add win32 qemu-thread implementation
For now, qemu_cond_timedwait and qemu_mutex_timedlock are left as
POSIX-only functions. They can be removed later, once the patches
that remove their uses are in.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/qemu-thread-win32.c b/qemu-thread-win32.c
new file mode 100644
index 0000000..2edcb1a
--- /dev/null
+++ b/qemu-thread-win32.c
@@ -0,0 +1,260 @@
+/*
+ * Win32 implementation for mutex/cond/thread functions
+ *
+ * Copyright Red Hat, Inc. 2010
+ *
+ * Author:
+ * Paolo Bonzini <pbonzini@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+#include "qemu-common.h"
+#include "qemu-thread.h"
+#include <process.h>
+#include <assert.h>
+#include <limits.h>
+
+static void error_exit(int err, const char *msg)
+{
+ char *pstr;
+
+ FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ALLOCATE_BUFFER,
+ NULL, err, 0, (LPTSTR)&pstr, 2, NULL);
+ fprintf(stderr, "qemu: %s: %s\n", msg, pstr);
+ LocalFree(pstr);
+ exit(1);
+}
+
+void qemu_mutex_init(QemuMutex *mutex)
+{
+ mutex->owner = 0;
+ InitializeCriticalSection(&mutex->lock);
+}
+
+void qemu_mutex_lock(QemuMutex *mutex)
+{
+ EnterCriticalSection(&mutex->lock);
+
+ /* Win32 CRITICAL_SECTIONs are recursive. Assert that we're not
+ * using them as such.
+ */
+ assert(mutex->owner == 0);
+ mutex->owner = GetCurrentThreadId();
+}
+
+int qemu_mutex_trylock(QemuMutex *mutex)
+{
+ int owned;
+
+ owned = TryEnterCriticalSection(&mutex->lock);
+ if (owned) {
+ assert(mutex->owner == 0);
+ mutex->owner = GetCurrentThreadId();
+ }
+ return !owned;
+}
+
+void qemu_mutex_unlock(QemuMutex *mutex)
+{
+ assert(mutex->owner == GetCurrentThreadId());
+ mutex->owner = 0;
+ LeaveCriticalSection(&mutex->lock);
+}
+
+void qemu_cond_init(QemuCond *cond)
+{
+ memset(cond, 0, sizeof(*cond));
+
+ cond->sema = CreateSemaphore(NULL, 0, LONG_MAX, NULL);
+ if (!cond->sema) {
+ error_exit(GetLastError(), __func__);
+ }
+ cond->continue_event = CreateEvent(NULL, /* security */
+ FALSE, /* auto-reset */
+ FALSE, /* not signaled */
+ NULL); /* name */
+ if (!cond->continue_event) {
+ error_exit(GetLastError(), __func__);
+ }
+}
+
+void qemu_cond_signal(QemuCond *cond)
+{
+ DWORD result;
+
+ /*
+ * Signal only when there are waiters. cond->waiters is
+ * incremented by pthread_cond_wait under the external lock,
+ * so we are safe about that.
+ */
+ if (cond->waiters == 0) {
+ return;
+ }
+
+ /*
+ * Waiting threads decrement it outside the external lock, but
+ * only if another thread is executing pthread_cond_broadcast and
+ * has the mutex. So, it also cannot be decremented concurrently
+ * with this particular access.
+ */
+ cond->target = cond->waiters - 1;
+ result = SignalObjectAndWait(cond->sema, cond->continue_event,
+ INFINITE, FALSE);
+ if (result == WAIT_ABANDONED || result == WAIT_FAILED) {
+ error_exit(GetLastError(), __func__);
+ }
+}
+
+void qemu_cond_broadcast(QemuCond *cond)
+{
+ BOOLEAN result;
+ /*
+ * As in pthread_cond_signal, access to cond->waiters and
+ * cond->target is locked via the external mutex.
+ */
+ if (cond->waiters == 0) {
+ return;
+ }
+
+ cond->target = 0;
+ result = ReleaseSemaphore(cond->sema, cond->waiters, NULL);
+ if (!result) {
+ error_exit(GetLastError(), __func__);
+ }
+
+ /*
+ * At this point all waiters continue. Each one takes its
+ * slice of the semaphore. Now it's our turn to wait: Since
+ * the external mutex is held, no thread can leave cond_wait,
+ * yet. For this reason, we can be sure that no thread gets
+ * a chance to eat *more* than one slice. OTOH, it means
+ * that the last waiter must send us a wake-up.
+ */
+ WaitForSingleObject(cond->continue_event, INFINITE);
+}
+
+void qemu_cond_wait(QemuCond *cond, QemuMutex *mutex)
+{
+ /*
+ * This access is protected under the mutex.
+ */
+ cond->waiters++;
+
+ /*
+ * Unlock external mutex and wait for signal.
+ * NOTE: we've held mutex locked long enough to increment
+ * waiters count above, so there's no problem with
+ * leaving mutex unlocked before we wait on semaphore.
+ */
+ qemu_mutex_unlock(mutex);
+ WaitForSingleObject(cond->sema, INFINITE);
+
+ /* Now waiters must rendez-vous with the signaling thread and
+ * let it continue. For cond_broadcast this has heavy contention
+ * and triggers thundering herd. So goes life.
+ *
+ * Decrease waiters count. The mutex is not taken, so we have
+ * to do this atomically.
+ *
+ * All waiters contend for the mutex at the end of this function
+ * until the signaling thread relinquishes it. To ensure
+ * each waiter consumes exactly one slice of the semaphore,
+ * the signaling thread stops until it is told by the last
+ * waiter that it can go on.
+ */
+ if (InterlockedDecrement(&cond->waiters) == cond->target) {
+ SetEvent(cond->continue_event);
+ }
+
+ qemu_mutex_lock(mutex);
+}
+
+struct QemuThreadData {
+ QemuThread *thread;
+ void *(*start_routine)(void *);
+ void *arg;
+};
+
+static int qemu_thread_tls_index = TLS_OUT_OF_INDEXES;
+
+static unsigned __stdcall win32_start_routine(void *arg)
+{
+ struct QemuThreadData data = *(struct QemuThreadData *) arg;
+ QemuThread *thread = data.thread;
+
+ free(arg);
+ TlsSetValue(qemu_thread_tls_index, thread);
+
+ /*
+ * Use DuplicateHandle instead of assigning thread->thread in the
+ * creating thread to avoid races. It's simpler this way than with
+ * synchronization.
+ */
+ DuplicateHandle(GetCurrentProcess(), GetCurrentThread(),
+ GetCurrentProcess(), &thread->thread,
+ 0, FALSE, DUPLICATE_SAME_ACCESS);
+
+ qemu_thread_exit(data.start_routine(data.arg));
+ abort();
+}
+
+void qemu_thread_exit(void *arg)
+{
+ QemuThread *thread = TlsGetValue(qemu_thread_tls_index);
+ thread->ret = arg;
+ CloseHandle(thread->thread);
+ thread->thread = NULL;
+ ExitThread(0);
+}
+
+static inline void qemu_thread_init(void)
+{
+ if (qemu_thread_tls_index == TLS_OUT_OF_INDEXES) {
+ qemu_thread_tls_index = TlsAlloc();
+ if (qemu_thread_tls_index == TLS_OUT_OF_INDEXES) {
+ error_exit(ERROR_NO_SYSTEM_RESOURCES, __func__);
+ }
+ }
+}
+
+
+void qemu_thread_create(QemuThread *thread,
+ void *(*start_routine)(void *),
+ void *arg)
+{
+ HANDLE hThread;
+
+ struct QemuThreadData *data;
+ qemu_thread_init();
+ data = qemu_malloc(sizeof *data);
+ data->thread = thread;
+ data->start_routine = start_routine;
+ data->arg = arg;
+
+ hThread = (HANDLE) _beginthreadex(NULL, 0, win32_start_routine,
+ data, 0, NULL);
+ if (!hThread) {
+ error_exit(GetLastError(), __func__);
+ }
+ CloseHandle(hThread);
+}
+
+void qemu_thread_get_self(QemuThread *thread)
+{
+ if (!thread->thread) {
+ /* In the main thread of the process. Initialize the QemuThread
+ pointer in TLS, and use the dummy GetCurrentThread handle as
+ the identifier for qemu_thread_is_self. */
+ qemu_thread_init();
+ TlsSetValue(qemu_thread_tls_index, thread);
+ thread->thread = GetCurrentThread();
+ }
+}
+
+int qemu_thread_is_self(QemuThread *thread)
+{
+ QemuThread *this_thread = TlsGetValue(qemu_thread_tls_index);
+ return this_thread->thread == thread->thread;
+}