1 /******************************************************************************
2 *
3 * Copyright © International Business Machines Corp., 2006-2008
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
13 * the GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
18 *
19 * NAME
20 * librttest.c
21 *
22 * DESCRIPTION
23 * A set of commonly used convenience functions for writing
24 * threaded realtime test cases.
25 *
26 * USAGE:
27 * To be included in testcases.
28 *
29 * AUTHOR
30 * Darren Hart <dvhltc@us.ibm.com>
31 *
32 * HISTORY
33 * 2006-Apr-26: Initial version by Darren Hart
34 * 2006-May-08: Added atomic_{inc,set,get}, thread struct, debug function,
35 * rt_init, buffered printing -- Vernon Mauery
36 * 2006-May-09: improved command line argument handling
37 * 2007-Jul-12: Added latency tracing functions and I/O helper functions
38 * -- Josh triplett
39 * 2008-Jan-10: Added RR thread support to tests -- Chirag Jog
40 *
41 *****************************************************************************/
42
43 #include <librttest.h>
44 #include <libstats.h>
45
46 #include <stdio.h>
47 #include <stdlib.h>
48 #include <signal.h>
49 #include <time.h>
50 #include <string.h>
51 #include <pthread.h>
52 #include <sched.h>
53 #include <errno.h>
54 #include <unistd.h>
55 #include <getopt.h>
56 #include <sys/prctl.h>
57 #include <sys/stat.h>
58 #include <sys/syscall.h>
59 #include <sys/types.h>
60 #include <sys/mman.h>
61 #include <fcntl.h>
62 #include <math.h>
63
64 static LIST_HEAD(_threads);
65 static atomic_t _thread_count = { -1 };
66 static unsigned long iters_per_us;
67
68 pthread_mutex_t _buffer_mutex;
69 char *_print_buffer = NULL;
70 int _print_buffer_offset = 0;
71 int _dbg_lvl = 0;
72 double pass_criteria;
73
74 static int _use_pi = 1;
75
76 /* function implementations */
rt_help(void)77 void rt_help(void)
78 {
79 printf("librt standard options:\n");
80 printf
81 (" -b(0,1) 1:enable buffered output, 0:diable buffered output\n");
82 printf(" -p(0,1) 0:don't use pi mutexes, 1:use pi mutexes\n");
83 printf(" -m use mlockall\n");
84 printf
85 (" -v[0-4] 0:no debug, 1:DBG_ERR, 2:DBG_WARN, 3:DBG_INFO, 4:DBG_DEBUG\n");
86 printf(" -s Enable saving stats data (default disabled)\n");
87 printf(" -c Set pass criteria\n");
88 }
89
90 /* Calibrate the busy work loop */
calibrate_busyloop(void)91 void calibrate_busyloop(void)
92 {
93 volatile int i = CALIBRATE_LOOPS;
94 nsec_t start, end;
95
96 start = rt_gettime();
97 while (--i > 0) {
98 continue;
99 }
100 end = rt_gettime();
101
102 iters_per_us = (CALIBRATE_LOOPS * NS_PER_US) / (end - start);
103 }
104
rt_init_long(const char * options,const struct option * longopts,int (* parse_arg)(int option,char * value),int argc,char * argv[])105 int rt_init_long(const char *options, const struct option *longopts,
106 int (*parse_arg) (int option, char *value), int argc,
107 char *argv[])
108 {
109 const struct option *cur_opt;
110 int use_buffer = 1;
111 char *longopt_vals;
112 size_t i;
113 int c;
114 opterr = 0;
115 int mlock = 0;
116 char *all_options;
117
118 if (asprintf(&all_options, ":b:mp:v:sc:%s", options) == -1) {
119 fprintf(stderr,
120 "Failed to allocate string for option string\n");
121 exit(1);
122 }
123
124 /* Check for duplicate options in optstring */
125 for (i = 0; i < strlen(all_options); i++) {
126 char opt = all_options[i];
127
128 if (opt == ':')
129 continue;
130
131 /* Search ahead */
132 if (strchr(&all_options[i + 1], opt)) {
133 fprintf(stderr,
134 "Programmer error -- argument -%c already used at least twice\n",
135 opt);
136 exit(1);
137 }
138 }
139
140 /* Ensure each long options has a known unique short option in val. */
141 longopt_vals = "";
142 cur_opt = longopts;
143 while (cur_opt && cur_opt->name) {
144 if (cur_opt->flag) {
145 fprintf(stderr, "Programmer error -- argument --%s flag"
146 " is non-null\n", cur_opt->name);
147 exit(1);
148 }
149 if (!strchr(all_options, cur_opt->val)) {
150 fprintf(stderr, "Programmer error -- argument --%s "
151 "shortopt -%c wasn't listed in options (%s)\n",
152 cur_opt->name, cur_opt->val, all_options);
153 exit(1);
154 }
155 if (strchr(longopt_vals, cur_opt->val)) {
156 fprintf(stderr, "Programmer error -- argument --%s "
157 "shortopt -%c is used more than once\n",
158 cur_opt->name, cur_opt->val);
159 exit(1);
160 }
161 if (asprintf(&longopt_vals, "%s%c", longopt_vals, cur_opt->val)
162 < 0) {
163 perror("asprintf");
164 exit(2);
165 }
166 cur_opt++;
167 }
168
169 while ((c = getopt_long(argc, argv, all_options, longopts, NULL)) != -1) {
170 switch (c) {
171 case 'c':
172 pass_criteria = atof(optarg);
173 break;
174 case 'b':
175 use_buffer = atoi(optarg);
176 break;
177 case 'p':
178 _use_pi = atoi(optarg);
179 break;
180 case 'm':
181 mlock = 1;
182 break;
183 case 'v':
184 _dbg_lvl = atoi(optarg);
185 break;
186 case 's':
187 save_stats = 1;
188 break;
189 case ':':
190 if (optopt == '-')
191 fprintf(stderr, "long option missing arg\n");
192 else
193 fprintf(stderr, "option -%c: missing arg\n",
194 optopt);
195 parse_arg('h', optarg); /* Just to display usage */
196 exit(1); /* Just in case. (should normally be done by usage()) */
197 case '?':
198 if (optopt == '-')
199 fprintf(stderr, "unrecognized long option\n");
200 else
201 fprintf(stderr, "option -%c not recognized\n",
202 optopt);
203 parse_arg('h', optarg); /* Just to display usage */
204 exit(1); /* Just in case. (should normally be done by usage()) */
205 default:
206 if (parse_arg && parse_arg(c, optarg))
207 break; /* Application option */
208
209 fprintf(stderr,
210 "Programmer error -- option -%c defined but not handled\n",
211 c);
212 exit(1);
213 }
214 }
215 if (!_use_pi)
216 printf
217 ("Priority Inheritance has been disabled for this run.\n");
218 if (use_buffer)
219 buffer_init();
220 if (mlock) {
221 if (mlockall(MCL_CURRENT | MCL_FUTURE)) {
222 perror("failed to lock memory\n");
223 exit(1);
224 }
225 }
226
227 calibrate_busyloop();
228
229 free(all_options);
230
231 /*
232 * atexit() order matters here - buffer_print() will be called before
233 * buffer_fini().
234 */
235 atexit(buffer_fini);
236 atexit(buffer_print);
237 return 0;
238 }
239
rt_init(const char * options,int (* parse_arg)(int option,char * value),int argc,char * argv[])240 int rt_init(const char *options, int (*parse_arg) (int option, char *value),
241 int argc, char *argv[])
242 {
243 return rt_init_long(options, NULL, parse_arg, argc, argv);
244 }
245
buffer_init(void)246 void buffer_init(void)
247 {
248 _print_buffer = malloc(PRINT_BUFFER_SIZE);
249 if (!_print_buffer)
250 fprintf(stderr,
251 "insufficient memory for print buffer - printing directly to stderr\n");
252 else
253 memset(_print_buffer, 0, PRINT_BUFFER_SIZE);
254 }
255
buffer_print(void)256 void buffer_print(void)
257 {
258 if (_print_buffer) {
259 fprintf(stderr, "%s", _print_buffer);
260 memset(_print_buffer, 0, PRINT_BUFFER_SIZE);
261 _print_buffer_offset = 0;
262 }
263 }
264
buffer_fini(void)265 void buffer_fini(void)
266 {
267 if (_print_buffer)
268 free(_print_buffer);
269 _print_buffer = NULL;
270 }
271
cleanup(int i)272 void cleanup(int i)
273 {
274 printf("Test terminated with asynchronous signal\n");
275 buffer_print();
276 buffer_fini();
277 if (i)
278 exit(i);
279 }
280
setup(void)281 void setup(void)
282 {
283 signal(SIGINT, cleanup);
284 signal(SIGQUIT, cleanup);
285 signal(SIGTERM, cleanup);
286 }
287
create_thread(void * (* func)(void *),void * arg,int prio,int policy)288 int create_thread(void *(*func) (void *), void *arg, int prio, int policy)
289 {
290 struct sched_param param;
291 int id, ret;
292 struct thread *thread;
293
294 id = atomic_inc(&_thread_count);
295
296 thread = malloc(sizeof(struct thread));
297 if (!thread)
298 return -1;
299
300 list_add_tail(&thread->_threads, &_threads);
301 pthread_cond_init(&thread->cond, NULL); // Accept the defaults
302 init_pi_mutex(&thread->mutex);
303 thread->id = id;
304 thread->priority = prio;
305 thread->policy = policy;
306 thread->flags = 0;
307 thread->arg = arg;
308 thread->func = func;
309 param.sched_priority = prio;
310
311 pthread_attr_init(&thread->attr);
312 pthread_attr_setinheritsched(&thread->attr, PTHREAD_EXPLICIT_SCHED);
313 pthread_attr_setschedpolicy(&thread->attr, thread->policy);
314 pthread_attr_setschedparam(&thread->attr, ¶m);
315
316 if ((ret =
317 pthread_create(&thread->pthread, &thread->attr, func,
318 (void *)thread))) {
319 printf("pthread_create failed: %d (%s)\n", ret, strerror(ret));
320 list_del(&thread->_threads);
321 pthread_attr_destroy(&thread->attr);
322 free(thread);
323 return -1;
324 }
325 pthread_attr_destroy(&thread->attr);
326
327 return id;
328 }
329
create_fifo_thread(void * (* func)(void *),void * arg,int prio)330 int create_fifo_thread(void *(*func) (void *), void *arg, int prio)
331 {
332 return create_thread(func, arg, prio, SCHED_FIFO);
333 }
334
create_rr_thread(void * (* func)(void *),void * arg,int prio)335 int create_rr_thread(void *(*func) (void *), void *arg, int prio)
336 {
337 return create_thread(func, arg, prio, SCHED_RR);
338 }
339
create_other_thread(void * (* func)(void *),void * arg)340 int create_other_thread(void *(*func) (void *), void *arg)
341 {
342 return create_thread(func, arg, 0, SCHED_OTHER);
343 }
344
set_thread_priority(pthread_t pthread,int prio)345 int set_thread_priority(pthread_t pthread, int prio)
346 {
347 struct sched_param sched_param;
348 sched_param.sched_priority = prio;
349 int policy;
350
351 policy = (prio > 0) ? SCHED_FIFO : SCHED_OTHER;
352
353 return pthread_setschedparam(pthread, policy, &sched_param);
354 }
355
set_priority(int prio)356 int set_priority(int prio)
357 {
358 struct sched_param sp;
359 int ret = 0;
360
361 sp.sched_priority = prio;
362 if (sched_setscheduler(0, SCHED_FIFO, &sp) != 0) {
363 perror("sched_setscheduler");
364 ret = -1;
365 }
366 return ret;
367 }
368
join_thread(int i)369 void join_thread(int i)
370 {
371 struct thread *p, *t = NULL;
372 list_for_each_entry(p, &_threads, _threads) {
373 if (p->id == i) {
374 t = p;
375 break;
376 }
377 }
378 if (t) {
379 t->flags |= THREAD_QUIT;
380 if (t->pthread)
381 pthread_join(t->pthread, NULL);
382 list_del(&t->_threads);
383 free(t);
384 }
385 }
386
all_threads_quit(void)387 void all_threads_quit(void)
388 {
389 struct thread *p;
390 list_for_each_entry(p, &_threads, _threads) {
391 p->flags |= THREAD_QUIT;
392 }
393 }
394
join_threads(void)395 void join_threads(void)
396 {
397 all_threads_quit();
398 struct thread *p, *t;
399 list_for_each_entry_safe(p, t, &_threads, _threads) {
400 if (p->pthread)
401 pthread_join(p->pthread, NULL);
402 list_del(&p->_threads);
403 free(p);
404 }
405 }
406
get_thread(int i)407 struct thread *get_thread(int i)
408 {
409 struct thread *p;
410 list_for_each_entry(p, &_threads, _threads) {
411 if (p->id == i) {
412 return p;
413 }
414 }
415 return NULL;
416 }
417
ts_minus(struct timespec * ts_end,struct timespec * ts_start,struct timespec * ts_delta)418 void ts_minus(struct timespec *ts_end, struct timespec *ts_start,
419 struct timespec *ts_delta)
420 {
421 if (ts_end == NULL || ts_start == NULL || ts_delta == NULL) {
422 printf("ERROR in %s: one or more of the timespecs is NULL",
423 __FUNCTION__);
424 return;
425 }
426
427 ts_delta->tv_sec = ts_end->tv_sec - ts_start->tv_sec;
428 ts_delta->tv_nsec = ts_end->tv_nsec - ts_start->tv_nsec;
429 ts_normalize(ts_delta);
430 }
431
ts_plus(struct timespec * ts_a,struct timespec * ts_b,struct timespec * ts_sum)432 void ts_plus(struct timespec *ts_a, struct timespec *ts_b,
433 struct timespec *ts_sum)
434 {
435 if (ts_a == NULL || ts_b == NULL || ts_sum == NULL) {
436 printf("ERROR in %s: one or more of the timespecs is NULL",
437 __FUNCTION__);
438 return;
439 }
440
441 ts_sum->tv_sec = ts_a->tv_sec + ts_b->tv_sec;
442 ts_sum->tv_nsec = ts_a->tv_nsec + ts_b->tv_nsec;
443 ts_normalize(ts_sum);
444 }
445
ts_normalize(struct timespec * ts)446 void ts_normalize(struct timespec *ts)
447 {
448 if (ts == NULL) {
449 /* FIXME: write a real error logging system */
450 printf("ERROR in %s: ts is NULL\n", __FUNCTION__);
451 return;
452 }
453
454 /* get the abs(nsec) < NS_PER_SEC */
455 while (ts->tv_nsec > NS_PER_SEC) {
456 ts->tv_sec++;
457 ts->tv_nsec -= NS_PER_SEC;
458 }
459 while (ts->tv_nsec < -NS_PER_SEC) {
460 ts->tv_sec--;
461 ts->tv_nsec += NS_PER_SEC;
462 }
463
464 /* get the values to the same polarity */
465 if (ts->tv_sec > 0 && ts->tv_nsec < 0) {
466 ts->tv_sec--;
467 ts->tv_nsec += NS_PER_SEC;
468 }
469 if (ts->tv_sec < 0 && ts->tv_nsec > 0) {
470 ts->tv_sec++;
471 ts->tv_nsec -= NS_PER_SEC;
472 }
473 }
474
ts_to_nsec(struct timespec * ts,nsec_t * ns)475 int ts_to_nsec(struct timespec *ts, nsec_t * ns)
476 {
477 struct timespec t;
478 if (ts == NULL) {
479 /* FIXME: write a real error logging system */
480 printf("ERROR in %s: ts is NULL\n", __FUNCTION__);
481 return -1;
482 }
483 t.tv_sec = ts->tv_sec;
484 t.tv_nsec = ts->tv_nsec;
485 ts_normalize(&t);
486
487 if (t.tv_sec <= 0 && t.tv_nsec < 0) {
488 printf("ERROR in %s: ts is negative\n", __FUNCTION__);
489 return -1;
490 }
491
492 *ns = (nsec_t) ts->tv_sec * NS_PER_SEC + ts->tv_nsec;
493 return 0;
494 }
495
nsec_to_ts(nsec_t ns,struct timespec * ts)496 void nsec_to_ts(nsec_t ns, struct timespec *ts)
497 {
498 if (ts == NULL) {
499 /* FIXME: write a real error logging system */
500 printf("ERROR in %s: ts is NULL\n", __FUNCTION__);
501 return;
502 }
503 ts->tv_sec = ns / NS_PER_SEC;
504 ts->tv_nsec = ns % NS_PER_SEC;
505 }
506
507 /* return difference in microseconds */
tsc_minus(unsigned long long tsc_start,unsigned long long tsc_end)508 unsigned long long tsc_minus(unsigned long long tsc_start,
509 unsigned long long tsc_end)
510 {
511 unsigned long long delta;
512 if (tsc_start <= tsc_end)
513 delta = tsc_end - tsc_start;
514 else {
515 delta = ULL_MAX - (tsc_end - tsc_start) + 1;
516 printf("TSC wrapped, delta=%llu\n", delta);
517 }
518 return delta;
519 }
520
rt_nanosleep_until(nsec_t ns)521 void rt_nanosleep_until(nsec_t ns)
522 {
523 struct timespec ts_sleep, ts_rem;
524 int rc;
525 nsec_to_ts(ns, &ts_sleep);
526 rc = clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &ts_sleep,
527 &ts_rem);
528 /* FIXME: when should we display the remainder ? */
529 if (rc != 0) {
530 printf("WARNING: rt_nanosleep() returned early by %d s %d ns\n",
531 (int)ts_rem.tv_sec, (int)ts_rem.tv_nsec);
532 }
533 }
534
rt_nanosleep(nsec_t ns)535 void rt_nanosleep(nsec_t ns)
536 {
537 struct timespec ts_sleep, ts_rem;
538 int rc;
539 nsec_to_ts(ns, &ts_sleep);
540 rc = clock_nanosleep(CLOCK_MONOTONIC, 0, &ts_sleep, &ts_rem);
541 /* FIXME: when should we display the remainder ? */
542 if (rc != 0) {
543 printf("WARNING: rt_nanosleep() returned early by %d s %d ns\n",
544 (int)ts_rem.tv_sec, (int)ts_rem.tv_nsec);
545 }
546 }
547
rt_gettime(void)548 nsec_t rt_gettime(void)
549 {
550 struct timespec ts;
551 nsec_t ns;
552 int rc;
553
554 rc = clock_gettime(CLOCK_MONOTONIC, &ts);
555 if (rc != 0) {
556 printf("ERROR in %s: clock_gettime() returned %d\n",
557 __FUNCTION__, rc);
558 perror("clock_gettime() failed");
559 return 0;
560 }
561
562 ts_to_nsec(&ts, &ns);
563 return ns;
564 }
565
busy_work_ms(int ms)566 void *busy_work_ms(int ms)
567 {
568 busy_work_us(ms * US_PER_MS);
569 return NULL;
570 }
571
busy_work_us(int us)572 void *busy_work_us(int us)
573 {
574 volatile int i;
575 nsec_t start, now;
576 int delta; /* time in us */
577
578 i = us * iters_per_us;
579
580 start = rt_gettime();
581 while (--i > 0) {
582 continue;
583 }
584 now = rt_gettime();
585
586 delta = (now - start) / NS_PER_US;
587 /* uncomment to tune to your machine */
588 /* printf("busy_work_us requested: %dus actual: %dus\n", us, delta); */
589 return NULL;
590 }
591
init_pi_mutex(pthread_mutex_t * m)592 void init_pi_mutex(pthread_mutex_t * m)
593 {
594 #if HAS_PRIORITY_INHERIT
595 pthread_mutexattr_t attr;
596 int ret;
597 int protocol;
598
599 if ((ret = pthread_mutexattr_init(&attr)) != 0) {
600 printf("Failed to init mutexattr: %d (%s)\n", ret,
601 strerror(ret));
602 };
603 if (_use_pi
604 && (ret =
605 pthread_mutexattr_setprotocol(&attr,
606 PTHREAD_PRIO_INHERIT)) != 0) {
607 printf("Can't set protocol prio inherit: %d (%s)\n", ret,
608 strerror(ret));
609 }
610 if ((ret = pthread_mutexattr_getprotocol(&attr, &protocol)) != 0) {
611 printf("Can't get mutexattr protocol: %d (%s)\n", ret,
612 strerror(ret));
613 }
614 if ((ret = pthread_mutex_init(m, &attr)) != 0) {
615 printf("Failed to init mutex: %d (%s)\n", ret, strerror(ret));
616 }
617 #endif
618
619 /* FIXME: does any of this need to be destroyed ? */
620 }
621
622 /* Write the entirety of data. Complain if unable to do so. */
write_or_complain(int fd,const void * data,size_t len)623 static void write_or_complain(int fd, const void *data, size_t len)
624 {
625 const char *remaining = data;
626
627 while (len > 0) {
628 ssize_t ret = write(fd, remaining, len);
629 if (ret <= 0) {
630 if (errno != EAGAIN && errno != EINTR) {
631 perror("write");
632 return;
633 }
634 } else {
635 remaining += ret;
636 len -= ret;
637 }
638 }
639 }
640
641 /* Write the given data to the existing file specified by pathname. Complain
642 * if unable to do so. */
write_file(const char * pathname,const void * data,size_t len)643 static void write_file(const char *pathname, const void *data, size_t len)
644 {
645 int fd = open(pathname, O_WRONLY);
646 if (fd < 0) {
647 printf("Failed to open file \"%s\": %d (%s)\n",
648 pathname, errno, strerror(errno));
649 return;
650 }
651
652 write_or_complain(fd, data, len);
653
654 if (close(fd) < 0) {
655 printf("Failed to close file \"%s\": %d (%s)\n",
656 pathname, errno, strerror(errno));
657 }
658 }
659
660 /* Write the given '\0'-terminated string to the existing file specified by
661 * pathname. Complain if unable to do so. */
write_string_to_file(const char * pathname,const char * string)662 static void write_string_to_file(const char *pathname, const char *string)
663 {
664 write_file(pathname, string, strlen(string));
665 }
666
read_and_print(const char * pathname,int output_fd)667 static void read_and_print(const char *pathname, int output_fd)
668 {
669 char data[4096];
670 int fd = open(pathname, O_RDONLY);
671 if (fd < 0) {
672 printf("Failed to open file \"%s\": %d (%s)\n",
673 pathname, errno, strerror(errno));
674 return;
675 }
676
677 while (1) {
678 ssize_t ret = read(fd, data, sizeof(data));
679 if (ret < 0) {
680 if (errno != EAGAIN && errno != EINTR) {
681 printf
682 ("Failed to read from file \"%s\": %d (%s)\n",
683 pathname, errno, strerror(errno));
684 break;
685 }
686 } else if (ret == 0)
687 break;
688 else
689 write_or_complain(output_fd, data, ret);
690 }
691
692 if (close(fd) < 0) {
693 printf("Failed to close file \"%s\": %d (%s)\n",
694 pathname, errno, strerror(errno));
695 }
696 }
697
latency_trace_enable(void)698 void latency_trace_enable(void)
699 {
700 printf("Enabling latency tracer.\n");
701 write_string_to_file("/proc/sys/kernel/trace_use_raw_cycles", "1");
702 write_string_to_file("/proc/sys/kernel/trace_all_cpus", "1");
703 write_string_to_file("/proc/sys/kernel/trace_enabled", "1");
704 write_string_to_file("/proc/sys/kernel/trace_freerunning", "1");
705 write_string_to_file("/proc/sys/kernel/trace_print_on_crash", "0");
706 write_string_to_file("/proc/sys/kernel/trace_user_triggered", "1");
707 write_string_to_file("/proc/sys/kernel/trace_user_trigger_irq", "-1");
708 write_string_to_file("/proc/sys/kernel/trace_verbose", "0");
709 write_string_to_file("/proc/sys/kernel/preempt_thresh", "0");
710 write_string_to_file("/proc/sys/kernel/wakeup_timing", "0");
711 write_string_to_file("/proc/sys/kernel/mcount_enabled", "1");
712 write_string_to_file("/proc/sys/kernel/preempt_max_latency", "0");
713 }
714
715 #ifndef PR_SET_TRACING
716 #define PR_SET_TRACING 0
717 #endif
718
latency_trace_start(void)719 void latency_trace_start(void)
720 {
721 if (prctl(PR_SET_TRACING, 1) < 0)
722 perror("Failed to start tracing");
723 }
724
latency_trace_stop(void)725 void latency_trace_stop(void)
726 {
727 if (prctl(PR_SET_TRACING, 0) < 0)
728 perror("Failed to stop tracing");
729 }
730
latency_trace_print(void)731 void latency_trace_print(void)
732 {
733 read_and_print("/proc/latency_trace", STDOUT_FILENO);
734 }
735