root / qemu-thread-win32.c @ 9257d46d
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/*
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* Win32 implementation for mutex/cond/thread functions
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*
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* Copyright Red Hat, Inc. 2010
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*
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* Author:
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* Paolo Bonzini <pbonzini@redhat.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*
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*/
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#include "qemu-common.h" |
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#include "qemu-thread.h" |
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#include <process.h> |
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#include <assert.h> |
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#include <limits.h> |
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static void error_exit(int err, const char *msg) |
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{ |
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char *pstr;
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FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ALLOCATE_BUFFER, |
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NULL, err, 0, (LPTSTR)&pstr, 2, NULL); |
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fprintf(stderr, "qemu: %s: %s\n", msg, pstr);
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LocalFree(pstr); |
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exit(1);
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} |
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void qemu_mutex_init(QemuMutex *mutex)
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{ |
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mutex->owner = 0;
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InitializeCriticalSection(&mutex->lock); |
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} |
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void qemu_mutex_lock(QemuMutex *mutex)
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{ |
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EnterCriticalSection(&mutex->lock); |
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/* Win32 CRITICAL_SECTIONs are recursive. Assert that we're not
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* using them as such.
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*/
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assert(mutex->owner == 0);
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mutex->owner = GetCurrentThreadId(); |
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} |
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int qemu_mutex_trylock(QemuMutex *mutex)
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{ |
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int owned;
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owned = TryEnterCriticalSection(&mutex->lock); |
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if (owned) {
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assert(mutex->owner == 0);
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mutex->owner = GetCurrentThreadId(); |
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} |
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return !owned;
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} |
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void qemu_mutex_unlock(QemuMutex *mutex)
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{ |
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assert(mutex->owner == GetCurrentThreadId()); |
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mutex->owner = 0;
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LeaveCriticalSection(&mutex->lock); |
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} |
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void qemu_cond_init(QemuCond *cond)
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{ |
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memset(cond, 0, sizeof(*cond)); |
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cond->sema = CreateSemaphore(NULL, 0, LONG_MAX, NULL); |
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if (!cond->sema) {
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error_exit(GetLastError(), __func__); |
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} |
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cond->continue_event = CreateEvent(NULL, /* security */ |
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FALSE, /* auto-reset */
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FALSE, /* not signaled */
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NULL); /* name */ |
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if (!cond->continue_event) {
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error_exit(GetLastError(), __func__); |
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} |
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} |
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void qemu_cond_signal(QemuCond *cond)
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{ |
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DWORD result; |
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/*
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* Signal only when there are waiters. cond->waiters is
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* incremented by pthread_cond_wait under the external lock,
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* so we are safe about that.
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*/
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if (cond->waiters == 0) { |
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return;
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} |
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/*
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* Waiting threads decrement it outside the external lock, but
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* only if another thread is executing pthread_cond_broadcast and
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* has the mutex. So, it also cannot be decremented concurrently
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* with this particular access.
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*/
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cond->target = cond->waiters - 1;
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result = SignalObjectAndWait(cond->sema, cond->continue_event, |
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INFINITE, FALSE); |
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if (result == WAIT_ABANDONED || result == WAIT_FAILED) {
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error_exit(GetLastError(), __func__); |
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} |
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} |
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void qemu_cond_broadcast(QemuCond *cond)
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{ |
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BOOLEAN result; |
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/*
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* As in pthread_cond_signal, access to cond->waiters and
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* cond->target is locked via the external mutex.
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*/
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if (cond->waiters == 0) { |
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return;
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} |
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cond->target = 0;
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result = ReleaseSemaphore(cond->sema, cond->waiters, NULL);
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if (!result) {
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error_exit(GetLastError(), __func__); |
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} |
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/*
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* At this point all waiters continue. Each one takes its
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* slice of the semaphore. Now it's our turn to wait: Since
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* the external mutex is held, no thread can leave cond_wait,
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* yet. For this reason, we can be sure that no thread gets
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* a chance to eat *more* than one slice. OTOH, it means
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* that the last waiter must send us a wake-up.
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*/
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WaitForSingleObject(cond->continue_event, INFINITE); |
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} |
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void qemu_cond_wait(QemuCond *cond, QemuMutex *mutex)
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{ |
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/*
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* This access is protected under the mutex.
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*/
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cond->waiters++; |
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/*
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* Unlock external mutex and wait for signal.
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* NOTE: we've held mutex locked long enough to increment
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* waiters count above, so there's no problem with
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* leaving mutex unlocked before we wait on semaphore.
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*/
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qemu_mutex_unlock(mutex); |
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WaitForSingleObject(cond->sema, INFINITE); |
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/* Now waiters must rendez-vous with the signaling thread and
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* let it continue. For cond_broadcast this has heavy contention
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* and triggers thundering herd. So goes life.
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*
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* Decrease waiters count. The mutex is not taken, so we have
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* to do this atomically.
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*
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* All waiters contend for the mutex at the end of this function
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* until the signaling thread relinquishes it. To ensure
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* each waiter consumes exactly one slice of the semaphore,
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* the signaling thread stops until it is told by the last
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* waiter that it can go on.
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*/
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if (InterlockedDecrement(&cond->waiters) == cond->target) {
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SetEvent(cond->continue_event); |
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} |
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qemu_mutex_lock(mutex); |
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} |
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struct QemuThreadData {
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QemuThread *thread; |
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void *(*start_routine)(void *); |
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void *arg;
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}; |
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static int qemu_thread_tls_index = TLS_OUT_OF_INDEXES; |
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static unsigned __stdcall win32_start_routine(void *arg) |
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{ |
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struct QemuThreadData data = *(struct QemuThreadData *) arg; |
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QemuThread *thread = data.thread; |
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free(arg); |
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TlsSetValue(qemu_thread_tls_index, thread); |
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/*
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* Use DuplicateHandle instead of assigning thread->thread in the
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* creating thread to avoid races. It's simpler this way than with
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* synchronization.
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*/
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DuplicateHandle(GetCurrentProcess(), GetCurrentThread(), |
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GetCurrentProcess(), &thread->thread, |
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0, FALSE, DUPLICATE_SAME_ACCESS);
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qemu_thread_exit(data.start_routine(data.arg)); |
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abort(); |
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} |
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void qemu_thread_exit(void *arg) |
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{ |
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QemuThread *thread = TlsGetValue(qemu_thread_tls_index); |
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thread->ret = arg; |
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CloseHandle(thread->thread); |
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thread->thread = NULL;
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ExitThread(0);
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} |
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static inline void qemu_thread_init(void) |
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{ |
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if (qemu_thread_tls_index == TLS_OUT_OF_INDEXES) {
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qemu_thread_tls_index = TlsAlloc(); |
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if (qemu_thread_tls_index == TLS_OUT_OF_INDEXES) {
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error_exit(ERROR_NO_SYSTEM_RESOURCES, __func__); |
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} |
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} |
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} |
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void qemu_thread_create(QemuThread *thread,
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void *(*start_routine)(void *), |
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void *arg)
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{ |
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HANDLE hThread; |
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struct QemuThreadData *data;
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qemu_thread_init(); |
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data = qemu_malloc(sizeof *data);
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data->thread = thread; |
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data->start_routine = start_routine; |
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data->arg = arg; |
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hThread = (HANDLE) _beginthreadex(NULL, 0, win32_start_routine, |
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data, 0, NULL); |
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if (!hThread) {
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error_exit(GetLastError(), __func__); |
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} |
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CloseHandle(hThread); |
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} |
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void qemu_thread_get_self(QemuThread *thread)
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{ |
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if (!thread->thread) {
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/* In the main thread of the process. Initialize the QemuThread
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pointer in TLS, and use the dummy GetCurrentThread handle as
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the identifier for qemu_thread_is_self. */
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qemu_thread_init(); |
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TlsSetValue(qemu_thread_tls_index, thread); |
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thread->thread = GetCurrentThread(); |
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} |
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} |
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int qemu_thread_is_self(QemuThread *thread)
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{ |
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QemuThread *this_thread = TlsGetValue(qemu_thread_tls_index); |
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return this_thread->thread == thread->thread;
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} |