2 * trace task wakeup timings
4 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
5 * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
7 * Based on code from the latency_tracer, that is:
9 * Copyright (C) 2004-2006 Ingo Molnar
10 * Copyright (C) 2004 Nadia Yvette Chambers
12 #include <linux/module.h>
14 #include <linux/debugfs.h>
15 #include <linux/kallsyms.h>
16 #include <linux/uaccess.h>
17 #include <linux/ftrace.h>
18 #include <linux/sched/rt.h>
19 #include <linux/sched/deadline.h>
20 #include <trace/events/sched.h>
23 static struct trace_array *wakeup_trace;
24 static int __read_mostly tracer_enabled;
26 static struct task_struct *wakeup_task;
27 static int wakeup_cpu;
28 static int wakeup_current_cpu;
29 static unsigned wakeup_prio = -1;
32 static int tracing_dl = 0;
34 static arch_spinlock_t wakeup_lock =
35 (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
37 static void wakeup_reset(struct trace_array *tr);
38 static void __wakeup_reset(struct trace_array *tr);
39 static int wakeup_graph_entry(struct ftrace_graph_ent *trace);
40 static void wakeup_graph_return(struct ftrace_graph_ret *trace);
42 static int save_flags;
43 static bool function_enabled;
45 #define TRACE_DISPLAY_GRAPH 1
47 static struct tracer_opt trace_opts[] = {
48 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
49 /* display latency trace as call graph */
50 { TRACER_OPT(display-graph, TRACE_DISPLAY_GRAPH) },
55 static struct tracer_flags tracer_flags = {
60 #define is_graph() (tracer_flags.val & TRACE_DISPLAY_GRAPH)
62 #ifdef CONFIG_FUNCTION_TRACER
65 * Prologue for the wakeup function tracers.
67 * Returns 1 if it is OK to continue, and preemption
68 * is disabled and data->disabled is incremented.
69 * 0 if the trace is to be ignored, and preemption
70 * is not disabled and data->disabled is
73 * Note, this function is also used outside this ifdef but
74 * inside the #ifdef of the function graph tracer below.
75 * This is OK, since the function graph tracer is
76 * dependent on the function tracer.
79 func_prolog_preempt_disable(struct trace_array *tr,
80 struct trace_array_cpu **data,
86 if (likely(!wakeup_task))
89 *pc = preempt_count();
90 preempt_disable_notrace();
92 cpu = raw_smp_processor_id();
93 if (cpu != wakeup_current_cpu)
96 *data = per_cpu_ptr(tr->trace_buffer.data, cpu);
97 disabled = atomic_inc_return(&(*data)->disabled);
98 if (unlikely(disabled != 1))
104 atomic_dec(&(*data)->disabled);
107 preempt_enable_notrace();
112 * wakeup uses its own tracer function to keep the overhead down:
115 wakeup_tracer_call(unsigned long ip, unsigned long parent_ip,
116 struct ftrace_ops *op, struct pt_regs *pt_regs)
118 struct trace_array *tr = wakeup_trace;
119 struct trace_array_cpu *data;
123 if (!func_prolog_preempt_disable(tr, &data, &pc))
126 local_irq_save(flags);
127 trace_function(tr, ip, parent_ip, flags, pc);
128 local_irq_restore(flags);
130 atomic_dec(&data->disabled);
131 preempt_enable_notrace();
133 #endif /* CONFIG_FUNCTION_TRACER */
135 static int register_wakeup_function(struct trace_array *tr, int graph, int set)
139 /* 'set' is set if TRACE_ITER_FUNCTION is about to be set */
140 if (function_enabled || (!set && !(trace_flags & TRACE_ITER_FUNCTION)))
144 ret = register_ftrace_graph(&wakeup_graph_return,
145 &wakeup_graph_entry);
147 ret = register_ftrace_function(tr->ops);
150 function_enabled = true;
155 static void unregister_wakeup_function(struct trace_array *tr, int graph)
157 if (!function_enabled)
161 unregister_ftrace_graph();
163 unregister_ftrace_function(tr->ops);
165 function_enabled = false;
168 static void wakeup_function_set(struct trace_array *tr, int set)
171 register_wakeup_function(tr, is_graph(), 1);
173 unregister_wakeup_function(tr, is_graph());
176 static int wakeup_flag_changed(struct trace_array *tr, u32 mask, int set)
178 struct tracer *tracer = tr->current_trace;
180 if (mask & TRACE_ITER_FUNCTION)
181 wakeup_function_set(tr, set);
183 return trace_keep_overwrite(tracer, mask, set);
186 static int start_func_tracer(struct trace_array *tr, int graph)
190 ret = register_wakeup_function(tr, graph, 0);
192 if (!ret && tracing_is_enabled())
200 static void stop_func_tracer(struct trace_array *tr, int graph)
204 unregister_wakeup_function(tr, graph);
207 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
209 wakeup_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
212 if (!(bit & TRACE_DISPLAY_GRAPH))
215 if (!(is_graph() ^ set))
218 stop_func_tracer(tr, !set);
220 wakeup_reset(wakeup_trace);
223 return start_func_tracer(tr, set);
226 static int wakeup_graph_entry(struct ftrace_graph_ent *trace)
228 struct trace_array *tr = wakeup_trace;
229 struct trace_array_cpu *data;
233 if (!func_prolog_preempt_disable(tr, &data, &pc))
236 local_save_flags(flags);
237 ret = __trace_graph_entry(tr, trace, flags, pc);
238 atomic_dec(&data->disabled);
239 preempt_enable_notrace();
244 static void wakeup_graph_return(struct ftrace_graph_ret *trace)
246 struct trace_array *tr = wakeup_trace;
247 struct trace_array_cpu *data;
251 if (!func_prolog_preempt_disable(tr, &data, &pc))
254 local_save_flags(flags);
255 __trace_graph_return(tr, trace, flags, pc);
256 atomic_dec(&data->disabled);
258 preempt_enable_notrace();
262 static void wakeup_trace_open(struct trace_iterator *iter)
265 graph_trace_open(iter);
268 static void wakeup_trace_close(struct trace_iterator *iter)
271 graph_trace_close(iter);
274 #define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_PROC | \
275 TRACE_GRAPH_PRINT_ABS_TIME | \
276 TRACE_GRAPH_PRINT_DURATION)
278 static enum print_line_t wakeup_print_line(struct trace_iterator *iter)
281 * In graph mode call the graph tracer output function,
282 * otherwise go with the TRACE_FN event handler
285 return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS);
287 return TRACE_TYPE_UNHANDLED;
290 static void wakeup_print_header(struct seq_file *s)
293 print_graph_headers_flags(s, GRAPH_TRACER_FLAGS);
295 trace_default_header(s);
299 __trace_function(struct trace_array *tr,
300 unsigned long ip, unsigned long parent_ip,
301 unsigned long flags, int pc)
304 trace_graph_function(tr, ip, parent_ip, flags, pc);
306 trace_function(tr, ip, parent_ip, flags, pc);
309 #define __trace_function trace_function
312 wakeup_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
317 static int wakeup_graph_entry(struct ftrace_graph_ent *trace)
322 static enum print_line_t wakeup_print_line(struct trace_iterator *iter)
324 return TRACE_TYPE_UNHANDLED;
327 static void wakeup_graph_return(struct ftrace_graph_ret *trace) { }
328 static void wakeup_trace_open(struct trace_iterator *iter) { }
329 static void wakeup_trace_close(struct trace_iterator *iter) { }
331 #ifdef CONFIG_FUNCTION_TRACER
332 static void wakeup_print_header(struct seq_file *s)
334 trace_default_header(s);
337 static void wakeup_print_header(struct seq_file *s)
339 trace_latency_header(s);
341 #endif /* CONFIG_FUNCTION_TRACER */
342 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
345 * Should this new latency be reported/recorded?
347 static int report_latency(struct trace_array *tr, cycle_t delta)
349 if (tracing_thresh) {
350 if (delta < tracing_thresh)
353 if (delta <= tr->max_latency)
360 probe_wakeup_migrate_task(void *ignore, struct task_struct *task, int cpu)
362 if (task != wakeup_task)
365 wakeup_current_cpu = cpu;
369 tracing_sched_switch_trace(struct trace_array *tr,
370 struct task_struct *prev,
371 struct task_struct *next,
372 unsigned long flags, int pc)
374 struct ftrace_event_call *call = &event_context_switch;
375 struct ring_buffer *buffer = tr->trace_buffer.buffer;
376 struct ring_buffer_event *event;
377 struct ctx_switch_entry *entry;
379 event = trace_buffer_lock_reserve(buffer, TRACE_CTX,
380 sizeof(*entry), flags, pc);
383 entry = ring_buffer_event_data(event);
384 entry->prev_pid = prev->pid;
385 entry->prev_prio = prev->prio;
386 entry->prev_state = prev->state;
387 entry->next_pid = next->pid;
388 entry->next_prio = next->prio;
389 entry->next_state = next->state;
390 entry->next_cpu = task_cpu(next);
392 if (!call_filter_check_discard(call, entry, buffer, event))
393 trace_buffer_unlock_commit(buffer, event, flags, pc);
397 tracing_sched_wakeup_trace(struct trace_array *tr,
398 struct task_struct *wakee,
399 struct task_struct *curr,
400 unsigned long flags, int pc)
402 struct ftrace_event_call *call = &event_wakeup;
403 struct ring_buffer_event *event;
404 struct ctx_switch_entry *entry;
405 struct ring_buffer *buffer = tr->trace_buffer.buffer;
407 event = trace_buffer_lock_reserve(buffer, TRACE_WAKE,
408 sizeof(*entry), flags, pc);
411 entry = ring_buffer_event_data(event);
412 entry->prev_pid = curr->pid;
413 entry->prev_prio = curr->prio;
414 entry->prev_state = curr->state;
415 entry->next_pid = wakee->pid;
416 entry->next_prio = wakee->prio;
417 entry->next_state = wakee->state;
418 entry->next_cpu = task_cpu(wakee);
420 if (!call_filter_check_discard(call, entry, buffer, event))
421 trace_buffer_unlock_commit(buffer, event, flags, pc);
425 probe_wakeup_sched_switch(void *ignore,
426 struct task_struct *prev, struct task_struct *next)
428 struct trace_array_cpu *data;
429 cycle_t T0, T1, delta;
435 tracing_record_cmdline(prev);
437 if (unlikely(!tracer_enabled))
441 * When we start a new trace, we set wakeup_task to NULL
442 * and then set tracer_enabled = 1. We want to make sure
443 * that another CPU does not see the tracer_enabled = 1
444 * and the wakeup_task with an older task, that might
445 * actually be the same as next.
449 if (next != wakeup_task)
452 pc = preempt_count();
454 /* disable local data, not wakeup_cpu data */
455 cpu = raw_smp_processor_id();
456 disabled = atomic_inc_return(&per_cpu_ptr(wakeup_trace->trace_buffer.data, cpu)->disabled);
457 if (likely(disabled != 1))
460 local_irq_save(flags);
461 arch_spin_lock(&wakeup_lock);
463 /* We could race with grabbing wakeup_lock */
464 if (unlikely(!tracer_enabled || next != wakeup_task))
467 /* The task we are waiting for is waking up */
468 data = per_cpu_ptr(wakeup_trace->trace_buffer.data, wakeup_cpu);
470 __trace_function(wakeup_trace, CALLER_ADDR0, CALLER_ADDR1, flags, pc);
471 tracing_sched_switch_trace(wakeup_trace, prev, next, flags, pc);
473 T0 = data->preempt_timestamp;
474 T1 = ftrace_now(cpu);
477 if (!report_latency(wakeup_trace, delta))
480 if (likely(!is_tracing_stopped())) {
481 wakeup_trace->max_latency = delta;
482 update_max_tr(wakeup_trace, wakeup_task, wakeup_cpu);
486 __wakeup_reset(wakeup_trace);
487 arch_spin_unlock(&wakeup_lock);
488 local_irq_restore(flags);
490 atomic_dec(&per_cpu_ptr(wakeup_trace->trace_buffer.data, cpu)->disabled);
493 static void __wakeup_reset(struct trace_array *tr)
500 put_task_struct(wakeup_task);
505 static void wakeup_reset(struct trace_array *tr)
509 tracing_reset_online_cpus(&tr->trace_buffer);
511 local_irq_save(flags);
512 arch_spin_lock(&wakeup_lock);
514 arch_spin_unlock(&wakeup_lock);
515 local_irq_restore(flags);
519 probe_wakeup(void *ignore, struct task_struct *p, int success)
521 struct trace_array_cpu *data;
522 int cpu = smp_processor_id();
527 if (likely(!tracer_enabled))
530 tracing_record_cmdline(p);
531 tracing_record_cmdline(current);
534 * Semantic is like this:
535 * - wakeup tracer handles all tasks in the system, independently
536 * from their scheduling class;
537 * - wakeup_rt tracer handles tasks belonging to sched_dl and
539 * - wakeup_dl handles tasks belonging to sched_dl class only.
541 if (tracing_dl || (wakeup_dl && !dl_task(p)) ||
542 (wakeup_rt && !dl_task(p) && !rt_task(p)) ||
543 (!dl_task(p) && (p->prio >= wakeup_prio || p->prio >= current->prio)))
546 pc = preempt_count();
547 disabled = atomic_inc_return(&per_cpu_ptr(wakeup_trace->trace_buffer.data, cpu)->disabled);
548 if (unlikely(disabled != 1))
551 /* interrupts should be off from try_to_wake_up */
552 arch_spin_lock(&wakeup_lock);
554 /* check for races. */
555 if (!tracer_enabled || tracing_dl ||
556 (!dl_task(p) && p->prio >= wakeup_prio))
559 /* reset the trace */
560 __wakeup_reset(wakeup_trace);
562 wakeup_cpu = task_cpu(p);
563 wakeup_current_cpu = wakeup_cpu;
564 wakeup_prio = p->prio;
567 * Once you start tracing a -deadline task, don't bother tracing
568 * another task until the first one wakes up.
576 get_task_struct(wakeup_task);
578 local_save_flags(flags);
580 data = per_cpu_ptr(wakeup_trace->trace_buffer.data, wakeup_cpu);
581 data->preempt_timestamp = ftrace_now(cpu);
582 tracing_sched_wakeup_trace(wakeup_trace, p, current, flags, pc);
585 * We must be careful in using CALLER_ADDR2. But since wake_up
586 * is not called by an assembly function (where as schedule is)
587 * it should be safe to use it here.
589 __trace_function(wakeup_trace, CALLER_ADDR1, CALLER_ADDR2, flags, pc);
592 arch_spin_unlock(&wakeup_lock);
594 atomic_dec(&per_cpu_ptr(wakeup_trace->trace_buffer.data, cpu)->disabled);
597 static void start_wakeup_tracer(struct trace_array *tr)
601 ret = register_trace_sched_wakeup(probe_wakeup, NULL);
603 pr_info("wakeup trace: Couldn't activate tracepoint"
604 " probe to kernel_sched_wakeup\n");
608 ret = register_trace_sched_wakeup_new(probe_wakeup, NULL);
610 pr_info("wakeup trace: Couldn't activate tracepoint"
611 " probe to kernel_sched_wakeup_new\n");
615 ret = register_trace_sched_switch(probe_wakeup_sched_switch, NULL);
617 pr_info("sched trace: Couldn't activate tracepoint"
618 " probe to kernel_sched_switch\n");
619 goto fail_deprobe_wake_new;
622 ret = register_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL);
624 pr_info("wakeup trace: Couldn't activate tracepoint"
625 " probe to kernel_sched_migrate_task\n");
632 * Don't let the tracer_enabled = 1 show up before
633 * the wakeup_task is reset. This may be overkill since
634 * wakeup_reset does a spin_unlock after setting the
635 * wakeup_task to NULL, but I want to be safe.
636 * This is a slow path anyway.
640 if (start_func_tracer(tr, is_graph()))
641 printk(KERN_ERR "failed to start wakeup tracer\n");
644 fail_deprobe_wake_new:
645 unregister_trace_sched_wakeup_new(probe_wakeup, NULL);
647 unregister_trace_sched_wakeup(probe_wakeup, NULL);
650 static void stop_wakeup_tracer(struct trace_array *tr)
653 stop_func_tracer(tr, is_graph());
654 unregister_trace_sched_switch(probe_wakeup_sched_switch, NULL);
655 unregister_trace_sched_wakeup_new(probe_wakeup, NULL);
656 unregister_trace_sched_wakeup(probe_wakeup, NULL);
657 unregister_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL);
660 static bool wakeup_busy;
662 static int __wakeup_tracer_init(struct trace_array *tr)
664 save_flags = trace_flags;
666 /* non overwrite screws up the latency tracers */
667 set_tracer_flag(tr, TRACE_ITER_OVERWRITE, 1);
668 set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, 1);
672 ftrace_init_array_ops(tr, wakeup_tracer_call);
673 start_wakeup_tracer(tr);
679 static int wakeup_tracer_init(struct trace_array *tr)
686 return __wakeup_tracer_init(tr);
689 static int wakeup_rt_tracer_init(struct trace_array *tr)
696 return __wakeup_tracer_init(tr);
699 static int wakeup_dl_tracer_init(struct trace_array *tr)
706 return __wakeup_tracer_init(tr);
709 static void wakeup_tracer_reset(struct trace_array *tr)
711 int lat_flag = save_flags & TRACE_ITER_LATENCY_FMT;
712 int overwrite_flag = save_flags & TRACE_ITER_OVERWRITE;
714 stop_wakeup_tracer(tr);
715 /* make sure we put back any tasks we are tracing */
718 set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, lat_flag);
719 set_tracer_flag(tr, TRACE_ITER_OVERWRITE, overwrite_flag);
720 ftrace_reset_array_ops(tr);
724 static void wakeup_tracer_start(struct trace_array *tr)
730 static void wakeup_tracer_stop(struct trace_array *tr)
735 static struct tracer wakeup_tracer __read_mostly =
738 .init = wakeup_tracer_init,
739 .reset = wakeup_tracer_reset,
740 .start = wakeup_tracer_start,
741 .stop = wakeup_tracer_stop,
743 .print_header = wakeup_print_header,
744 .print_line = wakeup_print_line,
745 .flags = &tracer_flags,
746 .set_flag = wakeup_set_flag,
747 .flag_changed = wakeup_flag_changed,
748 #ifdef CONFIG_FTRACE_SELFTEST
749 .selftest = trace_selftest_startup_wakeup,
751 .open = wakeup_trace_open,
752 .close = wakeup_trace_close,
753 .allow_instances = true,
757 static struct tracer wakeup_rt_tracer __read_mostly =
760 .init = wakeup_rt_tracer_init,
761 .reset = wakeup_tracer_reset,
762 .start = wakeup_tracer_start,
763 .stop = wakeup_tracer_stop,
765 .print_header = wakeup_print_header,
766 .print_line = wakeup_print_line,
767 .flags = &tracer_flags,
768 .set_flag = wakeup_set_flag,
769 .flag_changed = wakeup_flag_changed,
770 #ifdef CONFIG_FTRACE_SELFTEST
771 .selftest = trace_selftest_startup_wakeup,
773 .open = wakeup_trace_open,
774 .close = wakeup_trace_close,
775 .allow_instances = true,
779 static struct tracer wakeup_dl_tracer __read_mostly =
782 .init = wakeup_dl_tracer_init,
783 .reset = wakeup_tracer_reset,
784 .start = wakeup_tracer_start,
785 .stop = wakeup_tracer_stop,
787 .print_header = wakeup_print_header,
788 .print_line = wakeup_print_line,
789 .flags = &tracer_flags,
790 .set_flag = wakeup_set_flag,
791 .flag_changed = wakeup_flag_changed,
792 #ifdef CONFIG_FTRACE_SELFTEST
793 .selftest = trace_selftest_startup_wakeup,
795 .open = wakeup_trace_open,
796 .close = wakeup_trace_close,
800 __init static int init_wakeup_tracer(void)
804 ret = register_tracer(&wakeup_tracer);
808 ret = register_tracer(&wakeup_rt_tracer);
812 ret = register_tracer(&wakeup_dl_tracer);
818 core_initcall(init_wakeup_tracer);