Launch the timer thread using lttng_thread
[lttng-tools.git] / src / bin / lttng-sessiond / timer.c
1 /*
2 * Copyright (C) 2017 - Julien Desfossez <jdesfossez@efficios.com>
3 * Copyright (C) 2018 - Jérémie Galarneau <jeremie.galarneau@efficios.com>
4 *
5 * This program is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License, version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This program is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
12 * more details.
13 *
14 * You should have received a copy of the GNU General Public License along with
15 * this program; if not, write to the Free Software Foundation, Inc., 51
16 * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
17 */
18
19 #define _LGPL_SOURCE
20 #include <assert.h>
21 #include <inttypes.h>
22 #include <signal.h>
23
24 #include "timer.h"
25 #include "health-sessiond.h"
26 #include "rotation-thread.h"
27 #include "thread.h"
28
29 #define LTTNG_SESSIOND_SIG_QS SIGRTMIN + 10
30 #define LTTNG_SESSIOND_SIG_EXIT SIGRTMIN + 11
31 #define LTTNG_SESSIOND_SIG_PENDING_ROTATION_CHECK SIGRTMIN + 12
32 #define LTTNG_SESSIOND_SIG_SCHEDULED_ROTATION SIGRTMIN + 13
33
34 #define UINT_TO_PTR(value) \
35 ({ \
36 assert(value <= UINTPTR_MAX); \
37 (void *) (uintptr_t) value; \
38 })
39 #define PTR_TO_UINT(ptr) ((uintptr_t) ptr)
40
41 /*
42 * Handle timer teardown race wrt memory free of private data by sessiond
43 * signals are handled by a single thread, which permits a synchronization
44 * point between handling of each signal. Internal lock ensures mutual
45 * exclusion.
46 */
47 static
48 struct timer_signal_data {
49 /* Thread managing signals. */
50 pthread_t tid;
51 int qs_done;
52 pthread_mutex_t lock;
53 } timer_signal = {
54 .tid = 0,
55 .qs_done = 0,
56 .lock = PTHREAD_MUTEX_INITIALIZER,
57 };
58
59 /*
60 * Set custom signal mask to current thread.
61 */
62 static
63 void setmask(sigset_t *mask)
64 {
65 int ret;
66
67 ret = sigemptyset(mask);
68 if (ret) {
69 PERROR("sigemptyset");
70 }
71 ret = sigaddset(mask, LTTNG_SESSIOND_SIG_QS);
72 if (ret) {
73 PERROR("sigaddset teardown");
74 }
75 ret = sigaddset(mask, LTTNG_SESSIOND_SIG_EXIT);
76 if (ret) {
77 PERROR("sigaddset exit");
78 }
79 ret = sigaddset(mask, LTTNG_SESSIOND_SIG_PENDING_ROTATION_CHECK);
80 if (ret) {
81 PERROR("sigaddset pending rotation check");
82 }
83 ret = sigaddset(mask, LTTNG_SESSIOND_SIG_SCHEDULED_ROTATION);
84 if (ret) {
85 PERROR("sigaddset scheduled rotation");
86 }
87 }
88
89 /*
90 * This is the same function as timer_signal_thread_qs, when it
91 * returns, it means that no timer signr is currently pending or being handled
92 * by the timer thread. This cannot be called from the timer thread.
93 */
94 static
95 void timer_signal_thread_qs(unsigned int signr)
96 {
97 sigset_t pending_set;
98 int ret;
99
100 /*
101 * We need to be the only thread interacting with the thread
102 * that manages signals for teardown synchronization.
103 */
104 pthread_mutex_lock(&timer_signal.lock);
105
106 /* Ensure we don't have any signal queued for this session. */
107 for (;;) {
108 ret = sigemptyset(&pending_set);
109 if (ret == -1) {
110 PERROR("sigemptyset");
111 }
112 ret = sigpending(&pending_set);
113 if (ret == -1) {
114 PERROR("sigpending");
115 }
116 if (!sigismember(&pending_set, signr)) {
117 break;
118 }
119 caa_cpu_relax();
120 }
121
122 /*
123 * From this point, no new signal handler will be fired that would try to
124 * access "session". However, we still need to wait for any currently
125 * executing handler to complete.
126 */
127 cmm_smp_mb();
128 CMM_STORE_SHARED(timer_signal.qs_done, 0);
129 cmm_smp_mb();
130
131 /*
132 * Kill with LTTNG_SESSIOND_SIG_QS, so signal management thread
133 * wakes up.
134 */
135 kill(getpid(), LTTNG_SESSIOND_SIG_QS);
136
137 while (!CMM_LOAD_SHARED(timer_signal.qs_done)) {
138 caa_cpu_relax();
139 }
140 cmm_smp_mb();
141
142 pthread_mutex_unlock(&timer_signal.lock);
143 }
144
145 /*
146 * Start a timer on a session that will fire at a given interval
147 * (timer_interval_us) and fire a given signal (signal).
148 *
149 * Returns a negative value on error, 0 if a timer was created, and
150 * a positive value if no timer was created (not an error).
151 */
152 static
153 int timer_start(timer_t *timer_id, struct ltt_session *session,
154 unsigned int timer_interval_us, int signal, bool one_shot)
155 {
156 int ret = 0, delete_ret;
157 struct sigevent sev;
158 struct itimerspec its;
159
160 sev.sigev_notify = SIGEV_SIGNAL;
161 sev.sigev_signo = signal;
162 sev.sigev_value.sival_ptr = session;
163 ret = timer_create(CLOCK_MONOTONIC, &sev, timer_id);
164 if (ret == -1) {
165 PERROR("timer_create");
166 goto end;
167 }
168
169 its.it_value.tv_sec = timer_interval_us / 1000000;
170 its.it_value.tv_nsec = (timer_interval_us % 1000000) * 1000;
171 if (one_shot) {
172 its.it_interval.tv_sec = 0;
173 its.it_interval.tv_nsec = 0;
174 } else {
175 its.it_interval.tv_sec = its.it_value.tv_sec;
176 its.it_interval.tv_nsec = its.it_value.tv_nsec;
177 }
178
179 ret = timer_settime(*timer_id, 0, &its, NULL);
180 if (ret == -1) {
181 PERROR("timer_settime");
182 goto error_destroy_timer;
183 }
184 goto end;
185
186 error_destroy_timer:
187 delete_ret = timer_delete(*timer_id);
188 if (delete_ret == -1) {
189 PERROR("timer_delete");
190 }
191
192 end:
193 return ret;
194 }
195
196 static
197 int timer_stop(timer_t *timer_id, int signal)
198 {
199 int ret = 0;
200
201 ret = timer_delete(*timer_id);
202 if (ret == -1) {
203 PERROR("timer_delete");
204 goto end;
205 }
206
207 timer_signal_thread_qs(signal);
208 *timer_id = 0;
209 end:
210 return ret;
211 }
212
213 int timer_session_rotation_pending_check_start(struct ltt_session *session,
214 unsigned int interval_us)
215 {
216 int ret;
217
218 if (!session_get(session)) {
219 ret = -1;
220 goto end;
221 }
222 DBG("Enabling session rotation pending check timer on session %" PRIu64,
223 session->id);
224 /*
225 * We arm this timer in a one-shot mode so we don't have to disable it
226 * explicitly (which could deadlock if the timer thread is blocked
227 * writing in the rotation_timer_pipe).
228 *
229 * Instead, we re-arm it if needed after the rotation_pending check as
230 * returned. Also, this timer is usually only needed once, so there is
231 * no need to go through the whole signal teardown scheme everytime.
232 */
233 ret = timer_start(&session->rotation_pending_check_timer,
234 session, interval_us,
235 LTTNG_SESSIOND_SIG_PENDING_ROTATION_CHECK,
236 /* one-shot */ true);
237 if (ret == 0) {
238 session->rotation_pending_check_timer_enabled = true;
239 }
240 end:
241 return ret;
242 }
243
244 /*
245 * Call with session and session_list locks held.
246 */
247 int timer_session_rotation_pending_check_stop(struct ltt_session *session)
248 {
249 int ret;
250
251 assert(session);
252 assert(session->rotation_pending_check_timer_enabled);
253
254 DBG("Disabling session rotation pending check timer on session %" PRIu64,
255 session->id);
256 ret = timer_stop(&session->rotation_pending_check_timer,
257 LTTNG_SESSIOND_SIG_PENDING_ROTATION_CHECK);
258 if (ret == -1) {
259 ERR("Failed to stop rotate_pending_check timer");
260 } else {
261 session->rotation_pending_check_timer_enabled = false;
262 /*
263 * The timer's reference to the session can be released safely.
264 */
265 session_put(session);
266 }
267 return ret;
268 }
269
270 /*
271 * Call with session and session_list locks held.
272 */
273 int timer_session_rotation_schedule_timer_start(struct ltt_session *session,
274 unsigned int interval_us)
275 {
276 int ret;
277
278 if (!session_get(session)) {
279 ret = -1;
280 goto end;
281 }
282 DBG("Enabling scheduled rotation timer on session \"%s\" (%ui µs)", session->name,
283 interval_us);
284 ret = timer_start(&session->rotation_schedule_timer, session,
285 interval_us, LTTNG_SESSIOND_SIG_SCHEDULED_ROTATION,
286 /* one-shot */ false);
287 if (ret < 0) {
288 goto end;
289 }
290 session->rotation_schedule_timer_enabled = true;
291 end:
292 return ret;
293 }
294
295 /*
296 * Call with session and session_list locks held.
297 */
298 int timer_session_rotation_schedule_timer_stop(struct ltt_session *session)
299 {
300 int ret = 0;
301
302 assert(session);
303
304 if (!session->rotation_schedule_timer_enabled) {
305 goto end;
306 }
307
308 DBG("Disabling scheduled rotation timer on session %s", session->name);
309 ret = timer_stop(&session->rotation_schedule_timer,
310 LTTNG_SESSIOND_SIG_SCHEDULED_ROTATION);
311 if (ret < 0) {
312 ERR("Failed to stop scheduled rotation timer of session \"%s\"",
313 session->name);
314 goto end;
315 }
316
317 session->rotation_schedule_timer_enabled = false;
318 /* The timer's reference to the session can be released safely. */
319 session_put(session);
320 ret = 0;
321 end:
322 return ret;
323 }
324
325 /*
326 * Block the RT signals for the entire process. It must be called from the
327 * sessiond main before creating the threads
328 */
329 int timer_signal_init(void)
330 {
331 int ret;
332 sigset_t mask;
333
334 /* Block signal for entire process, so only our thread processes it. */
335 setmask(&mask);
336 ret = pthread_sigmask(SIG_BLOCK, &mask, NULL);
337 if (ret) {
338 errno = ret;
339 PERROR("pthread_sigmask");
340 return -1;
341 }
342 return 0;
343 }
344
345 /*
346 * This thread is the sighandler for the timer signals.
347 */
348 static
349 void *thread_timer(void *data)
350 {
351 int signr;
352 sigset_t mask;
353 siginfo_t info;
354 struct timer_thread_parameters *ctx = data;
355
356 rcu_register_thread();
357 rcu_thread_online();
358
359 health_register(health_sessiond, HEALTH_SESSIOND_TYPE_TIMER);
360 health_code_update();
361
362 /* Only self thread will receive signal mask. */
363 setmask(&mask);
364 CMM_STORE_SHARED(timer_signal.tid, pthread_self());
365
366 while (1) {
367 health_code_update();
368
369 health_poll_entry();
370 signr = sigwaitinfo(&mask, &info);
371 health_poll_exit();
372
373 /*
374 * NOTE: cascading conditions are used instead of a switch case
375 * since the use of SIGRTMIN in the definition of the signals'
376 * values prevents the reduction to an integer constant.
377 */
378 if (signr == -1) {
379 if (errno != EINTR) {
380 PERROR("sigwaitinfo");
381 }
382 continue;
383 } else if (signr == LTTNG_SESSIOND_SIG_QS) {
384 cmm_smp_mb();
385 CMM_STORE_SHARED(timer_signal.qs_done, 1);
386 cmm_smp_mb();
387 } else if (signr == LTTNG_SESSIOND_SIG_EXIT) {
388 goto end;
389 } else if (signr == LTTNG_SESSIOND_SIG_PENDING_ROTATION_CHECK) {
390 struct ltt_session *session =
391 (struct ltt_session *) info.si_value.sival_ptr;
392
393 rotation_thread_enqueue_job(ctx->rotation_thread_job_queue,
394 ROTATION_THREAD_JOB_TYPE_CHECK_PENDING_ROTATION,
395 session);
396 } else if (signr == LTTNG_SESSIOND_SIG_SCHEDULED_ROTATION) {
397 rotation_thread_enqueue_job(ctx->rotation_thread_job_queue,
398 ROTATION_THREAD_JOB_TYPE_SCHEDULED_ROTATION,
399 (struct ltt_session *) info.si_value.sival_ptr);
400 /*
401 * The scheduled periodic rotation timer is not in
402 * "one-shot" mode. The reference to the session is not
403 * released since the timer is still enabled and can
404 * still fire.
405 */
406 } else {
407 ERR("Unexpected signal %d\n", info.si_signo);
408 }
409 }
410
411 end:
412 DBG("[timer-thread] Exit");
413 health_unregister(health_sessiond);
414 rcu_thread_offline();
415 rcu_unregister_thread();
416 return NULL;
417 }
418
419 static
420 bool shutdown_timer_thread(void *data)
421 {
422 return kill(getpid(), LTTNG_SESSIOND_SIG_EXIT) == 0;
423 }
424
425 bool launch_timer_thread(
426 struct timer_thread_parameters *timer_thread_parameters)
427 {
428 struct lttng_thread *thread;
429
430 thread = lttng_thread_create("Timer",
431 thread_timer,
432 shutdown_timer_thread,
433 NULL,
434 timer_thread_parameters);
435 if (!thread) {
436 goto error;
437 }
438 lttng_thread_put(thread);
439 return true;
440 error:
441 return false;
442 }
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