 0, t0 = 0, t1 = 0;
119         struct trace_array_cpu *data;
120         cycle_t T0, T1, delta;
121         unsigned long flags;
122         long disabled;
123         int cpu;
124
125         tracing_record_cmdline(prev);
126
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
142         /* The task we are waiting for is waking up */
143         data = wakeup_trace->data[wakeup_cpu];
144
145         /* disable local data, not wakeup_cpu data */
146         cpu = raw_smp_processor_id();
147         disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
148         if (likely(disabled != 1))
149                 goto out;
150
151         local_irq_save(flags);
152         __raw_spin_lock(&wakeup_lock);
153
154         /* We could race with grabbing wakeup_lock */
155         if (unlikely(!tracer_enabled || next != wakeup_task))
156                 goto out_unlock;
157
158         trace_function(wakeup_trace, data, CALLER_ADDR1, CALLER_ADDR2, flags);
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         struct trace_array_cpu *data;
190         int cpu;
191
192         for_each_possible_cpu(cpu) {
193                 data = tr->data[cpu];
194                 tracing_reset(tr, cpu);
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
206 static void wakeup_reset(struct trace_array *tr)
207 {
208         unsigned long flags;
209
210         local_irq_save(flags);
211         __raw_spin_lock(&wakeup_lock);
212         __wakeup_reset(tr);
213         __raw_spin_unlock(&wakeup_lock);
214         local_irq_restore(flags);
215 }
216
217 static void
218 probe_wakeup(struct rq *rq, struct task_struct *p)
219 {
220         int cpu = smp_processor_id();
221         unsigned long flags;
222         long disabled;
223
224         if (likely(!tracer_enabled))
225                 return;
226
227         tracing_record_cmdline(p);
228         tracing_record_cmdline(current);
229
230         if (likely(!rt_task(p)) ||
231                         p->prio >= wakeup_prio ||
232                         p->prio >= current->prio)
233                 return;
234
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         wakeup_trace->data[wakeup_cpu]->preempt_timestamp = ftrace_now(cpu);
258         trace_function(wakeup_trace, wakeup_trace->data[wakeup_cpu],
259                        CALLER_ADDR1, CALLER_ADDR2, flags);
260
261 out_locked:
262         __raw_spin_unlock(&wakeup_lock);
263 out:
264         atomic_dec(&wakeup_trace->data[cpu]->disabled);
265 }
266
267 static void start_wakeup_tracer(struct trace_array *tr)
268 {
269         int ret;
270
271         ret = register_trace_sched_wakeup(probe_wakeup);
272         if (ret) {
273                 pr_info("wakeup trace: Couldn't activate tracepoint"
274                         " probe to kernel_sched_wakeup\n");
275                 return;
276         }
277
278         ret = register_trace_sched_wakeup_new(probe_wakeup);
279         if (ret) {
280                 pr_info("wakeup trace: Couldn't activate tracepoint"
281                         " probe to kernel_sched_wakeup_new\n");
282                 goto fail_deprobe;
283         }
284
285         ret = register_trace_sched_switch(probe_wakeup_sched_switch);
286         if (ret) {
287                 pr_info("sched trace: Couldn't activate tracepoint"
288                         " probe to kernel_sched_schedule\n");
289                 goto fail_deprobe_wake_new;
290         }
291
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
303         register_ftrace_function(&trace_ops);
304
305         tracer_enabled = 1;
306
307         return;
308 fail_deprobe_wake_new:
309         unregister_trace_sched_wakeup_new(probe_wakeup);
310 fail_deprobe:
311         unregister_trace_sched_wakeup(probe_wakeup);
312 }
313
314 static void stop_wakeup_tracer(struct trace_array *tr)
315 {
316         tracer_enabled = 0;
317         unregister_ftrace_function(&trace_ops);
318         unregister_trace_sched_switch(probe_wakeup_sched_switch);
319         unregister_trace_sched_wakeup_new(probe_wakeup);
320         unregister_trace_sched_wakeup(probe_wakeup);
321 }
322
323 static void wakeup_tracer_init(struct trace_array *tr)
324 {
325         wakeup_trace = tr;
326
327         if (tr->ctrl)
328                 start_wakeup_tracer(tr);
329 }
330
331 static void wakeup_tracer_reset(struct trace_array *tr)
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
348 static void wakeup_tracer_open(struct trace_iterator *iter)
349 {
350         /* stop the trace while dumping */
351         if (iter->tr->ctrl)
352                 stop_wakeup_tracer(iter->tr);
353 }
354
355 static void wakeup_tracer_close(struct trace_iterator *iter)
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,
371 #ifdef CONFIG_FTRACE_SELFTEST
372         .selftest    = trace_selftest_startup_wakeup,
373 #endif
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);