util/qemu-thread-posix.c

   1 /*
   2  * Wrappers around mutex/cond/thread functions
   3  *
   4  * Copyright Red Hat, Inc. 2009
   5  *
   6  * Author:
   7  *  Marcelo Tosatti <mtosatti@redhat.com>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  10  * See the COPYING file in the top-level directory.
  11  *
  12  */
  13 #include "qemu/osdep.h"
  14 #include "qemu/thread.h"
  15 #include "qemu/atomic.h"
  16 #include "qemu/notify.h"
  17 #include "qemu-thread-common.h"
  18 #include "qemu/tsan.h"
  19
  20 static bool name_threads;
  21
  22 void qemu_thread_naming(bool enable)
  23 {
  24     name_threads = enable;
  25
  26 #ifndef CONFIG_THREAD_SETNAME_BYTHREAD
  27     /* This is a debugging option, not fatal */
  28     if (enable) {
  29         fprintf(stderr, "qemu: thread naming not supported on this host\n");
  30     }
  31 #endif
  32 }
  33
  34 static void error_exit(int err, const char *msg)
  35 {
  36     fprintf(stderr, "qemu: %s: %s\n", msg, strerror(err));
  37     abort();
  38 }
  39
  40 static void compute_abs_deadline(struct timespec *ts, int ms)
  41 {
  42     struct timeval tv;
  43     gettimeofday(&tv, NULL);
  44     ts->tv_nsec = tv.tv_usec * 1000 + (ms % 1000) * 1000000;
  45     ts->tv_sec = tv.tv_sec + ms / 1000;
  46     if (ts->tv_nsec >= 1000000000) {
  47         ts->tv_sec++;
  48         ts->tv_nsec -= 1000000000;
  49     }
  50 }
  51
  52 void qemu_mutex_init(QemuMutex *mutex)
  53 {
  54     int err;
  55
  56     err = pthread_mutex_init(&mutex->lock, NULL);
  57     if (err)
  58         error_exit(err, __func__);
  59     qemu_mutex_post_init(mutex);
  60 }
  61
  62 void qemu_mutex_destroy(QemuMutex *mutex)
  63 {
  64     int err;
  65
  66     assert(mutex->initialized);
  67     mutex->initialized = false;
  68     err = pthread_mutex_destroy(&mutex->lock);
  69     if (err)
  70         error_exit(err, __func__);
  71 }
  72
  73 void qemu_mutex_lock_impl(QemuMutex *mutex, const char *file, const int line)
  74 {
  75     int err;
  76
  77     assert(mutex->initialized);
  78     qemu_mutex_pre_lock(mutex, file, line);
  79     err = pthread_mutex_lock(&mutex->lock);
  80     if (err)
  81         error_exit(err, __func__);
  82     qemu_mutex_post_lock(mutex, file, line);
  83 }
  84
  85 int qemu_mutex_trylock_impl(QemuMutex *mutex, const char *file, const int line)
  86 {
  87     int err;
  88
  89     assert(mutex->initialized);
  90     err = pthread_mutex_trylock(&mutex->lock);
  91     if (err == 0) {
  92         qemu_mutex_post_lock(mutex, file, line);
  93         return 0;
  94     }
  95     if (err != EBUSY) {
  96         error_exit(err, __func__);
  97     }
  98     return -EBUSY;
  99 }
 100
 101 void qemu_mutex_unlock_impl(QemuMutex *mutex, const char *file, const int line)
 102 {
 103     int err;
 104
 105     assert(mutex->initialized);
 106     qemu_mutex_pre_unlock(mutex, file, line);
 107     err = pthread_mutex_unlock(&mutex->lock);
 108     if (err)
 109         error_exit(err, __func__);
 110 }
 111
 112 void qemu_rec_mutex_init(QemuRecMutex *mutex)
 113 {
 114     int err;
 115     pthread_mutexattr_t attr;
 116
 117     pthread_mutexattr_init(&attr);
 118     pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
 119     err = pthread_mutex_init(&mutex->lock, &attr);
 120     pthread_mutexattr_destroy(&attr);
 121     if (err) {
 122         error_exit(err, __func__);
 123     }
 124     mutex->initialized = true;
 125 }
 126
 127 void qemu_cond_init(QemuCond *cond)
 128 {
 129     int err;
 130
 131     err = pthread_cond_init(&cond->cond, NULL);
 132     if (err)
 133         error_exit(err, __func__);
 134     cond->initialized = true;
 135 }
 136
 137 void qemu_cond_destroy(QemuCond *cond)
 138 {
 139     int err;
 140
 141     assert(cond->initialized);
 142     cond->initialized = false;
 143     err = pthread_cond_destroy(&cond->cond);
 144     if (err)
 145         error_exit(err, __func__);
 146 }
 147
 148 void qemu_cond_signal(QemuCond *cond)
 149 {
 150     int err;
 151
 152     assert(cond->initialized);
 153     err = pthread_cond_signal(&cond->cond);
 154     if (err)
 155         error_exit(err, __func__);
 156 }
 157
 158 void qemu_cond_broadcast(QemuCond *cond)
 159 {
 160     int err;
 161
 162     assert(cond->initialized);
 163     err = pthread_cond_broadcast(&cond->cond);
 164     if (err)
 165         error_exit(err, __func__);
 166 }
 167
 168 void qemu_cond_wait_impl(QemuCond *cond, QemuMutex *mutex, const char *file, const int line)
 169 {
 170     int err;
 171
 172     assert(cond->initialized);
 173     qemu_mutex_pre_unlock(mutex, file, line);
 174     err = pthread_cond_wait(&cond->cond, &mutex->lock);
 175     qemu_mutex_post_lock(mutex, file, line);
 176     if (err)
 177         error_exit(err, __func__);
 178 }
 179
 180 bool qemu_cond_timedwait_impl(QemuCond *cond, QemuMutex *mutex, int ms,
 181                               const char *file, const int line)
 182 {
 183     int err;
 184     struct timespec ts;
 185
 186     assert(cond->initialized);
 187     trace_qemu_mutex_unlock(mutex, file, line);
 188     compute_abs_deadline(&ts, ms);
 189     err = pthread_cond_timedwait(&cond->cond, &mutex->lock, &ts);
 190     trace_qemu_mutex_locked(mutex, file, line);
 191     if (err && err != ETIMEDOUT) {
 192         error_exit(err, __func__);
 193     }
 194     return err != ETIMEDOUT;
 195 }
 196
 197 void qemu_sem_init(QemuSemaphore *sem, int init)
 198 {
 199     int rc;
 200
 201 #ifndef CONFIG_SEM_TIMEDWAIT
 202     rc = pthread_mutex_init(&sem->lock, NULL);
 203     if (rc != 0) {
 204         error_exit(rc, __func__);
 205     }
 206     rc = pthread_cond_init(&sem->cond, NULL);
 207     if (rc != 0) {
 208         error_exit(rc, __func__);
 209     }
 210     if (init < 0) {
 211         error_exit(EINVAL, __func__);
 212     }
 213     sem->count = init;
 214 #else
 215     rc = sem_init(&sem->sem, 0, init);
 216     if (rc < 0) {
 217         error_exit(errno, __func__);
 218     }
 219 #endif
 220     sem->initialized = true;
 221 }
 222
 223 void qemu_sem_destroy(QemuSemaphore *sem)
 224 {
 225     int rc;
 226
 227     assert(sem->initialized);
 228     sem->initialized = false;
 229 #ifndef CONFIG_SEM_TIMEDWAIT
 230     rc = pthread_cond_destroy(&sem->cond);
 231     if (rc < 0) {
 232         error_exit(rc, __func__);
 233     }
 234     rc = pthread_mutex_destroy(&sem->lock);
 235     if (rc < 0) {
 236         error_exit(rc, __func__);
 237     }
 238 #else
 239     rc = sem_destroy(&sem->sem);
 240     if (rc < 0) {
 241         error_exit(errno, __func__);
 242     }
 243 #endif
 244 }
 245
 246 void qemu_sem_post(QemuSemaphore *sem)
 247 {
 248     int rc;
 249
 250     assert(sem->initialized);
 251 #ifndef CONFIG_SEM_TIMEDWAIT
 252     pthread_mutex_lock(&sem->lock);
 253     if (sem->count == UINT_MAX) {
 254         rc = EINVAL;
 255     } else {
 256         sem->count++;
 257         rc = pthread_cond_signal(&sem->cond);
 258     }
 259     pthread_mutex_unlock(&sem->lock);
 260     if (rc != 0) {
 261         error_exit(rc, __func__);
 262     }
 263 #else
 264     rc = sem_post(&sem->sem);
 265     if (rc < 0) {
 266         error_exit(errno, __func__);
 267     }
 268 #endif
 269 }
 270
 271 int qemu_sem_timedwait(QemuSemaphore *sem, int ms)
 272 {
 273     int rc;
 274     struct timespec ts;
 275
 276     assert(sem->initialized);
 277 #ifndef CONFIG_SEM_TIMEDWAIT
 278     rc = 0;
 279     compute_abs_deadline(&ts, ms);
 280     pthread_mutex_lock(&sem->lock);
 281     while (sem->count == 0) {
 282         rc = pthread_cond_timedwait(&sem->cond, &sem->lock, &ts);
 283         if (rc == ETIMEDOUT) {
 284             break;
 285         }
 286         if (rc != 0) {
 287             error_exit(rc, __func__);
 288         }
 289     }
 290     if (rc != ETIMEDOUT) {
 291         --sem->count;
 292     }
 293     pthread_mutex_unlock(&sem->lock);
 294     return (rc == ETIMEDOUT ? -1 : 0);
 295 #else
 296     if (ms <= 0) {
 297         /* This is cheaper than sem_timedwait.  */
 298         do {
 299             rc = sem_trywait(&sem->sem);
 300         } while (rc == -1 && errno == EINTR);
 301         if (rc == -1 && errno == EAGAIN) {
 302             return -1;
 303         }
 304     } else {
 305         compute_abs_deadline(&ts, ms);
 306         do {
 307             rc = sem_timedwait(&sem->sem, &ts);
 308         } while (rc == -1 && errno == EINTR);
 309         if (rc == -1 && errno == ETIMEDOUT) {
 310             return -1;
 311         }
 312     }
 313     if (rc < 0) {
 314         error_exit(errno, __func__);
 315     }
 316     return 0;
 317 #endif
 318 }
 319
 320 void qemu_sem_wait(QemuSemaphore *sem)
 321 {
 322     int rc;
 323
 324     assert(sem->initialized);
 325 #ifndef CONFIG_SEM_TIMEDWAIT
 326     pthread_mutex_lock(&sem->lock);
 327     while (sem->count == 0) {
 328         rc = pthread_cond_wait(&sem->cond, &sem->lock);
 329         if (rc != 0) {
 330             error_exit(rc, __func__);
 331         }
 332     }
 333     --sem->count;
 334     pthread_mutex_unlock(&sem->lock);
 335 #else
 336     do {
 337         rc = sem_wait(&sem->sem);
 338     } while (rc == -1 && errno == EINTR);
 339     if (rc < 0) {
 340         error_exit(errno, __func__);
 341     }
 342 #endif
 343 }
 344
 345 #ifdef __linux__
 346 #include "qemu/futex.h"
 347 #else
 348 static inline void qemu_futex_wake(QemuEvent *ev, int n)
 349 {
 350     assert(ev->initialized);
 351     pthread_mutex_lock(&ev->lock);
 352     if (n == 1) {
 353         pthread_cond_signal(&ev->cond);
 354     } else {
 355         pthread_cond_broadcast(&ev->cond);
 356     }
 357     pthread_mutex_unlock(&ev->lock);
 358 }
 359
 360 static inline void qemu_futex_wait(QemuEvent *ev, unsigned val)
 361 {
 362     assert(ev->initialized);
 363     pthread_mutex_lock(&ev->lock);
 364     if (ev->value == val) {
 365         pthread_cond_wait(&ev->cond, &ev->lock);
 366     }
 367     pthread_mutex_unlock(&ev->lock);
 368 }
 369 #endif
 370
 371 /* Valid transitions:
 372  * - free->set, when setting the event
 373  * - busy->set, when setting the event, followed by qemu_futex_wake
 374  * - set->free, when resetting the event
 375  * - free->busy, when waiting
 376  *
 377  * set->busy does not happen (it can be observed from the outside but
 378  * it really is set->free->busy).
 379  *
 380  * busy->free provably cannot happen; to enforce it, the set->free transition
 381  * is done with an OR, which becomes a no-op if the event has concurrently
 382  * transitioned to free or busy.
 383  */
 384
 385 #define EV_SET         0
 386 #define EV_FREE        1
 387 #define EV_BUSY       -1
 388
 389 void qemu_event_init(QemuEvent *ev, bool init)
 390 {
 391 #ifndef __linux__
 392     pthread_mutex_init(&ev->lock, NULL);
 393     pthread_cond_init(&ev->cond, NULL);
 394 #endif
 395
 396     ev->value = (init ? EV_SET : EV_FREE);
 397     ev->initialized = true;
 398 }
 399
 400 void qemu_event_destroy(QemuEvent *ev)
 401 {
 402     assert(ev->initialized);
 403     ev->initialized = false;
 404 #ifndef __linux__
 405     pthread_mutex_destroy(&ev->lock);
 406     pthread_cond_destroy(&ev->cond);
 407 #endif
 408 }
 409
 410 void qemu_event_set(QemuEvent *ev)
 411 {
 412     /* qemu_event_set has release semantics, but because it *loads*
 413      * ev->value we need a full memory barrier here.
 414      */
 415     assert(ev->initialized);
 416     smp_mb();
 417     if (qatomic_read(&ev->value) != EV_SET) {
 418         if (qatomic_xchg(&ev->value, EV_SET) == EV_BUSY) {
 419             /* There were waiters, wake them up.  */
 420             qemu_futex_wake(ev, INT_MAX);
 421         }
 422     }
 423 }
 424
 425 void qemu_event_reset(QemuEvent *ev)
 426 {
 427     unsigned value;
 428
 429     assert(ev->initialized);
 430     value = qatomic_read(&ev->value);
 431     smp_mb_acquire();
 432     if (value == EV_SET) {
 433         /*
 434          * If there was a concurrent reset (or even reset+wait),
 435          * do nothing.  Otherwise change EV_SET->EV_FREE.
 436          */
 437         qatomic_or(&ev->value, EV_FREE);
 438     }
 439 }
 440
 441 void qemu_event_wait(QemuEvent *ev)
 442 {
 443     unsigned value;
 444
 445     assert(ev->initialized);
 446     value = qatomic_read(&ev->value);
 447     smp_mb_acquire();
 448     if (value != EV_SET) {
 449         if (value == EV_FREE) {
 450             /*
 451              * Leave the event reset and tell qemu_event_set that there
 452              * are waiters.  No need to retry, because there cannot be
 453              * a concurrent busy->free transition.  After the CAS, the
 454              * event will be either set or busy.
 455              */
 456             if (qatomic_cmpxchg(&ev->value, EV_FREE, EV_BUSY) == EV_SET) {
 457                 return;
 458             }
 459         }
 460         qemu_futex_wait(ev, EV_BUSY);
 461     }
 462 }
 463
 464 static __thread NotifierList thread_exit;
 465
 466 /*
 467  * Note that in this implementation you can register a thread-exit
 468  * notifier for the main thread, but it will never be called.
 469  * This is OK because main thread exit can only happen when the
 470  * entire process is exiting, and the API allows notifiers to not
 471  * be called on process exit.
 472  */
 473 void qemu_thread_atexit_add(Notifier *notifier)
 474 {
 475     notifier_list_add(&thread_exit, notifier);
 476 }
 477
 478 void qemu_thread_atexit_remove(Notifier *notifier)
 479 {
 480     notifier_remove(notifier);
 481 }
 482
 483 static void qemu_thread_atexit_notify(void *arg)
 484 {
 485     /*
 486      * Called when non-main thread exits (via qemu_thread_exit()
 487      * or by returning from its start routine.)
 488      */
 489     notifier_list_notify(&thread_exit, NULL);
 490 }
 491
 492 typedef struct {
 493     void *(*start_routine)(void *);
 494     void *arg;
 495     char *name;
 496 } QemuThreadArgs;
 497
 498 static void *qemu_thread_start(void *args)
 499 {
 500     QemuThreadArgs *qemu_thread_args = args;
 501     void *(*start_routine)(void *) = qemu_thread_args->start_routine;
 502     void *arg = qemu_thread_args->arg;
 503     void *r;
 504
 505 #ifdef CONFIG_THREAD_SETNAME_BYTHREAD
 506     /* Attempt to set the threads name; note that this is for debug, so
 507      * we're not going to fail if we can't set it.
 508      */
 509     if (name_threads && qemu_thread_args->name) {
 510 # if defined(CONFIG_PTHREAD_SETNAME_NP_W_TID)
 511         pthread_setname_np(pthread_self(), qemu_thread_args->name);
 512 # elif defined(CONFIG_PTHREAD_SETNAME_NP_WO_TID)
 513         pthread_setname_np(qemu_thread_args->name);
 514 # endif
 515     }
 516 #endif
 517     QEMU_TSAN_ANNOTATE_THREAD_NAME(qemu_thread_args->name);
 518     g_free(qemu_thread_args->name);
 519     g_free(qemu_thread_args);
 520     pthread_cleanup_push(qemu_thread_atexit_notify, NULL);
 521     r = start_routine(arg);
 522     pthread_cleanup_pop(1);
 523     return r;
 524 }
 525
 526 void qemu_thread_create(QemuThread *thread, const char *name,
 527                        void *(*start_routine)(void*),
 528                        void *arg, int mode)
 529 {
 530     sigset_t set, oldset;
 531     int err;
 532     pthread_attr_t attr;
 533     QemuThreadArgs *qemu_thread_args;
 534
 535     err = pthread_attr_init(&attr);
 536     if (err) {
 537         error_exit(err, __func__);
 538     }
 539
 540     if (mode == QEMU_THREAD_DETACHED) {
 541         pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
 542     }
 543
 544     /* Leave signal handling to the iothread.  */
 545     sigfillset(&set);
 546     /* Blocking the signals can result in undefined behaviour. */
 547     sigdelset(&set, SIGSEGV);
 548     sigdelset(&set, SIGFPE);
 549     sigdelset(&set, SIGILL);
 550     /* TODO avoid SIGBUS loss on macOS */
 551     pthread_sigmask(SIG_SETMASK, &set, &oldset);
 552
 553     qemu_thread_args = g_new0(QemuThreadArgs, 1);
 554     qemu_thread_args->name = g_strdup(name);
 555     qemu_thread_args->start_routine = start_routine;
 556     qemu_thread_args->arg = arg;
 557
 558     err = pthread_create(&thread->thread, &attr,
 559                          qemu_thread_start, qemu_thread_args);
 560
 561     if (err)
 562         error_exit(err, __func__);
 563
 564     pthread_sigmask(SIG_SETMASK, &oldset, NULL);
 565
 566     pthread_attr_destroy(&attr);
 567 }
 568
 569 void qemu_thread_get_self(QemuThread *thread)
 570 {
 571     thread->thread = pthread_self();
 572 }
 573
 574 bool qemu_thread_is_self(QemuThread *thread)
 575 {
 576    return pthread_equal(pthread_self(), thread->thread);
 577 }
 578
 579 void qemu_thread_exit(void *retval)
 580 {
 581     pthread_exit(retval);
 582 }
 583
 584 void *qemu_thread_join(QemuThread *thread)
 585 {
 586     int err;
 587     void *ret;
 588
 589     err = pthread_join(thread->thread, &ret);
 590     if (err) {
 591         error_exit(err, __func__);
 592     }
 593     return ret;
 594 }