| 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 | |
| 28 | #define LTTNG_SESSIOND_SIG_QS SIGRTMIN + 10 |
| 29 | #define LTTNG_SESSIOND_SIG_EXIT SIGRTMIN + 11 |
| 30 | #define LTTNG_SESSIOND_SIG_PENDING_ROTATION_CHECK SIGRTMIN + 12 |
| 31 | #define LTTNG_SESSIOND_SIG_SCHEDULED_ROTATION SIGRTMIN + 13 |
| 32 | |
| 33 | #define UINT_TO_PTR(value) \ |
| 34 | ({ \ |
| 35 | assert(value <= UINTPTR_MAX); \ |
| 36 | (void *) (uintptr_t) value; \ |
| 37 | }) |
| 38 | #define PTR_TO_UINT(ptr) ((uintptr_t) ptr) |
| 39 | |
| 40 | /* |
| 41 | * Handle timer teardown race wrt memory free of private data by sessiond |
| 42 | * signals are handled by a single thread, which permits a synchronization |
| 43 | * point between handling of each signal. Internal lock ensures mutual |
| 44 | * exclusion. |
| 45 | */ |
| 46 | static |
| 47 | struct timer_signal_data { |
| 48 | /* Thread managing signals. */ |
| 49 | pthread_t tid; |
| 50 | int qs_done; |
| 51 | pthread_mutex_t lock; |
| 52 | } timer_signal = { |
| 53 | .tid = 0, |
| 54 | .qs_done = 0, |
| 55 | .lock = PTHREAD_MUTEX_INITIALIZER, |
| 56 | }; |
| 57 | |
| 58 | /* |
| 59 | * Set custom signal mask to current thread. |
| 60 | */ |
| 61 | static |
| 62 | void setmask(sigset_t *mask) |
| 63 | { |
| 64 | int ret; |
| 65 | |
| 66 | ret = sigemptyset(mask); |
| 67 | if (ret) { |
| 68 | PERROR("sigemptyset"); |
| 69 | } |
| 70 | ret = sigaddset(mask, LTTNG_SESSIOND_SIG_QS); |
| 71 | if (ret) { |
| 72 | PERROR("sigaddset teardown"); |
| 73 | } |
| 74 | ret = sigaddset(mask, LTTNG_SESSIOND_SIG_EXIT); |
| 75 | if (ret) { |
| 76 | PERROR("sigaddset exit"); |
| 77 | } |
| 78 | ret = sigaddset(mask, LTTNG_SESSIOND_SIG_PENDING_ROTATION_CHECK); |
| 79 | if (ret) { |
| 80 | PERROR("sigaddset pending rotation check"); |
| 81 | } |
| 82 | ret = sigaddset(mask, LTTNG_SESSIOND_SIG_SCHEDULED_ROTATION); |
| 83 | if (ret) { |
| 84 | PERROR("sigaddset scheduled rotation"); |
| 85 | } |
| 86 | } |
| 87 | |
| 88 | /* |
| 89 | * This is the same function as timer_signal_thread_qs, when it |
| 90 | * returns, it means that no timer signr is currently pending or being handled |
| 91 | * by the timer thread. This cannot be called from the timer thread. |
| 92 | */ |
| 93 | static |
| 94 | void timer_signal_thread_qs(unsigned int signr) |
| 95 | { |
| 96 | sigset_t pending_set; |
| 97 | int ret; |
| 98 | |
| 99 | /* |
| 100 | * We need to be the only thread interacting with the thread |
| 101 | * that manages signals for teardown synchronization. |
| 102 | */ |
| 103 | pthread_mutex_lock(&timer_signal.lock); |
| 104 | |
| 105 | /* Ensure we don't have any signal queued for this session. */ |
| 106 | for (;;) { |
| 107 | ret = sigemptyset(&pending_set); |
| 108 | if (ret == -1) { |
| 109 | PERROR("sigemptyset"); |
| 110 | } |
| 111 | ret = sigpending(&pending_set); |
| 112 | if (ret == -1) { |
| 113 | PERROR("sigpending"); |
| 114 | } |
| 115 | if (!sigismember(&pending_set, signr)) { |
| 116 | break; |
| 117 | } |
| 118 | caa_cpu_relax(); |
| 119 | } |
| 120 | |
| 121 | /* |
| 122 | * From this point, no new signal handler will be fired that would try to |
| 123 | * access "session". However, we still need to wait for any currently |
| 124 | * executing handler to complete. |
| 125 | */ |
| 126 | cmm_smp_mb(); |
| 127 | CMM_STORE_SHARED(timer_signal.qs_done, 0); |
| 128 | cmm_smp_mb(); |
| 129 | |
| 130 | /* |
| 131 | * Kill with LTTNG_SESSIOND_SIG_QS, so signal management thread |
| 132 | * wakes up. |
| 133 | */ |
| 134 | kill(getpid(), LTTNG_SESSIOND_SIG_QS); |
| 135 | |
| 136 | while (!CMM_LOAD_SHARED(timer_signal.qs_done)) { |
| 137 | caa_cpu_relax(); |
| 138 | } |
| 139 | cmm_smp_mb(); |
| 140 | |
| 141 | pthread_mutex_unlock(&timer_signal.lock); |
| 142 | } |
| 143 | |
| 144 | /* |
| 145 | * Start a timer on a session that will fire at a given interval |
| 146 | * (timer_interval_us) and fire a given signal (signal). |
| 147 | * |
| 148 | * Returns a negative value on error, 0 if a timer was created, and |
| 149 | * a positive value if no timer was created (not an error). |
| 150 | */ |
| 151 | static |
| 152 | int timer_start(timer_t *timer_id, uint64_t session_id, |
| 153 | unsigned int timer_interval_us, int signal, bool one_shot) |
| 154 | { |
| 155 | int ret = 0, delete_ret; |
| 156 | struct sigevent sev; |
| 157 | struct itimerspec its; |
| 158 | |
| 159 | sev.sigev_notify = SIGEV_SIGNAL; |
| 160 | sev.sigev_signo = signal; |
| 161 | sev.sigev_value.sival_ptr = UINT_TO_PTR(session_id); |
| 162 | ret = timer_create(CLOCK_MONOTONIC, &sev, timer_id); |
| 163 | if (ret == -1) { |
| 164 | PERROR("timer_create"); |
| 165 | goto end; |
| 166 | } |
| 167 | |
| 168 | its.it_value.tv_sec = timer_interval_us / 1000000; |
| 169 | its.it_value.tv_nsec = (timer_interval_us % 1000000) * 1000; |
| 170 | if (one_shot) { |
| 171 | its.it_interval.tv_sec = 0; |
| 172 | its.it_interval.tv_nsec = 0; |
| 173 | } else { |
| 174 | its.it_interval.tv_sec = its.it_value.tv_sec; |
| 175 | its.it_interval.tv_nsec = its.it_value.tv_nsec; |
| 176 | } |
| 177 | |
| 178 | ret = timer_settime(*timer_id, 0, &its, NULL); |
| 179 | if (ret == -1) { |
| 180 | PERROR("timer_settime"); |
| 181 | goto error_destroy_timer; |
| 182 | } |
| 183 | goto end; |
| 184 | |
| 185 | error_destroy_timer: |
| 186 | delete_ret = timer_delete(*timer_id); |
| 187 | if (delete_ret == -1) { |
| 188 | PERROR("timer_delete"); |
| 189 | } |
| 190 | |
| 191 | end: |
| 192 | return ret; |
| 193 | } |
| 194 | |
| 195 | static |
| 196 | int timer_stop(timer_t *timer_id, int signal) |
| 197 | { |
| 198 | int ret = 0; |
| 199 | |
| 200 | ret = timer_delete(*timer_id); |
| 201 | if (ret == -1) { |
| 202 | PERROR("timer_delete"); |
| 203 | goto end; |
| 204 | } |
| 205 | |
| 206 | timer_signal_thread_qs(signal); |
| 207 | *timer_id = 0; |
| 208 | end: |
| 209 | return ret; |
| 210 | } |
| 211 | |
| 212 | int timer_session_rotation_pending_check_start(struct ltt_session *session, |
| 213 | unsigned int interval_us) |
| 214 | { |
| 215 | int ret; |
| 216 | |
| 217 | DBG("Enabling session rotation pending check timer on session %" PRIu64, |
| 218 | session->id); |
| 219 | /* |
| 220 | * We arm this timer in a one-shot mode so we don't have to disable it |
| 221 | * explicitly (which could deadlock if the timer thread is blocked |
| 222 | * writing in the rotation_timer_pipe). |
| 223 | * |
| 224 | * Instead, we re-arm it if needed after the rotation_pending check as |
| 225 | * returned. Also, this timer is usually only needed once, so there is |
| 226 | * no need to go through the whole signal teardown scheme everytime. |
| 227 | */ |
| 228 | ret = timer_start(&session->rotation_pending_check_timer, |
| 229 | session->id, interval_us, |
| 230 | LTTNG_SESSIOND_SIG_PENDING_ROTATION_CHECK, |
| 231 | /* one-shot */ true); |
| 232 | if (ret == 0) { |
| 233 | session->rotation_pending_check_timer_enabled = true; |
| 234 | } |
| 235 | |
| 236 | return ret; |
| 237 | } |
| 238 | |
| 239 | /* |
| 240 | * Call with session and session_list locks held. |
| 241 | */ |
| 242 | int timer_session_rotation_pending_check_stop(struct ltt_session *session) |
| 243 | { |
| 244 | int ret; |
| 245 | |
| 246 | assert(session); |
| 247 | |
| 248 | DBG("Disabling session rotation pending check timer on session %" PRIu64, |
| 249 | session->id); |
| 250 | ret = timer_stop(&session->rotation_pending_check_timer, |
| 251 | LTTNG_SESSIOND_SIG_PENDING_ROTATION_CHECK); |
| 252 | if (ret == -1) { |
| 253 | ERR("Failed to stop rotate_pending_check timer"); |
| 254 | } else { |
| 255 | session->rotation_pending_check_timer_enabled = false; |
| 256 | } |
| 257 | return ret; |
| 258 | } |
| 259 | |
| 260 | /* |
| 261 | * Call with session and session_list locks held. |
| 262 | */ |
| 263 | int timer_session_rotation_schedule_timer_start(struct ltt_session *session, |
| 264 | unsigned int interval_us) |
| 265 | { |
| 266 | int ret; |
| 267 | |
| 268 | DBG("Enabling scheduled rotation timer on session \"%s\" (%ui µs)", session->name, |
| 269 | interval_us); |
| 270 | ret = timer_start(&session->rotation_schedule_timer, session->id, |
| 271 | interval_us, LTTNG_SESSIOND_SIG_SCHEDULED_ROTATION, |
| 272 | /* one-shot */ false); |
| 273 | if (ret < 0) { |
| 274 | goto end; |
| 275 | } |
| 276 | session->rotation_schedule_timer_enabled = true; |
| 277 | end: |
| 278 | return ret; |
| 279 | } |
| 280 | |
| 281 | /* |
| 282 | * Call with session and session_list locks held. |
| 283 | */ |
| 284 | int timer_session_rotation_schedule_timer_stop(struct ltt_session *session) |
| 285 | { |
| 286 | int ret = 0; |
| 287 | |
| 288 | assert(session); |
| 289 | |
| 290 | if (!session->rotation_schedule_timer_enabled) { |
| 291 | goto end; |
| 292 | } |
| 293 | |
| 294 | DBG("Disabling scheduled rotation timer on session %s", session->name); |
| 295 | ret = timer_stop(&session->rotation_schedule_timer, |
| 296 | LTTNG_SESSIOND_SIG_SCHEDULED_ROTATION); |
| 297 | if (ret < 0) { |
| 298 | ERR("Failed to stop scheduled rotation timer of session \"%s\"", |
| 299 | session->name); |
| 300 | goto end; |
| 301 | } |
| 302 | |
| 303 | session->rotation_schedule_timer_enabled = false; |
| 304 | ret = 0; |
| 305 | end: |
| 306 | return ret; |
| 307 | } |
| 308 | |
| 309 | /* |
| 310 | * Block the RT signals for the entire process. It must be called from the |
| 311 | * sessiond main before creating the threads |
| 312 | */ |
| 313 | int timer_signal_init(void) |
| 314 | { |
| 315 | int ret; |
| 316 | sigset_t mask; |
| 317 | |
| 318 | /* Block signal for entire process, so only our thread processes it. */ |
| 319 | setmask(&mask); |
| 320 | ret = pthread_sigmask(SIG_BLOCK, &mask, NULL); |
| 321 | if (ret) { |
| 322 | errno = ret; |
| 323 | PERROR("pthread_sigmask"); |
| 324 | return -1; |
| 325 | } |
| 326 | return 0; |
| 327 | } |
| 328 | |
| 329 | /* |
| 330 | * This thread is the sighandler for the timer signals. |
| 331 | */ |
| 332 | void *timer_thread_func(void *data) |
| 333 | { |
| 334 | int signr; |
| 335 | sigset_t mask; |
| 336 | siginfo_t info; |
| 337 | struct timer_thread_parameters *ctx = data; |
| 338 | |
| 339 | rcu_register_thread(); |
| 340 | rcu_thread_online(); |
| 341 | |
| 342 | health_register(health_sessiond, HEALTH_SESSIOND_TYPE_TIMER); |
| 343 | health_code_update(); |
| 344 | |
| 345 | /* Only self thread will receive signal mask. */ |
| 346 | setmask(&mask); |
| 347 | CMM_STORE_SHARED(timer_signal.tid, pthread_self()); |
| 348 | |
| 349 | while (1) { |
| 350 | health_code_update(); |
| 351 | |
| 352 | health_poll_entry(); |
| 353 | signr = sigwaitinfo(&mask, &info); |
| 354 | health_poll_exit(); |
| 355 | |
| 356 | /* |
| 357 | * NOTE: cascading conditions are used instead of a switch case |
| 358 | * since the use of SIGRTMIN in the definition of the signals' |
| 359 | * values prevents the reduction to an integer constant. |
| 360 | */ |
| 361 | if (signr == -1) { |
| 362 | if (errno != EINTR) { |
| 363 | PERROR("sigwaitinfo"); |
| 364 | } |
| 365 | continue; |
| 366 | } else if (signr == LTTNG_SESSIOND_SIG_QS) { |
| 367 | cmm_smp_mb(); |
| 368 | CMM_STORE_SHARED(timer_signal.qs_done, 1); |
| 369 | cmm_smp_mb(); |
| 370 | } else if (signr == LTTNG_SESSIOND_SIG_EXIT) { |
| 371 | goto end; |
| 372 | } else if (signr == LTTNG_SESSIOND_SIG_PENDING_ROTATION_CHECK) { |
| 373 | rotation_thread_enqueue_job(ctx->rotation_thread_job_queue, |
| 374 | ROTATION_THREAD_JOB_TYPE_CHECK_PENDING_ROTATION, |
| 375 | /* session_id */ PTR_TO_UINT(info.si_value.sival_ptr)); |
| 376 | } else if (signr == LTTNG_SESSIOND_SIG_SCHEDULED_ROTATION) { |
| 377 | rotation_thread_enqueue_job(ctx->rotation_thread_job_queue, |
| 378 | ROTATION_THREAD_JOB_TYPE_SCHEDULED_ROTATION, |
| 379 | /* session_id */ PTR_TO_UINT(info.si_value.sival_ptr)); |
| 380 | } else { |
| 381 | ERR("Unexpected signal %d\n", info.si_signo); |
| 382 | } |
| 383 | } |
| 384 | |
| 385 | end: |
| 386 | DBG("[timer-thread] Exit"); |
| 387 | health_unregister(health_sessiond); |
| 388 | rcu_thread_offline(); |
| 389 | rcu_unregister_thread(); |
| 390 | return NULL; |
| 391 | } |
| 392 | |
| 393 | void timer_exit(void) |
| 394 | { |
| 395 | kill(getpid(), LTTNG_SESSIOND_SIG_EXIT); |
| 396 | } |