Merge branch 'slub/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/penberg...
[pandora-kernel.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 #include <trace/events/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 int                      wakeup_current_cpu;
28 static unsigned                 wakeup_prio = -1;
29 static int                      wakeup_rt;
30
31 static arch_spinlock_t wakeup_lock =
32         (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
33
34 static void __wakeup_reset(struct trace_array *tr);
35
36 static int save_lat_flag;
37
38 #ifdef CONFIG_FUNCTION_TRACER
39 /*
40  * irqsoff uses its own tracer function to keep the overhead down:
41  */
42 static void
43 wakeup_tracer_call(unsigned long ip, unsigned long parent_ip)
44 {
45         struct trace_array *tr = wakeup_trace;
46         struct trace_array_cpu *data;
47         unsigned long flags;
48         long disabled;
49         int resched;
50         int cpu;
51         int pc;
52
53         if (likely(!wakeup_task))
54                 return;
55
56         pc = preempt_count();
57         resched = ftrace_preempt_disable();
58
59         cpu = raw_smp_processor_id();
60         if (cpu != wakeup_current_cpu)
61                 goto out_enable;
62
63         data = tr->data[cpu];
64         disabled = atomic_inc_return(&data->disabled);
65         if (unlikely(disabled != 1))
66                 goto out;
67
68         local_irq_save(flags);
69
70         trace_function(tr, ip, parent_ip, flags, pc);
71
72         local_irq_restore(flags);
73
74  out:
75         atomic_dec(&data->disabled);
76  out_enable:
77         ftrace_preempt_enable(resched);
78 }
79
80 static struct ftrace_ops trace_ops __read_mostly =
81 {
82         .func = wakeup_tracer_call,
83 };
84 #endif /* CONFIG_FUNCTION_TRACER */
85
86 /*
87  * Should this new latency be reported/recorded?
88  */
89 static int report_latency(cycle_t delta)
90 {
91         if (tracing_thresh) {
92                 if (delta < tracing_thresh)
93                         return 0;
94         } else {
95                 if (delta <= tracing_max_latency)
96                         return 0;
97         }
98         return 1;
99 }
100
101 static void
102 probe_wakeup_migrate_task(void *ignore, struct task_struct *task, int cpu)
103 {
104         if (task != wakeup_task)
105                 return;
106
107         wakeup_current_cpu = cpu;
108 }
109
110 static void notrace
111 probe_wakeup_sched_switch(void *ignore,
112                           struct task_struct *prev, struct task_struct *next)
113 {
114         struct trace_array_cpu *data;
115         cycle_t T0, T1, delta;
116         unsigned long flags;
117         long disabled;
118         int cpu;
119         int pc;
120
121         tracing_record_cmdline(prev);
122
123         if (unlikely(!tracer_enabled))
124                 return;
125
126         /*
127          * When we start a new trace, we set wakeup_task to NULL
128          * and then set tracer_enabled = 1. We want to make sure
129          * that another CPU does not see the tracer_enabled = 1
130          * and the wakeup_task with an older task, that might
131          * actually be the same as next.
132          */
133         smp_rmb();
134
135         if (next != wakeup_task)
136                 return;
137
138         pc = preempt_count();
139
140         /* disable local data, not wakeup_cpu data */
141         cpu = raw_smp_processor_id();
142         disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
143         if (likely(disabled != 1))
144                 goto out;
145
146         local_irq_save(flags);
147         arch_spin_lock(&wakeup_lock);
148
149         /* We could race with grabbing wakeup_lock */
150         if (unlikely(!tracer_enabled || next != wakeup_task))
151                 goto out_unlock;
152
153         /* The task we are waiting for is waking up */
154         data = wakeup_trace->data[wakeup_cpu];
155
156         trace_function(wakeup_trace, CALLER_ADDR0, CALLER_ADDR1, flags, pc);
157         tracing_sched_switch_trace(wakeup_trace, prev, next, flags, pc);
158
159         T0 = data->preempt_timestamp;
160         T1 = ftrace_now(cpu);
161         delta = T1-T0;
162
163         if (!report_latency(delta))
164                 goto out_unlock;
165
166         if (likely(!is_tracing_stopped())) {
167                 tracing_max_latency = delta;
168                 update_max_tr(wakeup_trace, wakeup_task, wakeup_cpu);
169         }
170
171 out_unlock:
172         __wakeup_reset(wakeup_trace);
173         arch_spin_unlock(&wakeup_lock);
174         local_irq_restore(flags);
175 out:
176         atomic_dec(&wakeup_trace->data[cpu]->disabled);
177 }
178
179 static void __wakeup_reset(struct trace_array *tr)
180 {
181         wakeup_cpu = -1;
182         wakeup_prio = -1;
183
184         if (wakeup_task)
185                 put_task_struct(wakeup_task);
186
187         wakeup_task = NULL;
188 }
189
190 static void wakeup_reset(struct trace_array *tr)
191 {
192         unsigned long flags;
193
194         tracing_reset_online_cpus(tr);
195
196         local_irq_save(flags);
197         arch_spin_lock(&wakeup_lock);
198         __wakeup_reset(tr);
199         arch_spin_unlock(&wakeup_lock);
200         local_irq_restore(flags);
201 }
202
203 static void
204 probe_wakeup(void *ignore, struct task_struct *p, int success)
205 {
206         struct trace_array_cpu *data;
207         int cpu = smp_processor_id();
208         unsigned long flags;
209         long disabled;
210         int pc;
211
212         if (likely(!tracer_enabled))
213                 return;
214
215         tracing_record_cmdline(p);
216         tracing_record_cmdline(current);
217
218         if ((wakeup_rt && !rt_task(p)) ||
219                         p->prio >= wakeup_prio ||
220                         p->prio >= current->prio)
221                 return;
222
223         pc = preempt_count();
224         disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
225         if (unlikely(disabled != 1))
226                 goto out;
227
228         /* interrupts should be off from try_to_wake_up */
229         arch_spin_lock(&wakeup_lock);
230
231         /* check for races. */
232         if (!tracer_enabled || p->prio >= wakeup_prio)
233                 goto out_locked;
234
235         /* reset the trace */
236         __wakeup_reset(wakeup_trace);
237
238         wakeup_cpu = task_cpu(p);
239         wakeup_current_cpu = wakeup_cpu;
240         wakeup_prio = p->prio;
241
242         wakeup_task = p;
243         get_task_struct(wakeup_task);
244
245         local_save_flags(flags);
246
247         data = wakeup_trace->data[wakeup_cpu];
248         data->preempt_timestamp = ftrace_now(cpu);
249         tracing_sched_wakeup_trace(wakeup_trace, p, current, flags, pc);
250
251         /*
252          * We must be careful in using CALLER_ADDR2. But since wake_up
253          * is not called by an assembly function  (where as schedule is)
254          * it should be safe to use it here.
255          */
256         trace_function(wakeup_trace, CALLER_ADDR1, CALLER_ADDR2, flags, pc);
257
258 out_locked:
259         arch_spin_unlock(&wakeup_lock);
260 out:
261         atomic_dec(&wakeup_trace->data[cpu]->disabled);
262 }
263
264 static void start_wakeup_tracer(struct trace_array *tr)
265 {
266         int ret;
267
268         ret = register_trace_sched_wakeup(probe_wakeup, NULL);
269         if (ret) {
270                 pr_info("wakeup trace: Couldn't activate tracepoint"
271                         " probe to kernel_sched_wakeup\n");
272                 return;
273         }
274
275         ret = register_trace_sched_wakeup_new(probe_wakeup, NULL);
276         if (ret) {
277                 pr_info("wakeup trace: Couldn't activate tracepoint"
278                         " probe to kernel_sched_wakeup_new\n");
279                 goto fail_deprobe;
280         }
281
282         ret = register_trace_sched_switch(probe_wakeup_sched_switch, NULL);
283         if (ret) {
284                 pr_info("sched trace: Couldn't activate tracepoint"
285                         " probe to kernel_sched_switch\n");
286                 goto fail_deprobe_wake_new;
287         }
288
289         ret = register_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL);
290         if (ret) {
291                 pr_info("wakeup trace: Couldn't activate tracepoint"
292                         " probe to kernel_sched_migrate_task\n");
293                 return;
294         }
295
296         wakeup_reset(tr);
297
298         /*
299          * Don't let the tracer_enabled = 1 show up before
300          * the wakeup_task is reset. This may be overkill since
301          * wakeup_reset does a spin_unlock after setting the
302          * wakeup_task to NULL, but I want to be safe.
303          * This is a slow path anyway.
304          */
305         smp_wmb();
306
307         register_ftrace_function(&trace_ops);
308
309         if (tracing_is_enabled())
310                 tracer_enabled = 1;
311         else
312                 tracer_enabled = 0;
313
314         return;
315 fail_deprobe_wake_new:
316         unregister_trace_sched_wakeup_new(probe_wakeup, NULL);
317 fail_deprobe:
318         unregister_trace_sched_wakeup(probe_wakeup, NULL);
319 }
320
321 static void stop_wakeup_tracer(struct trace_array *tr)
322 {
323         tracer_enabled = 0;
324         unregister_ftrace_function(&trace_ops);
325         unregister_trace_sched_switch(probe_wakeup_sched_switch, NULL);
326         unregister_trace_sched_wakeup_new(probe_wakeup, NULL);
327         unregister_trace_sched_wakeup(probe_wakeup, NULL);
328         unregister_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL);
329 }
330
331 static int __wakeup_tracer_init(struct trace_array *tr)
332 {
333         save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
334         trace_flags |= TRACE_ITER_LATENCY_FMT;
335
336         tracing_max_latency = 0;
337         wakeup_trace = tr;
338         start_wakeup_tracer(tr);
339         return 0;
340 }
341
342 static int wakeup_tracer_init(struct trace_array *tr)
343 {
344         wakeup_rt = 0;
345         return __wakeup_tracer_init(tr);
346 }
347
348 static int wakeup_rt_tracer_init(struct trace_array *tr)
349 {
350         wakeup_rt = 1;
351         return __wakeup_tracer_init(tr);
352 }
353
354 static void wakeup_tracer_reset(struct trace_array *tr)
355 {
356         stop_wakeup_tracer(tr);
357         /* make sure we put back any tasks we are tracing */
358         wakeup_reset(tr);
359
360         if (!save_lat_flag)
361                 trace_flags &= ~TRACE_ITER_LATENCY_FMT;
362 }
363
364 static void wakeup_tracer_start(struct trace_array *tr)
365 {
366         wakeup_reset(tr);
367         tracer_enabled = 1;
368 }
369
370 static void wakeup_tracer_stop(struct trace_array *tr)
371 {
372         tracer_enabled = 0;
373 }
374
375 static struct tracer wakeup_tracer __read_mostly =
376 {
377         .name           = "wakeup",
378         .init           = wakeup_tracer_init,
379         .reset          = wakeup_tracer_reset,
380         .start          = wakeup_tracer_start,
381         .stop           = wakeup_tracer_stop,
382         .print_max      = 1,
383 #ifdef CONFIG_FTRACE_SELFTEST
384         .selftest    = trace_selftest_startup_wakeup,
385 #endif
386 };
387
388 static struct tracer wakeup_rt_tracer __read_mostly =
389 {
390         .name           = "wakeup_rt",
391         .init           = wakeup_rt_tracer_init,
392         .reset          = wakeup_tracer_reset,
393         .start          = wakeup_tracer_start,
394         .stop           = wakeup_tracer_stop,
395         .wait_pipe      = poll_wait_pipe,
396         .print_max      = 1,
397 #ifdef CONFIG_FTRACE_SELFTEST
398         .selftest    = trace_selftest_startup_wakeup,
399 #endif
400 };
401
402 __init static int init_wakeup_tracer(void)
403 {
404         int ret;
405
406         ret = register_tracer(&wakeup_tracer);
407         if (ret)
408                 return ret;
409
410         ret = register_tracer(&wakeup_rt_tracer);
411         if (ret)
412                 return ret;
413
414         return 0;
415 }
416 device_initcall(init_wakeup_tracer);