Merge branch 'fix/pcm-jiffies-check' into fix/asoc
[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 static int                      wakeup_rt;
29
30 static raw_spinlock_t wakeup_lock =
31         (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
32
33 static void __wakeup_reset(struct trace_array *tr);
34
35 static int save_lat_flag;
36
37 #ifdef CONFIG_FUNCTION_TRACER
38 /*
39  * irqsoff uses its own tracer function to keep the overhead down:
40  */
41 static void
42 wakeup_tracer_call(unsigned long ip, unsigned long parent_ip)
43 {
44         struct trace_array *tr = wakeup_trace;
45         struct trace_array_cpu *data;
46         unsigned long flags;
47         long disabled;
48         int resched;
49         int cpu;
50         int pc;
51
52         if (likely(!wakeup_task))
53                 return;
54
55         pc = preempt_count();
56         resched = ftrace_preempt_disable();
57
58         cpu = raw_smp_processor_id();
59         data = tr->data[cpu];
60         disabled = atomic_inc_return(&data->disabled);
61         if (unlikely(disabled != 1))
62                 goto out;
63
64         local_irq_save(flags);
65         __raw_spin_lock(&wakeup_lock);
66
67         if (unlikely(!wakeup_task))
68                 goto unlock;
69
70         /*
71          * The task can't disappear because it needs to
72          * wake up first, and we have the wakeup_lock.
73          */
74         if (task_cpu(wakeup_task) != cpu)
75                 goto unlock;
76
77         trace_function(tr, ip, parent_ip, flags, pc);
78
79  unlock:
80         __raw_spin_unlock(&wakeup_lock);
81         local_irq_restore(flags);
82
83  out:
84         atomic_dec(&data->disabled);
85
86         ftrace_preempt_enable(resched);
87 }
88
89 static struct ftrace_ops trace_ops __read_mostly =
90 {
91         .func = wakeup_tracer_call,
92 };
93 #endif /* CONFIG_FUNCTION_TRACER */
94
95 /*
96  * Should this new latency be reported/recorded?
97  */
98 static int report_latency(cycle_t delta)
99 {
100         if (tracing_thresh) {
101                 if (delta < tracing_thresh)
102                         return 0;
103         } else {
104                 if (delta <= tracing_max_latency)
105                         return 0;
106         }
107         return 1;
108 }
109
110 static void notrace
111 probe_wakeup_sched_switch(struct rq *rq, struct task_struct *prev,
112         struct task_struct *next)
113 {
114         unsigned long latency = 0, t0 = 0, t1 = 0;
115         struct trace_array_cpu *data;
116         cycle_t T0, T1, delta;
117         unsigned long flags;
118         long disabled;
119         int cpu;
120         int pc;
121
122         tracing_record_cmdline(prev);
123
124         if (unlikely(!tracer_enabled))
125                 return;
126
127         /*
128          * When we start a new trace, we set wakeup_task to NULL
129          * and then set tracer_enabled = 1. We want to make sure
130          * that another CPU does not see the tracer_enabled = 1
131          * and the wakeup_task with an older task, that might
132          * actually be the same as next.
133          */
134         smp_rmb();
135
136         if (next != wakeup_task)
137                 return;
138
139         pc = preempt_count();
140
141         /* The task we are waiting for is waking up */
142         data = wakeup_trace->data[wakeup_cpu];
143
144         /* disable local data, not wakeup_cpu data */
145         cpu = raw_smp_processor_id();
146         disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
147         if (likely(disabled != 1))
148                 goto out;
149
150         local_irq_save(flags);
151         __raw_spin_lock(&wakeup_lock);
152
153         /* We could race with grabbing wakeup_lock */
154         if (unlikely(!tracer_enabled || next != wakeup_task))
155                 goto out_unlock;
156
157         trace_function(wakeup_trace, CALLER_ADDR0, CALLER_ADDR1, flags, pc);
158         tracing_sched_switch_trace(wakeup_trace, prev, next, flags, pc);
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         int cpu;
190
191         for_each_possible_cpu(cpu)
192                 tracing_reset(tr, cpu);
193
194         wakeup_cpu = -1;
195         wakeup_prio = -1;
196
197         if (wakeup_task)
198                 put_task_struct(wakeup_task);
199
200         wakeup_task = NULL;
201 }
202
203 static void wakeup_reset(struct trace_array *tr)
204 {
205         unsigned long flags;
206
207         local_irq_save(flags);
208         __raw_spin_lock(&wakeup_lock);
209         __wakeup_reset(tr);
210         __raw_spin_unlock(&wakeup_lock);
211         local_irq_restore(flags);
212 }
213
214 static void
215 probe_wakeup(struct rq *rq, struct task_struct *p, int success)
216 {
217         struct trace_array_cpu *data;
218         int cpu = smp_processor_id();
219         unsigned long flags;
220         long disabled;
221         int pc;
222
223         if (likely(!tracer_enabled))
224                 return;
225
226         tracing_record_cmdline(p);
227         tracing_record_cmdline(current);
228
229         if ((wakeup_rt && !rt_task(p)) ||
230                         p->prio >= wakeup_prio ||
231                         p->prio >= current->prio)
232                 return;
233
234         pc = preempt_count();
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         data = wakeup_trace->data[wakeup_cpu];
258         data->preempt_timestamp = ftrace_now(cpu);
259         tracing_sched_wakeup_trace(wakeup_trace, p, current, flags, pc);
260
261         /*
262          * We must be careful in using CALLER_ADDR2. But since wake_up
263          * is not called by an assembly function  (where as schedule is)
264          * it should be safe to use it here.
265          */
266         trace_function(wakeup_trace, CALLER_ADDR1, CALLER_ADDR2, flags, pc);
267
268 out_locked:
269         __raw_spin_unlock(&wakeup_lock);
270 out:
271         atomic_dec(&wakeup_trace->data[cpu]->disabled);
272 }
273
274 static void start_wakeup_tracer(struct trace_array *tr)
275 {
276         int ret;
277
278         ret = register_trace_sched_wakeup(probe_wakeup);
279         if (ret) {
280                 pr_info("wakeup trace: Couldn't activate tracepoint"
281                         " probe to kernel_sched_wakeup\n");
282                 return;
283         }
284
285         ret = register_trace_sched_wakeup_new(probe_wakeup);
286         if (ret) {
287                 pr_info("wakeup trace: Couldn't activate tracepoint"
288                         " probe to kernel_sched_wakeup_new\n");
289                 goto fail_deprobe;
290         }
291
292         ret = register_trace_sched_switch(probe_wakeup_sched_switch);
293         if (ret) {
294                 pr_info("sched trace: Couldn't activate tracepoint"
295                         " probe to kernel_sched_switch\n");
296                 goto fail_deprobe_wake_new;
297         }
298
299         wakeup_reset(tr);
300
301         /*
302          * Don't let the tracer_enabled = 1 show up before
303          * the wakeup_task is reset. This may be overkill since
304          * wakeup_reset does a spin_unlock after setting the
305          * wakeup_task to NULL, but I want to be safe.
306          * This is a slow path anyway.
307          */
308         smp_wmb();
309
310         register_ftrace_function(&trace_ops);
311
312         if (tracing_is_enabled())
313                 tracer_enabled = 1;
314         else
315                 tracer_enabled = 0;
316
317         return;
318 fail_deprobe_wake_new:
319         unregister_trace_sched_wakeup_new(probe_wakeup);
320 fail_deprobe:
321         unregister_trace_sched_wakeup(probe_wakeup);
322 }
323
324 static void stop_wakeup_tracer(struct trace_array *tr)
325 {
326         tracer_enabled = 0;
327         unregister_ftrace_function(&trace_ops);
328         unregister_trace_sched_switch(probe_wakeup_sched_switch);
329         unregister_trace_sched_wakeup_new(probe_wakeup);
330         unregister_trace_sched_wakeup(probe_wakeup);
331 }
332
333 static int __wakeup_tracer_init(struct trace_array *tr)
334 {
335         save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
336         trace_flags |= TRACE_ITER_LATENCY_FMT;
337
338         tracing_max_latency = 0;
339         wakeup_trace = tr;
340         start_wakeup_tracer(tr);
341         return 0;
342 }
343
344 static int wakeup_tracer_init(struct trace_array *tr)
345 {
346         wakeup_rt = 0;
347         return __wakeup_tracer_init(tr);
348 }
349
350 static int wakeup_rt_tracer_init(struct trace_array *tr)
351 {
352         wakeup_rt = 1;
353         return __wakeup_tracer_init(tr);
354 }
355
356 static void wakeup_tracer_reset(struct trace_array *tr)
357 {
358         stop_wakeup_tracer(tr);
359         /* make sure we put back any tasks we are tracing */
360         wakeup_reset(tr);
361
362         if (!save_lat_flag)
363                 trace_flags &= ~TRACE_ITER_LATENCY_FMT;
364 }
365
366 static void wakeup_tracer_start(struct trace_array *tr)
367 {
368         wakeup_reset(tr);
369         tracer_enabled = 1;
370 }
371
372 static void wakeup_tracer_stop(struct trace_array *tr)
373 {
374         tracer_enabled = 0;
375 }
376
377 static struct tracer wakeup_tracer __read_mostly =
378 {
379         .name           = "wakeup",
380         .init           = wakeup_tracer_init,
381         .reset          = wakeup_tracer_reset,
382         .start          = wakeup_tracer_start,
383         .stop           = wakeup_tracer_stop,
384         .print_max      = 1,
385 #ifdef CONFIG_FTRACE_SELFTEST
386         .selftest    = trace_selftest_startup_wakeup,
387 #endif
388 };
389
390 static struct tracer wakeup_rt_tracer __read_mostly =
391 {
392         .name           = "wakeup_rt",
393         .init           = wakeup_rt_tracer_init,
394         .reset          = wakeup_tracer_reset,
395         .start          = wakeup_tracer_start,
396         .stop           = wakeup_tracer_stop,
397         .wait_pipe      = poll_wait_pipe,
398         .print_max      = 1,
399 #ifdef CONFIG_FTRACE_SELFTEST
400         .selftest    = trace_selftest_startup_wakeup,
401 #endif
402 };
403
404 __init static int init_wakeup_tracer(void)
405 {
406         int ret;
407
408         ret = register_tracer(&wakeup_tracer);
409         if (ret)
410                 return ret;
411
412         ret = register_tracer(&wakeup_rt_tracer);
413         if (ret)
414                 return ret;
415
416         return 0;
417 }
418 device_initcall(init_wakeup_tracer);