Root/kernel/trace/trace_selftest.c

1/* Include in trace.c */
2
3#include <linux/stringify.h>
4#include <linux/kthread.h>
5#include <linux/delay.h>
6#include <linux/slab.h>
7
8static inline int trace_valid_entry(struct trace_entry *entry)
9{
10    switch (entry->type) {
11    case TRACE_FN:
12    case TRACE_CTX:
13    case TRACE_WAKE:
14    case TRACE_STACK:
15    case TRACE_PRINT:
16    case TRACE_BRANCH:
17    case TRACE_GRAPH_ENT:
18    case TRACE_GRAPH_RET:
19        return 1;
20    }
21    return 0;
22}
23
24static int trace_test_buffer_cpu(struct trace_array *tr, int cpu)
25{
26    struct ring_buffer_event *event;
27    struct trace_entry *entry;
28    unsigned int loops = 0;
29
30    while ((event = ring_buffer_consume(tr->buffer, cpu, NULL, NULL))) {
31        entry = ring_buffer_event_data(event);
32
33        /*
34         * The ring buffer is a size of trace_buf_size, if
35         * we loop more than the size, there's something wrong
36         * with the ring buffer.
37         */
38        if (loops++ > trace_buf_size) {
39            printk(KERN_CONT ".. bad ring buffer ");
40            goto failed;
41        }
42        if (!trace_valid_entry(entry)) {
43            printk(KERN_CONT ".. invalid entry %d ",
44                entry->type);
45            goto failed;
46        }
47    }
48    return 0;
49
50 failed:
51    /* disable tracing */
52    tracing_disabled = 1;
53    printk(KERN_CONT ".. corrupted trace buffer .. ");
54    return -1;
55}
56
57/*
58 * Test the trace buffer to see if all the elements
59 * are still sane.
60 */
61static int trace_test_buffer(struct trace_array *tr, unsigned long *count)
62{
63    unsigned long flags, cnt = 0;
64    int cpu, ret = 0;
65
66    /* Don't allow flipping of max traces now */
67    local_irq_save(flags);
68    arch_spin_lock(&ftrace_max_lock);
69
70    cnt = ring_buffer_entries(tr->buffer);
71
72    /*
73     * The trace_test_buffer_cpu runs a while loop to consume all data.
74     * If the calling tracer is broken, and is constantly filling
75     * the buffer, this will run forever, and hard lock the box.
76     * We disable the ring buffer while we do this test to prevent
77     * a hard lock up.
78     */
79    tracing_off();
80    for_each_possible_cpu(cpu) {
81        ret = trace_test_buffer_cpu(tr, cpu);
82        if (ret)
83            break;
84    }
85    tracing_on();
86    arch_spin_unlock(&ftrace_max_lock);
87    local_irq_restore(flags);
88
89    if (count)
90        *count = cnt;
91
92    return ret;
93}
94
95static inline void warn_failed_init_tracer(struct tracer *trace, int init_ret)
96{
97    printk(KERN_WARNING "Failed to init %s tracer, init returned %d\n",
98        trace->name, init_ret);
99}
100#ifdef CONFIG_FUNCTION_TRACER
101
102#ifdef CONFIG_DYNAMIC_FTRACE
103
104static int trace_selftest_test_probe1_cnt;
105static void trace_selftest_test_probe1_func(unsigned long ip,
106                        unsigned long pip)
107{
108    trace_selftest_test_probe1_cnt++;
109}
110
111static int trace_selftest_test_probe2_cnt;
112static void trace_selftest_test_probe2_func(unsigned long ip,
113                        unsigned long pip)
114{
115    trace_selftest_test_probe2_cnt++;
116}
117
118static int trace_selftest_test_probe3_cnt;
119static void trace_selftest_test_probe3_func(unsigned long ip,
120                        unsigned long pip)
121{
122    trace_selftest_test_probe3_cnt++;
123}
124
125static int trace_selftest_test_global_cnt;
126static void trace_selftest_test_global_func(unsigned long ip,
127                        unsigned long pip)
128{
129    trace_selftest_test_global_cnt++;
130}
131
132static int trace_selftest_test_dyn_cnt;
133static void trace_selftest_test_dyn_func(unsigned long ip,
134                     unsigned long pip)
135{
136    trace_selftest_test_dyn_cnt++;
137}
138
139static struct ftrace_ops test_probe1 = {
140    .func = trace_selftest_test_probe1_func,
141};
142
143static struct ftrace_ops test_probe2 = {
144    .func = trace_selftest_test_probe2_func,
145};
146
147static struct ftrace_ops test_probe3 = {
148    .func = trace_selftest_test_probe3_func,
149};
150
151static struct ftrace_ops test_global = {
152    .func = trace_selftest_test_global_func,
153    .flags = FTRACE_OPS_FL_GLOBAL,
154};
155
156static void print_counts(void)
157{
158    printk("(%d %d %d %d %d) ",
159           trace_selftest_test_probe1_cnt,
160           trace_selftest_test_probe2_cnt,
161           trace_selftest_test_probe3_cnt,
162           trace_selftest_test_global_cnt,
163           trace_selftest_test_dyn_cnt);
164}
165
166static void reset_counts(void)
167{
168    trace_selftest_test_probe1_cnt = 0;
169    trace_selftest_test_probe2_cnt = 0;
170    trace_selftest_test_probe3_cnt = 0;
171    trace_selftest_test_global_cnt = 0;
172    trace_selftest_test_dyn_cnt = 0;
173}
174
175static int trace_selftest_ops(int cnt)
176{
177    int save_ftrace_enabled = ftrace_enabled;
178    struct ftrace_ops *dyn_ops;
179    char *func1_name;
180    char *func2_name;
181    int len1;
182    int len2;
183    int ret = -1;
184
185    printk(KERN_CONT "PASSED\n");
186    pr_info("Testing dynamic ftrace ops #%d: ", cnt);
187
188    ftrace_enabled = 1;
189    reset_counts();
190
191    /* Handle PPC64 '.' name */
192    func1_name = "*" __stringify(DYN_FTRACE_TEST_NAME);
193    func2_name = "*" __stringify(DYN_FTRACE_TEST_NAME2);
194    len1 = strlen(func1_name);
195    len2 = strlen(func2_name);
196
197    /*
198     * Probe 1 will trace function 1.
199     * Probe 2 will trace function 2.
200     * Probe 3 will trace functions 1 and 2.
201     */
202    ftrace_set_filter(&test_probe1, func1_name, len1, 1);
203    ftrace_set_filter(&test_probe2, func2_name, len2, 1);
204    ftrace_set_filter(&test_probe3, func1_name, len1, 1);
205    ftrace_set_filter(&test_probe3, func2_name, len2, 0);
206
207    register_ftrace_function(&test_probe1);
208    register_ftrace_function(&test_probe2);
209    register_ftrace_function(&test_probe3);
210    register_ftrace_function(&test_global);
211
212    DYN_FTRACE_TEST_NAME();
213
214    print_counts();
215
216    if (trace_selftest_test_probe1_cnt != 1)
217        goto out;
218    if (trace_selftest_test_probe2_cnt != 0)
219        goto out;
220    if (trace_selftest_test_probe3_cnt != 1)
221        goto out;
222    if (trace_selftest_test_global_cnt == 0)
223        goto out;
224
225    DYN_FTRACE_TEST_NAME2();
226
227    print_counts();
228
229    if (trace_selftest_test_probe1_cnt != 1)
230        goto out;
231    if (trace_selftest_test_probe2_cnt != 1)
232        goto out;
233    if (trace_selftest_test_probe3_cnt != 2)
234        goto out;
235
236    /* Add a dynamic probe */
237    dyn_ops = kzalloc(sizeof(*dyn_ops), GFP_KERNEL);
238    if (!dyn_ops) {
239        printk("MEMORY ERROR ");
240        goto out;
241    }
242
243    dyn_ops->func = trace_selftest_test_dyn_func;
244
245    register_ftrace_function(dyn_ops);
246
247    trace_selftest_test_global_cnt = 0;
248
249    DYN_FTRACE_TEST_NAME();
250
251    print_counts();
252
253    if (trace_selftest_test_probe1_cnt != 2)
254        goto out_free;
255    if (trace_selftest_test_probe2_cnt != 1)
256        goto out_free;
257    if (trace_selftest_test_probe3_cnt != 3)
258        goto out_free;
259    if (trace_selftest_test_global_cnt == 0)
260        goto out;
261    if (trace_selftest_test_dyn_cnt == 0)
262        goto out_free;
263
264    DYN_FTRACE_TEST_NAME2();
265
266    print_counts();
267
268    if (trace_selftest_test_probe1_cnt != 2)
269        goto out_free;
270    if (trace_selftest_test_probe2_cnt != 2)
271        goto out_free;
272    if (trace_selftest_test_probe3_cnt != 4)
273        goto out_free;
274
275    ret = 0;
276 out_free:
277    unregister_ftrace_function(dyn_ops);
278    kfree(dyn_ops);
279
280 out:
281    /* Purposely unregister in the same order */
282    unregister_ftrace_function(&test_probe1);
283    unregister_ftrace_function(&test_probe2);
284    unregister_ftrace_function(&test_probe3);
285    unregister_ftrace_function(&test_global);
286
287    /* Make sure everything is off */
288    reset_counts();
289    DYN_FTRACE_TEST_NAME();
290    DYN_FTRACE_TEST_NAME();
291
292    if (trace_selftest_test_probe1_cnt ||
293        trace_selftest_test_probe2_cnt ||
294        trace_selftest_test_probe3_cnt ||
295        trace_selftest_test_global_cnt ||
296        trace_selftest_test_dyn_cnt)
297        ret = -1;
298
299    ftrace_enabled = save_ftrace_enabled;
300
301    return ret;
302}
303
304/* Test dynamic code modification and ftrace filters */
305int trace_selftest_startup_dynamic_tracing(struct tracer *trace,
306                       struct trace_array *tr,
307                       int (*func)(void))
308{
309    int save_ftrace_enabled = ftrace_enabled;
310    int save_tracer_enabled = tracer_enabled;
311    unsigned long count;
312    char *func_name;
313    int ret;
314
315    /* The ftrace test PASSED */
316    printk(KERN_CONT "PASSED\n");
317    pr_info("Testing dynamic ftrace: ");
318
319    /* enable tracing, and record the filter function */
320    ftrace_enabled = 1;
321    tracer_enabled = 1;
322
323    /* passed in by parameter to fool gcc from optimizing */
324    func();
325
326    /*
327     * Some archs *cough*PowerPC*cough* add characters to the
328     * start of the function names. We simply put a '*' to
329     * accommodate them.
330     */
331    func_name = "*" __stringify(DYN_FTRACE_TEST_NAME);
332
333    /* filter only on our function */
334    ftrace_set_global_filter(func_name, strlen(func_name), 1);
335
336    /* enable tracing */
337    ret = tracer_init(trace, tr);
338    if (ret) {
339        warn_failed_init_tracer(trace, ret);
340        goto out;
341    }
342
343    /* Sleep for a 1/10 of a second */
344    msleep(100);
345
346    /* we should have nothing in the buffer */
347    ret = trace_test_buffer(tr, &count);
348    if (ret)
349        goto out;
350
351    if (count) {
352        ret = -1;
353        printk(KERN_CONT ".. filter did not filter .. ");
354        goto out;
355    }
356
357    /* call our function again */
358    func();
359
360    /* sleep again */
361    msleep(100);
362
363    /* stop the tracing. */
364    tracing_stop();
365    ftrace_enabled = 0;
366
367    /* check the trace buffer */
368    ret = trace_test_buffer(tr, &count);
369    tracing_start();
370
371    /* we should only have one item */
372    if (!ret && count != 1) {
373        trace->reset(tr);
374        printk(KERN_CONT ".. filter failed count=%ld ..", count);
375        ret = -1;
376        goto out;
377    }
378
379    /* Test the ops with global tracing running */
380    ret = trace_selftest_ops(1);
381    trace->reset(tr);
382
383 out:
384    ftrace_enabled = save_ftrace_enabled;
385    tracer_enabled = save_tracer_enabled;
386
387    /* Enable tracing on all functions again */
388    ftrace_set_global_filter(NULL, 0, 1);
389
390    /* Test the ops with global tracing off */
391    if (!ret)
392        ret = trace_selftest_ops(2);
393
394    return ret;
395}
396#else
397# define trace_selftest_startup_dynamic_tracing(trace, tr, func) ({ 0; })
398#endif /* CONFIG_DYNAMIC_FTRACE */
399
400/*
401 * Simple verification test of ftrace function tracer.
402 * Enable ftrace, sleep 1/10 second, and then read the trace
403 * buffer to see if all is in order.
404 */
405int
406trace_selftest_startup_function(struct tracer *trace, struct trace_array *tr)
407{
408    int save_ftrace_enabled = ftrace_enabled;
409    int save_tracer_enabled = tracer_enabled;
410    unsigned long count;
411    int ret;
412
413    /* make sure msleep has been recorded */
414    msleep(1);
415
416    /* start the tracing */
417    ftrace_enabled = 1;
418    tracer_enabled = 1;
419
420    ret = tracer_init(trace, tr);
421    if (ret) {
422        warn_failed_init_tracer(trace, ret);
423        goto out;
424    }
425
426    /* Sleep for a 1/10 of a second */
427    msleep(100);
428    /* stop the tracing. */
429    tracing_stop();
430    ftrace_enabled = 0;
431
432    /* check the trace buffer */
433    ret = trace_test_buffer(tr, &count);
434    trace->reset(tr);
435    tracing_start();
436
437    if (!ret && !count) {
438        printk(KERN_CONT ".. no entries found ..");
439        ret = -1;
440        goto out;
441    }
442
443    ret = trace_selftest_startup_dynamic_tracing(trace, tr,
444                             DYN_FTRACE_TEST_NAME);
445
446 out:
447    ftrace_enabled = save_ftrace_enabled;
448    tracer_enabled = save_tracer_enabled;
449
450    /* kill ftrace totally if we failed */
451    if (ret)
452        ftrace_kill();
453
454    return ret;
455}
456#endif /* CONFIG_FUNCTION_TRACER */
457
458
459#ifdef CONFIG_FUNCTION_GRAPH_TRACER
460
461/* Maximum number of functions to trace before diagnosing a hang */
462#define GRAPH_MAX_FUNC_TEST 100000000
463
464static void
465__ftrace_dump(bool disable_tracing, enum ftrace_dump_mode oops_dump_mode);
466static unsigned int graph_hang_thresh;
467
468/* Wrap the real function entry probe to avoid possible hanging */
469static int trace_graph_entry_watchdog(struct ftrace_graph_ent *trace)
470{
471    /* This is harmlessly racy, we want to approximately detect a hang */
472    if (unlikely(++graph_hang_thresh > GRAPH_MAX_FUNC_TEST)) {
473        ftrace_graph_stop();
474        printk(KERN_WARNING "BUG: Function graph tracer hang!\n");
475        if (ftrace_dump_on_oops)
476            __ftrace_dump(false, DUMP_ALL);
477        return 0;
478    }
479
480    return trace_graph_entry(trace);
481}
482
483/*
484 * Pretty much the same than for the function tracer from which the selftest
485 * has been borrowed.
486 */
487int
488trace_selftest_startup_function_graph(struct tracer *trace,
489                    struct trace_array *tr)
490{
491    int ret;
492    unsigned long count;
493
494    /*
495     * Simulate the init() callback but we attach a watchdog callback
496     * to detect and recover from possible hangs
497     */
498    tracing_reset_online_cpus(tr);
499    set_graph_array(tr);
500    ret = register_ftrace_graph(&trace_graph_return,
501                    &trace_graph_entry_watchdog);
502    if (ret) {
503        warn_failed_init_tracer(trace, ret);
504        goto out;
505    }
506    tracing_start_cmdline_record();
507
508    /* Sleep for a 1/10 of a second */
509    msleep(100);
510
511    /* Have we just recovered from a hang? */
512    if (graph_hang_thresh > GRAPH_MAX_FUNC_TEST) {
513        tracing_selftest_disabled = true;
514        ret = -1;
515        goto out;
516    }
517
518    tracing_stop();
519
520    /* check the trace buffer */
521    ret = trace_test_buffer(tr, &count);
522
523    trace->reset(tr);
524    tracing_start();
525
526    if (!ret && !count) {
527        printk(KERN_CONT ".. no entries found ..");
528        ret = -1;
529        goto out;
530    }
531
532    /* Don't test dynamic tracing, the function tracer already did */
533
534out:
535    /* Stop it if we failed */
536    if (ret)
537        ftrace_graph_stop();
538
539    return ret;
540}
541#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
542
543
544#ifdef CONFIG_IRQSOFF_TRACER
545int
546trace_selftest_startup_irqsoff(struct tracer *trace, struct trace_array *tr)
547{
548    unsigned long save_max = tracing_max_latency;
549    unsigned long count;
550    int ret;
551
552    /* start the tracing */
553    ret = tracer_init(trace, tr);
554    if (ret) {
555        warn_failed_init_tracer(trace, ret);
556        return ret;
557    }
558
559    /* reset the max latency */
560    tracing_max_latency = 0;
561    /* disable interrupts for a bit */
562    local_irq_disable();
563    udelay(100);
564    local_irq_enable();
565
566    /*
567     * Stop the tracer to avoid a warning subsequent
568     * to buffer flipping failure because tracing_stop()
569     * disables the tr and max buffers, making flipping impossible
570     * in case of parallels max irqs off latencies.
571     */
572    trace->stop(tr);
573    /* stop the tracing. */
574    tracing_stop();
575    /* check both trace buffers */
576    ret = trace_test_buffer(tr, NULL);
577    if (!ret)
578        ret = trace_test_buffer(&max_tr, &count);
579    trace->reset(tr);
580    tracing_start();
581
582    if (!ret && !count) {
583        printk(KERN_CONT ".. no entries found ..");
584        ret = -1;
585    }
586
587    tracing_max_latency = save_max;
588
589    return ret;
590}
591#endif /* CONFIG_IRQSOFF_TRACER */
592
593#ifdef CONFIG_PREEMPT_TRACER
594int
595trace_selftest_startup_preemptoff(struct tracer *trace, struct trace_array *tr)
596{
597    unsigned long save_max = tracing_max_latency;
598    unsigned long count;
599    int ret;
600
601    /*
602     * Now that the big kernel lock is no longer preemptable,
603     * and this is called with the BKL held, it will always
604     * fail. If preemption is already disabled, simply
605     * pass the test. When the BKL is removed, or becomes
606     * preemptible again, we will once again test this,
607     * so keep it in.
608     */
609    if (preempt_count()) {
610        printk(KERN_CONT "can not test ... force ");
611        return 0;
612    }
613
614    /* start the tracing */
615    ret = tracer_init(trace, tr);
616    if (ret) {
617        warn_failed_init_tracer(trace, ret);
618        return ret;
619    }
620
621    /* reset the max latency */
622    tracing_max_latency = 0;
623    /* disable preemption for a bit */
624    preempt_disable();
625    udelay(100);
626    preempt_enable();
627
628    /*
629     * Stop the tracer to avoid a warning subsequent
630     * to buffer flipping failure because tracing_stop()
631     * disables the tr and max buffers, making flipping impossible
632     * in case of parallels max preempt off latencies.
633     */
634    trace->stop(tr);
635    /* stop the tracing. */
636    tracing_stop();
637    /* check both trace buffers */
638    ret = trace_test_buffer(tr, NULL);
639    if (!ret)
640        ret = trace_test_buffer(&max_tr, &count);
641    trace->reset(tr);
642    tracing_start();
643
644    if (!ret && !count) {
645        printk(KERN_CONT ".. no entries found ..");
646        ret = -1;
647    }
648
649    tracing_max_latency = save_max;
650
651    return ret;
652}
653#endif /* CONFIG_PREEMPT_TRACER */
654
655#if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
656int
657trace_selftest_startup_preemptirqsoff(struct tracer *trace, struct trace_array *tr)
658{
659    unsigned long save_max = tracing_max_latency;
660    unsigned long count;
661    int ret;
662
663    /*
664     * Now that the big kernel lock is no longer preemptable,
665     * and this is called with the BKL held, it will always
666     * fail. If preemption is already disabled, simply
667     * pass the test. When the BKL is removed, or becomes
668     * preemptible again, we will once again test this,
669     * so keep it in.
670     */
671    if (preempt_count()) {
672        printk(KERN_CONT "can not test ... force ");
673        return 0;
674    }
675
676    /* start the tracing */
677    ret = tracer_init(trace, tr);
678    if (ret) {
679        warn_failed_init_tracer(trace, ret);
680        goto out_no_start;
681    }
682
683    /* reset the max latency */
684    tracing_max_latency = 0;
685
686    /* disable preemption and interrupts for a bit */
687    preempt_disable();
688    local_irq_disable();
689    udelay(100);
690    preempt_enable();
691    /* reverse the order of preempt vs irqs */
692    local_irq_enable();
693
694    /*
695     * Stop the tracer to avoid a warning subsequent
696     * to buffer flipping failure because tracing_stop()
697     * disables the tr and max buffers, making flipping impossible
698     * in case of parallels max irqs/preempt off latencies.
699     */
700    trace->stop(tr);
701    /* stop the tracing. */
702    tracing_stop();
703    /* check both trace buffers */
704    ret = trace_test_buffer(tr, NULL);
705    if (ret)
706        goto out;
707
708    ret = trace_test_buffer(&max_tr, &count);
709    if (ret)
710        goto out;
711
712    if (!ret && !count) {
713        printk(KERN_CONT ".. no entries found ..");
714        ret = -1;
715        goto out;
716    }
717
718    /* do the test by disabling interrupts first this time */
719    tracing_max_latency = 0;
720    tracing_start();
721    trace->start(tr);
722
723    preempt_disable();
724    local_irq_disable();
725    udelay(100);
726    preempt_enable();
727    /* reverse the order of preempt vs irqs */
728    local_irq_enable();
729
730    trace->stop(tr);
731    /* stop the tracing. */
732    tracing_stop();
733    /* check both trace buffers */
734    ret = trace_test_buffer(tr, NULL);
735    if (ret)
736        goto out;
737
738    ret = trace_test_buffer(&max_tr, &count);
739
740    if (!ret && !count) {
741        printk(KERN_CONT ".. no entries found ..");
742        ret = -1;
743        goto out;
744    }
745
746out:
747    tracing_start();
748out_no_start:
749    trace->reset(tr);
750    tracing_max_latency = save_max;
751
752    return ret;
753}
754#endif /* CONFIG_IRQSOFF_TRACER && CONFIG_PREEMPT_TRACER */
755
756#ifdef CONFIG_NOP_TRACER
757int
758trace_selftest_startup_nop(struct tracer *trace, struct trace_array *tr)
759{
760    /* What could possibly go wrong? */
761    return 0;
762}
763#endif
764
765#ifdef CONFIG_SCHED_TRACER
766static int trace_wakeup_test_thread(void *data)
767{
768    /* Make this a RT thread, doesn't need to be too high */
769    static const struct sched_param param = { .sched_priority = 5 };
770    struct completion *x = data;
771
772    sched_setscheduler(current, SCHED_FIFO, &param);
773
774    /* Make it know we have a new prio */
775    complete(x);
776
777    /* now go to sleep and let the test wake us up */
778    set_current_state(TASK_INTERRUPTIBLE);
779    schedule();
780
781    /* we are awake, now wait to disappear */
782    while (!kthread_should_stop()) {
783        /*
784         * This is an RT task, do short sleeps to let
785         * others run.
786         */
787        msleep(100);
788    }
789
790    return 0;
791}
792
793int
794trace_selftest_startup_wakeup(struct tracer *trace, struct trace_array *tr)
795{
796    unsigned long save_max = tracing_max_latency;
797    struct task_struct *p;
798    struct completion isrt;
799    unsigned long count;
800    int ret;
801
802    init_completion(&isrt);
803
804    /* create a high prio thread */
805    p = kthread_run(trace_wakeup_test_thread, &isrt, "ftrace-test");
806    if (IS_ERR(p)) {
807        printk(KERN_CONT "Failed to create ftrace wakeup test thread ");
808        return -1;
809    }
810
811    /* make sure the thread is running at an RT prio */
812    wait_for_completion(&isrt);
813
814    /* start the tracing */
815    ret = tracer_init(trace, tr);
816    if (ret) {
817        warn_failed_init_tracer(trace, ret);
818        return ret;
819    }
820
821    /* reset the max latency */
822    tracing_max_latency = 0;
823
824    /* sleep to let the RT thread sleep too */
825    msleep(100);
826
827    /*
828     * Yes this is slightly racy. It is possible that for some
829     * strange reason that the RT thread we created, did not
830     * call schedule for 100ms after doing the completion,
831     * and we do a wakeup on a task that already is awake.
832     * But that is extremely unlikely, and the worst thing that
833     * happens in such a case, is that we disable tracing.
834     * Honestly, if this race does happen something is horrible
835     * wrong with the system.
836     */
837
838    wake_up_process(p);
839
840    /* give a little time to let the thread wake up */
841    msleep(100);
842
843    /* stop the tracing. */
844    tracing_stop();
845    /* check both trace buffers */
846    ret = trace_test_buffer(tr, NULL);
847    if (!ret)
848        ret = trace_test_buffer(&max_tr, &count);
849
850
851    trace->reset(tr);
852    tracing_start();
853
854    tracing_max_latency = save_max;
855
856    /* kill the thread */
857    kthread_stop(p);
858
859    if (!ret && !count) {
860        printk(KERN_CONT ".. no entries found ..");
861        ret = -1;
862    }
863
864    return ret;
865}
866#endif /* CONFIG_SCHED_TRACER */
867
868#ifdef CONFIG_CONTEXT_SWITCH_TRACER
869int
870trace_selftest_startup_sched_switch(struct tracer *trace, struct trace_array *tr)
871{
872    unsigned long count;
873    int ret;
874
875    /* start the tracing */
876    ret = tracer_init(trace, tr);
877    if (ret) {
878        warn_failed_init_tracer(trace, ret);
879        return ret;
880    }
881
882    /* Sleep for a 1/10 of a second */
883    msleep(100);
884    /* stop the tracing. */
885    tracing_stop();
886    /* check the trace buffer */
887    ret = trace_test_buffer(tr, &count);
888    trace->reset(tr);
889    tracing_start();
890
891    if (!ret && !count) {
892        printk(KERN_CONT ".. no entries found ..");
893        ret = -1;
894    }
895
896    return ret;
897}
898#endif /* CONFIG_CONTEXT_SWITCH_TRACER */
899
900#ifdef CONFIG_BRANCH_TRACER
901int
902trace_selftest_startup_branch(struct tracer *trace, struct trace_array *tr)
903{
904    unsigned long count;
905    int ret;
906
907    /* start the tracing */
908    ret = tracer_init(trace, tr);
909    if (ret) {
910        warn_failed_init_tracer(trace, ret);
911        return ret;
912    }
913
914    /* Sleep for a 1/10 of a second */
915    msleep(100);
916    /* stop the tracing. */
917    tracing_stop();
918    /* check the trace buffer */
919    ret = trace_test_buffer(tr, &count);
920    trace->reset(tr);
921    tracing_start();
922
923    if (!ret && !count) {
924        printk(KERN_CONT ".. no entries found ..");
925        ret = -1;
926    }
927
928    return ret;
929}
930#endif /* CONFIG_BRANCH_TRACER */
931
932

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