Free Electrons

Embedded Linux Experts

  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
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
/* Include in trace.c */

#include <linux/stringify.h>
#include <linux/kthread.h>
#include <linux/delay.h>
#include <linux/slab.h>

static inline int trace_valid_entry(struct trace_entry *entry)
{
	switch (entry->type) {
	case TRACE_FN:
	case TRACE_CTX:
	case TRACE_WAKE:
	case TRACE_STACK:
	case TRACE_PRINT:
	case TRACE_BRANCH:
	case TRACE_GRAPH_ENT:
	case TRACE_GRAPH_RET:
		return 1;
	}
	return 0;
}

static int trace_test_buffer_cpu(struct trace_array *tr, int cpu)
{
	struct ring_buffer_event *event;
	struct trace_entry *entry;
	unsigned int loops = 0;

	while ((event = ring_buffer_consume(tr->buffer, cpu, NULL, NULL))) {
		entry = ring_buffer_event_data(event);

		/*
		 * The ring buffer is a size of trace_buf_size, if
		 * we loop more than the size, there's something wrong
		 * with the ring buffer.
		 */
		if (loops++ > trace_buf_size) {
			printk(KERN_CONT ".. bad ring buffer ");
			goto failed;
		}
		if (!trace_valid_entry(entry)) {
			printk(KERN_CONT ".. invalid entry %d ",
				entry->type);
			goto failed;
		}
	}
	return 0;

 failed:
	/* disable tracing */
	tracing_disabled = 1;
	printk(KERN_CONT ".. corrupted trace buffer .. ");
	return -1;
}

/*
 * Test the trace buffer to see if all the elements
 * are still sane.
 */
static int trace_test_buffer(struct trace_array *tr, unsigned long *count)
{
	unsigned long flags, cnt = 0;
	int cpu, ret = 0;

	/* Don't allow flipping of max traces now */
	local_irq_save(flags);
	arch_spin_lock(&ftrace_max_lock);

	cnt = ring_buffer_entries(tr->buffer);

	/*
	 * The trace_test_buffer_cpu runs a while loop to consume all data.
	 * If the calling tracer is broken, and is constantly filling
	 * the buffer, this will run forever, and hard lock the box.
	 * We disable the ring buffer while we do this test to prevent
	 * a hard lock up.
	 */
	tracing_off();
	for_each_possible_cpu(cpu) {
		ret = trace_test_buffer_cpu(tr, cpu);
		if (ret)
			break;
	}
	tracing_on();
	arch_spin_unlock(&ftrace_max_lock);
	local_irq_restore(flags);

	if (count)
		*count = cnt;

	return ret;
}

static inline void warn_failed_init_tracer(struct tracer *trace, int init_ret)
{
	printk(KERN_WARNING "Failed to init %s tracer, init returned %d\n",
		trace->name, init_ret);
}
#ifdef CONFIG_FUNCTION_TRACER

#ifdef CONFIG_DYNAMIC_FTRACE

static int trace_selftest_test_probe1_cnt;
static void trace_selftest_test_probe1_func(unsigned long ip,
					    unsigned long pip)
{
	trace_selftest_test_probe1_cnt++;
}

static int trace_selftest_test_probe2_cnt;
static void trace_selftest_test_probe2_func(unsigned long ip,
					    unsigned long pip)
{
	trace_selftest_test_probe2_cnt++;
}

static int trace_selftest_test_probe3_cnt;
static void trace_selftest_test_probe3_func(unsigned long ip,
					    unsigned long pip)
{
	trace_selftest_test_probe3_cnt++;
}

static int trace_selftest_test_global_cnt;
static void trace_selftest_test_global_func(unsigned long ip,
					    unsigned long pip)
{
	trace_selftest_test_global_cnt++;
}

static int trace_selftest_test_dyn_cnt;
static void trace_selftest_test_dyn_func(unsigned long ip,
					 unsigned long pip)
{
	trace_selftest_test_dyn_cnt++;
}

static struct ftrace_ops test_probe1 = {
	.func			= trace_selftest_test_probe1_func,
};

static struct ftrace_ops test_probe2 = {
	.func			= trace_selftest_test_probe2_func,
};

static struct ftrace_ops test_probe3 = {
	.func			= trace_selftest_test_probe3_func,
};

static struct ftrace_ops test_global = {
	.func			= trace_selftest_test_global_func,
	.flags			= FTRACE_OPS_FL_GLOBAL,
};

static void print_counts(void)
{
	printk("(%d %d %d %d %d) ",
	       trace_selftest_test_probe1_cnt,
	       trace_selftest_test_probe2_cnt,
	       trace_selftest_test_probe3_cnt,
	       trace_selftest_test_global_cnt,
	       trace_selftest_test_dyn_cnt);
}

static void reset_counts(void)
{
	trace_selftest_test_probe1_cnt = 0;
	trace_selftest_test_probe2_cnt = 0;
	trace_selftest_test_probe3_cnt = 0;
	trace_selftest_test_global_cnt = 0;
	trace_selftest_test_dyn_cnt = 0;
}

static int trace_selftest_ops(int cnt)
{
	int save_ftrace_enabled = ftrace_enabled;
	struct ftrace_ops *dyn_ops;
	char *func1_name;
	char *func2_name;
	int len1;
	int len2;
	int ret = -1;

	printk(KERN_CONT "PASSED\n");
	pr_info("Testing dynamic ftrace ops #%d: ", cnt);

	ftrace_enabled = 1;
	reset_counts();

	/* Handle PPC64 '.' name */
	func1_name = "*" __stringify(DYN_FTRACE_TEST_NAME);
	func2_name = "*" __stringify(DYN_FTRACE_TEST_NAME2);
	len1 = strlen(func1_name);
	len2 = strlen(func2_name);

	/*
	 * Probe 1 will trace function 1.
	 * Probe 2 will trace function 2.
	 * Probe 3 will trace functions 1 and 2.
	 */
	ftrace_set_filter(&test_probe1, func1_name, len1, 1);
	ftrace_set_filter(&test_probe2, func2_name, len2, 1);
	ftrace_set_filter(&test_probe3, func1_name, len1, 1);
	ftrace_set_filter(&test_probe3, func2_name, len2, 0);

	register_ftrace_function(&test_probe1);
	register_ftrace_function(&test_probe2);
	register_ftrace_function(&test_probe3);
	register_ftrace_function(&test_global);

	DYN_FTRACE_TEST_NAME();

	print_counts();

	if (trace_selftest_test_probe1_cnt != 1)
		goto out;
	if (trace_selftest_test_probe2_cnt != 0)
		goto out;
	if (trace_selftest_test_probe3_cnt != 1)
		goto out;
	if (trace_selftest_test_global_cnt == 0)
		goto out;

	DYN_FTRACE_TEST_NAME2();

	print_counts();

	if (trace_selftest_test_probe1_cnt != 1)
		goto out;
	if (trace_selftest_test_probe2_cnt != 1)
		goto out;
	if (trace_selftest_test_probe3_cnt != 2)
		goto out;

	/* Add a dynamic probe */
	dyn_ops = kzalloc(sizeof(*dyn_ops), GFP_KERNEL);
	if (!dyn_ops) {
		printk("MEMORY ERROR ");
		goto out;
	}

	dyn_ops->func = trace_selftest_test_dyn_func;

	register_ftrace_function(dyn_ops);

	trace_selftest_test_global_cnt = 0;

	DYN_FTRACE_TEST_NAME();

	print_counts();

	if (trace_selftest_test_probe1_cnt != 2)
		goto out_free;
	if (trace_selftest_test_probe2_cnt != 1)
		goto out_free;
	if (trace_selftest_test_probe3_cnt != 3)
		goto out_free;
	if (trace_selftest_test_global_cnt == 0)
		goto out;
	if (trace_selftest_test_dyn_cnt == 0)
		goto out_free;

	DYN_FTRACE_TEST_NAME2();

	print_counts();

	if (trace_selftest_test_probe1_cnt != 2)
		goto out_free;
	if (trace_selftest_test_probe2_cnt != 2)
		goto out_free;
	if (trace_selftest_test_probe3_cnt != 4)
		goto out_free;

	ret = 0;
 out_free:
	unregister_ftrace_function(dyn_ops);
	kfree(dyn_ops);

 out:
	/* Purposely unregister in the same order */
	unregister_ftrace_function(&test_probe1);
	unregister_ftrace_function(&test_probe2);
	unregister_ftrace_function(&test_probe3);
	unregister_ftrace_function(&test_global);

	/* Make sure everything is off */
	reset_counts();
	DYN_FTRACE_TEST_NAME();
	DYN_FTRACE_TEST_NAME();

	if (trace_selftest_test_probe1_cnt ||
	    trace_selftest_test_probe2_cnt ||
	    trace_selftest_test_probe3_cnt ||
	    trace_selftest_test_global_cnt ||
	    trace_selftest_test_dyn_cnt)
		ret = -1;

	ftrace_enabled = save_ftrace_enabled;

	return ret;
}

/* Test dynamic code modification and ftrace filters */
int trace_selftest_startup_dynamic_tracing(struct tracer *trace,
					   struct trace_array *tr,
					   int (*func)(void))
{
	int save_ftrace_enabled = ftrace_enabled;
	int save_tracer_enabled = tracer_enabled;
	unsigned long count;
	char *func_name;
	int ret;

	/* The ftrace test PASSED */
	printk(KERN_CONT "PASSED\n");
	pr_info("Testing dynamic ftrace: ");

	/* enable tracing, and record the filter function */
	ftrace_enabled = 1;
	tracer_enabled = 1;

	/* passed in by parameter to fool gcc from optimizing */
	func();

	/*
	 * Some archs *cough*PowerPC*cough* add characters to the
	 * start of the function names. We simply put a '*' to
	 * accommodate them.
	 */
	func_name = "*" __stringify(DYN_FTRACE_TEST_NAME);

	/* filter only on our function */
	ftrace_set_global_filter(func_name, strlen(func_name), 1);

	/* enable tracing */
	ret = tracer_init(trace, tr);
	if (ret) {
		warn_failed_init_tracer(trace, ret);
		goto out;
	}

	/* Sleep for a 1/10 of a second */
	msleep(100);

	/* we should have nothing in the buffer */
	ret = trace_test_buffer(tr, &count);
	if (ret)
		goto out;

	if (count) {
		ret = -1;
		printk(KERN_CONT ".. filter did not filter .. ");
		goto out;
	}

	/* call our function again */
	func();

	/* sleep again */
	msleep(100);

	/* stop the tracing. */
	tracing_stop();
	ftrace_enabled = 0;

	/* check the trace buffer */
	ret = trace_test_buffer(tr, &count);
	tracing_start();

	/* we should only have one item */
	if (!ret && count != 1) {
		trace->reset(tr);
		printk(KERN_CONT ".. filter failed count=%ld ..", count);
		ret = -1;
		goto out;
	}

	/* Test the ops with global tracing running */
	ret = trace_selftest_ops(1);
	trace->reset(tr);

 out:
	ftrace_enabled = save_ftrace_enabled;
	tracer_enabled = save_tracer_enabled;

	/* Enable tracing on all functions again */
	ftrace_set_global_filter(NULL, 0, 1);

	/* Test the ops with global tracing off */
	if (!ret)
		ret = trace_selftest_ops(2);

	return ret;
}
#else
# define trace_selftest_startup_dynamic_tracing(trace, tr, func) ({ 0; })
#endif /* CONFIG_DYNAMIC_FTRACE */

/*
 * Simple verification test of ftrace function tracer.
 * Enable ftrace, sleep 1/10 second, and then read the trace
 * buffer to see if all is in order.
 */
int
trace_selftest_startup_function(struct tracer *trace, struct trace_array *tr)
{
	int save_ftrace_enabled = ftrace_enabled;
	int save_tracer_enabled = tracer_enabled;
	unsigned long count;
	int ret;

	/* make sure msleep has been recorded */
	msleep(1);

	/* start the tracing */
	ftrace_enabled = 1;
	tracer_enabled = 1;

	ret = tracer_init(trace, tr);
	if (ret) {
		warn_failed_init_tracer(trace, ret);
		goto out;
	}

	/* Sleep for a 1/10 of a second */
	msleep(100);
	/* stop the tracing. */
	tracing_stop();
	ftrace_enabled = 0;

	/* check the trace buffer */
	ret = trace_test_buffer(tr, &count);
	trace->reset(tr);
	tracing_start();

	if (!ret && !count) {
		printk(KERN_CONT ".. no entries found ..");
		ret = -1;
		goto out;
	}

	ret = trace_selftest_startup_dynamic_tracing(trace, tr,
						     DYN_FTRACE_TEST_NAME);

 out:
	ftrace_enabled = save_ftrace_enabled;
	tracer_enabled = save_tracer_enabled;

	/* kill ftrace totally if we failed */
	if (ret)
		ftrace_kill();

	return ret;
}
#endif /* CONFIG_FUNCTION_TRACER */


#ifdef CONFIG_FUNCTION_GRAPH_TRACER

/* Maximum number of functions to trace before diagnosing a hang */
#define GRAPH_MAX_FUNC_TEST	100000000

static void
__ftrace_dump(bool disable_tracing, enum ftrace_dump_mode oops_dump_mode);
static unsigned int graph_hang_thresh;

/* Wrap the real function entry probe to avoid possible hanging */
static int trace_graph_entry_watchdog(struct ftrace_graph_ent *trace)
{
	/* This is harmlessly racy, we want to approximately detect a hang */
	if (unlikely(++graph_hang_thresh > GRAPH_MAX_FUNC_TEST)) {
		ftrace_graph_stop();
		printk(KERN_WARNING "BUG: Function graph tracer hang!\n");
		if (ftrace_dump_on_oops)
			__ftrace_dump(false, DUMP_ALL);
		return 0;
	}

	return trace_graph_entry(trace);
}

/*
 * Pretty much the same than for the function tracer from which the selftest
 * has been borrowed.
 */
int
trace_selftest_startup_function_graph(struct tracer *trace,
					struct trace_array *tr)
{
	int ret;
	unsigned long count;

	/*
	 * Simulate the init() callback but we attach a watchdog callback
	 * to detect and recover from possible hangs
	 */
	tracing_reset_online_cpus(tr);
	set_graph_array(tr);
	ret = register_ftrace_graph(&trace_graph_return,
				    &trace_graph_entry_watchdog);
	if (ret) {
		warn_failed_init_tracer(trace, ret);
		goto out;
	}
	tracing_start_cmdline_record();

	/* Sleep for a 1/10 of a second */
	msleep(100);

	/* Have we just recovered from a hang? */
	if (graph_hang_thresh > GRAPH_MAX_FUNC_TEST) {
		tracing_selftest_disabled = true;
		ret = -1;
		goto out;
	}

	tracing_stop();

	/* check the trace buffer */
	ret = trace_test_buffer(tr, &count);

	trace->reset(tr);
	tracing_start();

	if (!ret && !count) {
		printk(KERN_CONT ".. no entries found ..");
		ret = -1;
		goto out;
	}

	/* Don't test dynamic tracing, the function tracer already did */

out:
	/* Stop it if we failed */
	if (ret)
		ftrace_graph_stop();

	return ret;
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */


#ifdef CONFIG_IRQSOFF_TRACER
int
trace_selftest_startup_irqsoff(struct tracer *trace, struct trace_array *tr)
{
	unsigned long save_max = tracing_max_latency;
	unsigned long count;
	int ret;

	/* start the tracing */
	ret = tracer_init(trace, tr);
	if (ret) {
		warn_failed_init_tracer(trace, ret);
		return ret;
	}

	/* reset the max latency */
	tracing_max_latency = 0;
	/* disable interrupts for a bit */
	local_irq_disable();
	udelay(100);
	local_irq_enable();

	/*
	 * Stop the tracer to avoid a warning subsequent
	 * to buffer flipping failure because tracing_stop()
	 * disables the tr and max buffers, making flipping impossible
	 * in case of parallels max irqs off latencies.
	 */
	trace->stop(tr);
	/* stop the tracing. */
	tracing_stop();
	/* check both trace buffers */
	ret = trace_test_buffer(tr, NULL);
	if (!ret)
		ret = trace_test_buffer(&max_tr, &count);
	trace->reset(tr);
	tracing_start();

	if (!ret && !count) {
		printk(KERN_CONT ".. no entries found ..");
		ret = -1;
	}

	tracing_max_latency = save_max;

	return ret;
}
#endif /* CONFIG_IRQSOFF_TRACER */

#ifdef CONFIG_PREEMPT_TRACER
int
trace_selftest_startup_preemptoff(struct tracer *trace, struct trace_array *tr)
{
	unsigned long save_max = tracing_max_latency;
	unsigned long count;
	int ret;

	/*
	 * Now that the big kernel lock is no longer preemptable,
	 * and this is called with the BKL held, it will always
	 * fail. If preemption is already disabled, simply
	 * pass the test. When the BKL is removed, or becomes
	 * preemptible again, we will once again test this,
	 * so keep it in.
	 */
	if (preempt_count()) {
		printk(KERN_CONT "can not test ... force ");
		return 0;
	}

	/* start the tracing */
	ret = tracer_init(trace, tr);
	if (ret) {
		warn_failed_init_tracer(trace, ret);
		return ret;
	}

	/* reset the max latency */
	tracing_max_latency = 0;
	/* disable preemption for a bit */
	preempt_disable();
	udelay(100);
	preempt_enable();

	/*
	 * Stop the tracer to avoid a warning subsequent
	 * to buffer flipping failure because tracing_stop()
	 * disables the tr and max buffers, making flipping impossible
	 * in case of parallels max preempt off latencies.
	 */
	trace->stop(tr);
	/* stop the tracing. */
	tracing_stop();
	/* check both trace buffers */
	ret = trace_test_buffer(tr, NULL);
	if (!ret)
		ret = trace_test_buffer(&max_tr, &count);
	trace->reset(tr);
	tracing_start();

	if (!ret && !count) {
		printk(KERN_CONT ".. no entries found ..");
		ret = -1;
	}

	tracing_max_latency = save_max;

	return ret;
}
#endif /* CONFIG_PREEMPT_TRACER */

#if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
int
trace_selftest_startup_preemptirqsoff(struct tracer *trace, struct trace_array *tr)
{
	unsigned long save_max = tracing_max_latency;
	unsigned long count;
	int ret;

	/*
	 * Now that the big kernel lock is no longer preemptable,
	 * and this is called with the BKL held, it will always
	 * fail. If preemption is already disabled, simply
	 * pass the test. When the BKL is removed, or becomes
	 * preemptible again, we will once again test this,
	 * so keep it in.
	 */
	if (preempt_count()) {
		printk(KERN_CONT "can not test ... force ");
		return 0;
	}

	/* start the tracing */
	ret = tracer_init(trace, tr);
	if (ret) {
		warn_failed_init_tracer(trace, ret);
		goto out_no_start;
	}

	/* reset the max latency */
	tracing_max_latency = 0;

	/* disable preemption and interrupts for a bit */
	preempt_disable();
	local_irq_disable();
	udelay(100);
	preempt_enable();
	/* reverse the order of preempt vs irqs */
	local_irq_enable();

	/*
	 * Stop the tracer to avoid a warning subsequent
	 * to buffer flipping failure because tracing_stop()
	 * disables the tr and max buffers, making flipping impossible
	 * in case of parallels max irqs/preempt off latencies.
	 */
	trace->stop(tr);
	/* stop the tracing. */
	tracing_stop();
	/* check both trace buffers */
	ret = trace_test_buffer(tr, NULL);
	if (ret)
		goto out;

	ret = trace_test_buffer(&max_tr, &count);
	if (ret)
		goto out;

	if (!ret && !count) {
		printk(KERN_CONT ".. no entries found ..");
		ret = -1;
		goto out;
	}

	/* do the test by disabling interrupts first this time */
	tracing_max_latency = 0;
	tracing_start();
	trace->start(tr);

	preempt_disable();
	local_irq_disable();
	udelay(100);
	preempt_enable();
	/* reverse the order of preempt vs irqs */
	local_irq_enable();

	trace->stop(tr);
	/* stop the tracing. */
	tracing_stop();
	/* check both trace buffers */
	ret = trace_test_buffer(tr, NULL);
	if (ret)
		goto out;

	ret = trace_test_buffer(&max_tr, &count);

	if (!ret && !count) {
		printk(KERN_CONT ".. no entries found ..");
		ret = -1;
		goto out;
	}

out:
	tracing_start();
out_no_start:
	trace->reset(tr);
	tracing_max_latency = save_max;

	return ret;
}
#endif /* CONFIG_IRQSOFF_TRACER && CONFIG_PREEMPT_TRACER */

#ifdef CONFIG_NOP_TRACER
int
trace_selftest_startup_nop(struct tracer *trace, struct trace_array *tr)
{
	/* What could possibly go wrong? */
	return 0;
}
#endif

#ifdef CONFIG_SCHED_TRACER
static int trace_wakeup_test_thread(void *data)
{
	/* Make this a RT thread, doesn't need to be too high */
	static const struct sched_param param = { .sched_priority = 5 };
	struct completion *x = data;

	sched_setscheduler(current, SCHED_FIFO, &param);

	/* Make it know we have a new prio */
	complete(x);

	/* now go to sleep and let the test wake us up */
	set_current_state(TASK_INTERRUPTIBLE);
	schedule();

	/* we are awake, now wait to disappear */
	while (!kthread_should_stop()) {
		/*
		 * This is an RT task, do short sleeps to let
		 * others run.
		 */
		msleep(100);
	}

	return 0;
}

int
trace_selftest_startup_wakeup(struct tracer *trace, struct trace_array *tr)
{
	unsigned long save_max = tracing_max_latency;
	struct task_struct *p;
	struct completion isrt;
	unsigned long count;
	int ret;

	init_completion(&isrt);

	/* create a high prio thread */
	p = kthread_run(trace_wakeup_test_thread, &isrt, "ftrace-test");
	if (IS_ERR(p)) {
		printk(KERN_CONT "Failed to create ftrace wakeup test thread ");
		return -1;
	}

	/* make sure the thread is running at an RT prio */
	wait_for_completion(&isrt);

	/* start the tracing */
	ret = tracer_init(trace, tr);
	if (ret) {
		warn_failed_init_tracer(trace, ret);
		return ret;
	}

	/* reset the max latency */
	tracing_max_latency = 0;

	/* sleep to let the RT thread sleep too */
	msleep(100);

	/*
	 * Yes this is slightly racy. It is possible that for some
	 * strange reason that the RT thread we created, did not
	 * call schedule for 100ms after doing the completion,
	 * and we do a wakeup on a task that already is awake.
	 * But that is extremely unlikely, and the worst thing that
	 * happens in such a case, is that we disable tracing.
	 * Honestly, if this race does happen something is horrible
	 * wrong with the system.
	 */

	wake_up_process(p);

	/* give a little time to let the thread wake up */
	msleep(100);

	/* stop the tracing. */
	tracing_stop();
	/* check both trace buffers */
	ret = trace_test_buffer(tr, NULL);
	if (!ret)
		ret = trace_test_buffer(&max_tr, &count);


	trace->reset(tr);
	tracing_start();

	tracing_max_latency = save_max;

	/* kill the thread */
	kthread_stop(p);

	if (!ret && !count) {
		printk(KERN_CONT ".. no entries found ..");
		ret = -1;
	}

	return ret;
}
#endif /* CONFIG_SCHED_TRACER */

#ifdef CONFIG_CONTEXT_SWITCH_TRACER
int
trace_selftest_startup_sched_switch(struct tracer *trace, struct trace_array *tr)
{
	unsigned long count;
	int ret;

	/* start the tracing */
	ret = tracer_init(trace, tr);
	if (ret) {
		warn_failed_init_tracer(trace, ret);
		return ret;
	}

	/* Sleep for a 1/10 of a second */
	msleep(100);
	/* stop the tracing. */
	tracing_stop();
	/* check the trace buffer */
	ret = trace_test_buffer(tr, &count);
	trace->reset(tr);
	tracing_start();

	if (!ret && !count) {
		printk(KERN_CONT ".. no entries found ..");
		ret = -1;
	}

	return ret;
}
#endif /* CONFIG_CONTEXT_SWITCH_TRACER */

#ifdef CONFIG_BRANCH_TRACER
int
trace_selftest_startup_branch(struct tracer *trace, struct trace_array *tr)
{
	unsigned long count;
	int ret;

	/* start the tracing */
	ret = tracer_init(trace, tr);
	if (ret) {
		warn_failed_init_tracer(trace, ret);
		return ret;
	}

	/* Sleep for a 1/10 of a second */
	msleep(100);
	/* stop the tracing. */
	tracing_stop();
	/* check the trace buffer */
	ret = trace_test_buffer(tr, &count);
	trace->reset(tr);
	tracing_start();

	if (!ret && !count) {
		printk(KERN_CONT ".. no entries found ..");
		ret = -1;
	}

	return ret;
}
#endif /* CONFIG_BRANCH_TRACER */