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-common.h"
  16 #include "qemu/thread.h"
  17 #include "qemu/notify.h"
  18 #include "qemu-thread-common.h"
  19 #include <process.h>
  20
  21 static bool name_threads;
  22
  23 void qemu_thread_naming(bool enable)
  24 {
  25     /* But note we don't actually name them on Windows yet */
  26     name_threads = enable;
  27
  28     fprintf(stderr, "qemu: thread naming not supported on this host\n");
  29 }
  30
  31 static void error_exit(int err, const char *msg)
  32 {
  33     char *pstr;
  34
  35     FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ALLOCATE_BUFFER,
  36                   NULL, err, 0, (LPTSTR)&pstr, 2, NULL);
  37     fprintf(stderr, "qemu: %s: %s\n", msg, pstr);
  38     LocalFree(pstr);
  39     abort();
  40 }
  41
  42 void qemu_mutex_init(QemuMutex *mutex)
  43 {
  44     InitializeSRWLock(&mutex->lock);
  45     qemu_mutex_post_init(mutex);
  46 }
  47
  48 void qemu_mutex_destroy(QemuMutex *mutex)
  49 {
  50     assert(mutex->initialized);
  51     mutex->initialized = false;
  52     InitializeSRWLock(&mutex->lock);
  53 }
  54
  55 void qemu_mutex_lock_impl(QemuMutex *mutex, const char *file, const int line)
  56 {
  57     assert(mutex->initialized);
  58     qemu_mutex_pre_lock(mutex, file, line);
  59     AcquireSRWLockExclusive(&mutex->lock);
  60     qemu_mutex_post_lock(mutex, file, line);
  61 }
  62
  63 int qemu_mutex_trylock_impl(QemuMutex *mutex, const char *file, const int line)
  64 {
  65     int owned;
  66
  67     assert(mutex->initialized);
  68     owned = TryAcquireSRWLockExclusive(&mutex->lock);
  69     if (owned) {
  70         qemu_mutex_post_lock(mutex, file, line);
  71         return 0;
  72     }
  73     return -EBUSY;
  74 }
  75
  76 void qemu_mutex_unlock_impl(QemuMutex *mutex, const char *file, const int line)
  77 {
  78     assert(mutex->initialized);
  79     qemu_mutex_pre_unlock(mutex, file, line);
  80     ReleaseSRWLockExclusive(&mutex->lock);
  81 }
  82
  83 void qemu_rec_mutex_init(QemuRecMutex *mutex)
  84 {
  85     InitializeCriticalSection(&mutex->lock);
  86     mutex->initialized = true;
  87 }
  88
  89 void qemu_rec_mutex_destroy(QemuRecMutex *mutex)
  90 {
  91     assert(mutex->initialized);
  92     mutex->initialized = false;
  93     DeleteCriticalSection(&mutex->lock);
  94 }
  95
  96 void qemu_rec_mutex_lock_impl(QemuRecMutex *mutex, const char *file, int line)
  97 {
  98     assert(mutex->initialized);
  99     EnterCriticalSection(&mutex->lock);
 100 }
 101
 102 int qemu_rec_mutex_trylock_impl(QemuRecMutex *mutex, const char *file, int line)
 103 {
 104     assert(mutex->initialized);
 105     return !TryEnterCriticalSection(&mutex->lock);
 106 }
 107
 108 void qemu_rec_mutex_unlock(QemuRecMutex *mutex)
 109 {
 110     assert(mutex->initialized);
 111     LeaveCriticalSection(&mutex->lock);
 112 }
 113
 114 void qemu_cond_init(QemuCond *cond)
 115 {
 116     memset(cond, 0, sizeof(*cond));
 117     InitializeConditionVariable(&cond->var);
 118     cond->initialized = true;
 119 }
 120
 121 void qemu_cond_destroy(QemuCond *cond)
 122 {
 123     assert(cond->initialized);
 124     cond->initialized = false;
 125     InitializeConditionVariable(&cond->var);
 126 }
 127
 128 void qemu_cond_signal(QemuCond *cond)
 129 {
 130     assert(cond->initialized);
 131     WakeConditionVariable(&cond->var);
 132 }
 133
 134 void qemu_cond_broadcast(QemuCond *cond)
 135 {
 136     assert(cond->initialized);
 137     WakeAllConditionVariable(&cond->var);
 138 }
 139
 140 void qemu_cond_wait_impl(QemuCond *cond, QemuMutex *mutex, const char *file, const int line)
 141 {
 142     assert(cond->initialized);
 143     qemu_mutex_pre_unlock(mutex, file, line);
 144     SleepConditionVariableSRW(&cond->var, &mutex->lock, INFINITE, 0);
 145     qemu_mutex_post_lock(mutex, file, line);
 146 }
 147
 148 bool qemu_cond_timedwait_impl(QemuCond *cond, QemuMutex *mutex, int ms,
 149                               const char *file, const int line)
 150 {
 151     int rc = 0;
 152
 153     assert(cond->initialized);
 154     trace_qemu_mutex_unlock(mutex, file, line);
 155     if (!SleepConditionVariableSRW(&cond->var, &mutex->lock, ms, 0)) {
 156         rc = GetLastError();
 157     }
 158     trace_qemu_mutex_locked(mutex, file, line);
 159     if (rc && rc != ERROR_TIMEOUT) {
 160         error_exit(rc, __func__);
 161     }
 162     return rc != ERROR_TIMEOUT;
 163 }
 164
 165 void qemu_sem_init(QemuSemaphore *sem, int init)
 166 {
 167     /* Manual reset.  */
 168     sem->sema = CreateSemaphore(NULL, init, LONG_MAX, NULL);
 169     sem->initialized = true;
 170 }
 171
 172 void qemu_sem_destroy(QemuSemaphore *sem)
 173 {
 174     assert(sem->initialized);
 175     sem->initialized = false;
 176     CloseHandle(sem->sema);
 177 }
 178
 179 void qemu_sem_post(QemuSemaphore *sem)
 180 {
 181     assert(sem->initialized);
 182     ReleaseSemaphore(sem->sema, 1, NULL);
 183 }
 184
 185 int qemu_sem_timedwait(QemuSemaphore *sem, int ms)
 186 {
 187     int rc;
 188
 189     assert(sem->initialized);
 190     rc = WaitForSingleObject(sem->sema, ms);
 191     if (rc == WAIT_OBJECT_0) {
 192         return 0;
 193     }
 194     if (rc != WAIT_TIMEOUT) {
 195         error_exit(GetLastError(), __func__);
 196     }
 197     return -1;
 198 }
 199
 200 void qemu_sem_wait(QemuSemaphore *sem)
 201 {
 202     assert(sem->initialized);
 203     if (WaitForSingleObject(sem->sema, INFINITE) != WAIT_OBJECT_0) {
 204         error_exit(GetLastError(), __func__);
 205     }
 206 }
 207
 208 /* Wrap a Win32 manual-reset event with a fast userspace path.  The idea
 209  * is to reset the Win32 event lazily, as part of a test-reset-test-wait
 210  * sequence.  Such a sequence is, indeed, how QemuEvents are used by
 211  * RCU and other subsystems!
 212  *
 213  * Valid transitions:
 214  * - free->set, when setting the event
 215  * - busy->set, when setting the event, followed by SetEvent
 216  * - set->free, when resetting the event
 217  * - free->busy, when waiting
 218  *
 219  * set->busy does not happen (it can be observed from the outside but
 220  * it really is set->free->busy).
 221  *
 222  * busy->free provably cannot happen; to enforce it, the set->free transition
 223  * is done with an OR, which becomes a no-op if the event has concurrently
 224  * transitioned to free or busy (and is faster than cmpxchg).
 225  */
 226
 227 #define EV_SET         0
 228 #define EV_FREE        1
 229 #define EV_BUSY       -1
 230
 231 void qemu_event_init(QemuEvent *ev, bool init)
 232 {
 233     /* Manual reset.  */
 234     ev->event = CreateEvent(NULL, TRUE, TRUE, NULL);
 235     ev->value = (init ? EV_SET : EV_FREE);
 236     ev->initialized = true;
 237 }
 238
 239 void qemu_event_destroy(QemuEvent *ev)
 240 {
 241     assert(ev->initialized);
 242     ev->initialized = false;
 243     CloseHandle(ev->event);
 244 }
 245
 246 void qemu_event_set(QemuEvent *ev)
 247 {
 248     assert(ev->initialized);
 249     /* qemu_event_set has release semantics, but because it *loads*
 250      * ev->value we need a full memory barrier here.
 251      */
 252     smp_mb();
 253     if (qatomic_read(&ev->value) != EV_SET) {
 254         if (qatomic_xchg(&ev->value, EV_SET) == EV_BUSY) {
 255             /* There were waiters, wake them up.  */
 256             SetEvent(ev->event);
 257         }
 258     }
 259 }
 260
 261 void qemu_event_reset(QemuEvent *ev)
 262 {
 263     unsigned value;
 264
 265     assert(ev->initialized);
 266     value = qatomic_read(&ev->value);
 267     smp_mb_acquire();
 268     if (value == EV_SET) {
 269         /* If there was a concurrent reset (or even reset+wait),
 270          * do nothing.  Otherwise change EV_SET->EV_FREE.
 271          */
 272         qatomic_or(&ev->value, EV_FREE);
 273     }
 274 }
 275
 276 void qemu_event_wait(QemuEvent *ev)
 277 {
 278     unsigned value;
 279
 280     assert(ev->initialized);
 281     value = qatomic_read(&ev->value);
 282     smp_mb_acquire();
 283     if (value != EV_SET) {
 284         if (value == EV_FREE) {
 285             /* qemu_event_set is not yet going to call SetEvent, but we are
 286              * going to do another check for EV_SET below when setting EV_BUSY.
 287              * At that point it is safe to call WaitForSingleObject.
 288              */
 289             ResetEvent(ev->event);
 290
 291             /* Tell qemu_event_set that there are waiters.  No need to retry
 292              * because there cannot be a concurrent busy->free transition.
 293              * After the CAS, the event will be either set or busy.
 294              */
 295             if (qatomic_cmpxchg(&ev->value, EV_FREE, EV_BUSY) == EV_SET) {
 296                 value = EV_SET;
 297             } else {
 298                 value = EV_BUSY;
 299             }
 300         }
 301         if (value == EV_BUSY) {
 302             WaitForSingleObject(ev->event, INFINITE);
 303         }
 304     }
 305 }
 306
 307 struct QemuThreadData {
 308     /* Passed to win32_start_routine.  */
 309     void             *(*start_routine)(void *);
 310     void             *arg;
 311     short             mode;
 312     NotifierList      exit;
 313
 314     /* Only used for joinable threads. */
 315     bool              exited;
 316     void             *ret;
 317     CRITICAL_SECTION  cs;
 318 };
 319
 320 static bool atexit_registered;
 321 static NotifierList main_thread_exit;
 322
 323 static __thread QemuThreadData *qemu_thread_data;
 324
 325 static void run_main_thread_exit(void)
 326 {
 327     notifier_list_notify(&main_thread_exit, NULL);
 328 }
 329
 330 void qemu_thread_atexit_add(Notifier *notifier)
 331 {
 332     if (!qemu_thread_data) {
 333         if (!atexit_registered) {
 334             atexit_registered = true;
 335             atexit(run_main_thread_exit);
 336         }
 337         notifier_list_add(&main_thread_exit, notifier);
 338     } else {
 339         notifier_list_add(&qemu_thread_data->exit, notifier);
 340     }
 341 }
 342
 343 void qemu_thread_atexit_remove(Notifier *notifier)
 344 {
 345     notifier_remove(notifier);
 346 }
 347
 348 static unsigned __stdcall win32_start_routine(void *arg)
 349 {
 350     QemuThreadData *data = (QemuThreadData *) arg;
 351     void *(*start_routine)(void *) = data->start_routine;
 352     void *thread_arg = data->arg;
 353
 354     qemu_thread_data = data;
 355     qemu_thread_exit(start_routine(thread_arg));
 356     abort();
 357 }
 358
 359 void qemu_thread_exit(void *arg)
 360 {
 361     QemuThreadData *data = qemu_thread_data;
 362
 363     notifier_list_notify(&data->exit, NULL);
 364     if (data->mode == QEMU_THREAD_JOINABLE) {
 365         data->ret = arg;
 366         EnterCriticalSection(&data->cs);
 367         data->exited = true;
 368         LeaveCriticalSection(&data->cs);
 369     } else {
 370         g_free(data);
 371     }
 372     _endthreadex(0);
 373 }
 374
 375 void *qemu_thread_join(QemuThread *thread)
 376 {
 377     QemuThreadData *data;
 378     void *ret;
 379     HANDLE handle;
 380
 381     data = thread->data;
 382     if (data->mode == QEMU_THREAD_DETACHED) {
 383         return NULL;
 384     }
 385
 386     /*
 387      * Because multiple copies of the QemuThread can exist via
 388      * qemu_thread_get_self, we need to store a value that cannot
 389      * leak there.  The simplest, non racy way is to store the TID,
 390      * discard the handle that _beginthreadex gives back, and
 391      * get another copy of the handle here.
 392      */
 393     handle = qemu_thread_get_handle(thread);
 394     if (handle) {
 395         WaitForSingleObject(handle, INFINITE);
 396         CloseHandle(handle);
 397     }
 398     ret = data->ret;
 399     DeleteCriticalSection(&data->cs);
 400     g_free(data);
 401     return ret;
 402 }
 403
 404 void qemu_thread_create(QemuThread *thread, const char *name,
 405                        void *(*start_routine)(void *),
 406                        void *arg, int mode)
 407 {
 408     HANDLE hThread;
 409     struct QemuThreadData *data;
 410
 411     data = g_malloc(sizeof *data);
 412     data->start_routine = start_routine;
 413     data->arg = arg;
 414     data->mode = mode;
 415     data->exited = false;
 416     notifier_list_init(&data->exit);
 417
 418     if (data->mode != QEMU_THREAD_DETACHED) {
 419         InitializeCriticalSection(&data->cs);
 420     }
 421
 422     hThread = (HANDLE) _beginthreadex(NULL, 0, win32_start_routine,
 423                                       data, 0, &thread->tid);
 424     if (!hThread) {
 425         error_exit(GetLastError(), __func__);
 426     }
 427     CloseHandle(hThread);
 428     thread->data = data;
 429 }
 430
 431 void qemu_thread_get_self(QemuThread *thread)
 432 {
 433     thread->data = qemu_thread_data;
 434     thread->tid = GetCurrentThreadId();
 435 }
 436
 437 HANDLE qemu_thread_get_handle(QemuThread *thread)
 438 {
 439     QemuThreadData *data;
 440     HANDLE handle;
 441
 442     data = thread->data;
 443     if (data->mode == QEMU_THREAD_DETACHED) {
 444         return NULL;
 445     }
 446
 447     EnterCriticalSection(&data->cs);
 448     if (!data->exited) {
 449         handle = OpenThread(SYNCHRONIZE | THREAD_SUSPEND_RESUME |
 450                             THREAD_SET_CONTEXT, FALSE, thread->tid);
 451     } else {
 452         handle = NULL;
 453     }
 454     LeaveCriticalSection(&data->cs);
 455     return handle;
 456 }
 457
 458 bool qemu_thread_is_self(QemuThread *thread)
 459 {
 460     return GetCurrentThreadId() == thread->tid;
 461 }