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 #include "qemu-common.h"
  14 #include "qemu/thread.h"
  15 #include "qemu/notify.h"
  16 #include <process.h>
  17 #include <assert.h>
  18 #include <limits.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     mutex->owner = 0;
  44     InitializeCriticalSection(&mutex->lock);
  45 }
  46
  47 void qemu_mutex_destroy(QemuMutex *mutex)
  48 {
  49     assert(mutex->owner == 0);
  50     DeleteCriticalSection(&mutex->lock);
  51 }
  52
  53 void qemu_mutex_lock(QemuMutex *mutex)
  54 {
  55     EnterCriticalSection(&mutex->lock);
  56
  57     /* Win32 CRITICAL_SECTIONs are recursive.  Assert that we're not
  58      * using them as such.
  59      */
  60     assert(mutex->owner == 0);
  61     mutex->owner = GetCurrentThreadId();
  62 }
  63
  64 int qemu_mutex_trylock(QemuMutex *mutex)
  65 {
  66     int owned;
  67
  68     owned = TryEnterCriticalSection(&mutex->lock);
  69     if (owned) {
  70         assert(mutex->owner == 0);
  71         mutex->owner = GetCurrentThreadId();
  72     }
  73     return !owned;
  74 }
  75
  76 void qemu_mutex_unlock(QemuMutex *mutex)
  77 {
  78     assert(mutex->owner == GetCurrentThreadId());
  79     mutex->owner = 0;
  80     LeaveCriticalSection(&mutex->lock);
  81 }
  82
  83 void qemu_cond_init(QemuCond *cond)
  84 {
  85     memset(cond, 0, sizeof(*cond));
  86
  87     cond->sema = CreateSemaphore(NULL, 0, LONG_MAX, NULL);
  88     if (!cond->sema) {
  89         error_exit(GetLastError(), __func__);
  90     }
  91     cond->continue_event = CreateEvent(NULL,    /* security */
  92                                        FALSE,   /* auto-reset */
  93                                        FALSE,   /* not signaled */
  94                                        NULL);   /* name */
  95     if (!cond->continue_event) {
  96         error_exit(GetLastError(), __func__);
  97     }
  98 }
  99
 100 void qemu_cond_destroy(QemuCond *cond)
 101 {
 102     BOOL result;
 103     result = CloseHandle(cond->continue_event);
 104     if (!result) {
 105         error_exit(GetLastError(), __func__);
 106     }
 107     cond->continue_event = 0;
 108     result = CloseHandle(cond->sema);
 109     if (!result) {
 110         error_exit(GetLastError(), __func__);
 111     }
 112     cond->sema = 0;
 113 }
 114
 115 void qemu_cond_signal(QemuCond *cond)
 116 {
 117     DWORD result;
 118
 119     /*
 120      * Signal only when there are waiters.  cond->waiters is
 121      * incremented by pthread_cond_wait under the external lock,
 122      * so we are safe about that.
 123      */
 124     if (cond->waiters == 0) {
 125         return;
 126     }
 127
 128     /*
 129      * Waiting threads decrement it outside the external lock, but
 130      * only if another thread is executing pthread_cond_broadcast and
 131      * has the mutex.  So, it also cannot be decremented concurrently
 132      * with this particular access.
 133      */
 134     cond->target = cond->waiters - 1;
 135     result = SignalObjectAndWait(cond->sema, cond->continue_event,
 136                                  INFINITE, FALSE);
 137     if (result == WAIT_ABANDONED || result == WAIT_FAILED) {
 138         error_exit(GetLastError(), __func__);
 139     }
 140 }
 141
 142 void qemu_cond_broadcast(QemuCond *cond)
 143 {
 144     BOOLEAN result;
 145     /*
 146      * As in pthread_cond_signal, access to cond->waiters and
 147      * cond->target is locked via the external mutex.
 148      */
 149     if (cond->waiters == 0) {
 150         return;
 151     }
 152
 153     cond->target = 0;
 154     result = ReleaseSemaphore(cond->sema, cond->waiters, NULL);
 155     if (!result) {
 156         error_exit(GetLastError(), __func__);
 157     }
 158
 159     /*
 160      * At this point all waiters continue. Each one takes its
 161      * slice of the semaphore. Now it's our turn to wait: Since
 162      * the external mutex is held, no thread can leave cond_wait,
 163      * yet. For this reason, we can be sure that no thread gets
 164      * a chance to eat *more* than one slice. OTOH, it means
 165      * that the last waiter must send us a wake-up.
 166      */
 167     WaitForSingleObject(cond->continue_event, INFINITE);
 168 }
 169
 170 void qemu_cond_wait(QemuCond *cond, QemuMutex *mutex)
 171 {
 172     /*
 173      * This access is protected under the mutex.
 174      */
 175     cond->waiters++;
 176
 177     /*
 178      * Unlock external mutex and wait for signal.
 179      * NOTE: we've held mutex locked long enough to increment
 180      * waiters count above, so there's no problem with
 181      * leaving mutex unlocked before we wait on semaphore.
 182      */
 183     qemu_mutex_unlock(mutex);
 184     WaitForSingleObject(cond->sema, INFINITE);
 185
 186     /* Now waiters must rendez-vous with the signaling thread and
 187      * let it continue.  For cond_broadcast this has heavy contention
 188      * and triggers thundering herd.  So goes life.
 189      *
 190      * Decrease waiters count.  The mutex is not taken, so we have
 191      * to do this atomically.
 192      *
 193      * All waiters contend for the mutex at the end of this function
 194      * until the signaling thread relinquishes it.  To ensure
 195      * each waiter consumes exactly one slice of the semaphore,
 196      * the signaling thread stops until it is told by the last
 197      * waiter that it can go on.
 198      */
 199     if (InterlockedDecrement(&cond->waiters) == cond->target) {
 200         SetEvent(cond->continue_event);
 201     }
 202
 203     qemu_mutex_lock(mutex);
 204 }
 205
 206 void qemu_sem_init(QemuSemaphore *sem, int init)
 207 {
 208     /* Manual reset.  */
 209     sem->sema = CreateSemaphore(NULL, init, LONG_MAX, NULL);
 210 }
 211
 212 void qemu_sem_destroy(QemuSemaphore *sem)
 213 {
 214     CloseHandle(sem->sema);
 215 }
 216
 217 void qemu_sem_post(QemuSemaphore *sem)
 218 {
 219     ReleaseSemaphore(sem->sema, 1, NULL);
 220 }
 221
 222 int qemu_sem_timedwait(QemuSemaphore *sem, int ms)
 223 {
 224     int rc = WaitForSingleObject(sem->sema, ms);
 225     if (rc == WAIT_OBJECT_0) {
 226         return 0;
 227     }
 228     if (rc != WAIT_TIMEOUT) {
 229         error_exit(GetLastError(), __func__);
 230     }
 231     return -1;
 232 }
 233
 234 void qemu_sem_wait(QemuSemaphore *sem)
 235 {
 236     if (WaitForSingleObject(sem->sema, INFINITE) != WAIT_OBJECT_0) {
 237         error_exit(GetLastError(), __func__);
 238     }
 239 }
 240
 241 void qemu_event_init(QemuEvent *ev, bool init)
 242 {
 243     /* Manual reset.  */
 244     ev->event = CreateEvent(NULL, TRUE, init, NULL);
 245 }
 246
 247 void qemu_event_destroy(QemuEvent *ev)
 248 {
 249     CloseHandle(ev->event);
 250 }
 251
 252 void qemu_event_set(QemuEvent *ev)
 253 {
 254     SetEvent(ev->event);
 255 }
 256
 257 void qemu_event_reset(QemuEvent *ev)
 258 {
 259     ResetEvent(ev->event);
 260 }
 261
 262 void qemu_event_wait(QemuEvent *ev)
 263 {
 264     WaitForSingleObject(ev->event, INFINITE);
 265 }
 266
 267 struct QemuThreadData {
 268     /* Passed to win32_start_routine.  */
 269     void             *(*start_routine)(void *);
 270     void             *arg;
 271     short             mode;
 272     NotifierList      exit;
 273
 274     /* Only used for joinable threads. */
 275     bool              exited;
 276     void             *ret;
 277     CRITICAL_SECTION  cs;
 278 };
 279
 280 static bool atexit_registered;
 281 static NotifierList main_thread_exit;
 282
 283 static __thread QemuThreadData *qemu_thread_data;
 284
 285 static void run_main_thread_exit(void)
 286 {
 287     notifier_list_notify(&main_thread_exit, NULL);
 288 }
 289
 290 void qemu_thread_atexit_add(Notifier *notifier)
 291 {
 292     if (!qemu_thread_data) {
 293         if (!atexit_registered) {
 294             atexit_registered = true;
 295             atexit(run_main_thread_exit);
 296         }
 297         notifier_list_add(&main_thread_exit, notifier);
 298     } else {
 299         notifier_list_add(&qemu_thread_data->exit, notifier);
 300     }
 301 }
 302
 303 void qemu_thread_atexit_remove(Notifier *notifier)
 304 {
 305     notifier_remove(notifier);
 306 }
 307
 308 static unsigned __stdcall win32_start_routine(void *arg)
 309 {
 310     QemuThreadData *data = (QemuThreadData *) arg;
 311     void *(*start_routine)(void *) = data->start_routine;
 312     void *thread_arg = data->arg;
 313
 314     qemu_thread_data = data;
 315     qemu_thread_exit(start_routine(thread_arg));
 316     abort();
 317 }
 318
 319 void qemu_thread_exit(void *arg)
 320 {
 321     QemuThreadData *data = qemu_thread_data;
 322
 323     notifier_list_notify(&data->exit, NULL);
 324     if (data->mode == QEMU_THREAD_JOINABLE) {
 325         data->ret = arg;
 326         EnterCriticalSection(&data->cs);
 327         data->exited = true;
 328         LeaveCriticalSection(&data->cs);
 329     } else {
 330         g_free(data);
 331     }
 332     _endthreadex(0);
 333 }
 334
 335 void *qemu_thread_join(QemuThread *thread)
 336 {
 337     QemuThreadData *data;
 338     void *ret;
 339     HANDLE handle;
 340
 341     data = thread->data;
 342     if (data->mode == QEMU_THREAD_DETACHED) {
 343         return NULL;
 344     }
 345
 346     /*
 347      * Because multiple copies of the QemuThread can exist via
 348      * qemu_thread_get_self, we need to store a value that cannot
 349      * leak there.  The simplest, non racy way is to store the TID,
 350      * discard the handle that _beginthreadex gives back, and
 351      * get another copy of the handle here.
 352      */
 353     handle = qemu_thread_get_handle(thread);
 354     if (handle) {
 355         WaitForSingleObject(handle, INFINITE);
 356         CloseHandle(handle);
 357     }
 358     ret = data->ret;
 359     DeleteCriticalSection(&data->cs);
 360     g_free(data);
 361     return ret;
 362 }
 363
 364 void qemu_thread_create(QemuThread *thread, const char *name,
 365                        void *(*start_routine)(void *),
 366                        void *arg, int mode)
 367 {
 368     HANDLE hThread;
 369     struct QemuThreadData *data;
 370
 371     data = g_malloc(sizeof *data);
 372     data->start_routine = start_routine;
 373     data->arg = arg;
 374     data->mode = mode;
 375     data->exited = false;
 376     notifier_list_init(&data->exit);
 377
 378     if (data->mode != QEMU_THREAD_DETACHED) {
 379         InitializeCriticalSection(&data->cs);
 380     }
 381
 382     hThread = (HANDLE) _beginthreadex(NULL, 0, win32_start_routine,
 383                                       data, 0, &thread->tid);
 384     if (!hThread) {
 385         error_exit(GetLastError(), __func__);
 386     }
 387     CloseHandle(hThread);
 388     thread->data = data;
 389 }
 390
 391 void qemu_thread_get_self(QemuThread *thread)
 392 {
 393     thread->data = qemu_thread_data;
 394     thread->tid = GetCurrentThreadId();
 395 }
 396
 397 HANDLE qemu_thread_get_handle(QemuThread *thread)
 398 {
 399     QemuThreadData *data;
 400     HANDLE handle;
 401
 402     data = thread->data;
 403     if (data->mode == QEMU_THREAD_DETACHED) {
 404         return NULL;
 405     }
 406
 407     EnterCriticalSection(&data->cs);
 408     if (!data->exited) {
 409         handle = OpenThread(SYNCHRONIZE | THREAD_SUSPEND_RESUME, FALSE,
 410                             thread->tid);
 411     } else {
 412         handle = NULL;
 413     }
 414     LeaveCriticalSection(&data->cs);
 415     return handle;
 416 }
 417
 418 bool qemu_thread_is_self(QemuThread *thread)
 419 {
 420     return GetCurrentThreadId() == thread->tid;
 421 }