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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/uaccess.h>
14#include <linux/module.h>
15#include <linux/ftrace.h>
16
17#include "trace.h"
18
19static struct trace_array *irqsoff_trace __read_mostly;
20static int tracer_enabled __read_mostly;
21
22static DEFINE_PER_CPU(int, tracing_cpu);
23
24static DEFINE_RAW_SPINLOCK(max_trace_lock);
25
26enum {
27 TRACER_IRQS_OFF = (1 << 1),
28 TRACER_PREEMPT_OFF = (1 << 2),
29};
30
31static int trace_type __read_mostly;
32
33static int save_flags;
34
35static void stop_irqsoff_tracer(struct trace_array *tr, int graph);
36static int start_irqsoff_tracer(struct trace_array *tr, int graph);
37
38#ifdef CONFIG_PREEMPT_TRACER
39static inline int
40preempt_trace(void)
41{
42 return ((trace_type & TRACER_PREEMPT_OFF) && preempt_count());
43}
44#else
45# define preempt_trace() (0)
46#endif
47
48#ifdef CONFIG_IRQSOFF_TRACER
49static inline int
50irq_trace(void)
51{
52 return ((trace_type & TRACER_IRQS_OFF) &&
53 irqs_disabled());
54}
55#else
56# define irq_trace() (0)
57#endif
58
59#ifdef CONFIG_FUNCTION_GRAPH_TRACER
60static int irqsoff_display_graph(struct trace_array *tr, int set);
61# define is_graph(tr) ((tr)->trace_flags & TRACE_ITER_DISPLAY_GRAPH)
62#else
63static inline int irqsoff_display_graph(struct trace_array *tr, int set)
64{
65 return -EINVAL;
66}
67# define is_graph(tr) false
68#endif
69
70/*
71 * Sequence count - we record it when starting a measurement and
72 * skip the latency if the sequence has changed - some other section
73 * did a maximum and could disturb our measurement with serial console
74 * printouts, etc. Truly coinciding maximum latencies should be rare
75 * and what happens together happens separately as well, so this doesn't
76 * decrease the validity of the maximum found:
77 */
78static __cacheline_aligned_in_smp unsigned long max_sequence;
79
80#ifdef CONFIG_FUNCTION_TRACER
81/*
82 * Prologue for the preempt and irqs off function tracers.
83 *
84 * Returns 1 if it is OK to continue, and data->disabled is
85 * incremented.
86 * 0 if the trace is to be ignored, and data->disabled
87 * is kept the same.
88 *
89 * Note, this function is also used outside this ifdef but
90 * inside the #ifdef of the function graph tracer below.
91 * This is OK, since the function graph tracer is
92 * dependent on the function tracer.
93 */
94static int func_prolog_dec(struct trace_array *tr,
95 struct trace_array_cpu **data,
96 unsigned long *flags)
97{
98 long disabled;
99 int cpu;
100
101 /*
102 * Does not matter if we preempt. We test the flags
103 * afterward, to see if irqs are disabled or not.
104 * If we preempt and get a false positive, the flags
105 * test will fail.
106 */
107 cpu = raw_smp_processor_id();
108 if (likely(!per_cpu(tracing_cpu, cpu)))
109 return 0;
110
111 local_save_flags(*flags);
112 /*
113 * Slight chance to get a false positive on tracing_cpu,
114 * although I'm starting to think there isn't a chance.
115 * Leave this for now just to be paranoid.
116 */
117 if (!irqs_disabled_flags(*flags) && !preempt_count())
118 return 0;
119
120 *data = per_cpu_ptr(tr->trace_buffer.data, cpu);
121 disabled = atomic_inc_return(&(*data)->disabled);
122
123 if (likely(disabled == 1))
124 return 1;
125
126 atomic_dec(&(*data)->disabled);
127
128 return 0;
129}
130
131/*
132 * irqsoff uses its own tracer function to keep the overhead down:
133 */
134static void
135irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip,
136 struct ftrace_ops *op, struct pt_regs *pt_regs)
137{
138 struct trace_array *tr = irqsoff_trace;
139 struct trace_array_cpu *data;
140 unsigned long flags;
141
142 if (!func_prolog_dec(tr, &data, &flags))
143 return;
144
145 trace_function(tr, ip, parent_ip, flags, preempt_count());
146
147 atomic_dec(&data->disabled);
148}
149#endif /* CONFIG_FUNCTION_TRACER */
150
151#ifdef CONFIG_FUNCTION_GRAPH_TRACER
152static int irqsoff_display_graph(struct trace_array *tr, int set)
153{
154 int cpu;
155
156 if (!(is_graph(tr) ^ set))
157 return 0;
158
159 stop_irqsoff_tracer(irqsoff_trace, !set);
160
161 for_each_possible_cpu(cpu)
162 per_cpu(tracing_cpu, cpu) = 0;
163
164 tr->max_latency = 0;
165 tracing_reset_online_cpus(&irqsoff_trace->trace_buffer);
166
167 return start_irqsoff_tracer(irqsoff_trace, set);
168}
169
170static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
171{
172 struct trace_array *tr = irqsoff_trace;
173 struct trace_array_cpu *data;
174 unsigned long flags;
175 int ret;
176 int pc;
177
178 if (ftrace_graph_ignore_func(trace))
179 return 0;
180 /*
181 * Do not trace a function if it's filtered by set_graph_notrace.
182 * Make the index of ret stack negative to indicate that it should
183 * ignore further functions. But it needs its own ret stack entry
184 * to recover the original index in order to continue tracing after
185 * returning from the function.
186 */
187 if (ftrace_graph_notrace_addr(trace->func))
188 return 1;
189
190 if (!func_prolog_dec(tr, &data, &flags))
191 return 0;
192
193 pc = preempt_count();
194 ret = __trace_graph_entry(tr, trace, flags, pc);
195 atomic_dec(&data->disabled);
196
197 return ret;
198}
199
200static void irqsoff_graph_return(struct ftrace_graph_ret *trace)
201{
202 struct trace_array *tr = irqsoff_trace;
203 struct trace_array_cpu *data;
204 unsigned long flags;
205 int pc;
206
207 if (!func_prolog_dec(tr, &data, &flags))
208 return;
209
210 pc = preempt_count();
211 __trace_graph_return(tr, trace, flags, pc);
212 atomic_dec(&data->disabled);
213}
214
215static void irqsoff_trace_open(struct trace_iterator *iter)
216{
217 if (is_graph(iter->tr))
218 graph_trace_open(iter);
219
220}
221
222static void irqsoff_trace_close(struct trace_iterator *iter)
223{
224 if (iter->private)
225 graph_trace_close(iter);
226}
227
228#define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_CPU | \
229 TRACE_GRAPH_PRINT_PROC | \
230 TRACE_GRAPH_PRINT_ABS_TIME | \
231 TRACE_GRAPH_PRINT_DURATION)
232
233static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
234{
235 /*
236 * In graph mode call the graph tracer output function,
237 * otherwise go with the TRACE_FN event handler
238 */
239 if (is_graph(iter->tr))
240 return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS);
241
242 return TRACE_TYPE_UNHANDLED;
243}
244
245static void irqsoff_print_header(struct seq_file *s)
246{
247 struct trace_array *tr = irqsoff_trace;
248
249 if (is_graph(tr))
250 print_graph_headers_flags(s, GRAPH_TRACER_FLAGS);
251 else
252 trace_default_header(s);
253}
254
255static void
256__trace_function(struct trace_array *tr,
257 unsigned long ip, unsigned long parent_ip,
258 unsigned long flags, int pc)
259{
260 if (is_graph(tr))
261 trace_graph_function(tr, ip, parent_ip, flags, pc);
262 else
263 trace_function(tr, ip, parent_ip, flags, pc);
264}
265
266#else
267#define __trace_function trace_function
268
269#ifdef CONFIG_FUNCTION_TRACER
270static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
271{
272 return -1;
273}
274#endif
275
276static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
277{
278 return TRACE_TYPE_UNHANDLED;
279}
280
281static void irqsoff_trace_open(struct trace_iterator *iter) { }
282static void irqsoff_trace_close(struct trace_iterator *iter) { }
283
284#ifdef CONFIG_FUNCTION_TRACER
285static void irqsoff_graph_return(struct ftrace_graph_ret *trace) { }
286static void irqsoff_print_header(struct seq_file *s)
287{
288 trace_default_header(s);
289}
290#else
291static void irqsoff_print_header(struct seq_file *s)
292{
293 trace_latency_header(s);
294}
295#endif /* CONFIG_FUNCTION_TRACER */
296#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
297
298/*
299 * Should this new latency be reported/recorded?
300 */
301static bool report_latency(struct trace_array *tr, u64 delta)
302{
303 if (tracing_thresh) {
304 if (delta < tracing_thresh)
305 return false;
306 } else {
307 if (delta <= tr->max_latency)
308 return false;
309 }
310 return true;
311}
312
313static void
314check_critical_timing(struct trace_array *tr,
315 struct trace_array_cpu *data,
316 unsigned long parent_ip,
317 int cpu)
318{
319 u64 T0, T1, delta;
320 unsigned long flags;
321 int pc;
322
323 T0 = data->preempt_timestamp;
324 T1 = ftrace_now(cpu);
325 delta = T1-T0;
326
327 local_save_flags(flags);
328
329 pc = preempt_count();
330
331 if (!report_latency(tr, delta))
332 goto out;
333
334 raw_spin_lock_irqsave(&max_trace_lock, flags);
335
336 /* check if we are still the max latency */
337 if (!report_latency(tr, delta))
338 goto out_unlock;
339
340 __trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
341 /* Skip 5 functions to get to the irq/preempt enable function */
342 __trace_stack(tr, flags, 5, pc);
343
344 if (data->critical_sequence != max_sequence)
345 goto out_unlock;
346
347 data->critical_end = parent_ip;
348
349 if (likely(!is_tracing_stopped())) {
350 tr->max_latency = delta;
351 update_max_tr_single(tr, current, cpu);
352 }
353
354 max_sequence++;
355
356out_unlock:
357 raw_spin_unlock_irqrestore(&max_trace_lock, flags);
358
359out:
360 data->critical_sequence = max_sequence;
361 data->preempt_timestamp = ftrace_now(cpu);
362 __trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
363}
364
365static inline void
366start_critical_timing(unsigned long ip, unsigned long parent_ip)
367{
368 int cpu;
369 struct trace_array *tr = irqsoff_trace;
370 struct trace_array_cpu *data;
371 unsigned long flags;
372
373 if (!tracer_enabled || !tracing_is_enabled())
374 return;
375
376 cpu = raw_smp_processor_id();
377
378 if (per_cpu(tracing_cpu, cpu))
379 return;
380
381 data = per_cpu_ptr(tr->trace_buffer.data, cpu);
382
383 if (unlikely(!data) || atomic_read(&data->disabled))
384 return;
385
386 atomic_inc(&data->disabled);
387
388 data->critical_sequence = max_sequence;
389 data->preempt_timestamp = ftrace_now(cpu);
390 data->critical_start = parent_ip ? : ip;
391
392 local_save_flags(flags);
393
394 __trace_function(tr, ip, parent_ip, flags, preempt_count());
395
396 per_cpu(tracing_cpu, cpu) = 1;
397
398 atomic_dec(&data->disabled);
399}
400
401static inline void
402stop_critical_timing(unsigned long ip, unsigned long parent_ip)
403{
404 int cpu;
405 struct trace_array *tr = irqsoff_trace;
406 struct trace_array_cpu *data;
407 unsigned long flags;
408
409 cpu = raw_smp_processor_id();
410 /* Always clear the tracing cpu on stopping the trace */
411 if (unlikely(per_cpu(tracing_cpu, cpu)))
412 per_cpu(tracing_cpu, cpu) = 0;
413 else
414 return;
415
416 if (!tracer_enabled || !tracing_is_enabled())
417 return;
418
419 data = per_cpu_ptr(tr->trace_buffer.data, cpu);
420
421 if (unlikely(!data) ||
422 !data->critical_start || atomic_read(&data->disabled))
423 return;
424
425 atomic_inc(&data->disabled);
426
427 local_save_flags(flags);
428 __trace_function(tr, ip, parent_ip, flags, preempt_count());
429 check_critical_timing(tr, data, parent_ip ? : ip, cpu);
430 data->critical_start = 0;
431 atomic_dec(&data->disabled);
432}
433
434/* start and stop critical timings used to for stoppage (in idle) */
435void start_critical_timings(void)
436{
437 if (preempt_trace() || irq_trace())
438 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
439}
440EXPORT_SYMBOL_GPL(start_critical_timings);
441
442void stop_critical_timings(void)
443{
444 if (preempt_trace() || irq_trace())
445 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
446}
447EXPORT_SYMBOL_GPL(stop_critical_timings);
448
449#ifdef CONFIG_IRQSOFF_TRACER
450#ifdef CONFIG_PROVE_LOCKING
451void time_hardirqs_on(unsigned long a0, unsigned long a1)
452{
453 if (!preempt_trace() && irq_trace())
454 stop_critical_timing(a0, a1);
455}
456
457void time_hardirqs_off(unsigned long a0, unsigned long a1)
458{
459 if (!preempt_trace() && irq_trace())
460 start_critical_timing(a0, a1);
461}
462
463#else /* !CONFIG_PROVE_LOCKING */
464
465/*
466 * Stubs:
467 */
468
469void trace_softirqs_on(unsigned long ip)
470{
471}
472
473void trace_softirqs_off(unsigned long ip)
474{
475}
476
477inline void print_irqtrace_events(struct task_struct *curr)
478{
479}
480
481/*
482 * We are only interested in hardirq on/off events:
483 */
484void trace_hardirqs_on(void)
485{
486 if (!preempt_trace() && irq_trace())
487 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
488}
489EXPORT_SYMBOL(trace_hardirqs_on);
490
491void trace_hardirqs_off(void)
492{
493 if (!preempt_trace() && irq_trace())
494 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
495}
496EXPORT_SYMBOL(trace_hardirqs_off);
497
498__visible void trace_hardirqs_on_caller(unsigned long caller_addr)
499{
500 if (!preempt_trace() && irq_trace())
501 stop_critical_timing(CALLER_ADDR0, caller_addr);
502}
503EXPORT_SYMBOL(trace_hardirqs_on_caller);
504
505__visible void trace_hardirqs_off_caller(unsigned long caller_addr)
506{
507 if (!preempt_trace() && irq_trace())
508 start_critical_timing(CALLER_ADDR0, caller_addr);
509}
510EXPORT_SYMBOL(trace_hardirqs_off_caller);
511
512#endif /* CONFIG_PROVE_LOCKING */
513#endif /* CONFIG_IRQSOFF_TRACER */
514
515#ifdef CONFIG_PREEMPT_TRACER
516void trace_preempt_on(unsigned long a0, unsigned long a1)
517{
518 if (preempt_trace() && !irq_trace())
519 stop_critical_timing(a0, a1);
520}
521
522void trace_preempt_off(unsigned long a0, unsigned long a1)
523{
524 if (preempt_trace() && !irq_trace())
525 start_critical_timing(a0, a1);
526}
527#endif /* CONFIG_PREEMPT_TRACER */
528
529#ifdef CONFIG_FUNCTION_TRACER
530static bool function_enabled;
531
532static int register_irqsoff_function(struct trace_array *tr, int graph, int set)
533{
534 int ret;
535
536 /* 'set' is set if TRACE_ITER_FUNCTION is about to be set */
537 if (function_enabled || (!set && !(tr->trace_flags & TRACE_ITER_FUNCTION)))
538 return 0;
539
540 if (graph)
541 ret = register_ftrace_graph(&irqsoff_graph_return,
542 &irqsoff_graph_entry);
543 else
544 ret = register_ftrace_function(tr->ops);
545
546 if (!ret)
547 function_enabled = true;
548
549 return ret;
550}
551
552static void unregister_irqsoff_function(struct trace_array *tr, int graph)
553{
554 if (!function_enabled)
555 return;
556
557 if (graph)
558 unregister_ftrace_graph();
559 else
560 unregister_ftrace_function(tr->ops);
561
562 function_enabled = false;
563}
564
565static int irqsoff_function_set(struct trace_array *tr, u32 mask, int set)
566{
567 if (!(mask & TRACE_ITER_FUNCTION))
568 return 0;
569
570 if (set)
571 register_irqsoff_function(tr, is_graph(tr), 1);
572 else
573 unregister_irqsoff_function(tr, is_graph(tr));
574 return 1;
575}
576#else
577static int register_irqsoff_function(struct trace_array *tr, int graph, int set)
578{
579 return 0;
580}
581static void unregister_irqsoff_function(struct trace_array *tr, int graph) { }
582static inline int irqsoff_function_set(struct trace_array *tr, u32 mask, int set)
583{
584 return 0;
585}
586#endif /* CONFIG_FUNCTION_TRACER */
587
588static int irqsoff_flag_changed(struct trace_array *tr, u32 mask, int set)
589{
590 struct tracer *tracer = tr->current_trace;
591
592 if (irqsoff_function_set(tr, mask, set))
593 return 0;
594
595#ifdef CONFIG_FUNCTION_GRAPH_TRACER
596 if (mask & TRACE_ITER_DISPLAY_GRAPH)
597 return irqsoff_display_graph(tr, set);
598#endif
599
600 return trace_keep_overwrite(tracer, mask, set);
601}
602
603static int start_irqsoff_tracer(struct trace_array *tr, int graph)
604{
605 int ret;
606
607 ret = register_irqsoff_function(tr, graph, 0);
608
609 if (!ret && tracing_is_enabled())
610 tracer_enabled = 1;
611 else
612 tracer_enabled = 0;
613
614 return ret;
615}
616
617static void stop_irqsoff_tracer(struct trace_array *tr, int graph)
618{
619 tracer_enabled = 0;
620
621 unregister_irqsoff_function(tr, graph);
622}
623
624static bool irqsoff_busy;
625
626static int __irqsoff_tracer_init(struct trace_array *tr)
627{
628 if (irqsoff_busy)
629 return -EBUSY;
630
631 save_flags = tr->trace_flags;
632
633 /* non overwrite screws up the latency tracers */
634 set_tracer_flag(tr, TRACE_ITER_OVERWRITE, 1);
635 set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, 1);
636
637 tr->max_latency = 0;
638 irqsoff_trace = tr;
639 /* make sure that the tracer is visible */
640 smp_wmb();
641
642 ftrace_init_array_ops(tr, irqsoff_tracer_call);
643
644 /* Only toplevel instance supports graph tracing */
645 if (start_irqsoff_tracer(tr, (tr->flags & TRACE_ARRAY_FL_GLOBAL &&
646 is_graph(tr))))
647 printk(KERN_ERR "failed to start irqsoff tracer\n");
648
649 irqsoff_busy = true;
650 return 0;
651}
652
653static void irqsoff_tracer_reset(struct trace_array *tr)
654{
655 int lat_flag = save_flags & TRACE_ITER_LATENCY_FMT;
656 int overwrite_flag = save_flags & TRACE_ITER_OVERWRITE;
657
658 stop_irqsoff_tracer(tr, is_graph(tr));
659
660 set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, lat_flag);
661 set_tracer_flag(tr, TRACE_ITER_OVERWRITE, overwrite_flag);
662 ftrace_reset_array_ops(tr);
663
664 irqsoff_busy = false;
665}
666
667static void irqsoff_tracer_start(struct trace_array *tr)
668{
669 tracer_enabled = 1;
670}
671
672static void irqsoff_tracer_stop(struct trace_array *tr)
673{
674 tracer_enabled = 0;
675}
676
677#ifdef CONFIG_IRQSOFF_TRACER
678static int irqsoff_tracer_init(struct trace_array *tr)
679{
680 trace_type = TRACER_IRQS_OFF;
681
682 return __irqsoff_tracer_init(tr);
683}
684static struct tracer irqsoff_tracer __read_mostly =
685{
686 .name = "irqsoff",
687 .init = irqsoff_tracer_init,
688 .reset = irqsoff_tracer_reset,
689 .start = irqsoff_tracer_start,
690 .stop = irqsoff_tracer_stop,
691 .print_max = true,
692 .print_header = irqsoff_print_header,
693 .print_line = irqsoff_print_line,
694 .flag_changed = irqsoff_flag_changed,
695#ifdef CONFIG_FTRACE_SELFTEST
696 .selftest = trace_selftest_startup_irqsoff,
697#endif
698 .open = irqsoff_trace_open,
699 .close = irqsoff_trace_close,
700 .allow_instances = true,
701 .use_max_tr = true,
702};
703# define register_irqsoff(trace) register_tracer(&trace)
704#else
705# define register_irqsoff(trace) do { } while (0)
706#endif
707
708#ifdef CONFIG_PREEMPT_TRACER
709static int preemptoff_tracer_init(struct trace_array *tr)
710{
711 trace_type = TRACER_PREEMPT_OFF;
712
713 return __irqsoff_tracer_init(tr);
714}
715
716static struct tracer preemptoff_tracer __read_mostly =
717{
718 .name = "preemptoff",
719 .init = preemptoff_tracer_init,
720 .reset = irqsoff_tracer_reset,
721 .start = irqsoff_tracer_start,
722 .stop = irqsoff_tracer_stop,
723 .print_max = true,
724 .print_header = irqsoff_print_header,
725 .print_line = irqsoff_print_line,
726 .flag_changed = irqsoff_flag_changed,
727#ifdef CONFIG_FTRACE_SELFTEST
728 .selftest = trace_selftest_startup_preemptoff,
729#endif
730 .open = irqsoff_trace_open,
731 .close = irqsoff_trace_close,
732 .allow_instances = true,
733 .use_max_tr = true,
734};
735# define register_preemptoff(trace) register_tracer(&trace)
736#else
737# define register_preemptoff(trace) do { } while (0)
738#endif
739
740#if defined(CONFIG_IRQSOFF_TRACER) && \
741 defined(CONFIG_PREEMPT_TRACER)
742
743static int preemptirqsoff_tracer_init(struct trace_array *tr)
744{
745 trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
746
747 return __irqsoff_tracer_init(tr);
748}
749
750static struct tracer preemptirqsoff_tracer __read_mostly =
751{
752 .name = "preemptirqsoff",
753 .init = preemptirqsoff_tracer_init,
754 .reset = irqsoff_tracer_reset,
755 .start = irqsoff_tracer_start,
756 .stop = irqsoff_tracer_stop,
757 .print_max = true,
758 .print_header = irqsoff_print_header,
759 .print_line = irqsoff_print_line,
760 .flag_changed = irqsoff_flag_changed,
761#ifdef CONFIG_FTRACE_SELFTEST
762 .selftest = trace_selftest_startup_preemptirqsoff,
763#endif
764 .open = irqsoff_trace_open,
765 .close = irqsoff_trace_close,
766 .allow_instances = true,
767 .use_max_tr = true,
768};
769
770# define register_preemptirqsoff(trace) register_tracer(&trace)
771#else
772# define register_preemptirqsoff(trace) do { } while (0)
773#endif
774
775__init static int init_irqsoff_tracer(void)
776{
777 register_irqsoff(irqsoff_tracer);
778 register_preemptoff(preemptoff_tracer);
779 register_preemptirqsoff(preemptirqsoff_tracer);
780
781 return 0;
782}
783core_initcall(init_irqsoff_tracer);
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
21static struct trace_array *irqsoff_trace __read_mostly;
22static int tracer_enabled __read_mostly;
23
24static DEFINE_PER_CPU(int, tracing_cpu);
25
26static DEFINE_RAW_SPINLOCK(max_trace_lock);
27
28enum {
29 TRACER_IRQS_OFF = (1 << 1),
30 TRACER_PREEMPT_OFF = (1 << 2),
31};
32
33static int trace_type __read_mostly;
34
35static int save_flags;
36static bool function_enabled;
37
38static void stop_irqsoff_tracer(struct trace_array *tr, int graph);
39static int start_irqsoff_tracer(struct trace_array *tr, int graph);
40
41#ifdef CONFIG_PREEMPT_TRACER
42static inline int
43preempt_trace(void)
44{
45 return ((trace_type & TRACER_PREEMPT_OFF) && preempt_count());
46}
47#else
48# define preempt_trace() (0)
49#endif
50
51#ifdef CONFIG_IRQSOFF_TRACER
52static inline int
53irq_trace(void)
54{
55 return ((trace_type & TRACER_IRQS_OFF) &&
56 irqs_disabled());
57}
58#else
59# define irq_trace() (0)
60#endif
61
62#define TRACE_DISPLAY_GRAPH 1
63
64static struct tracer_opt trace_opts[] = {
65#ifdef CONFIG_FUNCTION_GRAPH_TRACER
66 /* display latency trace as call graph */
67 { TRACER_OPT(display-graph, TRACE_DISPLAY_GRAPH) },
68#endif
69 { } /* Empty entry */
70};
71
72static struct tracer_flags tracer_flags = {
73 .val = 0,
74 .opts = trace_opts,
75};
76
77#define is_graph() (tracer_flags.val & TRACE_DISPLAY_GRAPH)
78
79/*
80 * Sequence count - we record it when starting a measurement and
81 * skip the latency if the sequence has changed - some other section
82 * did a maximum and could disturb our measurement with serial console
83 * printouts, etc. Truly coinciding maximum latencies should be rare
84 * and what happens together happens separately as well, so this doesn't
85 * decrease the validity of the maximum found:
86 */
87static __cacheline_aligned_in_smp unsigned long max_sequence;
88
89#ifdef CONFIG_FUNCTION_TRACER
90/*
91 * Prologue for the preempt and irqs off function tracers.
92 *
93 * Returns 1 if it is OK to continue, and data->disabled is
94 * incremented.
95 * 0 if the trace is to be ignored, and data->disabled
96 * is kept the same.
97 *
98 * Note, this function is also used outside this ifdef but
99 * inside the #ifdef of the function graph tracer below.
100 * This is OK, since the function graph tracer is
101 * dependent on the function tracer.
102 */
103static int func_prolog_dec(struct trace_array *tr,
104 struct trace_array_cpu **data,
105 unsigned long *flags)
106{
107 long disabled;
108 int cpu;
109
110 /*
111 * Does not matter if we preempt. We test the flags
112 * afterward, to see if irqs are disabled or not.
113 * If we preempt and get a false positive, the flags
114 * test will fail.
115 */
116 cpu = raw_smp_processor_id();
117 if (likely(!per_cpu(tracing_cpu, cpu)))
118 return 0;
119
120 local_save_flags(*flags);
121 /* slight chance to get a false positive on tracing_cpu */
122 if (!irqs_disabled_flags(*flags))
123 return 0;
124
125 *data = per_cpu_ptr(tr->trace_buffer.data, cpu);
126 disabled = atomic_inc_return(&(*data)->disabled);
127
128 if (likely(disabled == 1))
129 return 1;
130
131 atomic_dec(&(*data)->disabled);
132
133 return 0;
134}
135
136/*
137 * irqsoff uses its own tracer function to keep the overhead down:
138 */
139static void
140irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip,
141 struct ftrace_ops *op, struct pt_regs *pt_regs)
142{
143 struct trace_array *tr = irqsoff_trace;
144 struct trace_array_cpu *data;
145 unsigned long flags;
146
147 if (!func_prolog_dec(tr, &data, &flags))
148 return;
149
150 trace_function(tr, ip, parent_ip, flags, preempt_count());
151
152 atomic_dec(&data->disabled);
153}
154
155static struct ftrace_ops trace_ops __read_mostly =
156{
157 .func = irqsoff_tracer_call,
158 .flags = FTRACE_OPS_FL_GLOBAL | FTRACE_OPS_FL_RECURSION_SAFE,
159};
160#endif /* CONFIG_FUNCTION_TRACER */
161
162#ifdef CONFIG_FUNCTION_GRAPH_TRACER
163static int
164irqsoff_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
165{
166 int cpu;
167
168 if (!(bit & TRACE_DISPLAY_GRAPH))
169 return -EINVAL;
170
171 if (!(is_graph() ^ set))
172 return 0;
173
174 stop_irqsoff_tracer(irqsoff_trace, !set);
175
176 for_each_possible_cpu(cpu)
177 per_cpu(tracing_cpu, cpu) = 0;
178
179 tracing_max_latency = 0;
180 tracing_reset_online_cpus(&irqsoff_trace->trace_buffer);
181
182 return start_irqsoff_tracer(irqsoff_trace, set);
183}
184
185static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
186{
187 struct trace_array *tr = irqsoff_trace;
188 struct trace_array_cpu *data;
189 unsigned long flags;
190 int ret;
191 int pc;
192
193 if (!func_prolog_dec(tr, &data, &flags))
194 return 0;
195
196 pc = preempt_count();
197 ret = __trace_graph_entry(tr, trace, flags, pc);
198 atomic_dec(&data->disabled);
199
200 return ret;
201}
202
203static void irqsoff_graph_return(struct ftrace_graph_ret *trace)
204{
205 struct trace_array *tr = irqsoff_trace;
206 struct trace_array_cpu *data;
207 unsigned long flags;
208 int pc;
209
210 if (!func_prolog_dec(tr, &data, &flags))
211 return;
212
213 pc = preempt_count();
214 __trace_graph_return(tr, trace, flags, pc);
215 atomic_dec(&data->disabled);
216}
217
218static void irqsoff_trace_open(struct trace_iterator *iter)
219{
220 if (is_graph())
221 graph_trace_open(iter);
222
223}
224
225static void irqsoff_trace_close(struct trace_iterator *iter)
226{
227 if (iter->private)
228 graph_trace_close(iter);
229}
230
231#define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_CPU | \
232 TRACE_GRAPH_PRINT_PROC | \
233 TRACE_GRAPH_PRINT_ABS_TIME | \
234 TRACE_GRAPH_PRINT_DURATION)
235
236static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
237{
238 /*
239 * In graph mode call the graph tracer output function,
240 * otherwise go with the TRACE_FN event handler
241 */
242 if (is_graph())
243 return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS);
244
245 return TRACE_TYPE_UNHANDLED;
246}
247
248static void irqsoff_print_header(struct seq_file *s)
249{
250 if (is_graph())
251 print_graph_headers_flags(s, GRAPH_TRACER_FLAGS);
252 else
253 trace_default_header(s);
254}
255
256static void
257__trace_function(struct trace_array *tr,
258 unsigned long ip, unsigned long parent_ip,
259 unsigned long flags, int pc)
260{
261 if (is_graph())
262 trace_graph_function(tr, ip, parent_ip, flags, pc);
263 else
264 trace_function(tr, ip, parent_ip, flags, pc);
265}
266
267#else
268#define __trace_function trace_function
269
270static int
271irqsoff_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
272{
273 return -EINVAL;
274}
275
276static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
277{
278 return -1;
279}
280
281static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
282{
283 return TRACE_TYPE_UNHANDLED;
284}
285
286static void irqsoff_graph_return(struct ftrace_graph_ret *trace) { }
287static void irqsoff_trace_open(struct trace_iterator *iter) { }
288static void irqsoff_trace_close(struct trace_iterator *iter) { }
289
290#ifdef CONFIG_FUNCTION_TRACER
291static void irqsoff_print_header(struct seq_file *s)
292{
293 trace_default_header(s);
294}
295#else
296static void irqsoff_print_header(struct seq_file *s)
297{
298 trace_latency_header(s);
299}
300#endif /* CONFIG_FUNCTION_TRACER */
301#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
302
303/*
304 * Should this new latency be reported/recorded?
305 */
306static int report_latency(cycle_t delta)
307{
308 if (tracing_thresh) {
309 if (delta < tracing_thresh)
310 return 0;
311 } else {
312 if (delta <= tracing_max_latency)
313 return 0;
314 }
315 return 1;
316}
317
318static void
319check_critical_timing(struct trace_array *tr,
320 struct trace_array_cpu *data,
321 unsigned long parent_ip,
322 int cpu)
323{
324 cycle_t T0, T1, delta;
325 unsigned long flags;
326 int pc;
327
328 T0 = data->preempt_timestamp;
329 T1 = ftrace_now(cpu);
330 delta = T1-T0;
331
332 local_save_flags(flags);
333
334 pc = preempt_count();
335
336 if (!report_latency(delta))
337 goto out;
338
339 raw_spin_lock_irqsave(&max_trace_lock, flags);
340
341 /* check if we are still the max latency */
342 if (!report_latency(delta))
343 goto out_unlock;
344
345 __trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
346 /* Skip 5 functions to get to the irq/preempt enable function */
347 __trace_stack(tr, flags, 5, pc);
348
349 if (data->critical_sequence != max_sequence)
350 goto out_unlock;
351
352 data->critical_end = parent_ip;
353
354 if (likely(!is_tracing_stopped())) {
355 tracing_max_latency = delta;
356 update_max_tr_single(tr, current, cpu);
357 }
358
359 max_sequence++;
360
361out_unlock:
362 raw_spin_unlock_irqrestore(&max_trace_lock, flags);
363
364out:
365 data->critical_sequence = max_sequence;
366 data->preempt_timestamp = ftrace_now(cpu);
367 __trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
368}
369
370static inline void
371start_critical_timing(unsigned long ip, unsigned long parent_ip)
372{
373 int cpu;
374 struct trace_array *tr = irqsoff_trace;
375 struct trace_array_cpu *data;
376 unsigned long flags;
377
378 if (!tracer_enabled || !tracing_is_enabled())
379 return;
380
381 cpu = raw_smp_processor_id();
382
383 if (per_cpu(tracing_cpu, cpu))
384 return;
385
386 data = per_cpu_ptr(tr->trace_buffer.data, cpu);
387
388 if (unlikely(!data) || atomic_read(&data->disabled))
389 return;
390
391 atomic_inc(&data->disabled);
392
393 data->critical_sequence = max_sequence;
394 data->preempt_timestamp = ftrace_now(cpu);
395 data->critical_start = parent_ip ? : ip;
396
397 local_save_flags(flags);
398
399 __trace_function(tr, ip, parent_ip, flags, preempt_count());
400
401 per_cpu(tracing_cpu, cpu) = 1;
402
403 atomic_dec(&data->disabled);
404}
405
406static inline void
407stop_critical_timing(unsigned long ip, unsigned long parent_ip)
408{
409 int cpu;
410 struct trace_array *tr = irqsoff_trace;
411 struct trace_array_cpu *data;
412 unsigned long flags;
413
414 cpu = raw_smp_processor_id();
415 /* Always clear the tracing cpu on stopping the trace */
416 if (unlikely(per_cpu(tracing_cpu, cpu)))
417 per_cpu(tracing_cpu, cpu) = 0;
418 else
419 return;
420
421 if (!tracer_enabled || !tracing_is_enabled())
422 return;
423
424 data = per_cpu_ptr(tr->trace_buffer.data, cpu);
425
426 if (unlikely(!data) ||
427 !data->critical_start || atomic_read(&data->disabled))
428 return;
429
430 atomic_inc(&data->disabled);
431
432 local_save_flags(flags);
433 __trace_function(tr, ip, parent_ip, flags, preempt_count());
434 check_critical_timing(tr, data, parent_ip ? : ip, cpu);
435 data->critical_start = 0;
436 atomic_dec(&data->disabled);
437}
438
439/* start and stop critical timings used to for stoppage (in idle) */
440void start_critical_timings(void)
441{
442 if (preempt_trace() || irq_trace())
443 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
444}
445EXPORT_SYMBOL_GPL(start_critical_timings);
446
447void stop_critical_timings(void)
448{
449 if (preempt_trace() || irq_trace())
450 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
451}
452EXPORT_SYMBOL_GPL(stop_critical_timings);
453
454#ifdef CONFIG_IRQSOFF_TRACER
455#ifdef CONFIG_PROVE_LOCKING
456void time_hardirqs_on(unsigned long a0, unsigned long a1)
457{
458 if (!preempt_trace() && irq_trace())
459 stop_critical_timing(a0, a1);
460}
461
462void time_hardirqs_off(unsigned long a0, unsigned long a1)
463{
464 if (!preempt_trace() && irq_trace())
465 start_critical_timing(a0, a1);
466}
467
468#else /* !CONFIG_PROVE_LOCKING */
469
470/*
471 * Stubs:
472 */
473
474void trace_softirqs_on(unsigned long ip)
475{
476}
477
478void trace_softirqs_off(unsigned long ip)
479{
480}
481
482inline void print_irqtrace_events(struct task_struct *curr)
483{
484}
485
486/*
487 * We are only interested in hardirq on/off events:
488 */
489void trace_hardirqs_on(void)
490{
491 if (!preempt_trace() && irq_trace())
492 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
493}
494EXPORT_SYMBOL(trace_hardirqs_on);
495
496void trace_hardirqs_off(void)
497{
498 if (!preempt_trace() && irq_trace())
499 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
500}
501EXPORT_SYMBOL(trace_hardirqs_off);
502
503__visible void trace_hardirqs_on_caller(unsigned long caller_addr)
504{
505 if (!preempt_trace() && irq_trace())
506 stop_critical_timing(CALLER_ADDR0, caller_addr);
507}
508EXPORT_SYMBOL(trace_hardirqs_on_caller);
509
510__visible void trace_hardirqs_off_caller(unsigned long caller_addr)
511{
512 if (!preempt_trace() && irq_trace())
513 start_critical_timing(CALLER_ADDR0, caller_addr);
514}
515EXPORT_SYMBOL(trace_hardirqs_off_caller);
516
517#endif /* CONFIG_PROVE_LOCKING */
518#endif /* CONFIG_IRQSOFF_TRACER */
519
520#ifdef CONFIG_PREEMPT_TRACER
521void trace_preempt_on(unsigned long a0, unsigned long a1)
522{
523 if (preempt_trace() && !irq_trace())
524 stop_critical_timing(a0, a1);
525}
526
527void trace_preempt_off(unsigned long a0, unsigned long a1)
528{
529 if (preempt_trace() && !irq_trace())
530 start_critical_timing(a0, a1);
531}
532#endif /* CONFIG_PREEMPT_TRACER */
533
534static int register_irqsoff_function(int graph, int set)
535{
536 int ret;
537
538 /* 'set' is set if TRACE_ITER_FUNCTION is about to be set */
539 if (function_enabled || (!set && !(trace_flags & TRACE_ITER_FUNCTION)))
540 return 0;
541
542 if (graph)
543 ret = register_ftrace_graph(&irqsoff_graph_return,
544 &irqsoff_graph_entry);
545 else
546 ret = register_ftrace_function(&trace_ops);
547
548 if (!ret)
549 function_enabled = true;
550
551 return ret;
552}
553
554static void unregister_irqsoff_function(int graph)
555{
556 if (!function_enabled)
557 return;
558
559 if (graph)
560 unregister_ftrace_graph();
561 else
562 unregister_ftrace_function(&trace_ops);
563
564 function_enabled = false;
565}
566
567static void irqsoff_function_set(int set)
568{
569 if (set)
570 register_irqsoff_function(is_graph(), 1);
571 else
572 unregister_irqsoff_function(is_graph());
573}
574
575static int irqsoff_flag_changed(struct trace_array *tr, u32 mask, int set)
576{
577 struct tracer *tracer = tr->current_trace;
578
579 if (mask & TRACE_ITER_FUNCTION)
580 irqsoff_function_set(set);
581
582 return trace_keep_overwrite(tracer, mask, set);
583}
584
585static int start_irqsoff_tracer(struct trace_array *tr, int graph)
586{
587 int ret;
588
589 ret = register_irqsoff_function(graph, 0);
590
591 if (!ret && tracing_is_enabled())
592 tracer_enabled = 1;
593 else
594 tracer_enabled = 0;
595
596 return ret;
597}
598
599static void stop_irqsoff_tracer(struct trace_array *tr, int graph)
600{
601 tracer_enabled = 0;
602
603 unregister_irqsoff_function(graph);
604}
605
606static void __irqsoff_tracer_init(struct trace_array *tr)
607{
608 save_flags = trace_flags;
609
610 /* non overwrite screws up the latency tracers */
611 set_tracer_flag(tr, TRACE_ITER_OVERWRITE, 1);
612 set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, 1);
613
614 tracing_max_latency = 0;
615 irqsoff_trace = tr;
616 /* make sure that the tracer is visible */
617 smp_wmb();
618 tracing_reset_online_cpus(&tr->trace_buffer);
619
620 if (start_irqsoff_tracer(tr, is_graph()))
621 printk(KERN_ERR "failed to start irqsoff tracer\n");
622}
623
624static void irqsoff_tracer_reset(struct trace_array *tr)
625{
626 int lat_flag = save_flags & TRACE_ITER_LATENCY_FMT;
627 int overwrite_flag = save_flags & TRACE_ITER_OVERWRITE;
628
629 stop_irqsoff_tracer(tr, is_graph());
630
631 set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, lat_flag);
632 set_tracer_flag(tr, TRACE_ITER_OVERWRITE, overwrite_flag);
633}
634
635static void irqsoff_tracer_start(struct trace_array *tr)
636{
637 tracer_enabled = 1;
638}
639
640static void irqsoff_tracer_stop(struct trace_array *tr)
641{
642 tracer_enabled = 0;
643}
644
645#ifdef CONFIG_IRQSOFF_TRACER
646static int irqsoff_tracer_init(struct trace_array *tr)
647{
648 trace_type = TRACER_IRQS_OFF;
649
650 __irqsoff_tracer_init(tr);
651 return 0;
652}
653static struct tracer irqsoff_tracer __read_mostly =
654{
655 .name = "irqsoff",
656 .init = irqsoff_tracer_init,
657 .reset = irqsoff_tracer_reset,
658 .start = irqsoff_tracer_start,
659 .stop = irqsoff_tracer_stop,
660 .print_max = true,
661 .print_header = irqsoff_print_header,
662 .print_line = irqsoff_print_line,
663 .flags = &tracer_flags,
664 .set_flag = irqsoff_set_flag,
665 .flag_changed = irqsoff_flag_changed,
666#ifdef CONFIG_FTRACE_SELFTEST
667 .selftest = trace_selftest_startup_irqsoff,
668#endif
669 .open = irqsoff_trace_open,
670 .close = irqsoff_trace_close,
671 .use_max_tr = true,
672};
673# define register_irqsoff(trace) register_tracer(&trace)
674#else
675# define register_irqsoff(trace) do { } while (0)
676#endif
677
678#ifdef CONFIG_PREEMPT_TRACER
679static int preemptoff_tracer_init(struct trace_array *tr)
680{
681 trace_type = TRACER_PREEMPT_OFF;
682
683 __irqsoff_tracer_init(tr);
684 return 0;
685}
686
687static struct tracer preemptoff_tracer __read_mostly =
688{
689 .name = "preemptoff",
690 .init = preemptoff_tracer_init,
691 .reset = irqsoff_tracer_reset,
692 .start = irqsoff_tracer_start,
693 .stop = irqsoff_tracer_stop,
694 .print_max = true,
695 .print_header = irqsoff_print_header,
696 .print_line = irqsoff_print_line,
697 .flags = &tracer_flags,
698 .set_flag = irqsoff_set_flag,
699 .flag_changed = irqsoff_flag_changed,
700#ifdef CONFIG_FTRACE_SELFTEST
701 .selftest = trace_selftest_startup_preemptoff,
702#endif
703 .open = irqsoff_trace_open,
704 .close = irqsoff_trace_close,
705 .use_max_tr = true,
706};
707# define register_preemptoff(trace) register_tracer(&trace)
708#else
709# define register_preemptoff(trace) do { } while (0)
710#endif
711
712#if defined(CONFIG_IRQSOFF_TRACER) && \
713 defined(CONFIG_PREEMPT_TRACER)
714
715static int preemptirqsoff_tracer_init(struct trace_array *tr)
716{
717 trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
718
719 __irqsoff_tracer_init(tr);
720 return 0;
721}
722
723static struct tracer preemptirqsoff_tracer __read_mostly =
724{
725 .name = "preemptirqsoff",
726 .init = preemptirqsoff_tracer_init,
727 .reset = irqsoff_tracer_reset,
728 .start = irqsoff_tracer_start,
729 .stop = irqsoff_tracer_stop,
730 .print_max = true,
731 .print_header = irqsoff_print_header,
732 .print_line = irqsoff_print_line,
733 .flags = &tracer_flags,
734 .set_flag = irqsoff_set_flag,
735 .flag_changed = irqsoff_flag_changed,
736#ifdef CONFIG_FTRACE_SELFTEST
737 .selftest = trace_selftest_startup_preemptirqsoff,
738#endif
739 .open = irqsoff_trace_open,
740 .close = irqsoff_trace_close,
741 .use_max_tr = true,
742};
743
744# define register_preemptirqsoff(trace) register_tracer(&trace)
745#else
746# define register_preemptirqsoff(trace) do { } while (0)
747#endif
748
749__init static int init_irqsoff_tracer(void)
750{
751 register_irqsoff(irqsoff_tracer);
752 register_preemptoff(preemptoff_tracer);
753 register_preemptirqsoff(preemptirqsoff_tracer);
754
755 return 0;
756}
757core_initcall(init_irqsoff_tracer);