2 * trace irqs off critical timings
4 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
5 * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
7 * From code in the latency_tracer, that is:
9 * Copyright (C) 2004-2006 Ingo Molnar
10 * Copyright (C) 2004 William Lee Irwin III
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>
21 static struct trace_array *irqsoff_trace __read_mostly;
22 static int tracer_enabled __read_mostly;
24 static DEFINE_PER_CPU(int, tracing_cpu);
26 static DEFINE_RAW_SPINLOCK(max_trace_lock);
29 TRACER_IRQS_OFF = (1 << 1),
30 TRACER_PREEMPT_OFF = (1 << 2),
33 static int trace_type __read_mostly;
35 static int save_lat_flag;
37 static void stop_irqsoff_tracer(struct trace_array *tr, int graph);
38 static int start_irqsoff_tracer(struct trace_array *tr, int graph);
40 #ifdef CONFIG_PREEMPT_TRACER
44 return ((trace_type & TRACER_PREEMPT_OFF) && preempt_count());
47 # define preempt_trace() (0)
50 #ifdef CONFIG_IRQSOFF_TRACER
54 return ((trace_type & TRACER_IRQS_OFF) &&
58 # define irq_trace() (0)
61 #define TRACE_DISPLAY_GRAPH 1
63 static struct tracer_opt trace_opts[] = {
64 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
65 /* display latency trace as call graph */
66 { TRACER_OPT(display-graph, TRACE_DISPLAY_GRAPH) },
71 static struct tracer_flags tracer_flags = {
76 #define is_graph() (tracer_flags.val & TRACE_DISPLAY_GRAPH)
79 * Sequence count - we record it when starting a measurement and
80 * skip the latency if the sequence has changed - some other section
81 * did a maximum and could disturb our measurement with serial console
82 * printouts, etc. Truly coinciding maximum latencies should be rare
83 * and what happens together happens separately as well, so this doesn't
84 * decrease the validity of the maximum found:
86 static __cacheline_aligned_in_smp unsigned long max_sequence;
88 #ifdef CONFIG_FUNCTION_TRACER
90 * Prologue for the preempt and irqs off function tracers.
92 * Returns 1 if it is OK to continue, and data->disabled is
94 * 0 if the trace is to be ignored, and data->disabled
97 * Note, this function is also used outside this ifdef but
98 * inside the #ifdef of the function graph tracer below.
99 * This is OK, since the function graph tracer is
100 * dependent on the function tracer.
102 static int func_prolog_dec(struct trace_array *tr,
103 struct trace_array_cpu **data,
104 unsigned long *flags)
110 * Does not matter if we preempt. We test the flags
111 * afterward, to see if irqs are disabled or not.
112 * If we preempt and get a false positive, the flags
115 cpu = raw_smp_processor_id();
116 if (likely(!per_cpu(tracing_cpu, cpu)))
119 local_save_flags(*flags);
120 /* slight chance to get a false positive on tracing_cpu */
121 if (!irqs_disabled_flags(*flags))
124 *data = tr->data[cpu];
125 disabled = atomic_inc_return(&(*data)->disabled);
127 if (likely(disabled == 1))
130 atomic_dec(&(*data)->disabled);
136 * irqsoff uses its own tracer function to keep the overhead down:
139 irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip)
141 struct trace_array *tr = irqsoff_trace;
142 struct trace_array_cpu *data;
145 if (!func_prolog_dec(tr, &data, &flags))
148 trace_function(tr, ip, parent_ip, flags, preempt_count());
150 atomic_dec(&data->disabled);
153 static struct ftrace_ops trace_ops __read_mostly =
155 .func = irqsoff_tracer_call,
156 .flags = FTRACE_OPS_FL_GLOBAL,
158 #endif /* CONFIG_FUNCTION_TRACER */
160 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
161 static int irqsoff_set_flag(u32 old_flags, u32 bit, int set)
165 if (!(bit & TRACE_DISPLAY_GRAPH))
168 if (!(is_graph() ^ set))
171 stop_irqsoff_tracer(irqsoff_trace, !set);
173 for_each_possible_cpu(cpu)
174 per_cpu(tracing_cpu, cpu) = 0;
176 tracing_max_latency = 0;
177 tracing_reset_online_cpus(irqsoff_trace);
179 return start_irqsoff_tracer(irqsoff_trace, set);
182 static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
184 struct trace_array *tr = irqsoff_trace;
185 struct trace_array_cpu *data;
190 if (!func_prolog_dec(tr, &data, &flags))
193 pc = preempt_count();
194 ret = __trace_graph_entry(tr, trace, flags, pc);
195 atomic_dec(&data->disabled);
200 static void irqsoff_graph_return(struct ftrace_graph_ret *trace)
202 struct trace_array *tr = irqsoff_trace;
203 struct trace_array_cpu *data;
207 if (!func_prolog_dec(tr, &data, &flags))
210 pc = preempt_count();
211 __trace_graph_return(tr, trace, flags, pc);
212 atomic_dec(&data->disabled);
215 static void irqsoff_trace_open(struct trace_iterator *iter)
218 graph_trace_open(iter);
222 static void irqsoff_trace_close(struct trace_iterator *iter)
225 graph_trace_close(iter);
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)
233 static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
236 * In graph mode call the graph tracer output function,
237 * otherwise go with the TRACE_FN event handler
240 return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS);
242 return TRACE_TYPE_UNHANDLED;
245 static void irqsoff_print_header(struct seq_file *s)
248 print_graph_headers_flags(s, GRAPH_TRACER_FLAGS);
250 trace_default_header(s);
254 __trace_function(struct trace_array *tr,
255 unsigned long ip, unsigned long parent_ip,
256 unsigned long flags, int pc)
259 trace_graph_function(tr, ip, parent_ip, flags, pc);
261 trace_function(tr, ip, parent_ip, flags, pc);
265 #define __trace_function trace_function
267 static int irqsoff_set_flag(u32 old_flags, u32 bit, int set)
272 static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
277 static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
279 return TRACE_TYPE_UNHANDLED;
282 static void irqsoff_graph_return(struct ftrace_graph_ret *trace) { }
283 static void irqsoff_print_header(struct seq_file *s) { }
284 static void irqsoff_trace_open(struct trace_iterator *iter) { }
285 static void irqsoff_trace_close(struct trace_iterator *iter) { }
286 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
289 * Should this new latency be reported/recorded?
291 static int report_latency(cycle_t delta)
293 if (tracing_thresh) {
294 if (delta < tracing_thresh)
297 if (delta <= tracing_max_latency)
304 check_critical_timing(struct trace_array *tr,
305 struct trace_array_cpu *data,
306 unsigned long parent_ip,
309 cycle_t T0, T1, delta;
313 T0 = data->preempt_timestamp;
314 T1 = ftrace_now(cpu);
317 local_save_flags(flags);
319 pc = preempt_count();
321 if (!report_latency(delta))
324 raw_spin_lock_irqsave(&max_trace_lock, flags);
326 /* check if we are still the max latency */
327 if (!report_latency(delta))
330 __trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
331 /* Skip 5 functions to get to the irq/preempt enable function */
332 __trace_stack(tr, flags, 5, pc);
334 if (data->critical_sequence != max_sequence)
337 data->critical_end = parent_ip;
339 if (likely(!is_tracing_stopped())) {
340 tracing_max_latency = delta;
341 update_max_tr_single(tr, current, cpu);
347 raw_spin_unlock_irqrestore(&max_trace_lock, flags);
350 data->critical_sequence = max_sequence;
351 data->preempt_timestamp = ftrace_now(cpu);
352 __trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
356 start_critical_timing(unsigned long ip, unsigned long parent_ip)
359 struct trace_array *tr = irqsoff_trace;
360 struct trace_array_cpu *data;
363 if (likely(!tracer_enabled))
366 cpu = raw_smp_processor_id();
368 if (per_cpu(tracing_cpu, cpu))
371 data = tr->data[cpu];
373 if (unlikely(!data) || atomic_read(&data->disabled))
376 atomic_inc(&data->disabled);
378 data->critical_sequence = max_sequence;
379 data->preempt_timestamp = ftrace_now(cpu);
380 data->critical_start = parent_ip ? : ip;
382 local_save_flags(flags);
384 __trace_function(tr, ip, parent_ip, flags, preempt_count());
386 per_cpu(tracing_cpu, cpu) = 1;
388 atomic_dec(&data->disabled);
392 stop_critical_timing(unsigned long ip, unsigned long parent_ip)
395 struct trace_array *tr = irqsoff_trace;
396 struct trace_array_cpu *data;
399 cpu = raw_smp_processor_id();
400 /* Always clear the tracing cpu on stopping the trace */
401 if (unlikely(per_cpu(tracing_cpu, cpu)))
402 per_cpu(tracing_cpu, cpu) = 0;
409 data = tr->data[cpu];
411 if (unlikely(!data) ||
412 !data->critical_start || atomic_read(&data->disabled))
415 atomic_inc(&data->disabled);
417 local_save_flags(flags);
418 __trace_function(tr, ip, parent_ip, flags, preempt_count());
419 check_critical_timing(tr, data, parent_ip ? : ip, cpu);
420 data->critical_start = 0;
421 atomic_dec(&data->disabled);
424 /* start and stop critical timings used to for stoppage (in idle) */
425 void start_critical_timings(void)
427 if (preempt_trace() || irq_trace())
428 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
430 EXPORT_SYMBOL_GPL(start_critical_timings);
432 void stop_critical_timings(void)
434 if (preempt_trace() || irq_trace())
435 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
437 EXPORT_SYMBOL_GPL(stop_critical_timings);
439 #ifdef CONFIG_IRQSOFF_TRACER
440 #ifdef CONFIG_PROVE_LOCKING
441 void time_hardirqs_on(unsigned long a0, unsigned long a1)
443 if (!preempt_trace() && irq_trace())
444 stop_critical_timing(a0, a1);
447 void time_hardirqs_off(unsigned long a0, unsigned long a1)
449 if (!preempt_trace() && irq_trace())
450 start_critical_timing(a0, a1);
453 #else /* !CONFIG_PROVE_LOCKING */
459 void trace_softirqs_on(unsigned long ip)
463 void trace_softirqs_off(unsigned long ip)
467 inline void print_irqtrace_events(struct task_struct *curr)
472 * We are only interested in hardirq on/off events:
474 void trace_hardirqs_on(void)
476 if (!preempt_trace() && irq_trace())
477 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
479 EXPORT_SYMBOL(trace_hardirqs_on);
481 void trace_hardirqs_off(void)
483 if (!preempt_trace() && irq_trace())
484 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
486 EXPORT_SYMBOL(trace_hardirqs_off);
488 void trace_hardirqs_on_caller(unsigned long caller_addr)
490 if (!preempt_trace() && irq_trace())
491 stop_critical_timing(CALLER_ADDR0, caller_addr);
493 EXPORT_SYMBOL(trace_hardirqs_on_caller);
495 void trace_hardirqs_off_caller(unsigned long caller_addr)
497 if (!preempt_trace() && irq_trace())
498 start_critical_timing(CALLER_ADDR0, caller_addr);
500 EXPORT_SYMBOL(trace_hardirqs_off_caller);
502 #endif /* CONFIG_PROVE_LOCKING */
503 #endif /* CONFIG_IRQSOFF_TRACER */
505 #ifdef CONFIG_PREEMPT_TRACER
506 void trace_preempt_on(unsigned long a0, unsigned long a1)
508 if (preempt_trace() && !irq_trace())
509 stop_critical_timing(a0, a1);
512 void trace_preempt_off(unsigned long a0, unsigned long a1)
514 if (preempt_trace() && !irq_trace())
515 start_critical_timing(a0, a1);
517 #endif /* CONFIG_PREEMPT_TRACER */
519 static int start_irqsoff_tracer(struct trace_array *tr, int graph)
524 ret = register_ftrace_function(&trace_ops);
526 ret = register_ftrace_graph(&irqsoff_graph_return,
527 &irqsoff_graph_entry);
529 if (!ret && tracing_is_enabled())
537 static void stop_irqsoff_tracer(struct trace_array *tr, int graph)
542 unregister_ftrace_function(&trace_ops);
544 unregister_ftrace_graph();
547 static void __irqsoff_tracer_init(struct trace_array *tr)
549 save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
550 trace_flags |= TRACE_ITER_LATENCY_FMT;
552 tracing_max_latency = 0;
554 /* make sure that the tracer is visible */
556 tracing_reset_online_cpus(tr);
558 if (start_irqsoff_tracer(tr, is_graph()))
559 printk(KERN_ERR "failed to start irqsoff tracer\n");
562 static void irqsoff_tracer_reset(struct trace_array *tr)
564 stop_irqsoff_tracer(tr, is_graph());
567 trace_flags &= ~TRACE_ITER_LATENCY_FMT;
570 static void irqsoff_tracer_start(struct trace_array *tr)
575 static void irqsoff_tracer_stop(struct trace_array *tr)
580 #ifdef CONFIG_IRQSOFF_TRACER
581 static int irqsoff_tracer_init(struct trace_array *tr)
583 trace_type = TRACER_IRQS_OFF;
585 __irqsoff_tracer_init(tr);
588 static struct tracer irqsoff_tracer __read_mostly =
591 .init = irqsoff_tracer_init,
592 .reset = irqsoff_tracer_reset,
593 .start = irqsoff_tracer_start,
594 .stop = irqsoff_tracer_stop,
596 .print_header = irqsoff_print_header,
597 .print_line = irqsoff_print_line,
598 .flags = &tracer_flags,
599 .set_flag = irqsoff_set_flag,
600 #ifdef CONFIG_FTRACE_SELFTEST
601 .selftest = trace_selftest_startup_irqsoff,
603 .open = irqsoff_trace_open,
604 .close = irqsoff_trace_close,
607 # define register_irqsoff(trace) register_tracer(&trace)
609 # define register_irqsoff(trace) do { } while (0)
612 #ifdef CONFIG_PREEMPT_TRACER
613 static int preemptoff_tracer_init(struct trace_array *tr)
615 trace_type = TRACER_PREEMPT_OFF;
617 __irqsoff_tracer_init(tr);
621 static struct tracer preemptoff_tracer __read_mostly =
623 .name = "preemptoff",
624 .init = preemptoff_tracer_init,
625 .reset = irqsoff_tracer_reset,
626 .start = irqsoff_tracer_start,
627 .stop = irqsoff_tracer_stop,
629 .print_header = irqsoff_print_header,
630 .print_line = irqsoff_print_line,
631 .flags = &tracer_flags,
632 .set_flag = irqsoff_set_flag,
633 #ifdef CONFIG_FTRACE_SELFTEST
634 .selftest = trace_selftest_startup_preemptoff,
636 .open = irqsoff_trace_open,
637 .close = irqsoff_trace_close,
640 # define register_preemptoff(trace) register_tracer(&trace)
642 # define register_preemptoff(trace) do { } while (0)
645 #if defined(CONFIG_IRQSOFF_TRACER) && \
646 defined(CONFIG_PREEMPT_TRACER)
648 static int preemptirqsoff_tracer_init(struct trace_array *tr)
650 trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
652 __irqsoff_tracer_init(tr);
656 static struct tracer preemptirqsoff_tracer __read_mostly =
658 .name = "preemptirqsoff",
659 .init = preemptirqsoff_tracer_init,
660 .reset = irqsoff_tracer_reset,
661 .start = irqsoff_tracer_start,
662 .stop = irqsoff_tracer_stop,
664 .print_header = irqsoff_print_header,
665 .print_line = irqsoff_print_line,
666 .flags = &tracer_flags,
667 .set_flag = irqsoff_set_flag,
668 #ifdef CONFIG_FTRACE_SELFTEST
669 .selftest = trace_selftest_startup_preemptirqsoff,
671 .open = irqsoff_trace_open,
672 .close = irqsoff_trace_close,
676 # define register_preemptirqsoff(trace) register_tracer(&trace)
678 # define register_preemptirqsoff(trace) do { } while (0)
681 __init static int init_irqsoff_tracer(void)
683 register_irqsoff(irqsoff_tracer);
684 register_preemptoff(preemptoff_tracer);
685 register_preemptirqsoff(preemptirqsoff_tracer);
689 device_initcall(init_irqsoff_tracer);