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