ftrace: timestamp syncing, prepare
[linux-2.6.git] / kernel / trace / trace_irqsoff.c
1 /*
2  * trace irqs off criticall timings
3  *
4  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
5  * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
6  *
7  * From code in 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/kallsyms.h>
13 #include <linux/debugfs.h>
14 #include <linux/uaccess.h>
15 #include <linux/module.h>
16 #include <linux/ftrace.h>
17 #include <linux/fs.h>
18
19 #include "trace.h"
20
21 static struct trace_array               *irqsoff_trace __read_mostly;
22 static int                              tracer_enabled __read_mostly;
23
24 static DEFINE_PER_CPU(int, tracing_cpu);
25
26 static DEFINE_SPINLOCK(max_trace_lock);
27
28 enum {
29         TRACER_IRQS_OFF         = (1 << 1),
30         TRACER_PREEMPT_OFF      = (1 << 2),
31 };
32
33 static int trace_type __read_mostly;
34
35 #ifdef CONFIG_PREEMPT_TRACER
36 static inline int notrace
37 preempt_trace(void)
38 {
39         return ((trace_type & TRACER_PREEMPT_OFF) && preempt_count());
40 }
41 #else
42 # define preempt_trace() (0)
43 #endif
44
45 #ifdef CONFIG_IRQSOFF_TRACER
46 static inline int notrace
47 irq_trace(void)
48 {
49         return ((trace_type & TRACER_IRQS_OFF) &&
50                 irqs_disabled());
51 }
52 #else
53 # define irq_trace() (0)
54 #endif
55
56 /*
57  * Sequence count - we record it when starting a measurement and
58  * skip the latency if the sequence has changed - some other section
59  * did a maximum and could disturb our measurement with serial console
60  * printouts, etc. Truly coinciding maximum latencies should be rare
61  * and what happens together happens separately as well, so this doesnt
62  * decrease the validity of the maximum found:
63  */
64 static __cacheline_aligned_in_smp       unsigned long max_sequence;
65
66 #ifdef CONFIG_FTRACE
67 /*
68  * irqsoff uses its own tracer function to keep the overhead down:
69  */
70 static void notrace
71 irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip)
72 {
73         struct trace_array *tr = irqsoff_trace;
74         struct trace_array_cpu *data;
75         unsigned long flags;
76         long disabled;
77         int cpu;
78
79         /*
80          * Does not matter if we preempt. We test the flags
81          * afterward, to see if irqs are disabled or not.
82          * If we preempt and get a false positive, the flags
83          * test will fail.
84          */
85         cpu = raw_smp_processor_id();
86         if (likely(!per_cpu(tracing_cpu, cpu)))
87                 return;
88
89         local_save_flags(flags);
90         /* slight chance to get a false positive on tracing_cpu */
91         if (!irqs_disabled_flags(flags))
92                 return;
93
94         data = tr->data[cpu];
95         disabled = atomic_inc_return(&data->disabled);
96
97         if (likely(disabled == 1))
98                 ftrace(tr, data, ip, parent_ip, flags);
99
100         atomic_dec(&data->disabled);
101 }
102
103 static struct ftrace_ops trace_ops __read_mostly =
104 {
105         .func = irqsoff_tracer_call,
106 };
107 #endif /* CONFIG_FTRACE */
108
109 /*
110  * Should this new latency be reported/recorded?
111  */
112 static int notrace report_latency(cycle_t delta)
113 {
114         if (tracing_thresh) {
115                 if (delta < tracing_thresh)
116                         return 0;
117         } else {
118                 if (delta <= tracing_max_latency)
119                         return 0;
120         }
121         return 1;
122 }
123
124 static void notrace
125 check_critical_timing(struct trace_array *tr,
126                       struct trace_array_cpu *data,
127                       unsigned long parent_ip,
128                       int cpu)
129 {
130         unsigned long latency, t0, t1;
131         cycle_t T0, T1, delta;
132         unsigned long flags;
133
134         /*
135          * usecs conversion is slow so we try to delay the conversion
136          * as long as possible:
137          */
138         T0 = data->preempt_timestamp;
139         T1 = ftrace_now(cpu);
140         delta = T1-T0;
141
142         local_save_flags(flags);
143
144         if (!report_latency(delta))
145                 goto out;
146
147         spin_lock_irqsave(&max_trace_lock, flags);
148
149         /* check if we are still the max latency */
150         if (!report_latency(delta))
151                 goto out_unlock;
152
153         ftrace(tr, data, CALLER_ADDR0, parent_ip, flags);
154
155         latency = nsecs_to_usecs(delta);
156
157         if (data->critical_sequence != max_sequence)
158                 goto out_unlock;
159
160         tracing_max_latency = delta;
161         t0 = nsecs_to_usecs(T0);
162         t1 = nsecs_to_usecs(T1);
163
164         data->critical_end = parent_ip;
165
166         update_max_tr_single(tr, current, cpu);
167
168         if (tracing_thresh) {
169                 printk(KERN_INFO "(%16s-%-5d|#%d):"
170                         " %lu us critical section violates %lu us threshold.\n",
171                                 current->comm, current->pid,
172                                 raw_smp_processor_id(),
173                                 latency, nsecs_to_usecs(tracing_thresh));
174         } else {
175                 printk(KERN_INFO "(%16s-%-5d|#%d):"
176                        " new %lu us maximum-latency critical section.\n",
177                                 current->comm, current->pid,
178                                 raw_smp_processor_id(),
179                                 latency);
180         }
181
182         max_sequence++;
183
184 out_unlock:
185         spin_unlock_irqrestore(&max_trace_lock, flags);
186
187 out:
188         data->critical_sequence = max_sequence;
189         data->preempt_timestamp = ftrace_now(cpu);
190         tracing_reset(data);
191         ftrace(tr, data, CALLER_ADDR0, parent_ip, flags);
192 }
193
194 static inline void notrace
195 start_critical_timing(unsigned long ip, unsigned long parent_ip)
196 {
197         int cpu;
198         struct trace_array *tr = irqsoff_trace;
199         struct trace_array_cpu *data;
200         unsigned long flags;
201
202         if (likely(!tracer_enabled))
203                 return;
204
205         if (__get_cpu_var(tracing_cpu))
206                 return;
207
208         cpu = raw_smp_processor_id();
209         data = tr->data[cpu];
210
211         if (unlikely(!data) || unlikely(!head_page(data)) ||
212             atomic_read(&data->disabled))
213                 return;
214
215         atomic_inc(&data->disabled);
216
217         data->critical_sequence = max_sequence;
218         data->preempt_timestamp = ftrace_now(cpu);
219         data->critical_start = parent_ip ? : ip;
220         tracing_reset(data);
221
222         local_save_flags(flags);
223
224         ftrace(tr, data, ip, parent_ip, flags);
225
226         __get_cpu_var(tracing_cpu) = 1;
227
228         atomic_dec(&data->disabled);
229 }
230
231 static inline void notrace
232 stop_critical_timing(unsigned long ip, unsigned long parent_ip)
233 {
234         int cpu;
235         struct trace_array *tr = irqsoff_trace;
236         struct trace_array_cpu *data;
237         unsigned long flags;
238
239         /* Always clear the tracing cpu on stopping the trace */
240         if (unlikely(__get_cpu_var(tracing_cpu)))
241                 __get_cpu_var(tracing_cpu) = 0;
242         else
243                 return;
244
245         if (!tracer_enabled)
246                 return;
247
248         cpu = raw_smp_processor_id();
249         data = tr->data[cpu];
250
251         if (unlikely(!data) || unlikely(!head_page(data)) ||
252             !data->critical_start || atomic_read(&data->disabled))
253                 return;
254
255         atomic_inc(&data->disabled);
256         local_save_flags(flags);
257         ftrace(tr, data, ip, parent_ip, flags);
258         check_critical_timing(tr, data, parent_ip ? : ip, cpu);
259         data->critical_start = 0;
260         atomic_dec(&data->disabled);
261 }
262
263 /* start and stop critical timings used to for stoppage (in idle) */
264 void notrace start_critical_timings(void)
265 {
266         if (preempt_trace() || irq_trace())
267                 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
268 }
269
270 void notrace stop_critical_timings(void)
271 {
272         if (preempt_trace() || irq_trace())
273                 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
274 }
275
276 #ifdef CONFIG_IRQSOFF_TRACER
277 #ifdef CONFIG_PROVE_LOCKING
278 void notrace time_hardirqs_on(unsigned long a0, unsigned long a1)
279 {
280         if (!preempt_trace() && irq_trace())
281                 stop_critical_timing(a0, a1);
282 }
283
284 void notrace time_hardirqs_off(unsigned long a0, unsigned long a1)
285 {
286         if (!preempt_trace() && irq_trace())
287                 start_critical_timing(a0, a1);
288 }
289
290 #else /* !CONFIG_PROVE_LOCKING */
291
292 /*
293  * Stubs:
294  */
295
296 void early_boot_irqs_off(void)
297 {
298 }
299
300 void early_boot_irqs_on(void)
301 {
302 }
303
304 void trace_softirqs_on(unsigned long ip)
305 {
306 }
307
308 void trace_softirqs_off(unsigned long ip)
309 {
310 }
311
312 inline void print_irqtrace_events(struct task_struct *curr)
313 {
314 }
315
316 /*
317  * We are only interested in hardirq on/off events:
318  */
319 void notrace trace_hardirqs_on(void)
320 {
321         if (!preempt_trace() && irq_trace())
322                 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
323 }
324 EXPORT_SYMBOL(trace_hardirqs_on);
325
326 void notrace trace_hardirqs_off(void)
327 {
328         if (!preempt_trace() && irq_trace())
329                 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
330 }
331 EXPORT_SYMBOL(trace_hardirqs_off);
332
333 void notrace trace_hardirqs_on_caller(unsigned long caller_addr)
334 {
335         if (!preempt_trace() && irq_trace())
336                 stop_critical_timing(CALLER_ADDR0, caller_addr);
337 }
338 EXPORT_SYMBOL(trace_hardirqs_on_caller);
339
340 void notrace trace_hardirqs_off_caller(unsigned long caller_addr)
341 {
342         if (!preempt_trace() && irq_trace())
343                 start_critical_timing(CALLER_ADDR0, caller_addr);
344 }
345 EXPORT_SYMBOL(trace_hardirqs_off_caller);
346
347 #endif /* CONFIG_PROVE_LOCKING */
348 #endif /*  CONFIG_IRQSOFF_TRACER */
349
350 #ifdef CONFIG_PREEMPT_TRACER
351 void notrace trace_preempt_on(unsigned long a0, unsigned long a1)
352 {
353         stop_critical_timing(a0, a1);
354 }
355
356 void notrace trace_preempt_off(unsigned long a0, unsigned long a1)
357 {
358         start_critical_timing(a0, a1);
359 }
360 #endif /* CONFIG_PREEMPT_TRACER */
361
362 static void start_irqsoff_tracer(struct trace_array *tr)
363 {
364         register_ftrace_function(&trace_ops);
365         tracer_enabled = 1;
366 }
367
368 static void stop_irqsoff_tracer(struct trace_array *tr)
369 {
370         tracer_enabled = 0;
371         unregister_ftrace_function(&trace_ops);
372 }
373
374 static void __irqsoff_tracer_init(struct trace_array *tr)
375 {
376         irqsoff_trace = tr;
377         /* make sure that the tracer is visibel */
378         smp_wmb();
379
380         if (tr->ctrl)
381                 start_irqsoff_tracer(tr);
382 }
383
384 static void irqsoff_tracer_reset(struct trace_array *tr)
385 {
386         if (tr->ctrl)
387                 stop_irqsoff_tracer(tr);
388 }
389
390 static void irqsoff_tracer_ctrl_update(struct trace_array *tr)
391 {
392         if (tr->ctrl)
393                 start_irqsoff_tracer(tr);
394         else
395                 stop_irqsoff_tracer(tr);
396 }
397
398 static void notrace irqsoff_tracer_open(struct trace_iterator *iter)
399 {
400         /* stop the trace while dumping */
401         if (iter->tr->ctrl)
402                 stop_irqsoff_tracer(iter->tr);
403 }
404
405 static void notrace irqsoff_tracer_close(struct trace_iterator *iter)
406 {
407         if (iter->tr->ctrl)
408                 start_irqsoff_tracer(iter->tr);
409 }
410
411 #ifdef CONFIG_IRQSOFF_TRACER
412 static void irqsoff_tracer_init(struct trace_array *tr)
413 {
414         trace_type = TRACER_IRQS_OFF;
415
416         __irqsoff_tracer_init(tr);
417 }
418 static struct tracer irqsoff_tracer __read_mostly =
419 {
420         .name           = "irqsoff",
421         .init           = irqsoff_tracer_init,
422         .reset          = irqsoff_tracer_reset,
423         .open           = irqsoff_tracer_open,
424         .close          = irqsoff_tracer_close,
425         .ctrl_update    = irqsoff_tracer_ctrl_update,
426         .print_max      = 1,
427 #ifdef CONFIG_FTRACE_SELFTEST
428         .selftest    = trace_selftest_startup_irqsoff,
429 #endif
430 };
431 # define register_irqsoff(trace) register_tracer(&trace)
432 #else
433 # define register_irqsoff(trace) do { } while (0)
434 #endif
435
436 #ifdef CONFIG_PREEMPT_TRACER
437 static void preemptoff_tracer_init(struct trace_array *tr)
438 {
439         trace_type = TRACER_PREEMPT_OFF;
440
441         __irqsoff_tracer_init(tr);
442 }
443
444 static struct tracer preemptoff_tracer __read_mostly =
445 {
446         .name           = "preemptoff",
447         .init           = preemptoff_tracer_init,
448         .reset          = irqsoff_tracer_reset,
449         .open           = irqsoff_tracer_open,
450         .close          = irqsoff_tracer_close,
451         .ctrl_update    = irqsoff_tracer_ctrl_update,
452         .print_max      = 1,
453 #ifdef CONFIG_FTRACE_SELFTEST
454         .selftest    = trace_selftest_startup_preemptoff,
455 #endif
456 };
457 # define register_preemptoff(trace) register_tracer(&trace)
458 #else
459 # define register_preemptoff(trace) do { } while (0)
460 #endif
461
462 #if defined(CONFIG_IRQSOFF_TRACER) && \
463         defined(CONFIG_PREEMPT_TRACER)
464
465 static void preemptirqsoff_tracer_init(struct trace_array *tr)
466 {
467         trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
468
469         __irqsoff_tracer_init(tr);
470 }
471
472 static struct tracer preemptirqsoff_tracer __read_mostly =
473 {
474         .name           = "preemptirqsoff",
475         .init           = preemptirqsoff_tracer_init,
476         .reset          = irqsoff_tracer_reset,
477         .open           = irqsoff_tracer_open,
478         .close          = irqsoff_tracer_close,
479         .ctrl_update    = irqsoff_tracer_ctrl_update,
480         .print_max      = 1,
481 #ifdef CONFIG_FTRACE_SELFTEST
482         .selftest    = trace_selftest_startup_preemptirqsoff,
483 #endif
484 };
485
486 # define register_preemptirqsoff(trace) register_tracer(&trace)
487 #else
488 # define register_preemptirqsoff(trace) do { } while (0)
489 #endif
490
491 __init static int init_irqsoff_tracer(void)
492 {
493         register_irqsoff(irqsoff_tracer);
494         register_preemptoff(preemptoff_tracer);
495         register_preemptirqsoff(preemptirqsoff_tracer);
496
497         return 0;
498 }
499 device_initcall(init_irqsoff_tracer);