ftrace: only trace preempt off with preempt tracer
[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
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
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
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                 trace_function(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 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
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         trace_function(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         max_sequence++;
169
170 out_unlock:
171         spin_unlock_irqrestore(&max_trace_lock, flags);
172
173 out:
174         data->critical_sequence = max_sequence;
175         data->preempt_timestamp = ftrace_now(cpu);
176         tracing_reset(data);
177         trace_function(tr, data, CALLER_ADDR0, parent_ip, flags);
178 }
179
180 static inline void
181 start_critical_timing(unsigned long ip, unsigned long parent_ip)
182 {
183         int cpu;
184         struct trace_array *tr = irqsoff_trace;
185         struct trace_array_cpu *data;
186         unsigned long flags;
187
188         if (likely(!tracer_enabled))
189                 return;
190
191         cpu = raw_smp_processor_id();
192
193         if (per_cpu(tracing_cpu, cpu))
194                 return;
195
196         data = tr->data[cpu];
197
198         if (unlikely(!data) || atomic_read(&data->disabled))
199                 return;
200
201         atomic_inc(&data->disabled);
202
203         data->critical_sequence = max_sequence;
204         data->preempt_timestamp = ftrace_now(cpu);
205         data->critical_start = parent_ip ? : ip;
206         tracing_reset(data);
207
208         local_save_flags(flags);
209
210         trace_function(tr, data, ip, parent_ip, flags);
211
212         per_cpu(tracing_cpu, cpu) = 1;
213
214         atomic_dec(&data->disabled);
215 }
216
217 static inline void
218 stop_critical_timing(unsigned long ip, unsigned long parent_ip)
219 {
220         int cpu;
221         struct trace_array *tr = irqsoff_trace;
222         struct trace_array_cpu *data;
223         unsigned long flags;
224
225         cpu = raw_smp_processor_id();
226         /* Always clear the tracing cpu on stopping the trace */
227         if (unlikely(per_cpu(tracing_cpu, cpu)))
228                 per_cpu(tracing_cpu, cpu) = 0;
229         else
230                 return;
231
232         if (!tracer_enabled)
233                 return;
234
235         data = tr->data[cpu];
236
237         if (unlikely(!data) || unlikely(!head_page(data)) ||
238             !data->critical_start || atomic_read(&data->disabled))
239                 return;
240
241         atomic_inc(&data->disabled);
242
243         local_save_flags(flags);
244         trace_function(tr, data, ip, parent_ip, flags);
245         check_critical_timing(tr, data, parent_ip ? : ip, cpu);
246         data->critical_start = 0;
247         atomic_dec(&data->disabled);
248 }
249
250 /* start and stop critical timings used to for stoppage (in idle) */
251 void start_critical_timings(void)
252 {
253         if (preempt_trace() || irq_trace())
254                 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
255 }
256
257 void stop_critical_timings(void)
258 {
259         if (preempt_trace() || irq_trace())
260                 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
261 }
262
263 #ifdef CONFIG_IRQSOFF_TRACER
264 #ifdef CONFIG_PROVE_LOCKING
265 void time_hardirqs_on(unsigned long a0, unsigned long a1)
266 {
267         if (!preempt_trace() && irq_trace())
268                 stop_critical_timing(a0, a1);
269 }
270
271 void time_hardirqs_off(unsigned long a0, unsigned long a1)
272 {
273         if (!preempt_trace() && irq_trace())
274                 start_critical_timing(a0, a1);
275 }
276
277 #else /* !CONFIG_PROVE_LOCKING */
278
279 /*
280  * Stubs:
281  */
282
283 void early_boot_irqs_off(void)
284 {
285 }
286
287 void early_boot_irqs_on(void)
288 {
289 }
290
291 void trace_softirqs_on(unsigned long ip)
292 {
293 }
294
295 void trace_softirqs_off(unsigned long ip)
296 {
297 }
298
299 inline void print_irqtrace_events(struct task_struct *curr)
300 {
301 }
302
303 /*
304  * We are only interested in hardirq on/off events:
305  */
306 void trace_hardirqs_on(void)
307 {
308         if (!preempt_trace() && irq_trace())
309                 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
310 }
311 EXPORT_SYMBOL(trace_hardirqs_on);
312
313 void trace_hardirqs_off(void)
314 {
315         if (!preempt_trace() && irq_trace())
316                 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
317 }
318 EXPORT_SYMBOL(trace_hardirqs_off);
319
320 void trace_hardirqs_on_caller(unsigned long caller_addr)
321 {
322         if (!preempt_trace() && irq_trace())
323                 stop_critical_timing(CALLER_ADDR0, caller_addr);
324 }
325 EXPORT_SYMBOL(trace_hardirqs_on_caller);
326
327 void trace_hardirqs_off_caller(unsigned long caller_addr)
328 {
329         if (!preempt_trace() && irq_trace())
330                 start_critical_timing(CALLER_ADDR0, caller_addr);
331 }
332 EXPORT_SYMBOL(trace_hardirqs_off_caller);
333
334 #endif /* CONFIG_PROVE_LOCKING */
335 #endif /*  CONFIG_IRQSOFF_TRACER */
336
337 #ifdef CONFIG_PREEMPT_TRACER
338 void trace_preempt_on(unsigned long a0, unsigned long a1)
339 {
340         if (preempt_trace())
341                 stop_critical_timing(a0, a1);
342 }
343
344 void trace_preempt_off(unsigned long a0, unsigned long a1)
345 {
346         if (preempt_trace())
347                 start_critical_timing(a0, a1);
348 }
349 #endif /* CONFIG_PREEMPT_TRACER */
350
351 static void start_irqsoff_tracer(struct trace_array *tr)
352 {
353         register_ftrace_function(&trace_ops);
354         tracer_enabled = 1;
355 }
356
357 static void stop_irqsoff_tracer(struct trace_array *tr)
358 {
359         tracer_enabled = 0;
360         unregister_ftrace_function(&trace_ops);
361 }
362
363 static void __irqsoff_tracer_init(struct trace_array *tr)
364 {
365         irqsoff_trace = tr;
366         /* make sure that the tracer is visible */
367         smp_wmb();
368
369         if (tr->ctrl)
370                 start_irqsoff_tracer(tr);
371 }
372
373 static void irqsoff_tracer_reset(struct trace_array *tr)
374 {
375         if (tr->ctrl)
376                 stop_irqsoff_tracer(tr);
377 }
378
379 static void irqsoff_tracer_ctrl_update(struct trace_array *tr)
380 {
381         if (tr->ctrl)
382                 start_irqsoff_tracer(tr);
383         else
384                 stop_irqsoff_tracer(tr);
385 }
386
387 static void irqsoff_tracer_open(struct trace_iterator *iter)
388 {
389         /* stop the trace while dumping */
390         if (iter->tr->ctrl)
391                 stop_irqsoff_tracer(iter->tr);
392 }
393
394 static void irqsoff_tracer_close(struct trace_iterator *iter)
395 {
396         if (iter->tr->ctrl)
397                 start_irqsoff_tracer(iter->tr);
398 }
399
400 #ifdef CONFIG_IRQSOFF_TRACER
401 static void irqsoff_tracer_init(struct trace_array *tr)
402 {
403         trace_type = TRACER_IRQS_OFF;
404
405         __irqsoff_tracer_init(tr);
406 }
407 static struct tracer irqsoff_tracer __read_mostly =
408 {
409         .name           = "irqsoff",
410         .init           = irqsoff_tracer_init,
411         .reset          = irqsoff_tracer_reset,
412         .open           = irqsoff_tracer_open,
413         .close          = irqsoff_tracer_close,
414         .ctrl_update    = irqsoff_tracer_ctrl_update,
415         .print_max      = 1,
416 #ifdef CONFIG_FTRACE_SELFTEST
417         .selftest    = trace_selftest_startup_irqsoff,
418 #endif
419 };
420 # define register_irqsoff(trace) register_tracer(&trace)
421 #else
422 # define register_irqsoff(trace) do { } while (0)
423 #endif
424
425 #ifdef CONFIG_PREEMPT_TRACER
426 static void preemptoff_tracer_init(struct trace_array *tr)
427 {
428         trace_type = TRACER_PREEMPT_OFF;
429
430         __irqsoff_tracer_init(tr);
431 }
432
433 static struct tracer preemptoff_tracer __read_mostly =
434 {
435         .name           = "preemptoff",
436         .init           = preemptoff_tracer_init,
437         .reset          = irqsoff_tracer_reset,
438         .open           = irqsoff_tracer_open,
439         .close          = irqsoff_tracer_close,
440         .ctrl_update    = irqsoff_tracer_ctrl_update,
441         .print_max      = 1,
442 #ifdef CONFIG_FTRACE_SELFTEST
443         .selftest    = trace_selftest_startup_preemptoff,
444 #endif
445 };
446 # define register_preemptoff(trace) register_tracer(&trace)
447 #else
448 # define register_preemptoff(trace) do { } while (0)
449 #endif
450
451 #if defined(CONFIG_IRQSOFF_TRACER) && \
452         defined(CONFIG_PREEMPT_TRACER)
453
454 static void preemptirqsoff_tracer_init(struct trace_array *tr)
455 {
456         trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
457
458         __irqsoff_tracer_init(tr);
459 }
460
461 static struct tracer preemptirqsoff_tracer __read_mostly =
462 {
463         .name           = "preemptirqsoff",
464         .init           = preemptirqsoff_tracer_init,
465         .reset          = irqsoff_tracer_reset,
466         .open           = irqsoff_tracer_open,
467         .close          = irqsoff_tracer_close,
468         .ctrl_update    = irqsoff_tracer_ctrl_update,
469         .print_max      = 1,
470 #ifdef CONFIG_FTRACE_SELFTEST
471         .selftest    = trace_selftest_startup_preemptirqsoff,
472 #endif
473 };
474
475 # define register_preemptirqsoff(trace) register_tracer(&trace)
476 #else
477 # define register_preemptirqsoff(trace) do { } while (0)
478 #endif
479
480 __init static int init_irqsoff_tracer(void)
481 {
482         register_irqsoff(irqsoff_tracer);
483         register_preemptoff(preemptoff_tracer);
484         register_preemptirqsoff(preemptirqsoff_tracer);
485
486         return 0;
487 }
488 device_initcall(init_irqsoff_tracer);