summaryrefslogtreecommitdiffstats
path: root/kernel/trace/trace_irqsoff.c
blob: 73a6b0601f2e301c0cd5575cc96f7f0b788853d9 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
/*
 * trace irqs off critical timings
 *
 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
 * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
 *
 * From code in the latency_tracer, that is:
 *
 *  Copyright (C) 2004-2006 Ingo Molnar
 *  Copyright (C) 2004 William Lee Irwin III
 */
#include <linux/kallsyms.h>
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/ftrace.h>
#include <linux/fs.h>

#include "trace.h"

static struct trace_array		*irqsoff_trace __read_mostly;
static int				tracer_enabled __read_mostly;

static DEFINE_PER_CPU(int, tracing_cpu);

static DEFINE_SPINLOCK(max_trace_lock);

enum {
	TRACER_IRQS_OFF		= (1 << 1),
	TRACER_PREEMPT_OFF	= (1 << 2),
};

static int trace_type __read_mostly;

static int save_lat_flag;

static void stop_irqsoff_tracer(struct trace_array *tr, int graph);
static int start_irqsoff_tracer(struct trace_array *tr, int graph);

#ifdef CONFIG_PREEMPT_TRACER
static inline int
preempt_trace(void)
{
	return ((trace_type & TRACER_PREEMPT_OFF) && preempt_count());
}
#else
# define preempt_trace() (0)
#endif

#ifdef CONFIG_IRQSOFF_TRACER
static inline int
irq_trace(void)
{
	return ((trace_type & TRACER_IRQS_OFF) &&
		irqs_disabled());
}
#else
# define irq_trace() (0)
#endif

#define TRACE_DISPLAY_GRAPH	1

static struct tracer_opt trace_opts[] = {
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
	/* display latency trace as call graph */
	{ TRACER_OPT(display-graph, TRACE_DISPLAY_GRAPH) },
#endif
	{ } /* Empty entry */
};

static struct tracer_flags tracer_flags = {
	.val  = 0,
	.opts = trace_opts,
};

#define is_graph() (tracer_flags.val & TRACE_DISPLAY_GRAPH)

/*
 * Sequence count - we record it when starting a measurement and
 * skip the latency if the sequence has changed - some other section
 * did a maximum and could disturb our measurement with serial console
 * printouts, etc. Truly coinciding maximum latencies should be rare
 * and what happens together happens separately as well, so this doesnt
 * decrease the validity of the maximum found:
 */
static __cacheline_aligned_in_smp	unsigned long max_sequence;

#ifdef CONFIG_FUNCTION_TRACER
/*
 * irqsoff uses its own tracer function to keep the overhead down:
 */
static void
irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip)
{
	struct trace_array *tr = irqsoff_trace;
	struct trace_array_cpu *data;
	unsigned long flags;
	long disabled;
	int cpu;

	/*
	 * Does not matter if we preempt. We test the flags
	 * afterward, to see if irqs are disabled or not.
	 * If we preempt and get a false positive, the flags
	 * test will fail.
	 */
	cpu = raw_smp_processor_id();
	if (likely(!per_cpu(tracing_cpu, cpu)))
		return;

	local_save_flags(flags);
	/* slight chance to get a false positive on tracing_cpu */
	if (!irqs_disabled_flags(flags))
		return;

	data = tr->data[cpu];
	disabled = atomic_inc_return(&data->disabled);

	if (likely(disabled == 1))
		trace_function(tr, ip, parent_ip, flags, preempt_count());

	atomic_dec(&data->disabled);
}

static struct ftrace_ops trace_ops __read_mostly =
{
	.func = irqsoff_tracer_call,
};
#endif /* CONFIG_FUNCTION_TRACER */

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
static int irqsoff_set_flag(u32 old_flags, u32 bit, int set)
{
	int cpu;

	if (!(bit & TRACE_DISPLAY_GRAPH))
		return -EINVAL;

	if (!(is_graph() ^ set))
		return 0;

	stop_irqsoff_tracer(irqsoff_trace, !set);

	for_each_possible_cpu(cpu)
		per_cpu(tracing_cpu, cpu) = 0;

	tracing_max_latency = 0;
	tracing_reset_online_cpus(irqsoff_trace);

	return start_irqsoff_tracer(irqsoff_trace, set);
}

static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
{
	struct trace_array *tr = irqsoff_trace;
	struct trace_array_cpu *data;
	unsigned long flags;
	long disabled;
	int ret;
	int cpu;
	int pc;

	cpu = raw_smp_processor_id();
	if (likely(!per_cpu(tracing_cpu, cpu)))
		return 0;

	local_save_flags(flags);
	/* slight chance to get a false positive on tracing_cpu */
	if (!irqs_disabled_flags(flags))
		return 0;

	data = tr->data[cpu];
	disabled = atomic_inc_return(&data->disabled);

	if (likely(disabled == 1)) {
		pc = preempt_count();
		ret = __trace_graph_entry(tr, trace, flags, pc);
	} else
		ret = 0;

	atomic_dec(&data->disabled);
	return ret;
}

static void irqsoff_graph_return(struct ftrace_graph_ret *trace)
{
	struct trace_array *tr = irqsoff_trace;
	struct trace_array_cpu *data;
	unsigned long flags;
	long disabled;
	int cpu;
	int pc;

	cpu = raw_smp_processor_id();
	if (likely(!per_cpu(tracing_cpu, cpu)))
		return;

	local_save_flags(flags);
	/* slight chance to get a false positive on tracing_cpu */
	if (!irqs_disabled_flags(flags))
		return;

	data = tr->data[cpu];
	disabled = atomic_inc_return(&data->disabled);

	if (likely(disabled == 1)) {
		pc = preempt_count();
		__trace_graph_return(tr, trace, flags, pc);
	}

	atomic_dec(&data->disabled);
}

static void irqsoff_trace_open(struct trace_iterator *iter)
{
	if (is_graph())
		graph_trace_open(iter);

}

static void irqsoff_trace_close(struct trace_iterator *iter)
{
	if (iter->private)
		graph_trace_close(iter);
}

#define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_CPU | \
			    TRACE_GRAPH_PRINT_PROC)

static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
{
	u32 flags = GRAPH_TRACER_FLAGS;

	if (trace_flags & TRACE_ITER_LATENCY_FMT)
		flags |= TRACE_GRAPH_PRINT_DURATION;
	else
		flags |= TRACE_GRAPH_PRINT_ABS_TIME;

	/*
	 * In graph mode call the graph tracer output function,
	 * otherwise go with the TRACE_FN event handler
	 */
	if (is_graph())
		return print_graph_function_flags(iter, flags);

	return TRACE_TYPE_UNHANDLED;
}

static void irqsoff_print_header(struct seq_file *s)
{
	if (is_graph()) {
		struct trace_iterator *iter = s->private;
		u32 flags = GRAPH_TRACER_FLAGS;

		if (trace_flags & TRACE_ITER_LATENCY_FMT) {
			/* print nothing if the buffers are empty */
			if (trace_empty(iter))
				return;

			print_trace_header(s, iter);
			flags |= TRACE_GRAPH_PRINT_DURATION;
		} else
			flags |= TRACE_GRAPH_PRINT_ABS_TIME;

		print_graph_headers_flags(s, flags);
	} else
		trace_default_header(s);
}

static void
trace_graph_function(struct trace_array *tr,
		 unsigned long ip, unsigned long flags, int pc)
{
	u64 time = trace_clock_local();
	struct ftrace_graph_ent ent = {
		.func  = ip,
		.depth = 0,
	};
	struct ftrace_graph_ret ret = {
		.func     = ip,
		.depth    = 0,
		.calltime = time,
		.rettime  = time,
	};

	__trace_graph_entry(tr, &ent, flags, pc);
	__trace_graph_return(tr, &ret, flags, pc);
}

static void
__trace_function(struct trace_array *tr,
		 unsigned long ip, unsigned long parent_ip,
		 unsigned long flags, int pc)
{
	if (!is_graph())
		trace_function(tr, ip, parent_ip, flags, pc);
	else {
		trace_graph_function(tr, parent_ip, flags, pc);
		trace_graph_function(tr, ip, flags, pc);
	}
}

#else
#define __trace_function trace_function

static int irqsoff_set_flag(u32 old_flags, u32 bit, int set)
{
	return -EINVAL;
}

static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
{
	return -1;
}

static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
{
	return TRACE_TYPE_UNHANDLED;
}

static void irqsoff_graph_return(struct ftrace_graph_ret *trace) { }
static void irqsoff_print_header(struct seq_file *s) { }
static void irqsoff_trace_open(struct trace_iterator *iter) { }
static void irqsoff_trace_close(struct trace_iterator *iter) { }
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

/*
 * Should this new latency be reported/recorded?
 */
static int report_latency(cycle_t delta)
{
	if (tracing_thresh) {
		if (delta < tracing_thresh)
			return 0;
	} else {
		if (delta <= tracing_max_latency)
			return 0;
	}
	return 1;
}

static void
check_critical_timing(struct trace_array *tr,
		      struct trace_array_cpu *data,
		      unsigned long parent_ip,
		      int cpu)
{
	cycle_t T0, T1, delta;
	unsigned long flags;
	int pc;

	T0 = data->preempt_timestamp;
	T1 = ftrace_now(cpu);
	delta = T1-T0;

	local_save_flags(flags);

	pc = preempt_count();

	if (!report_latency(delta))
		goto out;

	spin_lock_irqsave(&max_trace_lock, flags);

	/* check if we are still the max latency */
	if (!report_latency(delta))
		goto out_unlock;

	__trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
	/* Skip 5 functions to get to the irq/preempt enable function */
	__trace_stack(tr, flags, 5, pc);

	if (data->critical_sequence != max_sequence)
		goto out_unlock;

	data->critical_end = parent_ip;

	if (likely(!is_tracing_stopped())) {
		tracing_max_latency = delta;
		update_max_tr_single(tr, current, cpu);
	}

	max_sequence++;

out_unlock:
	spin_unlock_irqrestore(&max_trace_lock, flags);

out:
	data->critical_sequence = max_sequence;
	data->preempt_timestamp = ftrace_now(cpu);
	__trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
}

static inline void
start_critical_timing(unsigned long ip, unsigned long parent_ip)
{
	int cpu;
	struct trace_array *tr = irqsoff_trace;
	struct trace_array_cpu *data;
	unsigned long flags;

	if (likely(!tracer_enabled))
		return;

	cpu = raw_smp_processor_id();

	if (per_cpu(tracing_cpu, cpu))
		return;

	data = tr->data[cpu];

	if (unlikely(!data) || atomic_read(&data->disabled))
		return;

	atomic_inc(&data->disabled);

	data->critical_sequence = max_sequence;
	data->preempt_timestamp = ftrace_now(cpu);
	data->critical_start = parent_ip ? : ip;

	local_save_flags(flags);

	__trace_function(tr, ip, parent_ip, flags, preempt_count());

	per_cpu(tracing_cpu, cpu) = 1;

	atomic_dec(&data->disabled);
}

static inline void
stop_critical_timing(unsigned long ip, unsigned long parent_ip)
{
	int cpu;
	struct trace_array *tr = irqsoff_trace;
	struct trace_array_cpu *data;
	unsigned long flags;

	cpu = raw_smp_processor_id();
	/* Always clear the tracing cpu on stopping the trace */
	if (unlikely(per_cpu(tracing_cpu, cpu)))
		per_cpu(tracing_cpu, cpu) = 0;
	else
		return;

	if (!tracer_enabled)
		return;

	data = tr->data[cpu];

	if (unlikely(!data) ||
	    !data->critical_start || atomic_read(&data->disabled))
		return;

	atomic_inc(&data->disabled);

	local_save_flags(flags);
	__trace_function(tr, ip, parent_ip, flags, preempt_count());
	check_critical_timing(tr, data, parent_ip ? : ip, cpu);
	data->critical_start = 0;
	atomic_dec(&data->disabled);
}

/* start and stop critical timings used to for stoppage (in idle) */
void start_critical_timings(void)
{
	if (preempt_trace() || irq_trace())
		start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
}
EXPORT_SYMBOL_GPL(start_critical_timings);

void stop_critical_timings(void)
{
	if (preempt_trace() || irq_trace())
		stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
}
EXPORT_SYMBOL_GPL(stop_critical_timings);

#ifdef CONFIG_IRQSOFF_TRACER
#ifdef CONFIG_PROVE_LOCKING
void time_hardirqs_on(unsigned long a0, unsigned long a1)
{
	if (!preempt_trace() && irq_trace())
		stop_critical_timing(a0, a1);
}

void time_hardirqs_off(unsigned long a0, unsigned long a1)
{
	if (!preempt_trace() && irq_trace())
		start_critical_timing(a0, a1);
}

#else /* !CONFIG_PROVE_LOCKING */

/*
 * Stubs:
 */

void early_boot_irqs_off(void)
{
}

void early_boot_irqs_on(void)
{
}

void trace_softirqs_on(unsigned long ip)
{
}

void trace_softirqs_off(unsigned long ip)
{
}

inline void print_irqtrace_events(struct task_struct *curr)
{
}

/*
 * We are only interested in hardirq on/off events:
 */
void trace_hardirqs_on(void)
{
	if (!preempt_trace() && irq_trace())
		stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
}
EXPORT_SYMBOL(trace_hardirqs_on);

void trace_hardirqs_off(void)
{
	if (!preempt_trace() && irq_trace())
		start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
}
EXPORT_SYMBOL(trace_hardirqs_off);

void trace_hardirqs_on_caller(unsigned long caller_addr)
{
	if (!preempt_trace() && irq_trace())
		stop_critical_timing(CALLER_ADDR0, caller_addr);
}
EXPORT_SYMBOL(trace_hardirqs_on_caller);

void trace_hardirqs_off_caller(unsigned long caller_addr)
{
	if (!preempt_trace() && irq_trace())
		start_critical_timing(CALLER_ADDR0, caller_addr);
}
EXPORT_SYMBOL(trace_hardirqs_off_caller);

#endif /* CONFIG_PROVE_LOCKING */
#endif /*  CONFIG_IRQSOFF_TRACER */

#ifdef CONFIG_PREEMPT_TRACER
void trace_preempt_on(unsigned long a0, unsigned long a1)
{
	if (preempt_trace())
		stop_critical_timing(a0, a1);
}

void trace_preempt_off(unsigned long a0, unsigned long a1)
{
	if (preempt_trace())
		start_critical_timing(a0, a1);
}
#endif /* CONFIG_PREEMPT_TRACER */

static int start_irqsoff_tracer(struct trace_array *tr, int graph)
{
	int ret = 0;

	if (!graph)
		ret = register_ftrace_function(&trace_ops);
	else
		ret = register_ftrace_graph(&irqsoff_graph_return,
					    &irqsoff_graph_entry);

	if (!ret && tracing_is_enabled())
		tracer_enabled = 1;
	else
		tracer_enabled = 0;

	return ret;
}

static void stop_irqsoff_tracer(struct trace_array *tr, int graph)
{
	tracer_enabled = 0;

	if (!graph)
		unregister_ftrace_function(&trace_ops);
	else
		unregister_ftrace_graph();
}

static void __irqsoff_tracer_init(struct trace_array *tr)
{
	save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
	trace_flags |= TRACE_ITER_LATENCY_FMT;

	tracing_max_latency = 0;
	irqsoff_trace = tr;
	/* make sure that the tracer is visible */
	smp_wmb();
	tracing_reset_online_cpus(tr);

	if (start_irqsoff_tracer(tr, is_graph()))
		printk(KERN_ERR "failed to start irqsoff tracer\n");
}

static void irqsoff_tracer_reset(struct trace_array *tr)
{
	stop_irqsoff_tracer(tr, is_graph());

	if (!save_lat_flag)
		trace_flags &= ~TRACE_ITER_LATENCY_FMT;
}

static void irqsoff_tracer_start(struct trace_array *tr)
{
	tracer_enabled = 1;
}

static void irqsoff_tracer_stop(struct trace_array *tr)
{
	tracer_enabled = 0;
}

#ifdef CONFIG_IRQSOFF_TRACER
static int irqsoff_tracer_init(struct trace_array *tr)
{
	trace_type = TRACER_IRQS_OFF;

	__irqsoff_tracer_init(tr);
	return 0;
}
static struct tracer irqsoff_tracer __read_mostly =
{
	.name		= "irqsoff",
	.init		= irqsoff_tracer_init,
	.reset		= irqsoff_tracer_reset,
	.start		= irqsoff_tracer_start,
	.stop		= irqsoff_tracer_stop,
	.print_max	= 1,
	.print_header   = irqsoff_print_header,
	.print_line     = irqsoff_print_line,
	.flags		= &tracer_flags,
	.set_flag	= irqsoff_set_flag,
#ifdef CONFIG_FTRACE_SELFTEST
	.selftest    = trace_selftest_startup_irqsoff,
#endif
	.open           = irqsoff_trace_open,
	.close          = irqsoff_trace_close,
	.use_max_tr	= 1,
};
# define register_irqsoff(trace) register_tracer(&trace)
#else
# define register_irqsoff(trace) do { } while (0)
#endif

#ifdef CONFIG_PREEMPT_TRACER
static int preemptoff_tracer_init(struct trace_array *tr)
{
	trace_type = TRACER_PREEMPT_OFF;

	__irqsoff_tracer_init(tr);
	return 0;
}

static struct tracer preemptoff_tracer __read_mostly =
{
	.name		= "preemptoff",
	.init		= preemptoff_tracer_init,
	.reset		= irqsoff_tracer_reset,
	.start		= irqsoff_tracer_start,
	.stop		= irqsoff_tracer_stop,
	.print_max	= 1,
	.print_header   = irqsoff_print_header,
	.print_line     = irqsoff_print_line,
	.flags		= &tracer_flags,
	.set_flag	= irqsoff_set_flag,
#ifdef CONFIG_FTRACE_SELFTEST
	.selftest    = trace_selftest_startup_preemptoff,
#endif
	.open		= irqsoff_trace_open,
	.close		= irqsoff_trace_close,
	.use_max_tr	= 1,
};
# define register_preemptoff(trace) register_tracer(&trace)
#else
# define register_preemptoff(trace) do { } while (0)
#endif

#if defined(CONFIG_IRQSOFF_TRACER) && \
	defined(CONFIG_PREEMPT_TRACER)

static int preemptirqsoff_tracer_init(struct trace_array *tr)
{
	trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;

	__irqsoff_tracer_init(tr);
	return 0;
}

static struct tracer preemptirqsoff_tracer __read_mostly =
{
	.name		= "preemptirqsoff",
	.init		= preemptirqsoff_tracer_init,
	.reset		= irqsoff_tracer_reset,
	.start		= irqsoff_tracer_start,
	.stop		= irqsoff_tracer_stop,
	.print_max	= 1,
	.print_header   = irqsoff_print_header,
	.print_line     = irqsoff_print_line,
	.flags		= &tracer_flags,
	.set_flag	= irqsoff_set_flag,
#ifdef CONFIG_FTRACE_SELFTEST
	.selftest    = trace_selftest_startup_preemptirqsoff,
#endif
	.open		= irqsoff_trace_open,
	.close		= irqsoff_trace_close,
	.use_max_tr	= 1,
};

# define register_preemptirqsoff(trace) register_tracer(&trace)
#else
# define register_preemptirqsoff(trace) do { } while (0)
#endif

__init static int init_irqsoff_tracer(void)
{
	register_irqsoff(irqsoff_tracer);
	register_preemptoff(preemptoff_tracer);
	register_preemptirqsoff(preemptirqsoff_tracer);

	return 0;
}
device_initcall(init_irqsoff_tracer);