xref: /linux/kernel/trace/trace_irqsoff.c (revision b889fcf63cb62e7fdb7816565e28f44dbe4a76a5)
1 /*
2  * trace irqs off critical 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 Nadia Yvette Chambers
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_RAW_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 static int save_lat_flag;
36 
37 static void stop_irqsoff_tracer(struct trace_array *tr, int graph);
38 static int start_irqsoff_tracer(struct trace_array *tr, int graph);
39 
40 #ifdef CONFIG_PREEMPT_TRACER
41 static inline int
42 preempt_trace(void)
43 {
44 	return ((trace_type & TRACER_PREEMPT_OFF) && preempt_count());
45 }
46 #else
47 # define preempt_trace() (0)
48 #endif
49 
50 #ifdef CONFIG_IRQSOFF_TRACER
51 static inline int
52 irq_trace(void)
53 {
54 	return ((trace_type & TRACER_IRQS_OFF) &&
55 		irqs_disabled());
56 }
57 #else
58 # define irq_trace() (0)
59 #endif
60 
61 #define TRACE_DISPLAY_GRAPH	1
62 
63 static struct tracer_opt trace_opts[] = {
64 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
65 	/* display latency trace as call graph */
66 	{ TRACER_OPT(display-graph, TRACE_DISPLAY_GRAPH) },
67 #endif
68 	{ } /* Empty entry */
69 };
70 
71 static struct tracer_flags tracer_flags = {
72 	.val  = 0,
73 	.opts = trace_opts,
74 };
75 
76 #define is_graph() (tracer_flags.val & TRACE_DISPLAY_GRAPH)
77 
78 /*
79  * Sequence count - we record it when starting a measurement and
80  * skip the latency if the sequence has changed - some other section
81  * did a maximum and could disturb our measurement with serial console
82  * printouts, etc. Truly coinciding maximum latencies should be rare
83  * and what happens together happens separately as well, so this doesn't
84  * decrease the validity of the maximum found:
85  */
86 static __cacheline_aligned_in_smp	unsigned long max_sequence;
87 
88 #ifdef CONFIG_FUNCTION_TRACER
89 /*
90  * Prologue for the preempt and irqs off function tracers.
91  *
92  * Returns 1 if it is OK to continue, and data->disabled is
93  *            incremented.
94  *         0 if the trace is to be ignored, and data->disabled
95  *            is kept the same.
96  *
97  * Note, this function is also used outside this ifdef but
98  *  inside the #ifdef of the function graph tracer below.
99  *  This is OK, since the function graph tracer is
100  *  dependent on the function tracer.
101  */
102 static int func_prolog_dec(struct trace_array *tr,
103 			   struct trace_array_cpu **data,
104 			   unsigned long *flags)
105 {
106 	long disabled;
107 	int cpu;
108 
109 	/*
110 	 * Does not matter if we preempt. We test the flags
111 	 * afterward, to see if irqs are disabled or not.
112 	 * If we preempt and get a false positive, the flags
113 	 * test will fail.
114 	 */
115 	cpu = raw_smp_processor_id();
116 	if (likely(!per_cpu(tracing_cpu, cpu)))
117 		return 0;
118 
119 	local_save_flags(*flags);
120 	/* slight chance to get a false positive on tracing_cpu */
121 	if (!irqs_disabled_flags(*flags))
122 		return 0;
123 
124 	*data = tr->data[cpu];
125 	disabled = atomic_inc_return(&(*data)->disabled);
126 
127 	if (likely(disabled == 1))
128 		return 1;
129 
130 	atomic_dec(&(*data)->disabled);
131 
132 	return 0;
133 }
134 
135 /*
136  * irqsoff uses its own tracer function to keep the overhead down:
137  */
138 static void
139 irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip,
140 		    struct ftrace_ops *op, struct pt_regs *pt_regs)
141 {
142 	struct trace_array *tr = irqsoff_trace;
143 	struct trace_array_cpu *data;
144 	unsigned long flags;
145 
146 	if (!func_prolog_dec(tr, &data, &flags))
147 		return;
148 
149 	trace_function(tr, ip, parent_ip, flags, preempt_count());
150 
151 	atomic_dec(&data->disabled);
152 }
153 
154 static struct ftrace_ops trace_ops __read_mostly =
155 {
156 	.func = irqsoff_tracer_call,
157 	.flags = FTRACE_OPS_FL_GLOBAL | FTRACE_OPS_FL_RECURSION_SAFE,
158 };
159 #endif /* CONFIG_FUNCTION_TRACER */
160 
161 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
162 static int irqsoff_set_flag(u32 old_flags, u32 bit, int set)
163 {
164 	int cpu;
165 
166 	if (!(bit & TRACE_DISPLAY_GRAPH))
167 		return -EINVAL;
168 
169 	if (!(is_graph() ^ set))
170 		return 0;
171 
172 	stop_irqsoff_tracer(irqsoff_trace, !set);
173 
174 	for_each_possible_cpu(cpu)
175 		per_cpu(tracing_cpu, cpu) = 0;
176 
177 	tracing_max_latency = 0;
178 	tracing_reset_online_cpus(irqsoff_trace);
179 
180 	return start_irqsoff_tracer(irqsoff_trace, set);
181 }
182 
183 static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
184 {
185 	struct trace_array *tr = irqsoff_trace;
186 	struct trace_array_cpu *data;
187 	unsigned long flags;
188 	int ret;
189 	int pc;
190 
191 	if (!func_prolog_dec(tr, &data, &flags))
192 		return 0;
193 
194 	pc = preempt_count();
195 	ret = __trace_graph_entry(tr, trace, flags, pc);
196 	atomic_dec(&data->disabled);
197 
198 	return ret;
199 }
200 
201 static void irqsoff_graph_return(struct ftrace_graph_ret *trace)
202 {
203 	struct trace_array *tr = irqsoff_trace;
204 	struct trace_array_cpu *data;
205 	unsigned long flags;
206 	int pc;
207 
208 	if (!func_prolog_dec(tr, &data, &flags))
209 		return;
210 
211 	pc = preempt_count();
212 	__trace_graph_return(tr, trace, flags, pc);
213 	atomic_dec(&data->disabled);
214 }
215 
216 static void irqsoff_trace_open(struct trace_iterator *iter)
217 {
218 	if (is_graph())
219 		graph_trace_open(iter);
220 
221 }
222 
223 static void irqsoff_trace_close(struct trace_iterator *iter)
224 {
225 	if (iter->private)
226 		graph_trace_close(iter);
227 }
228 
229 #define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_CPU | \
230 			    TRACE_GRAPH_PRINT_PROC | \
231 			    TRACE_GRAPH_PRINT_ABS_TIME | \
232 			    TRACE_GRAPH_PRINT_DURATION)
233 
234 static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
235 {
236 	/*
237 	 * In graph mode call the graph tracer output function,
238 	 * otherwise go with the TRACE_FN event handler
239 	 */
240 	if (is_graph())
241 		return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS);
242 
243 	return TRACE_TYPE_UNHANDLED;
244 }
245 
246 static void irqsoff_print_header(struct seq_file *s)
247 {
248 	if (is_graph())
249 		print_graph_headers_flags(s, GRAPH_TRACER_FLAGS);
250 	else
251 		trace_default_header(s);
252 }
253 
254 static void
255 __trace_function(struct trace_array *tr,
256 		 unsigned long ip, unsigned long parent_ip,
257 		 unsigned long flags, int pc)
258 {
259 	if (is_graph())
260 		trace_graph_function(tr, ip, parent_ip, flags, pc);
261 	else
262 		trace_function(tr, ip, parent_ip, flags, pc);
263 }
264 
265 #else
266 #define __trace_function trace_function
267 
268 static int irqsoff_set_flag(u32 old_flags, u32 bit, int set)
269 {
270 	return -EINVAL;
271 }
272 
273 static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
274 {
275 	return -1;
276 }
277 
278 static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
279 {
280 	return TRACE_TYPE_UNHANDLED;
281 }
282 
283 static void irqsoff_graph_return(struct ftrace_graph_ret *trace) { }
284 static void irqsoff_trace_open(struct trace_iterator *iter) { }
285 static void irqsoff_trace_close(struct trace_iterator *iter) { }
286 
287 #ifdef CONFIG_FUNCTION_TRACER
288 static void irqsoff_print_header(struct seq_file *s)
289 {
290 	trace_default_header(s);
291 }
292 #else
293 static void irqsoff_print_header(struct seq_file *s)
294 {
295 	trace_latency_header(s);
296 }
297 #endif /* CONFIG_FUNCTION_TRACER */
298 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
299 
300 /*
301  * Should this new latency be reported/recorded?
302  */
303 static int report_latency(cycle_t delta)
304 {
305 	if (tracing_thresh) {
306 		if (delta < tracing_thresh)
307 			return 0;
308 	} else {
309 		if (delta <= tracing_max_latency)
310 			return 0;
311 	}
312 	return 1;
313 }
314 
315 static void
316 check_critical_timing(struct trace_array *tr,
317 		      struct trace_array_cpu *data,
318 		      unsigned long parent_ip,
319 		      int cpu)
320 {
321 	cycle_t T0, T1, delta;
322 	unsigned long flags;
323 	int pc;
324 
325 	T0 = data->preempt_timestamp;
326 	T1 = ftrace_now(cpu);
327 	delta = T1-T0;
328 
329 	local_save_flags(flags);
330 
331 	pc = preempt_count();
332 
333 	if (!report_latency(delta))
334 		goto out;
335 
336 	raw_spin_lock_irqsave(&max_trace_lock, flags);
337 
338 	/* check if we are still the max latency */
339 	if (!report_latency(delta))
340 		goto out_unlock;
341 
342 	__trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
343 	/* Skip 5 functions to get to the irq/preempt enable function */
344 	__trace_stack(tr, flags, 5, pc);
345 
346 	if (data->critical_sequence != max_sequence)
347 		goto out_unlock;
348 
349 	data->critical_end = parent_ip;
350 
351 	if (likely(!is_tracing_stopped())) {
352 		tracing_max_latency = delta;
353 		update_max_tr_single(tr, current, cpu);
354 	}
355 
356 	max_sequence++;
357 
358 out_unlock:
359 	raw_spin_unlock_irqrestore(&max_trace_lock, flags);
360 
361 out:
362 	data->critical_sequence = max_sequence;
363 	data->preempt_timestamp = ftrace_now(cpu);
364 	__trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
365 }
366 
367 static inline void
368 start_critical_timing(unsigned long ip, unsigned long parent_ip)
369 {
370 	int cpu;
371 	struct trace_array *tr = irqsoff_trace;
372 	struct trace_array_cpu *data;
373 	unsigned long flags;
374 
375 	if (likely(!tracer_enabled))
376 		return;
377 
378 	cpu = raw_smp_processor_id();
379 
380 	if (per_cpu(tracing_cpu, cpu))
381 		return;
382 
383 	data = tr->data[cpu];
384 
385 	if (unlikely(!data) || atomic_read(&data->disabled))
386 		return;
387 
388 	atomic_inc(&data->disabled);
389 
390 	data->critical_sequence = max_sequence;
391 	data->preempt_timestamp = ftrace_now(cpu);
392 	data->critical_start = parent_ip ? : ip;
393 
394 	local_save_flags(flags);
395 
396 	__trace_function(tr, ip, parent_ip, flags, preempt_count());
397 
398 	per_cpu(tracing_cpu, cpu) = 1;
399 
400 	atomic_dec(&data->disabled);
401 }
402 
403 static inline void
404 stop_critical_timing(unsigned long ip, unsigned long parent_ip)
405 {
406 	int cpu;
407 	struct trace_array *tr = irqsoff_trace;
408 	struct trace_array_cpu *data;
409 	unsigned long flags;
410 
411 	cpu = raw_smp_processor_id();
412 	/* Always clear the tracing cpu on stopping the trace */
413 	if (unlikely(per_cpu(tracing_cpu, cpu)))
414 		per_cpu(tracing_cpu, cpu) = 0;
415 	else
416 		return;
417 
418 	if (!tracer_enabled)
419 		return;
420 
421 	data = tr->data[cpu];
422 
423 	if (unlikely(!data) ||
424 	    !data->critical_start || atomic_read(&data->disabled))
425 		return;
426 
427 	atomic_inc(&data->disabled);
428 
429 	local_save_flags(flags);
430 	__trace_function(tr, ip, parent_ip, flags, preempt_count());
431 	check_critical_timing(tr, data, parent_ip ? : ip, cpu);
432 	data->critical_start = 0;
433 	atomic_dec(&data->disabled);
434 }
435 
436 /* start and stop critical timings used to for stoppage (in idle) */
437 void start_critical_timings(void)
438 {
439 	if (preempt_trace() || irq_trace())
440 		start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
441 }
442 EXPORT_SYMBOL_GPL(start_critical_timings);
443 
444 void stop_critical_timings(void)
445 {
446 	if (preempt_trace() || irq_trace())
447 		stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
448 }
449 EXPORT_SYMBOL_GPL(stop_critical_timings);
450 
451 #ifdef CONFIG_IRQSOFF_TRACER
452 #ifdef CONFIG_PROVE_LOCKING
453 void time_hardirqs_on(unsigned long a0, unsigned long a1)
454 {
455 	if (!preempt_trace() && irq_trace())
456 		stop_critical_timing(a0, a1);
457 }
458 
459 void time_hardirqs_off(unsigned long a0, unsigned long a1)
460 {
461 	if (!preempt_trace() && irq_trace())
462 		start_critical_timing(a0, a1);
463 }
464 
465 #else /* !CONFIG_PROVE_LOCKING */
466 
467 /*
468  * Stubs:
469  */
470 
471 void trace_softirqs_on(unsigned long ip)
472 {
473 }
474 
475 void trace_softirqs_off(unsigned long ip)
476 {
477 }
478 
479 inline void print_irqtrace_events(struct task_struct *curr)
480 {
481 }
482 
483 /*
484  * We are only interested in hardirq on/off events:
485  */
486 void trace_hardirqs_on(void)
487 {
488 	if (!preempt_trace() && irq_trace())
489 		stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
490 }
491 EXPORT_SYMBOL(trace_hardirqs_on);
492 
493 void trace_hardirqs_off(void)
494 {
495 	if (!preempt_trace() && irq_trace())
496 		start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
497 }
498 EXPORT_SYMBOL(trace_hardirqs_off);
499 
500 void trace_hardirqs_on_caller(unsigned long caller_addr)
501 {
502 	if (!preempt_trace() && irq_trace())
503 		stop_critical_timing(CALLER_ADDR0, caller_addr);
504 }
505 EXPORT_SYMBOL(trace_hardirqs_on_caller);
506 
507 void trace_hardirqs_off_caller(unsigned long caller_addr)
508 {
509 	if (!preempt_trace() && irq_trace())
510 		start_critical_timing(CALLER_ADDR0, caller_addr);
511 }
512 EXPORT_SYMBOL(trace_hardirqs_off_caller);
513 
514 #endif /* CONFIG_PROVE_LOCKING */
515 #endif /*  CONFIG_IRQSOFF_TRACER */
516 
517 #ifdef CONFIG_PREEMPT_TRACER
518 void trace_preempt_on(unsigned long a0, unsigned long a1)
519 {
520 	if (preempt_trace() && !irq_trace())
521 		stop_critical_timing(a0, a1);
522 }
523 
524 void trace_preempt_off(unsigned long a0, unsigned long a1)
525 {
526 	if (preempt_trace() && !irq_trace())
527 		start_critical_timing(a0, a1);
528 }
529 #endif /* CONFIG_PREEMPT_TRACER */
530 
531 static int start_irqsoff_tracer(struct trace_array *tr, int graph)
532 {
533 	int ret = 0;
534 
535 	if (!graph)
536 		ret = register_ftrace_function(&trace_ops);
537 	else
538 		ret = register_ftrace_graph(&irqsoff_graph_return,
539 					    &irqsoff_graph_entry);
540 
541 	if (!ret && tracing_is_enabled())
542 		tracer_enabled = 1;
543 	else
544 		tracer_enabled = 0;
545 
546 	return ret;
547 }
548 
549 static void stop_irqsoff_tracer(struct trace_array *tr, int graph)
550 {
551 	tracer_enabled = 0;
552 
553 	if (!graph)
554 		unregister_ftrace_function(&trace_ops);
555 	else
556 		unregister_ftrace_graph();
557 }
558 
559 static void __irqsoff_tracer_init(struct trace_array *tr)
560 {
561 	save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
562 	trace_flags |= TRACE_ITER_LATENCY_FMT;
563 
564 	tracing_max_latency = 0;
565 	irqsoff_trace = tr;
566 	/* make sure that the tracer is visible */
567 	smp_wmb();
568 	tracing_reset_online_cpus(tr);
569 
570 	if (start_irqsoff_tracer(tr, is_graph()))
571 		printk(KERN_ERR "failed to start irqsoff tracer\n");
572 }
573 
574 static void irqsoff_tracer_reset(struct trace_array *tr)
575 {
576 	stop_irqsoff_tracer(tr, is_graph());
577 
578 	if (!save_lat_flag)
579 		trace_flags &= ~TRACE_ITER_LATENCY_FMT;
580 }
581 
582 static void irqsoff_tracer_start(struct trace_array *tr)
583 {
584 	tracer_enabled = 1;
585 }
586 
587 static void irqsoff_tracer_stop(struct trace_array *tr)
588 {
589 	tracer_enabled = 0;
590 }
591 
592 #ifdef CONFIG_IRQSOFF_TRACER
593 static int irqsoff_tracer_init(struct trace_array *tr)
594 {
595 	trace_type = TRACER_IRQS_OFF;
596 
597 	__irqsoff_tracer_init(tr);
598 	return 0;
599 }
600 static struct tracer irqsoff_tracer __read_mostly =
601 {
602 	.name		= "irqsoff",
603 	.init		= irqsoff_tracer_init,
604 	.reset		= irqsoff_tracer_reset,
605 	.start		= irqsoff_tracer_start,
606 	.stop		= irqsoff_tracer_stop,
607 	.print_max	= true,
608 	.print_header   = irqsoff_print_header,
609 	.print_line     = irqsoff_print_line,
610 	.flags		= &tracer_flags,
611 	.set_flag	= irqsoff_set_flag,
612 #ifdef CONFIG_FTRACE_SELFTEST
613 	.selftest    = trace_selftest_startup_irqsoff,
614 #endif
615 	.open           = irqsoff_trace_open,
616 	.close          = irqsoff_trace_close,
617 	.use_max_tr	= true,
618 };
619 # define register_irqsoff(trace) register_tracer(&trace)
620 #else
621 # define register_irqsoff(trace) do { } while (0)
622 #endif
623 
624 #ifdef CONFIG_PREEMPT_TRACER
625 static int preemptoff_tracer_init(struct trace_array *tr)
626 {
627 	trace_type = TRACER_PREEMPT_OFF;
628 
629 	__irqsoff_tracer_init(tr);
630 	return 0;
631 }
632 
633 static struct tracer preemptoff_tracer __read_mostly =
634 {
635 	.name		= "preemptoff",
636 	.init		= preemptoff_tracer_init,
637 	.reset		= irqsoff_tracer_reset,
638 	.start		= irqsoff_tracer_start,
639 	.stop		= irqsoff_tracer_stop,
640 	.print_max	= true,
641 	.print_header   = irqsoff_print_header,
642 	.print_line     = irqsoff_print_line,
643 	.flags		= &tracer_flags,
644 	.set_flag	= irqsoff_set_flag,
645 #ifdef CONFIG_FTRACE_SELFTEST
646 	.selftest    = trace_selftest_startup_preemptoff,
647 #endif
648 	.open		= irqsoff_trace_open,
649 	.close		= irqsoff_trace_close,
650 	.use_max_tr	= true,
651 };
652 # define register_preemptoff(trace) register_tracer(&trace)
653 #else
654 # define register_preemptoff(trace) do { } while (0)
655 #endif
656 
657 #if defined(CONFIG_IRQSOFF_TRACER) && \
658 	defined(CONFIG_PREEMPT_TRACER)
659 
660 static int preemptirqsoff_tracer_init(struct trace_array *tr)
661 {
662 	trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
663 
664 	__irqsoff_tracer_init(tr);
665 	return 0;
666 }
667 
668 static struct tracer preemptirqsoff_tracer __read_mostly =
669 {
670 	.name		= "preemptirqsoff",
671 	.init		= preemptirqsoff_tracer_init,
672 	.reset		= irqsoff_tracer_reset,
673 	.start		= irqsoff_tracer_start,
674 	.stop		= irqsoff_tracer_stop,
675 	.print_max	= true,
676 	.print_header   = irqsoff_print_header,
677 	.print_line     = irqsoff_print_line,
678 	.flags		= &tracer_flags,
679 	.set_flag	= irqsoff_set_flag,
680 #ifdef CONFIG_FTRACE_SELFTEST
681 	.selftest    = trace_selftest_startup_preemptirqsoff,
682 #endif
683 	.open		= irqsoff_trace_open,
684 	.close		= irqsoff_trace_close,
685 	.use_max_tr	= true,
686 };
687 
688 # define register_preemptirqsoff(trace) register_tracer(&trace)
689 #else
690 # define register_preemptirqsoff(trace) do { } while (0)
691 #endif
692 
693 __init static int init_irqsoff_tracer(void)
694 {
695 	register_irqsoff(irqsoff_tracer);
696 	register_preemptoff(preemptoff_tracer);
697 	register_preemptirqsoff(preemptirqsoff_tracer);
698 
699 	return 0;
700 }
701 core_initcall(init_irqsoff_tracer);
702