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