e6a62e7c6b6966e405b7beedfcbf30b408b700c1
[muen/linux.git] / kernel / trace / trace_irqsoff.c
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * trace irqs off critical timings
4  *
5  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
6  * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
7  *
8  * From code in the latency_tracer, that is:
9  *
10  *  Copyright (C) 2004-2006 Ingo Molnar
11  *  Copyright (C) 2004 Nadia Yvette Chambers
12  */
13 #include <linux/kallsyms.h>
14 #include <linux/uaccess.h>
15 #include <linux/module.h>
16 #include <linux/ftrace.h>
17
18 #include "trace.h"
19
20 #include <trace/events/preemptirq.h>
21
22 #if defined(CONFIG_IRQSOFF_TRACER) || defined(CONFIG_PREEMPT_TRACER)
23 static struct trace_array               *irqsoff_trace __read_mostly;
24 static int                              tracer_enabled __read_mostly;
25
26 static DEFINE_PER_CPU(int, tracing_cpu);
27
28 static DEFINE_RAW_SPINLOCK(max_trace_lock);
29
30 enum {
31         TRACER_IRQS_OFF         = (1 << 1),
32         TRACER_PREEMPT_OFF      = (1 << 2),
33 };
34
35 static int trace_type __read_mostly;
36
37 static int save_flags;
38
39 static void stop_irqsoff_tracer(struct trace_array *tr, int graph);
40 static int start_irqsoff_tracer(struct trace_array *tr, int graph);
41
42 #ifdef CONFIG_PREEMPT_TRACER
43 static inline int
44 preempt_trace(int pc)
45 {
46         return ((trace_type & TRACER_PREEMPT_OFF) && pc);
47 }
48 #else
49 # define preempt_trace(pc) (0)
50 #endif
51
52 #ifdef CONFIG_IRQSOFF_TRACER
53 static inline int
54 irq_trace(void)
55 {
56         return ((trace_type & TRACER_IRQS_OFF) &&
57                 irqs_disabled());
58 }
59 #else
60 # define irq_trace() (0)
61 #endif
62
63 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
64 static int irqsoff_display_graph(struct trace_array *tr, int set);
65 # define is_graph(tr) ((tr)->trace_flags & TRACE_ITER_DISPLAY_GRAPH)
66 #else
67 static inline int irqsoff_display_graph(struct trace_array *tr, int set)
68 {
69         return -EINVAL;
70 }
71 # define is_graph(tr) false
72 #endif
73
74 /*
75  * Sequence count - we record it when starting a measurement and
76  * skip the latency if the sequence has changed - some other section
77  * did a maximum and could disturb our measurement with serial console
78  * printouts, etc. Truly coinciding maximum latencies should be rare
79  * and what happens together happens separately as well, so this doesn't
80  * decrease the validity of the maximum found:
81  */
82 static __cacheline_aligned_in_smp       unsigned long max_sequence;
83
84 #ifdef CONFIG_FUNCTION_TRACER
85 /*
86  * Prologue for the preempt and irqs off function tracers.
87  *
88  * Returns 1 if it is OK to continue, and data->disabled is
89  *            incremented.
90  *         0 if the trace is to be ignored, and data->disabled
91  *            is kept the same.
92  *
93  * Note, this function is also used outside this ifdef but
94  *  inside the #ifdef of the function graph tracer below.
95  *  This is OK, since the function graph tracer is
96  *  dependent on the function tracer.
97  */
98 static int func_prolog_dec(struct trace_array *tr,
99                            struct trace_array_cpu **data,
100                            unsigned long *flags)
101 {
102         long disabled;
103         int cpu;
104
105         /*
106          * Does not matter if we preempt. We test the flags
107          * afterward, to see if irqs are disabled or not.
108          * If we preempt and get a false positive, the flags
109          * test will fail.
110          */
111         cpu = raw_smp_processor_id();
112         if (likely(!per_cpu(tracing_cpu, cpu)))
113                 return 0;
114
115         local_save_flags(*flags);
116         /*
117          * Slight chance to get a false positive on tracing_cpu,
118          * although I'm starting to think there isn't a chance.
119          * Leave this for now just to be paranoid.
120          */
121         if (!irqs_disabled_flags(*flags) && !preempt_count())
122                 return 0;
123
124         *data = per_cpu_ptr(tr->trace_buffer.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 #endif /* CONFIG_FUNCTION_TRACER */
154
155 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
156 static int irqsoff_display_graph(struct trace_array *tr, int set)
157 {
158         int cpu;
159
160         if (!(is_graph(tr) ^ set))
161                 return 0;
162
163         stop_irqsoff_tracer(irqsoff_trace, !set);
164
165         for_each_possible_cpu(cpu)
166                 per_cpu(tracing_cpu, cpu) = 0;
167
168         tr->max_latency = 0;
169         tracing_reset_online_cpus(&irqsoff_trace->trace_buffer);
170
171         return start_irqsoff_tracer(irqsoff_trace, set);
172 }
173
174 static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
175 {
176         struct trace_array *tr = irqsoff_trace;
177         struct trace_array_cpu *data;
178         unsigned long flags;
179         int ret;
180         int pc;
181
182         if (ftrace_graph_ignore_func(trace))
183                 return 0;
184         /*
185          * Do not trace a function if it's filtered by set_graph_notrace.
186          * Make the index of ret stack negative to indicate that it should
187          * ignore further functions.  But it needs its own ret stack entry
188          * to recover the original index in order to continue tracing after
189          * returning from the function.
190          */
191         if (ftrace_graph_notrace_addr(trace->func))
192                 return 1;
193
194         if (!func_prolog_dec(tr, &data, &flags))
195                 return 0;
196
197         pc = preempt_count();
198         ret = __trace_graph_entry(tr, trace, flags, pc);
199         atomic_dec(&data->disabled);
200
201         return ret;
202 }
203
204 static void irqsoff_graph_return(struct ftrace_graph_ret *trace)
205 {
206         struct trace_array *tr = irqsoff_trace;
207         struct trace_array_cpu *data;
208         unsigned long flags;
209         int pc;
210
211         ftrace_graph_addr_finish(trace);
212
213         if (!func_prolog_dec(tr, &data, &flags))
214                 return;
215
216         pc = preempt_count();
217         __trace_graph_return(tr, trace, flags, pc);
218         atomic_dec(&data->disabled);
219 }
220
221 static struct fgraph_ops fgraph_ops = {
222         .entryfunc              = &irqsoff_graph_entry,
223         .retfunc                = &irqsoff_graph_return,
224 };
225
226 static void irqsoff_trace_open(struct trace_iterator *iter)
227 {
228         if (is_graph(iter->tr))
229                 graph_trace_open(iter);
230
231 }
232
233 static void irqsoff_trace_close(struct trace_iterator *iter)
234 {
235         if (iter->private)
236                 graph_trace_close(iter);
237 }
238
239 #define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_CPU | \
240                             TRACE_GRAPH_PRINT_PROC | \
241                             TRACE_GRAPH_PRINT_REL_TIME | \
242                             TRACE_GRAPH_PRINT_DURATION)
243
244 static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
245 {
246         /*
247          * In graph mode call the graph tracer output function,
248          * otherwise go with the TRACE_FN event handler
249          */
250         if (is_graph(iter->tr))
251                 return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS);
252
253         return TRACE_TYPE_UNHANDLED;
254 }
255
256 static void irqsoff_print_header(struct seq_file *s)
257 {
258         struct trace_array *tr = irqsoff_trace;
259
260         if (is_graph(tr))
261                 print_graph_headers_flags(s, GRAPH_TRACER_FLAGS);
262         else
263                 trace_default_header(s);
264 }
265
266 static void
267 __trace_function(struct trace_array *tr,
268                  unsigned long ip, unsigned long parent_ip,
269                  unsigned long flags, int pc)
270 {
271         if (is_graph(tr))
272                 trace_graph_function(tr, ip, parent_ip, flags, pc);
273         else
274                 trace_function(tr, ip, parent_ip, flags, pc);
275 }
276
277 #else
278 #define __trace_function trace_function
279
280 static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
281 {
282         return TRACE_TYPE_UNHANDLED;
283 }
284
285 static void irqsoff_trace_open(struct trace_iterator *iter) { }
286 static void irqsoff_trace_close(struct trace_iterator *iter) { }
287
288 #ifdef CONFIG_FUNCTION_TRACER
289 static void irqsoff_print_header(struct seq_file *s)
290 {
291         trace_default_header(s);
292 }
293 #else
294 static void irqsoff_print_header(struct seq_file *s)
295 {
296         trace_latency_header(s);
297 }
298 #endif /* CONFIG_FUNCTION_TRACER */
299 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
300
301 /*
302  * Should this new latency be reported/recorded?
303  */
304 static bool report_latency(struct trace_array *tr, u64 delta)
305 {
306         if (tracing_thresh) {
307                 if (delta < tracing_thresh)
308                         return false;
309         } else {
310                 if (delta <= tr->max_latency)
311                         return false;
312         }
313         return true;
314 }
315
316 static void
317 check_critical_timing(struct trace_array *tr,
318                       struct trace_array_cpu *data,
319                       unsigned long parent_ip,
320                       int cpu)
321 {
322         u64 T0, T1, delta;
323         unsigned long flags;
324         int pc;
325
326         T0 = data->preempt_timestamp;
327         T1 = ftrace_now(cpu);
328         delta = T1-T0;
329
330         local_save_flags(flags);
331
332         pc = preempt_count();
333
334         if (!report_latency(tr, delta))
335                 goto out;
336
337         raw_spin_lock_irqsave(&max_trace_lock, flags);
338
339         /* check if we are still the max latency */
340         if (!report_latency(tr, delta))
341                 goto out_unlock;
342
343         __trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
344         /* Skip 5 functions to get to the irq/preempt enable function */
345         __trace_stack(tr, flags, 5, pc);
346
347         if (data->critical_sequence != max_sequence)
348                 goto out_unlock;
349
350         data->critical_end = parent_ip;
351
352         if (likely(!is_tracing_stopped())) {
353                 tr->max_latency = delta;
354                 update_max_tr_single(tr, current, cpu);
355         }
356
357         max_sequence++;
358
359 out_unlock:
360         raw_spin_unlock_irqrestore(&max_trace_lock, flags);
361
362 out:
363         data->critical_sequence = max_sequence;
364         data->preempt_timestamp = ftrace_now(cpu);
365         __trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
366 }
367
368 static inline void
369 start_critical_timing(unsigned long ip, unsigned long parent_ip, int pc)
370 {
371         int cpu;
372         struct trace_array *tr = irqsoff_trace;
373         struct trace_array_cpu *data;
374         unsigned long flags;
375
376         if (!tracer_enabled || !tracing_is_enabled())
377                 return;
378
379         cpu = raw_smp_processor_id();
380
381         if (per_cpu(tracing_cpu, cpu))
382                 return;
383
384         data = per_cpu_ptr(tr->trace_buffer.data, cpu);
385
386         if (unlikely(!data) || atomic_read(&data->disabled))
387                 return;
388
389         atomic_inc(&data->disabled);
390
391         data->critical_sequence = max_sequence;
392         data->preempt_timestamp = ftrace_now(cpu);
393         data->critical_start = parent_ip ? : ip;
394
395         local_save_flags(flags);
396
397         __trace_function(tr, ip, parent_ip, flags, pc);
398
399         per_cpu(tracing_cpu, cpu) = 1;
400
401         atomic_dec(&data->disabled);
402 }
403
404 static inline void
405 stop_critical_timing(unsigned long ip, unsigned long parent_ip, int pc)
406 {
407         int cpu;
408         struct trace_array *tr = irqsoff_trace;
409         struct trace_array_cpu *data;
410         unsigned long flags;
411
412         cpu = raw_smp_processor_id();
413         /* Always clear the tracing cpu on stopping the trace */
414         if (unlikely(per_cpu(tracing_cpu, cpu)))
415                 per_cpu(tracing_cpu, cpu) = 0;
416         else
417                 return;
418
419         if (!tracer_enabled || !tracing_is_enabled())
420                 return;
421
422         data = per_cpu_ptr(tr->trace_buffer.data, cpu);
423
424         if (unlikely(!data) ||
425             !data->critical_start || atomic_read(&data->disabled))
426                 return;
427
428         atomic_inc(&data->disabled);
429
430         local_save_flags(flags);
431         __trace_function(tr, ip, parent_ip, flags, pc);
432         check_critical_timing(tr, data, parent_ip ? : ip, cpu);
433         data->critical_start = 0;
434         atomic_dec(&data->disabled);
435 }
436
437 /* start and stop critical timings used to for stoppage (in idle) */
438 void start_critical_timings(void)
439 {
440         int pc = preempt_count();
441
442         if (preempt_trace(pc) || irq_trace())
443                 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1, pc);
444 }
445 EXPORT_SYMBOL_GPL(start_critical_timings);
446
447 void stop_critical_timings(void)
448 {
449         int pc = preempt_count();
450
451         if (preempt_trace(pc) || irq_trace())
452                 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1, pc);
453 }
454 EXPORT_SYMBOL_GPL(stop_critical_timings);
455
456 #ifdef CONFIG_FUNCTION_TRACER
457 static bool function_enabled;
458
459 static int register_irqsoff_function(struct trace_array *tr, int graph, int set)
460 {
461         int ret;
462
463         /* 'set' is set if TRACE_ITER_FUNCTION is about to be set */
464         if (function_enabled || (!set && !(tr->trace_flags & TRACE_ITER_FUNCTION)))
465                 return 0;
466
467         if (graph)
468                 ret = register_ftrace_graph(&fgraph_ops);
469         else
470                 ret = register_ftrace_function(tr->ops);
471
472         if (!ret)
473                 function_enabled = true;
474
475         return ret;
476 }
477
478 static void unregister_irqsoff_function(struct trace_array *tr, int graph)
479 {
480         if (!function_enabled)
481                 return;
482
483         if (graph)
484                 unregister_ftrace_graph(&fgraph_ops);
485         else
486                 unregister_ftrace_function(tr->ops);
487
488         function_enabled = false;
489 }
490
491 static int irqsoff_function_set(struct trace_array *tr, u32 mask, int set)
492 {
493         if (!(mask & TRACE_ITER_FUNCTION))
494                 return 0;
495
496         if (set)
497                 register_irqsoff_function(tr, is_graph(tr), 1);
498         else
499                 unregister_irqsoff_function(tr, is_graph(tr));
500         return 1;
501 }
502 #else
503 static int register_irqsoff_function(struct trace_array *tr, int graph, int set)
504 {
505         return 0;
506 }
507 static void unregister_irqsoff_function(struct trace_array *tr, int graph) { }
508 static inline int irqsoff_function_set(struct trace_array *tr, u32 mask, int set)
509 {
510         return 0;
511 }
512 #endif /* CONFIG_FUNCTION_TRACER */
513
514 static int irqsoff_flag_changed(struct trace_array *tr, u32 mask, int set)
515 {
516         struct tracer *tracer = tr->current_trace;
517
518         if (irqsoff_function_set(tr, mask, set))
519                 return 0;
520
521 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
522         if (mask & TRACE_ITER_DISPLAY_GRAPH)
523                 return irqsoff_display_graph(tr, set);
524 #endif
525
526         return trace_keep_overwrite(tracer, mask, set);
527 }
528
529 static int start_irqsoff_tracer(struct trace_array *tr, int graph)
530 {
531         int ret;
532
533         ret = register_irqsoff_function(tr, graph, 0);
534
535         if (!ret && tracing_is_enabled())
536                 tracer_enabled = 1;
537         else
538                 tracer_enabled = 0;
539
540         return ret;
541 }
542
543 static void stop_irqsoff_tracer(struct trace_array *tr, int graph)
544 {
545         tracer_enabled = 0;
546
547         unregister_irqsoff_function(tr, graph);
548 }
549
550 static bool irqsoff_busy;
551
552 static int __irqsoff_tracer_init(struct trace_array *tr)
553 {
554         if (irqsoff_busy)
555                 return -EBUSY;
556
557         save_flags = tr->trace_flags;
558
559         /* non overwrite screws up the latency tracers */
560         set_tracer_flag(tr, TRACE_ITER_OVERWRITE, 1);
561         set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, 1);
562
563         tr->max_latency = 0;
564         irqsoff_trace = tr;
565         /* make sure that the tracer is visible */
566         smp_wmb();
567
568         ftrace_init_array_ops(tr, irqsoff_tracer_call);
569
570         /* Only toplevel instance supports graph tracing */
571         if (start_irqsoff_tracer(tr, (tr->flags & TRACE_ARRAY_FL_GLOBAL &&
572                                       is_graph(tr))))
573                 printk(KERN_ERR "failed to start irqsoff tracer\n");
574
575         irqsoff_busy = true;
576         return 0;
577 }
578
579 static void __irqsoff_tracer_reset(struct trace_array *tr)
580 {
581         int lat_flag = save_flags & TRACE_ITER_LATENCY_FMT;
582         int overwrite_flag = save_flags & TRACE_ITER_OVERWRITE;
583
584         stop_irqsoff_tracer(tr, is_graph(tr));
585
586         set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, lat_flag);
587         set_tracer_flag(tr, TRACE_ITER_OVERWRITE, overwrite_flag);
588         ftrace_reset_array_ops(tr);
589
590         irqsoff_busy = false;
591 }
592
593 static void irqsoff_tracer_start(struct trace_array *tr)
594 {
595         tracer_enabled = 1;
596 }
597
598 static void irqsoff_tracer_stop(struct trace_array *tr)
599 {
600         tracer_enabled = 0;
601 }
602
603 #ifdef CONFIG_IRQSOFF_TRACER
604 /*
605  * We are only interested in hardirq on/off events:
606  */
607 void tracer_hardirqs_on(unsigned long a0, unsigned long a1)
608 {
609         unsigned int pc = preempt_count();
610
611         if (!preempt_trace(pc) && irq_trace())
612                 stop_critical_timing(a0, a1, pc);
613 }
614
615 void tracer_hardirqs_off(unsigned long a0, unsigned long a1)
616 {
617         unsigned int pc = preempt_count();
618
619         if (!preempt_trace(pc) && irq_trace())
620                 start_critical_timing(a0, a1, pc);
621 }
622
623 static int irqsoff_tracer_init(struct trace_array *tr)
624 {
625         trace_type = TRACER_IRQS_OFF;
626
627         return __irqsoff_tracer_init(tr);
628 }
629
630 static void irqsoff_tracer_reset(struct trace_array *tr)
631 {
632         __irqsoff_tracer_reset(tr);
633 }
634
635 static struct tracer irqsoff_tracer __read_mostly =
636 {
637         .name           = "irqsoff",
638         .init           = irqsoff_tracer_init,
639         .reset          = irqsoff_tracer_reset,
640         .start          = irqsoff_tracer_start,
641         .stop           = irqsoff_tracer_stop,
642         .print_max      = true,
643         .print_header   = irqsoff_print_header,
644         .print_line     = irqsoff_print_line,
645         .flag_changed   = irqsoff_flag_changed,
646 #ifdef CONFIG_FTRACE_SELFTEST
647         .selftest    = trace_selftest_startup_irqsoff,
648 #endif
649         .open           = irqsoff_trace_open,
650         .close          = irqsoff_trace_close,
651         .allow_instances = true,
652         .use_max_tr     = true,
653 };
654 #endif /*  CONFIG_IRQSOFF_TRACER */
655
656 #ifdef CONFIG_PREEMPT_TRACER
657 void tracer_preempt_on(unsigned long a0, unsigned long a1)
658 {
659         int pc = preempt_count();
660
661         if (preempt_trace(pc) && !irq_trace())
662                 stop_critical_timing(a0, a1, pc);
663 }
664
665 void tracer_preempt_off(unsigned long a0, unsigned long a1)
666 {
667         int pc = preempt_count();
668
669         if (preempt_trace(pc) && !irq_trace())
670                 start_critical_timing(a0, a1, pc);
671 }
672
673 static int preemptoff_tracer_init(struct trace_array *tr)
674 {
675         trace_type = TRACER_PREEMPT_OFF;
676
677         return __irqsoff_tracer_init(tr);
678 }
679
680 static void preemptoff_tracer_reset(struct trace_array *tr)
681 {
682         __irqsoff_tracer_reset(tr);
683 }
684
685 static struct tracer preemptoff_tracer __read_mostly =
686 {
687         .name           = "preemptoff",
688         .init           = preemptoff_tracer_init,
689         .reset          = preemptoff_tracer_reset,
690         .start          = irqsoff_tracer_start,
691         .stop           = irqsoff_tracer_stop,
692         .print_max      = true,
693         .print_header   = irqsoff_print_header,
694         .print_line     = irqsoff_print_line,
695         .flag_changed   = irqsoff_flag_changed,
696 #ifdef CONFIG_FTRACE_SELFTEST
697         .selftest    = trace_selftest_startup_preemptoff,
698 #endif
699         .open           = irqsoff_trace_open,
700         .close          = irqsoff_trace_close,
701         .allow_instances = true,
702         .use_max_tr     = true,
703 };
704 #endif /* CONFIG_PREEMPT_TRACER */
705
706 #if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
707
708 static int preemptirqsoff_tracer_init(struct trace_array *tr)
709 {
710         trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
711
712         return __irqsoff_tracer_init(tr);
713 }
714
715 static void preemptirqsoff_tracer_reset(struct trace_array *tr)
716 {
717         __irqsoff_tracer_reset(tr);
718 }
719
720 static struct tracer preemptirqsoff_tracer __read_mostly =
721 {
722         .name           = "preemptirqsoff",
723         .init           = preemptirqsoff_tracer_init,
724         .reset          = preemptirqsoff_tracer_reset,
725         .start          = irqsoff_tracer_start,
726         .stop           = irqsoff_tracer_stop,
727         .print_max      = true,
728         .print_header   = irqsoff_print_header,
729         .print_line     = irqsoff_print_line,
730         .flag_changed   = irqsoff_flag_changed,
731 #ifdef CONFIG_FTRACE_SELFTEST
732         .selftest    = trace_selftest_startup_preemptirqsoff,
733 #endif
734         .open           = irqsoff_trace_open,
735         .close          = irqsoff_trace_close,
736         .allow_instances = true,
737         .use_max_tr     = true,
738 };
739 #endif
740
741 __init static int init_irqsoff_tracer(void)
742 {
743 #ifdef CONFIG_IRQSOFF_TRACER
744         register_tracer(&irqsoff_tracer);
745 #endif
746 #ifdef CONFIG_PREEMPT_TRACER
747         register_tracer(&preemptoff_tracer);
748 #endif
749 #if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
750         register_tracer(&preemptirqsoff_tracer);
751 #endif
752
753         return 0;
754 }
755 core_initcall(init_irqsoff_tracer);
756 #endif /* IRQSOFF_TRACER || PREEMPTOFF_TRACER */