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->m.lock, &attr);
 120     pthread_mutexattr_destroy(&attr);
 121     if (err) {
 122         error_exit(err, __func__);
 123     }
 124     mutex->m.initialized = true;
 125 }
 126
 127 void qemu_rec_mutex_destroy(QemuRecMutex *mutex)
 128 {
 129     qemu_mutex_destroy(&mutex->m);
 130 }
 131
 132 void qemu_rec_mutex_lock_impl(QemuRecMutex *mutex, const char *file, int line)
 133 {
 134     qemu_mutex_lock_impl(&mutex->m, file, line);
 135 }
 136
 137 int qemu_rec_mutex_trylock_impl(QemuRecMutex *mutex, const char *file, int line)
 138 {
 139     return qemu_mutex_trylock_impl(&mutex->m, file, line);
 140 }
 141
 142 void qemu_rec_mutex_unlock_impl(QemuRecMutex *mutex, const char *file, int line)
 143 {
 144     qemu_mutex_unlock_impl(&mutex->m, file, line);
 145 }
 146
 147 void qemu_cond_init(QemuCond *cond)
 148 {
 149     int err;
 150
 151     err = pthread_cond_init(&cond->cond, NULL);
 152     if (err)
 153         error_exit(err, __func__);
 154     cond->initialized = true;
 155 }
 156
 157 void qemu_cond_destroy(QemuCond *cond)
 158 {
 159     int err;
 160
 161     assert(cond->initialized);
 162     cond->initialized = false;
 163     err = pthread_cond_destroy(&cond->cond);
 164     if (err)
 165         error_exit(err, __func__);
 166 }
 167
 168 void qemu_cond_signal(QemuCond *cond)
 169 {
 170     int err;
 171
 172     assert(cond->initialized);
 173     err = pthread_cond_signal(&cond->cond);
 174     if (err)
 175         error_exit(err, __func__);
 176 }
 177
 178 void qemu_cond_broadcast(QemuCond *cond)
 179 {
 180     int err;
 181
 182     assert(cond->initialized);
 183     err = pthread_cond_broadcast(&cond->cond);
 184     if (err)
 185         error_exit(err, __func__);
 186 }
 187
 188 void qemu_cond_wait_impl(QemuCond *cond, QemuMutex *mutex, const char *file, const int line)
 189 {
 190     int err;
 191
 192     assert(cond->initialized);
 193     qemu_mutex_pre_unlock(mutex, file, line);
 194     err = pthread_cond_wait(&cond->cond, &mutex->lock);
 195     qemu_mutex_post_lock(mutex, file, line);
 196     if (err)
 197         error_exit(err, __func__);
 198 }
 199
 200 bool qemu_cond_timedwait_impl(QemuCond *cond, QemuMutex *mutex, int ms,
 201                               const char *file, const int line)
 202 {
 203     int err;
 204     struct timespec ts;
 205
 206     assert(cond->initialized);
 207     trace_qemu_mutex_unlock(mutex, file, line);
 208     compute_abs_deadline(&ts, ms);
 209     err = pthread_cond_timedwait(&cond->cond, &mutex->lock, &ts);
 210     trace_qemu_mutex_locked(mutex, file, line);
 211     if (err && err != ETIMEDOUT) {
 212         error_exit(err, __func__);
 213     }
 214     return err != ETIMEDOUT;
 215 }
 216
 217 void qemu_sem_init(QemuSemaphore *sem, int init)
 218 {
 219     int rc;
 220
 221 #ifndef CONFIG_SEM_TIMEDWAIT
 222     rc = pthread_mutex_init(&sem->lock, NULL);
 223     if (rc != 0) {
 224         error_exit(rc, __func__);
 225     }
 226     rc = pthread_cond_init(&sem->cond, NULL);
 227     if (rc != 0) {
 228         error_exit(rc, __func__);
 229     }
 230     if (init < 0) {
 231         error_exit(EINVAL, __func__);
 232     }
 233     sem->count = init;
 234 #else
 235     rc = sem_init(&sem->sem, 0, init);
 236     if (rc < 0) {
 237         error_exit(errno, __func__);
 238     }
 239 #endif
 240     sem->initialized = true;
 241 }
 242
 243 void qemu_sem_destroy(QemuSemaphore *sem)
 244 {
 245     int rc;
 246
 247     assert(sem->initialized);
 248     sem->initialized = false;
 249 #ifndef CONFIG_SEM_TIMEDWAIT
 250     rc = pthread_cond_destroy(&sem->cond);
 251     if (rc < 0) {
 252         error_exit(rc, __func__);
 253     }
 254     rc = pthread_mutex_destroy(&sem->lock);
 255     if (rc < 0) {
 256         error_exit(rc, __func__);
 257     }
 258 #else
 259     rc = sem_destroy(&sem->sem);
 260     if (rc < 0) {
 261         error_exit(errno, __func__);
 262     }
 263 #endif
 264 }
 265
 266 void qemu_sem_post(QemuSemaphore *sem)
 267 {
 268     int rc;
 269
 270     assert(sem->initialized);
 271 #ifndef CONFIG_SEM_TIMEDWAIT
 272     pthread_mutex_lock(&sem->lock);
 273     if (sem->count == UINT_MAX) {
 274         rc = EINVAL;
 275     } else {
 276         sem->count++;
 277         rc = pthread_cond_signal(&sem->cond);
 278     }
 279     pthread_mutex_unlock(&sem->lock);
 280     if (rc != 0) {
 281         error_exit(rc, __func__);
 282     }
 283 #else
 284     rc = sem_post(&sem->sem);
 285     if (rc < 0) {
 286         error_exit(errno, __func__);
 287     }
 288 #endif
 289 }
 290
 291 int qemu_sem_timedwait(QemuSemaphore *sem, int ms)
 292 {
 293     int rc;
 294     struct timespec ts;
 295
 296     assert(sem->initialized);
 297 #ifndef CONFIG_SEM_TIMEDWAIT
 298     rc = 0;
 299     compute_abs_deadline(&ts, ms);
 300     pthread_mutex_lock(&sem->lock);
 301     while (sem->count == 0) {
 302         rc = pthread_cond_timedwait(&sem->cond, &sem->lock, &ts);
 303         if (rc == ETIMEDOUT) {
 304             break;
 305         }
 306         if (rc != 0) {
 307             error_exit(rc, __func__);
 308         }
 309     }
 310     if (rc != ETIMEDOUT) {
 311         --sem->count;
 312     }
 313     pthread_mutex_unlock(&sem->lock);
 314     return (rc == ETIMEDOUT ? -1 : 0);
 315 #else
 316     if (ms <= 0) {
 317         /* This is cheaper than sem_timedwait.  */
 318         do {
 319             rc = sem_trywait(&sem->sem);
 320         } while (rc == -1 && errno == EINTR);
 321         if (rc == -1 && errno == EAGAIN) {
 322             return -1;
 323         }
 324     } else {
 325         compute_abs_deadline(&ts, ms);
 326         do {
 327             rc = sem_timedwait(&sem->sem, &ts);
 328         } while (rc == -1 && errno == EINTR);
 329         if (rc == -1 && errno == ETIMEDOUT) {
 330             return -1;
 331         }
 332     }
 333     if (rc < 0) {
 334         error_exit(errno, __func__);
 335     }
 336     return 0;
 337 #endif
 338 }
 339
 340 void qemu_sem_wait(QemuSemaphore *sem)
 341 {
 342     int rc;
 343
 344     assert(sem->initialized);
 345 #ifndef CONFIG_SEM_TIMEDWAIT
 346     pthread_mutex_lock(&sem->lock);
 347     while (sem->count == 0) {
 348         rc = pthread_cond_wait(&sem->cond, &sem->lock);
 349         if (rc != 0) {
 350             error_exit(rc, __func__);
 351         }
 352     }
 353     --sem->count;
 354     pthread_mutex_unlock(&sem->lock);
 355 #else
 356     do {
 357         rc = sem_wait(&sem->sem);
 358     } while (rc == -1 && errno == EINTR);
 359     if (rc < 0) {
 360         error_exit(errno, __func__);
 361     }
 362 #endif
 363 }
 364
 365 #ifdef __linux__
 366 #include "qemu/futex.h"
 367 #else
 368 static inline void qemu_futex_wake(QemuEvent *ev, int n)
 369 {
 370     assert(ev->initialized);
 371     pthread_mutex_lock(&ev->lock);
 372     if (n == 1) {
 373         pthread_cond_signal(&ev->cond);
 374     } else {
 375         pthread_cond_broadcast(&ev->cond);
 376     }
 377     pthread_mutex_unlock(&ev->lock);
 378 }
 379
 380 static inline void qemu_futex_wait(QemuEvent *ev, unsigned val)
 381 {
 382     assert(ev->initialized);
 383     pthread_mutex_lock(&ev->lock);
 384     if (ev->value == val) {
 385         pthread_cond_wait(&ev->cond, &ev->lock);
 386     }
 387     pthread_mutex_unlock(&ev->lock);
 388 }
 389 #endif
 390
 391 /* Valid transitions:
 392  * - free->set, when setting the event
 393  * - busy->set, when setting the event, followed by qemu_futex_wake
 394  * - set->free, when resetting the event
 395  * - free->busy, when waiting
 396  *
 397  * set->busy does not happen (it can be observed from the outside but
 398  * it really is set->free->busy).
 399  *
 400  * busy->free provably cannot happen; to enforce it, the set->free transition
 401  * is done with an OR, which becomes a no-op if the event has concurrently
 402  * transitioned to free or busy.
 403  */
 404
 405 #define EV_SET         0
 406 #define EV_FREE        1
 407 #define EV_BUSY       -1
 408
 409 void qemu_event_init(QemuEvent *ev, bool init)
 410 {
 411 #ifndef __linux__
 412     pthread_mutex_init(&ev->lock, NULL);
 413     pthread_cond_init(&ev->cond, NULL);
 414 #endif
 415
 416     ev->value = (init ? EV_SET : EV_FREE);
 417     ev->initialized = true;
 418 }
 419
 420 void qemu_event_destroy(QemuEvent *ev)
 421 {
 422     assert(ev->initialized);
 423     ev->initialized = false;
 424 #ifndef __linux__
 425     pthread_mutex_destroy(&ev->lock);
 426     pthread_cond_destroy(&ev->cond);
 427 #endif
 428 }
 429
 430 void qemu_event_set(QemuEvent *ev)
 431 {
 432     /* qemu_event_set has release semantics, but because it *loads*
 433      * ev->value we need a full memory barrier here.
 434      */
 435     assert(ev->initialized);
 436     smp_mb();
 437     if (qatomic_read(&ev->value) != EV_SET) {
 438         if (qatomic_xchg(&ev->value, EV_SET) == EV_BUSY) {
 439             /* There were waiters, wake them up.  */
 440             qemu_futex_wake(ev, INT_MAX);
 441         }
 442     }
 443 }
 444
 445 void qemu_event_reset(QemuEvent *ev)
 446 {
 447     unsigned value;
 448
 449     assert(ev->initialized);
 450     value = qatomic_read(&ev->value);
 451     smp_mb_acquire();
 452     if (value == EV_SET) {
 453         /*
 454          * If there was a concurrent reset (or even reset+wait),
 455          * do nothing.  Otherwise change EV_SET->EV_FREE.
 456          */
 457         qatomic_or(&ev->value, EV_FREE);
 458     }
 459 }
 460
 461 void qemu_event_wait(QemuEvent *ev)
 462 {
 463     unsigned value;
 464
 465     assert(ev->initialized);
 466     value = qatomic_read(&ev->value);
 467     smp_mb_acquire();
 468     if (value != EV_SET) {
 469         if (value == EV_FREE) {
 470             /*
 471              * Leave the event reset and tell qemu_event_set that there
 472              * are waiters.  No need to retry, because there cannot be
 473              * a concurrent busy->free transition.  After the CAS, the
 474              * event will be either set or busy.
 475              */
 476             if (qatomic_cmpxchg(&ev->value, EV_FREE, EV_BUSY) == EV_SET) {
 477                 return;
 478             }
 479         }
 480         qemu_futex_wait(ev, EV_BUSY);
 481     }
 482 }
 483
 484 static __thread NotifierList thread_exit;
 485
 486 /*
 487  * Note that in this implementation you can register a thread-exit
 488  * notifier for the main thread, but it will never be called.
 489  * This is OK because main thread exit can only happen when the
 490  * entire process is exiting, and the API allows notifiers to not
 491  * be called on process exit.
 492  */
 493 void qemu_thread_atexit_add(Notifier *notifier)
 494 {
 495     notifier_list_add(&thread_exit, notifier);
 496 }
 497
 498 void qemu_thread_atexit_remove(Notifier *notifier)
 499 {
 500     notifier_remove(notifier);
 501 }
 502
 503 static void qemu_thread_atexit_notify(void *arg)
 504 {
 505     /*
 506      * Called when non-main thread exits (via qemu_thread_exit()
 507      * or by returning from its start routine.)
 508      */
 509     notifier_list_notify(&thread_exit, NULL);
 510 }
 511
 512 typedef struct {
 513     void *(*start_routine)(void *);
 514     void *arg;
 515     char *name;
 516 } QemuThreadArgs;
 517
 518 static void *qemu_thread_start(void *args)
 519 {
 520     QemuThreadArgs *qemu_thread_args = args;
 521     void *(*start_routine)(void *) = qemu_thread_args->start_routine;
 522     void *arg = qemu_thread_args->arg;
 523     void *r;
 524
 525 #ifdef CONFIG_THREAD_SETNAME_BYTHREAD
 526     /* Attempt to set the threads name; note that this is for debug, so
 527      * we're not going to fail if we can't set it.
 528      */
 529     if (name_threads && qemu_thread_args->name) {
 530 # if defined(CONFIG_PTHREAD_SETNAME_NP_W_TID)
 531         pthread_setname_np(pthread_self(), qemu_thread_args->name);
 532 # elif defined(CONFIG_PTHREAD_SETNAME_NP_WO_TID)
 533         pthread_setname_np(qemu_thread_args->name);
 534 # endif
 535     }
 536 #endif
 537     QEMU_TSAN_ANNOTATE_THREAD_NAME(qemu_thread_args->name);
 538     g_free(qemu_thread_args->name);
 539     g_free(qemu_thread_args);
 540
 541     /*
 542      * GCC 11 with glibc 2.17 on PowerPC reports
 543      *
 544      * qemu-thread-posix.c:540:5: error: ‘__sigsetjmp’ accessing 656 bytes
 545      *   in a region of size 528 [-Werror=stringop-overflow=]
 546      * 540 |     pthread_cleanup_push(qemu_thread_atexit_notify, NULL);
 547      *     |     ^~~~~~~~~~~~~~~~~~~~
 548      *
 549      * which is clearly nonsense.
 550      */
 551 #pragma GCC diagnostic push
 552 #ifndef __clang__
 553 #pragma GCC diagnostic ignored "-Wstringop-overflow"
 554 #endif
 555
 556     pthread_cleanup_push(qemu_thread_atexit_notify, NULL);
 557     r = start_routine(arg);
 558     pthread_cleanup_pop(1);
 559
 560 #pragma GCC diagnostic pop
 561
 562     return r;
 563 }
 564
 565 void qemu_thread_create(QemuThread *thread, const char *name,
 566                        void *(*start_routine)(void*),
 567                        void *arg, int mode)
 568 {
 569     sigset_t set, oldset;
 570     int err;
 571     pthread_attr_t attr;
 572     QemuThreadArgs *qemu_thread_args;
 573
 574     err = pthread_attr_init(&attr);
 575     if (err) {
 576         error_exit(err, __func__);
 577     }
 578
 579     if (mode == QEMU_THREAD_DETACHED) {
 580         pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
 581     }
 582
 583     /* Leave signal handling to the iothread.  */
 584     sigfillset(&set);
 585     /* Blocking the signals can result in undefined behaviour. */
 586     sigdelset(&set, SIGSEGV);
 587     sigdelset(&set, SIGFPE);
 588     sigdelset(&set, SIGILL);
 589     /* TODO avoid SIGBUS loss on macOS */
 590     pthread_sigmask(SIG_SETMASK, &set, &oldset);
 591
 592     qemu_thread_args = g_new0(QemuThreadArgs, 1);
 593     qemu_thread_args->name = g_strdup(name);
 594     qemu_thread_args->start_routine = start_routine;
 595     qemu_thread_args->arg = arg;
 596
 597     err = pthread_create(&thread->thread, &attr,
 598                          qemu_thread_start, qemu_thread_args);
 599
 600     if (err)
 601         error_exit(err, __func__);
 602
 603     pthread_sigmask(SIG_SETMASK, &oldset, NULL);
 604
 605     pthread_attr_destroy(&attr);
 606 }
 607
 608 void qemu_thread_get_self(QemuThread *thread)
 609 {
 610     thread->thread = pthread_self();
 611 }
 612
 613 bool qemu_thread_is_self(QemuThread *thread)
 614 {
 615    return pthread_equal(pthread_self(), thread->thread);
 616 }
 617
 618 void qemu_thread_exit(void *retval)
 619 {
 620     pthread_exit(retval);
 621 }
 622
 623 void *qemu_thread_join(QemuThread *thread)
 624 {
 625     int err;
 626     void *ret;
 627
 628     err = pthread_join(thread->thread, &ret);
 629     if (err) {
 630         error_exit(err, __func__);
 631     }
 632     return ret;
 633 }