util/qemu-thread-win32.c

   1 /*
   2  * Win32 implementation for mutex/cond/thread functions
   3  *
   4  * Copyright Red Hat, Inc. 2010
   5  *
   6  * Author:
   7  *  Paolo Bonzini <pbonzini@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
  14 #include "qemu/osdep.h"
  15 #include "qemu/thread.h"
  16 #include "qemu/notify.h"
  17 #include "qemu-thread-common.h"
  18 #include <process.h>
  19
  20 static bool name_threads;
  21
  22 void qemu_thread_naming(bool enable)
  23 {
  24     /* But note we don't actually name them on Windows yet */
  25     name_threads = enable;
  26
  27     fprintf(stderr, "qemu: thread naming not supported on this host\n");
  28 }
  29
  30 static void error_exit(int err, const char *msg)
  31 {
  32     char *pstr;
  33
  34     FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ALLOCATE_BUFFER,
  35                   NULL, err, 0, (LPTSTR)&pstr, 2, NULL);
  36     fprintf(stderr, "qemu: %s: %s\n", msg, pstr);
  37     LocalFree(pstr);
  38     abort();
  39 }
  40
  41 void qemu_mutex_init(QemuMutex *mutex)
  42 {
  43     InitializeSRWLock(&mutex->lock);
  44     qemu_mutex_post_init(mutex);
  45 }
  46
  47 void qemu_mutex_destroy(QemuMutex *mutex)
  48 {
  49     assert(mutex->initialized);
  50     mutex->initialized = false;
  51     InitializeSRWLock(&mutex->lock);
  52 }
  53
  54 void qemu_mutex_lock_impl(QemuMutex *mutex, const char *file, const int line)
  55 {
  56     assert(mutex->initialized);
  57     qemu_mutex_pre_lock(mutex, file, line);
  58     AcquireSRWLockExclusive(&mutex->lock);
  59     qemu_mutex_post_lock(mutex, file, line);
  60 }
  61
  62 int qemu_mutex_trylock_impl(QemuMutex *mutex, const char *file, const int line)
  63 {
  64     int owned;
  65
  66     assert(mutex->initialized);
  67     owned = TryAcquireSRWLockExclusive(&mutex->lock);
  68     if (owned) {
  69         qemu_mutex_post_lock(mutex, file, line);
  70         return 0;
  71     }
  72     return -EBUSY;
  73 }
  74
  75 void qemu_mutex_unlock_impl(QemuMutex *mutex, const char *file, const int line)
  76 {
  77     assert(mutex->initialized);
  78     qemu_mutex_pre_unlock(mutex, file, line);
  79     ReleaseSRWLockExclusive(&mutex->lock);
  80 }
  81
  82 void qemu_rec_mutex_init(QemuRecMutex *mutex)
  83 {
  84     InitializeCriticalSection(&mutex->lock);
  85     mutex->initialized = true;
  86 }
  87
  88 void qemu_rec_mutex_destroy(QemuRecMutex *mutex)
  89 {
  90     assert(mutex->initialized);
  91     mutex->initialized = false;
  92     DeleteCriticalSection(&mutex->lock);
  93 }
  94
  95 void qemu_rec_mutex_lock_impl(QemuRecMutex *mutex, const char *file, int line)
  96 {
  97     assert(mutex->initialized);
  98     EnterCriticalSection(&mutex->lock);
  99 }
 100
 101 int qemu_rec_mutex_trylock_impl(QemuRecMutex *mutex, const char *file, int line)
 102 {
 103     assert(mutex->initialized);
 104     return !TryEnterCriticalSection(&mutex->lock);
 105 }
 106
 107 void qemu_rec_mutex_unlock_impl(QemuRecMutex *mutex, const char *file, int line)
 108 {
 109     assert(mutex->initialized);
 110     LeaveCriticalSection(&mutex->lock);
 111 }
 112
 113 void qemu_cond_init(QemuCond *cond)
 114 {
 115     memset(cond, 0, sizeof(*cond));
 116     InitializeConditionVariable(&cond->var);
 117     cond->initialized = true;
 118 }
 119
 120 void qemu_cond_destroy(QemuCond *cond)
 121 {
 122     assert(cond->initialized);
 123     cond->initialized = false;
 124     InitializeConditionVariable(&cond->var);
 125 }
 126
 127 void qemu_cond_signal(QemuCond *cond)
 128 {
 129     assert(cond->initialized);
 130     WakeConditionVariable(&cond->var);
 131 }
 132
 133 void qemu_cond_broadcast(QemuCond *cond)
 134 {
 135     assert(cond->initialized);
 136     WakeAllConditionVariable(&cond->var);
 137 }
 138
 139 void qemu_cond_wait_impl(QemuCond *cond, QemuMutex *mutex, const char *file, const int line)
 140 {
 141     assert(cond->initialized);
 142     qemu_mutex_pre_unlock(mutex, file, line);
 143     SleepConditionVariableSRW(&cond->var, &mutex->lock, INFINITE, 0);
 144     qemu_mutex_post_lock(mutex, file, line);
 145 }
 146
 147 bool qemu_cond_timedwait_impl(QemuCond *cond, QemuMutex *mutex, int ms,
 148                               const char *file, const int line)
 149 {
 150     int rc = 0;
 151
 152     assert(cond->initialized);
 153     trace_qemu_mutex_unlock(mutex, file, line);
 154     if (!SleepConditionVariableSRW(&cond->var, &mutex->lock, ms, 0)) {
 155         rc = GetLastError();
 156     }
 157     trace_qemu_mutex_locked(mutex, file, line);
 158     if (rc && rc != ERROR_TIMEOUT) {
 159         error_exit(rc, __func__);
 160     }
 161     return rc != ERROR_TIMEOUT;
 162 }
 163
 164 void qemu_sem_init(QemuSemaphore *sem, int init)
 165 {
 166     /* Manual reset.  */
 167     sem->sema = CreateSemaphore(NULL, init, LONG_MAX, NULL);
 168     sem->initialized = true;
 169 }
 170
 171 void qemu_sem_destroy(QemuSemaphore *sem)
 172 {
 173     assert(sem->initialized);
 174     sem->initialized = false;
 175     CloseHandle(sem->sema);
 176 }
 177
 178 void qemu_sem_post(QemuSemaphore *sem)
 179 {
 180     assert(sem->initialized);
 181     ReleaseSemaphore(sem->sema, 1, NULL);
 182 }
 183
 184 int qemu_sem_timedwait(QemuSemaphore *sem, int ms)
 185 {
 186     int rc;
 187
 188     assert(sem->initialized);
 189     rc = WaitForSingleObject(sem->sema, ms);
 190     if (rc == WAIT_OBJECT_0) {
 191         return 0;
 192     }
 193     if (rc != WAIT_TIMEOUT) {
 194         error_exit(GetLastError(), __func__);
 195     }
 196     return -1;
 197 }
 198
 199 void qemu_sem_wait(QemuSemaphore *sem)
 200 {
 201     assert(sem->initialized);
 202     if (WaitForSingleObject(sem->sema, INFINITE) != WAIT_OBJECT_0) {
 203         error_exit(GetLastError(), __func__);
 204     }
 205 }
 206
 207 /* Wrap a Win32 manual-reset event with a fast userspace path.  The idea
 208  * is to reset the Win32 event lazily, as part of a test-reset-test-wait
 209  * sequence.  Such a sequence is, indeed, how QemuEvents are used by
 210  * RCU and other subsystems!
 211  *
 212  * Valid transitions:
 213  * - free->set, when setting the event
 214  * - busy->set, when setting the event, followed by SetEvent
 215  * - set->free, when resetting the event
 216  * - free->busy, when waiting
 217  *
 218  * set->busy does not happen (it can be observed from the outside but
 219  * it really is set->free->busy).
 220  *
 221  * busy->free provably cannot happen; to enforce it, the set->free transition
 222  * is done with an OR, which becomes a no-op if the event has concurrently
 223  * transitioned to free or busy (and is faster than cmpxchg).
 224  */
 225
 226 #define EV_SET         0
 227 #define EV_FREE        1
 228 #define EV_BUSY       -1
 229
 230 void qemu_event_init(QemuEvent *ev, bool init)
 231 {
 232     /* Manual reset.  */
 233     ev->event = CreateEvent(NULL, TRUE, TRUE, NULL);
 234     ev->value = (init ? EV_SET : EV_FREE);
 235     ev->initialized = true;
 236 }
 237
 238 void qemu_event_destroy(QemuEvent *ev)
 239 {
 240     assert(ev->initialized);
 241     ev->initialized = false;
 242     CloseHandle(ev->event);
 243 }
 244
 245 void qemu_event_set(QemuEvent *ev)
 246 {
 247     assert(ev->initialized);
 248     /* qemu_event_set has release semantics, but because it *loads*
 249      * ev->value we need a full memory barrier here.
 250      */
 251     smp_mb();
 252     if (qatomic_read(&ev->value) != EV_SET) {
 253         if (qatomic_xchg(&ev->value, EV_SET) == EV_BUSY) {
 254             /* There were waiters, wake them up.  */
 255             SetEvent(ev->event);
 256         }
 257     }
 258 }
 259
 260 void qemu_event_reset(QemuEvent *ev)
 261 {
 262     unsigned value;
 263
 264     assert(ev->initialized);
 265     value = qatomic_read(&ev->value);
 266     smp_mb_acquire();
 267     if (value == EV_SET) {
 268         /* If there was a concurrent reset (or even reset+wait),
 269          * do nothing.  Otherwise change EV_SET->EV_FREE.
 270          */
 271         qatomic_or(&ev->value, EV_FREE);
 272     }
 273 }
 274
 275 void qemu_event_wait(QemuEvent *ev)
 276 {
 277     unsigned value;
 278
 279     assert(ev->initialized);
 280     value = qatomic_read(&ev->value);
 281     smp_mb_acquire();
 282     if (value != EV_SET) {
 283         if (value == EV_FREE) {
 284             /* qemu_event_set is not yet going to call SetEvent, but we are
 285              * going to do another check for EV_SET below when setting EV_BUSY.
 286              * At that point it is safe to call WaitForSingleObject.
 287              */
 288             ResetEvent(ev->event);
 289
 290             /* Tell qemu_event_set that there are waiters.  No need to retry
 291              * because there cannot be a concurrent busy->free transition.
 292              * After the CAS, the event will be either set or busy.
 293              */
 294             if (qatomic_cmpxchg(&ev->value, EV_FREE, EV_BUSY) == EV_SET) {
 295                 value = EV_SET;
 296             } else {
 297                 value = EV_BUSY;
 298             }
 299         }
 300         if (value == EV_BUSY) {
 301             WaitForSingleObject(ev->event, INFINITE);
 302         }
 303     }
 304 }
 305
 306 struct QemuThreadData {
 307     /* Passed to win32_start_routine.  */
 308     void             *(*start_routine)(void *);
 309     void             *arg;
 310     short             mode;
 311     NotifierList      exit;
 312
 313     /* Only used for joinable threads. */
 314     bool              exited;
 315     void             *ret;
 316     CRITICAL_SECTION  cs;
 317 };
 318
 319 static bool atexit_registered;
 320 static NotifierList main_thread_exit;
 321
 322 static __thread QemuThreadData *qemu_thread_data;
 323
 324 static void run_main_thread_exit(void)
 325 {
 326     notifier_list_notify(&main_thread_exit, NULL);
 327 }
 328
 329 void qemu_thread_atexit_add(Notifier *notifier)
 330 {
 331     if (!qemu_thread_data) {
 332         if (!atexit_registered) {
 333             atexit_registered = true;
 334             atexit(run_main_thread_exit);
 335         }
 336         notifier_list_add(&main_thread_exit, notifier);
 337     } else {
 338         notifier_list_add(&qemu_thread_data->exit, notifier);
 339     }
 340 }
 341
 342 void qemu_thread_atexit_remove(Notifier *notifier)
 343 {
 344     notifier_remove(notifier);
 345 }
 346
 347 static unsigned __stdcall win32_start_routine(void *arg)
 348 {
 349     QemuThreadData *data = (QemuThreadData *) arg;
 350     void *(*start_routine)(void *) = data->start_routine;
 351     void *thread_arg = data->arg;
 352
 353     qemu_thread_data = data;
 354     qemu_thread_exit(start_routine(thread_arg));
 355     abort();
 356 }
 357
 358 void qemu_thread_exit(void *arg)
 359 {
 360     QemuThreadData *data = qemu_thread_data;
 361
 362     notifier_list_notify(&data->exit, NULL);
 363     if (data->mode == QEMU_THREAD_JOINABLE) {
 364         data->ret = arg;
 365         EnterCriticalSection(&data->cs);
 366         data->exited = true;
 367         LeaveCriticalSection(&data->cs);
 368     } else {
 369         g_free(data);
 370     }
 371     _endthreadex(0);
 372 }
 373
 374 void *qemu_thread_join(QemuThread *thread)
 375 {
 376     QemuThreadData *data;
 377     void *ret;
 378     HANDLE handle;
 379
 380     data = thread->data;
 381     if (data->mode == QEMU_THREAD_DETACHED) {
 382         return NULL;
 383     }
 384
 385     /*
 386      * Because multiple copies of the QemuThread can exist via
 387      * qemu_thread_get_self, we need to store a value that cannot
 388      * leak there.  The simplest, non racy way is to store the TID,
 389      * discard the handle that _beginthreadex gives back, and
 390      * get another copy of the handle here.
 391      */
 392     handle = qemu_thread_get_handle(thread);
 393     if (handle) {
 394         WaitForSingleObject(handle, INFINITE);
 395         CloseHandle(handle);
 396     }
 397     ret = data->ret;
 398     DeleteCriticalSection(&data->cs);
 399     g_free(data);
 400     return ret;
 401 }
 402
 403 void qemu_thread_create(QemuThread *thread, const char *name,
 404                        void *(*start_routine)(void *),
 405                        void *arg, int mode)
 406 {
 407     HANDLE hThread;
 408     struct QemuThreadData *data;
 409
 410     data = g_malloc(sizeof *data);
 411     data->start_routine = start_routine;
 412     data->arg = arg;
 413     data->mode = mode;
 414     data->exited = false;
 415     notifier_list_init(&data->exit);
 416
 417     if (data->mode != QEMU_THREAD_DETACHED) {
 418         InitializeCriticalSection(&data->cs);
 419     }
 420
 421     hThread = (HANDLE) _beginthreadex(NULL, 0, win32_start_routine,
 422                                       data, 0, &thread->tid);
 423     if (!hThread) {
 424         error_exit(GetLastError(), __func__);
 425     }
 426     CloseHandle(hThread);
 427     thread->data = data;
 428 }
 429
 430 void qemu_thread_get_self(QemuThread *thread)
 431 {
 432     thread->data = qemu_thread_data;
 433     thread->tid = GetCurrentThreadId();
 434 }
 435
 436 HANDLE qemu_thread_get_handle(QemuThread *thread)
 437 {
 438     QemuThreadData *data;
 439     HANDLE handle;
 440
 441     data = thread->data;
 442     if (data->mode == QEMU_THREAD_DETACHED) {
 443         return NULL;
 444     }
 445
 446     EnterCriticalSection(&data->cs);
 447     if (!data->exited) {
 448         handle = OpenThread(SYNCHRONIZE | THREAD_SUSPEND_RESUME |
 449                             THREAD_SET_CONTEXT, FALSE, thread->tid);
 450     } else {
 451         handle = NULL;
 452     }
 453     LeaveCriticalSection(&data->cs);
 454     return handle;
 455 }
 456
 457 bool qemu_thread_is_self(QemuThread *thread)
 458 {
 459     return GetCurrentThreadId() == thread->tid;
 460 }