Root/kernel/trace/trace_sched_wakeup.c

1/*
2 * trace task wakeup timings
3 *
4 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
5 * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
6 *
7 * Based on code from the latency_tracer, that is:
8 *
9 * Copyright (C) 2004-2006 Ingo Molnar
10 * Copyright (C) 2004 William Lee Irwin III
11 */
12#include <linux/module.h>
13#include <linux/fs.h>
14#include <linux/debugfs.h>
15#include <linux/kallsyms.h>
16#include <linux/uaccess.h>
17#include <linux/ftrace.h>
18#include <trace/events/sched.h>
19
20#include "trace.h"
21
22static struct trace_array *wakeup_trace;
23static int __read_mostly tracer_enabled;
24
25static struct task_struct *wakeup_task;
26static int wakeup_cpu;
27static int wakeup_current_cpu;
28static unsigned wakeup_prio = -1;
29static int wakeup_rt;
30
31static arch_spinlock_t wakeup_lock =
32    (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
33
34static void wakeup_reset(struct trace_array *tr);
35static void __wakeup_reset(struct trace_array *tr);
36static int wakeup_graph_entry(struct ftrace_graph_ent *trace);
37static void wakeup_graph_return(struct ftrace_graph_ret *trace);
38
39static int save_lat_flag;
40
41#define TRACE_DISPLAY_GRAPH 1
42
43static struct tracer_opt trace_opts[] = {
44#ifdef CONFIG_FUNCTION_GRAPH_TRACER
45    /* display latency trace as call graph */
46    { TRACER_OPT(display-graph, TRACE_DISPLAY_GRAPH) },
47#endif
48    { } /* Empty entry */
49};
50
51static struct tracer_flags tracer_flags = {
52    .val = 0,
53    .opts = trace_opts,
54};
55
56#define is_graph() (tracer_flags.val & TRACE_DISPLAY_GRAPH)
57
58#ifdef CONFIG_FUNCTION_TRACER
59
60/*
61 * Prologue for the wakeup function tracers.
62 *
63 * Returns 1 if it is OK to continue, and preemption
64 * is disabled and data->disabled is incremented.
65 * 0 if the trace is to be ignored, and preemption
66 * is not disabled and data->disabled is
67 * kept the same.
68 *
69 * Note, this function is also used outside this ifdef but
70 * inside the #ifdef of the function graph tracer below.
71 * This is OK, since the function graph tracer is
72 * dependent on the function tracer.
73 */
74static int
75func_prolog_preempt_disable(struct trace_array *tr,
76                struct trace_array_cpu **data,
77                int *pc)
78{
79    long disabled;
80    int cpu;
81
82    if (likely(!wakeup_task))
83        return 0;
84
85    *pc = preempt_count();
86    preempt_disable_notrace();
87
88    cpu = raw_smp_processor_id();
89    if (cpu != wakeup_current_cpu)
90        goto out_enable;
91
92    *data = tr->data[cpu];
93    disabled = atomic_inc_return(&(*data)->disabled);
94    if (unlikely(disabled != 1))
95        goto out;
96
97    return 1;
98
99out:
100    atomic_dec(&(*data)->disabled);
101
102out_enable:
103    preempt_enable_notrace();
104    return 0;
105}
106
107/*
108 * wakeup uses its own tracer function to keep the overhead down:
109 */
110static void
111wakeup_tracer_call(unsigned long ip, unsigned long parent_ip)
112{
113    struct trace_array *tr = wakeup_trace;
114    struct trace_array_cpu *data;
115    unsigned long flags;
116    int pc;
117
118    if (!func_prolog_preempt_disable(tr, &data, &pc))
119        return;
120
121    local_irq_save(flags);
122    trace_function(tr, ip, parent_ip, flags, pc);
123    local_irq_restore(flags);
124
125    atomic_dec(&data->disabled);
126    preempt_enable_notrace();
127}
128
129static struct ftrace_ops trace_ops __read_mostly =
130{
131    .func = wakeup_tracer_call,
132    .flags = FTRACE_OPS_FL_GLOBAL,
133};
134#endif /* CONFIG_FUNCTION_TRACER */
135
136static int start_func_tracer(int graph)
137{
138    int ret;
139
140    if (!graph)
141        ret = register_ftrace_function(&trace_ops);
142    else
143        ret = register_ftrace_graph(&wakeup_graph_return,
144                        &wakeup_graph_entry);
145
146    if (!ret && tracing_is_enabled())
147        tracer_enabled = 1;
148    else
149        tracer_enabled = 0;
150
151    return ret;
152}
153
154static void stop_func_tracer(int graph)
155{
156    tracer_enabled = 0;
157
158    if (!graph)
159        unregister_ftrace_function(&trace_ops);
160    else
161        unregister_ftrace_graph();
162}
163
164#ifdef CONFIG_FUNCTION_GRAPH_TRACER
165static int wakeup_set_flag(u32 old_flags, u32 bit, int set)
166{
167
168    if (!(bit & TRACE_DISPLAY_GRAPH))
169        return -EINVAL;
170
171    if (!(is_graph() ^ set))
172        return 0;
173
174    stop_func_tracer(!set);
175
176    wakeup_reset(wakeup_trace);
177    tracing_max_latency = 0;
178
179    return start_func_tracer(set);
180}
181
182static int wakeup_graph_entry(struct ftrace_graph_ent *trace)
183{
184    struct trace_array *tr = wakeup_trace;
185    struct trace_array_cpu *data;
186    unsigned long flags;
187    int pc, ret = 0;
188
189    if (!func_prolog_preempt_disable(tr, &data, &pc))
190        return 0;
191
192    local_save_flags(flags);
193    ret = __trace_graph_entry(tr, trace, flags, pc);
194    atomic_dec(&data->disabled);
195    preempt_enable_notrace();
196
197    return ret;
198}
199
200static void wakeup_graph_return(struct ftrace_graph_ret *trace)
201{
202    struct trace_array *tr = wakeup_trace;
203    struct trace_array_cpu *data;
204    unsigned long flags;
205    int pc;
206
207    if (!func_prolog_preempt_disable(tr, &data, &pc))
208        return;
209
210    local_save_flags(flags);
211    __trace_graph_return(tr, trace, flags, pc);
212    atomic_dec(&data->disabled);
213
214    preempt_enable_notrace();
215    return;
216}
217
218static void wakeup_trace_open(struct trace_iterator *iter)
219{
220    if (is_graph())
221        graph_trace_open(iter);
222}
223
224static void wakeup_trace_close(struct trace_iterator *iter)
225{
226    if (iter->private)
227        graph_trace_close(iter);
228}
229
230#define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_PROC)
231
232static enum print_line_t wakeup_print_line(struct trace_iterator *iter)
233{
234    /*
235     * In graph mode call the graph tracer output function,
236     * otherwise go with the TRACE_FN event handler
237     */
238    if (is_graph())
239        return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS);
240
241    return TRACE_TYPE_UNHANDLED;
242}
243
244static void wakeup_print_header(struct seq_file *s)
245{
246    if (is_graph())
247        print_graph_headers_flags(s, GRAPH_TRACER_FLAGS);
248    else
249        trace_default_header(s);
250}
251
252static void
253__trace_function(struct trace_array *tr,
254         unsigned long ip, unsigned long parent_ip,
255         unsigned long flags, int pc)
256{
257    if (is_graph())
258        trace_graph_function(tr, ip, parent_ip, flags, pc);
259    else
260        trace_function(tr, ip, parent_ip, flags, pc);
261}
262#else
263#define __trace_function trace_function
264
265static int wakeup_set_flag(u32 old_flags, u32 bit, int set)
266{
267    return -EINVAL;
268}
269
270static int wakeup_graph_entry(struct ftrace_graph_ent *trace)
271{
272    return -1;
273}
274
275static enum print_line_t wakeup_print_line(struct trace_iterator *iter)
276{
277    return TRACE_TYPE_UNHANDLED;
278}
279
280static void wakeup_graph_return(struct ftrace_graph_ret *trace) { }
281static void wakeup_print_header(struct seq_file *s) { }
282static void wakeup_trace_open(struct trace_iterator *iter) { }
283static void wakeup_trace_close(struct trace_iterator *iter) { }
284#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
285
286/*
287 * Should this new latency be reported/recorded?
288 */
289static int report_latency(cycle_t delta)
290{
291    if (tracing_thresh) {
292        if (delta < tracing_thresh)
293            return 0;
294    } else {
295        if (delta <= tracing_max_latency)
296            return 0;
297    }
298    return 1;
299}
300
301static void
302probe_wakeup_migrate_task(void *ignore, struct task_struct *task, int cpu)
303{
304    if (task != wakeup_task)
305        return;
306
307    wakeup_current_cpu = cpu;
308}
309
310static void notrace
311probe_wakeup_sched_switch(void *ignore,
312              struct task_struct *prev, struct task_struct *next)
313{
314    struct trace_array_cpu *data;
315    cycle_t T0, T1, delta;
316    unsigned long flags;
317    long disabled;
318    int cpu;
319    int pc;
320
321    tracing_record_cmdline(prev);
322
323    if (unlikely(!tracer_enabled))
324        return;
325
326    /*
327     * When we start a new trace, we set wakeup_task to NULL
328     * and then set tracer_enabled = 1. We want to make sure
329     * that another CPU does not see the tracer_enabled = 1
330     * and the wakeup_task with an older task, that might
331     * actually be the same as next.
332     */
333    smp_rmb();
334
335    if (next != wakeup_task)
336        return;
337
338    pc = preempt_count();
339
340    /* disable local data, not wakeup_cpu data */
341    cpu = raw_smp_processor_id();
342    disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
343    if (likely(disabled != 1))
344        goto out;
345
346    local_irq_save(flags);
347    arch_spin_lock(&wakeup_lock);
348
349    /* We could race with grabbing wakeup_lock */
350    if (unlikely(!tracer_enabled || next != wakeup_task))
351        goto out_unlock;
352
353    /* The task we are waiting for is waking up */
354    data = wakeup_trace->data[wakeup_cpu];
355
356    __trace_function(wakeup_trace, CALLER_ADDR0, CALLER_ADDR1, flags, pc);
357    tracing_sched_switch_trace(wakeup_trace, prev, next, flags, pc);
358
359    T0 = data->preempt_timestamp;
360    T1 = ftrace_now(cpu);
361    delta = T1-T0;
362
363    if (!report_latency(delta))
364        goto out_unlock;
365
366    if (likely(!is_tracing_stopped())) {
367        tracing_max_latency = delta;
368        update_max_tr(wakeup_trace, wakeup_task, wakeup_cpu);
369    }
370
371out_unlock:
372    __wakeup_reset(wakeup_trace);
373    arch_spin_unlock(&wakeup_lock);
374    local_irq_restore(flags);
375out:
376    atomic_dec(&wakeup_trace->data[cpu]->disabled);
377}
378
379static void __wakeup_reset(struct trace_array *tr)
380{
381    wakeup_cpu = -1;
382    wakeup_prio = -1;
383
384    if (wakeup_task)
385        put_task_struct(wakeup_task);
386
387    wakeup_task = NULL;
388}
389
390static void wakeup_reset(struct trace_array *tr)
391{
392    unsigned long flags;
393
394    tracing_reset_online_cpus(tr);
395
396    local_irq_save(flags);
397    arch_spin_lock(&wakeup_lock);
398    __wakeup_reset(tr);
399    arch_spin_unlock(&wakeup_lock);
400    local_irq_restore(flags);
401}
402
403static void
404probe_wakeup(void *ignore, struct task_struct *p, int success)
405{
406    struct trace_array_cpu *data;
407    int cpu = smp_processor_id();
408    unsigned long flags;
409    long disabled;
410    int pc;
411
412    if (likely(!tracer_enabled))
413        return;
414
415    tracing_record_cmdline(p);
416    tracing_record_cmdline(current);
417
418    if ((wakeup_rt && !rt_task(p)) ||
419            p->prio >= wakeup_prio ||
420            p->prio >= current->prio)
421        return;
422
423    pc = preempt_count();
424    disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
425    if (unlikely(disabled != 1))
426        goto out;
427
428    /* interrupts should be off from try_to_wake_up */
429    arch_spin_lock(&wakeup_lock);
430
431    /* check for races. */
432    if (!tracer_enabled || p->prio >= wakeup_prio)
433        goto out_locked;
434
435    /* reset the trace */
436    __wakeup_reset(wakeup_trace);
437
438    wakeup_cpu = task_cpu(p);
439    wakeup_current_cpu = wakeup_cpu;
440    wakeup_prio = p->prio;
441
442    wakeup_task = p;
443    get_task_struct(wakeup_task);
444
445    local_save_flags(flags);
446
447    data = wakeup_trace->data[wakeup_cpu];
448    data->preempt_timestamp = ftrace_now(cpu);
449    tracing_sched_wakeup_trace(wakeup_trace, p, current, flags, pc);
450
451    /*
452     * We must be careful in using CALLER_ADDR2. But since wake_up
453     * is not called by an assembly function (where as schedule is)
454     * it should be safe to use it here.
455     */
456    __trace_function(wakeup_trace, CALLER_ADDR1, CALLER_ADDR2, flags, pc);
457
458out_locked:
459    arch_spin_unlock(&wakeup_lock);
460out:
461    atomic_dec(&wakeup_trace->data[cpu]->disabled);
462}
463
464static void start_wakeup_tracer(struct trace_array *tr)
465{
466    int ret;
467
468    ret = register_trace_sched_wakeup(probe_wakeup, NULL);
469    if (ret) {
470        pr_info("wakeup trace: Couldn't activate tracepoint"
471            " probe to kernel_sched_wakeup\n");
472        return;
473    }
474
475    ret = register_trace_sched_wakeup_new(probe_wakeup, NULL);
476    if (ret) {
477        pr_info("wakeup trace: Couldn't activate tracepoint"
478            " probe to kernel_sched_wakeup_new\n");
479        goto fail_deprobe;
480    }
481
482    ret = register_trace_sched_switch(probe_wakeup_sched_switch, NULL);
483    if (ret) {
484        pr_info("sched trace: Couldn't activate tracepoint"
485            " probe to kernel_sched_switch\n");
486        goto fail_deprobe_wake_new;
487    }
488
489    ret = register_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL);
490    if (ret) {
491        pr_info("wakeup trace: Couldn't activate tracepoint"
492            " probe to kernel_sched_migrate_task\n");
493        return;
494    }
495
496    wakeup_reset(tr);
497
498    /*
499     * Don't let the tracer_enabled = 1 show up before
500     * the wakeup_task is reset. This may be overkill since
501     * wakeup_reset does a spin_unlock after setting the
502     * wakeup_task to NULL, but I want to be safe.
503     * This is a slow path anyway.
504     */
505    smp_wmb();
506
507    if (start_func_tracer(is_graph()))
508        printk(KERN_ERR "failed to start wakeup tracer\n");
509
510    return;
511fail_deprobe_wake_new:
512    unregister_trace_sched_wakeup_new(probe_wakeup, NULL);
513fail_deprobe:
514    unregister_trace_sched_wakeup(probe_wakeup, NULL);
515}
516
517static void stop_wakeup_tracer(struct trace_array *tr)
518{
519    tracer_enabled = 0;
520    stop_func_tracer(is_graph());
521    unregister_trace_sched_switch(probe_wakeup_sched_switch, NULL);
522    unregister_trace_sched_wakeup_new(probe_wakeup, NULL);
523    unregister_trace_sched_wakeup(probe_wakeup, NULL);
524    unregister_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL);
525}
526
527static int __wakeup_tracer_init(struct trace_array *tr)
528{
529    save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
530    trace_flags |= TRACE_ITER_LATENCY_FMT;
531
532    tracing_max_latency = 0;
533    wakeup_trace = tr;
534    start_wakeup_tracer(tr);
535    return 0;
536}
537
538static int wakeup_tracer_init(struct trace_array *tr)
539{
540    wakeup_rt = 0;
541    return __wakeup_tracer_init(tr);
542}
543
544static int wakeup_rt_tracer_init(struct trace_array *tr)
545{
546    wakeup_rt = 1;
547    return __wakeup_tracer_init(tr);
548}
549
550static void wakeup_tracer_reset(struct trace_array *tr)
551{
552    stop_wakeup_tracer(tr);
553    /* make sure we put back any tasks we are tracing */
554    wakeup_reset(tr);
555
556    if (!save_lat_flag)
557        trace_flags &= ~TRACE_ITER_LATENCY_FMT;
558}
559
560static void wakeup_tracer_start(struct trace_array *tr)
561{
562    wakeup_reset(tr);
563    tracer_enabled = 1;
564}
565
566static void wakeup_tracer_stop(struct trace_array *tr)
567{
568    tracer_enabled = 0;
569}
570
571static struct tracer wakeup_tracer __read_mostly =
572{
573    .name = "wakeup",
574    .init = wakeup_tracer_init,
575    .reset = wakeup_tracer_reset,
576    .start = wakeup_tracer_start,
577    .stop = wakeup_tracer_stop,
578    .print_max = 1,
579    .print_header = wakeup_print_header,
580    .print_line = wakeup_print_line,
581    .flags = &tracer_flags,
582    .set_flag = wakeup_set_flag,
583#ifdef CONFIG_FTRACE_SELFTEST
584    .selftest = trace_selftest_startup_wakeup,
585#endif
586    .open = wakeup_trace_open,
587    .close = wakeup_trace_close,
588    .use_max_tr = 1,
589};
590
591static struct tracer wakeup_rt_tracer __read_mostly =
592{
593    .name = "wakeup_rt",
594    .init = wakeup_rt_tracer_init,
595    .reset = wakeup_tracer_reset,
596    .start = wakeup_tracer_start,
597    .stop = wakeup_tracer_stop,
598    .wait_pipe = poll_wait_pipe,
599    .print_max = 1,
600    .print_header = wakeup_print_header,
601    .print_line = wakeup_print_line,
602    .flags = &tracer_flags,
603    .set_flag = wakeup_set_flag,
604#ifdef CONFIG_FTRACE_SELFTEST
605    .selftest = trace_selftest_startup_wakeup,
606#endif
607    .open = wakeup_trace_open,
608    .close = wakeup_trace_close,
609    .use_max_tr = 1,
610};
611
612__init static int init_wakeup_tracer(void)
613{
614    int ret;
615
616    ret = register_tracer(&wakeup_tracer);
617    if (ret)
618        return ret;
619
620    ret = register_tracer(&wakeup_rt_tracer);
621    if (ret)
622        return ret;
623
624    return 0;
625}
626device_initcall(init_wakeup_tracer);
627

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