[mirror_qemu.git] / util / qemu-thread-win32.c

/*
 * 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/osdep.h"
#include "qemu-common.h"
#include "qemu/thread.h"
#include "qemu/notify.h"
#include <process.h>

static bool name_threads;

void qemu_thread_naming(bool enable)
{
    /* But note we don't actually name them on Windows yet */
    name_threads = enable;

    fprintf(stderr, "qemu: thread naming not supported on this host\n");
}

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);
    abort();
}

void qemu_mutex_init(QemuMutex *mutex)
{
    mutex->owner = 0;
    InitializeCriticalSection(&mutex->lock);
}

void qemu_mutex_destroy(QemuMutex *mutex)
{
    assert(mutex->owner == 0);
    DeleteCriticalSection(&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_destroy(QemuCond *cond)
{
    BOOL result;
    result = CloseHandle(cond->continue_event);
    if (!result) {
        error_exit(GetLastError(), __func__);
    }
    cond->continue_event = 0;
    result = CloseHandle(cond->sema);
    if (!result) {
        error_exit(GetLastError(), __func__);
    }
    cond->sema = 0;
}

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);
}

void qemu_sem_init(QemuSemaphore *sem, int init)
{
    /* Manual reset.  */
    sem->sema = CreateSemaphore(NULL, init, LONG_MAX, NULL);
}

void qemu_sem_destroy(QemuSemaphore *sem)
{
    CloseHandle(sem->sema);
}

void qemu_sem_post(QemuSemaphore *sem)
{
    ReleaseSemaphore(sem->sema, 1, NULL);
}

int qemu_sem_timedwait(QemuSemaphore *sem, int ms)
{
    int rc = WaitForSingleObject(sem->sema, ms);
    if (rc == WAIT_OBJECT_0) {
        return 0;
    }
    if (rc != WAIT_TIMEOUT) {
        error_exit(GetLastError(), __func__);
    }
    return -1;
}

void qemu_sem_wait(QemuSemaphore *sem)
{
    if (WaitForSingleObject(sem->sema, INFINITE) != WAIT_OBJECT_0) {
        error_exit(GetLastError(), __func__);
    }
}

/* Wrap a Win32 manual-reset event with a fast userspace path.  The idea
 * is to reset the Win32 event lazily, as part of a test-reset-test-wait
 * sequence.  Such a sequence is, indeed, how QemuEvents are used by
 * RCU and other subsystems!
 *
 * Valid transitions:
 * - free->set, when setting the event
 * - busy->set, when setting the event, followed by futex_wake
 * - set->free, when resetting the event
 * - free->busy, when waiting
 *
 * set->busy does not happen (it can be observed from the outside but
 * it really is set->free->busy).
 *
 * busy->free provably cannot happen; to enforce it, the set->free transition
 * is done with an OR, which becomes a no-op if the event has concurrently
 * transitioned to free or busy (and is faster than cmpxchg).
 */

#define EV_SET         0
#define EV_FREE        1
#define EV_BUSY       -1

void qemu_event_init(QemuEvent *ev, bool init)
{
    /* Manual reset.  */
    ev->event = CreateEvent(NULL, TRUE, TRUE, NULL);
    ev->value = (init ? EV_SET : EV_FREE);
}

void qemu_event_destroy(QemuEvent *ev)
{
    CloseHandle(ev->event);
}

void qemu_event_set(QemuEvent *ev)
{
    if (atomic_mb_read(&ev->value) != EV_SET) {
        if (atomic_xchg(&ev->value, EV_SET) == EV_BUSY) {
            /* There were waiters, wake them up.  */
            SetEvent(ev->event);
        }
    }
}

void qemu_event_reset(QemuEvent *ev)
{
    if (atomic_mb_read(&ev->value) == EV_SET) {
        /* If there was a concurrent reset (or even reset+wait),
         * do nothing.  Otherwise change EV_SET->EV_FREE.
         */
        atomic_or(&ev->value, EV_FREE);
    }
}

void qemu_event_wait(QemuEvent *ev)
{
    unsigned value;

    value = atomic_mb_read(&ev->value);
    if (value != EV_SET) {
        if (value == EV_FREE) {
            /* qemu_event_set is not yet going to call SetEvent, but we are
             * going to do another check for EV_SET below when setting EV_BUSY.
             * At that point it is safe to call WaitForSingleObject.
             */
            ResetEvent(ev->event);

            /* Tell qemu_event_set that there are waiters.  No need to retry
             * because there cannot be a concurent busy->free transition.
             * After the CAS, the event will be either set or busy.
             */
            if (atomic_cmpxchg(&ev->value, EV_FREE, EV_BUSY) == EV_SET) {
                value = EV_SET;
            } else {
                value = EV_BUSY;
            }
        }
        if (value == EV_BUSY) {
            WaitForSingleObject(ev->event, INFINITE);
        }
    }
}

struct QemuThreadData {
    /* Passed to win32_start_routine.  */
    void             *(*start_routine)(void *);
    void             *arg;
    short             mode;
    NotifierList      exit;

    /* Only used for joinable threads. */
    bool              exited;
    void             *ret;
    CRITICAL_SECTION  cs;
};

static bool atexit_registered;
static NotifierList main_thread_exit;

static __thread QemuThreadData *qemu_thread_data;

static void run_main_thread_exit(void)
{
    notifier_list_notify(&main_thread_exit, NULL);
}

void qemu_thread_atexit_add(Notifier *notifier)
{
    if (!qemu_thread_data) {
        if (!atexit_registered) {
            atexit_registered = true;
            atexit(run_main_thread_exit);
        }
        notifier_list_add(&main_thread_exit, notifier);
    } else {
        notifier_list_add(&qemu_thread_data->exit, notifier);
    }
}

void qemu_thread_atexit_remove(Notifier *notifier)
{
    notifier_remove(notifier);
}

static unsigned __stdcall win32_start_routine(void *arg)
{
    QemuThreadData *data = (QemuThreadData *) arg;
    void *(*start_routine)(void *) = data->start_routine;
    void *thread_arg = data->arg;

    qemu_thread_data = data;
    qemu_thread_exit(start_routine(thread_arg));
    abort();
}

void qemu_thread_exit(void *arg)
{
    QemuThreadData *data = qemu_thread_data;

    notifier_list_notify(&data->exit, NULL);
    if (data->mode == QEMU_THREAD_JOINABLE) {
        data->ret = arg;
        EnterCriticalSection(&data->cs);
        data->exited = true;
        LeaveCriticalSection(&data->cs);
    } else {
        g_free(data);
    }
    _endthreadex(0);
}

void *qemu_thread_join(QemuThread *thread)
{
    QemuThreadData *data;
    void *ret;
    HANDLE handle;

    data = thread->data;
    if (data->mode == QEMU_THREAD_DETACHED) {
        return NULL;
    }

    /*
     * Because multiple copies of the QemuThread can exist via
     * qemu_thread_get_self, we need to store a value that cannot
     * leak there.  The simplest, non racy way is to store the TID,
     * discard the handle that _beginthreadex gives back, and
     * get another copy of the handle here.
     */
    handle = qemu_thread_get_handle(thread);
    if (handle) {
        WaitForSingleObject(handle, INFINITE);
        CloseHandle(handle);
    }
    ret = data->ret;
    DeleteCriticalSection(&data->cs);
    g_free(data);
    return ret;
}

void qemu_thread_create(QemuThread *thread, const char *name,
                       void *(*start_routine)(void *),
                       void *arg, int mode)
{
    HANDLE hThread;
    struct QemuThreadData *data;

    data = g_malloc(sizeof *data);
    data->start_routine = start_routine;
    data->arg = arg;
    data->mode = mode;
    data->exited = false;
    notifier_list_init(&data->exit);

    if (data->mode != QEMU_THREAD_DETACHED) {
        InitializeCriticalSection(&data->cs);
    }

    hThread = (HANDLE) _beginthreadex(NULL, 0, win32_start_routine,
                                      data, 0, &thread->tid);
    if (!hThread) {
        error_exit(GetLastError(), __func__);
    }
    CloseHandle(hThread);
    thread->data = data;
}

void qemu_thread_get_self(QemuThread *thread)
{
    thread->data = qemu_thread_data;
    thread->tid = GetCurrentThreadId();
}

HANDLE qemu_thread_get_handle(QemuThread *thread)
{
    QemuThreadData *data;
    HANDLE handle;

    data = thread->data;
    if (data->mode == QEMU_THREAD_DETACHED) {
        return NULL;
    }

    EnterCriticalSection(&data->cs);
    if (!data->exited) {
        handle = OpenThread(SYNCHRONIZE | THREAD_SUSPEND_RESUME, FALSE,
                            thread->tid);
    } else {
        handle = NULL;
    }
    LeaveCriticalSection(&data->cs);
    return handle;
}

bool qemu_thread_is_self(QemuThread *thread)
{
    return GetCurrentThreadId() == thread->tid;
}
Commit	Line	Data
9257d46d PB	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	*/
aafd7584	13	#include "qemu/osdep.h"
9257d46d	14	#include "qemu-common.h"
1de7afc9	15	#include "qemu/thread.h"
ef57137f	16	#include "qemu/notify.h"
9257d46d	17	#include <process.h>
9257d46d	18
8f480de0 DDAG	19	static bool name_threads;
	20
	21	void qemu_thread_naming(bool enable)
	22	{
	23	/* But note we don't actually name them on Windows yet */
	24	name_threads = enable;
5c312079 DDAG	25
5c312079 DDAG	26	fprintf(stderr, "qemu: thread naming not supported on this host\n");
8f480de0 DDAG	27	}
8f480de0 DDAG	28
9257d46d PB	29	static void error_exit(int err, const char *msg)
	30	{
	31	char *pstr;
	32
	33	FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM \| FORMAT_MESSAGE_ALLOCATE_BUFFER,
	34	NULL, err, 0, (LPTSTR)&pstr, 2, NULL);
	35	fprintf(stderr, "qemu: %s: %s\n", msg, pstr);
	36	LocalFree(pstr);
53380ac3	37	abort();
9257d46d PB	38	}
	39
	40	void qemu_mutex_init(QemuMutex *mutex)
	41	{
	42	mutex->owner = 0;
	43	InitializeCriticalSection(&mutex->lock);
	44	}
	45
1a290aea SW	46	void qemu_mutex_destroy(QemuMutex *mutex)
	47	{
	48	assert(mutex->owner == 0);
	49	DeleteCriticalSection(&mutex->lock);
	50	}
	51
9257d46d PB	52	void qemu_mutex_lock(QemuMutex *mutex)
	53	{
	54	EnterCriticalSection(&mutex->lock);
	55
	56	/* Win32 CRITICAL_SECTIONs are recursive. Assert that we're not
	57	* using them as such.
	58	*/
	59	assert(mutex->owner == 0);
	60	mutex->owner = GetCurrentThreadId();
	61	}
	62
	63	int qemu_mutex_trylock(QemuMutex *mutex)
	64	{
	65	int owned;
	66
	67	owned = TryEnterCriticalSection(&mutex->lock);
	68	if (owned) {
	69	assert(mutex->owner == 0);
	70	mutex->owner = GetCurrentThreadId();
	71	}
	72	return !owned;
	73	}
	74
	75	void qemu_mutex_unlock(QemuMutex *mutex)
	76	{
	77	assert(mutex->owner == GetCurrentThreadId());
	78	mutex->owner = 0;
	79	LeaveCriticalSection(&mutex->lock);
	80	}
	81
	82	void qemu_cond_init(QemuCond *cond)
	83	{
	84	memset(cond, 0, sizeof(*cond));
	85
	86	cond->sema = CreateSemaphore(NULL, 0, LONG_MAX, NULL);
	87	if (!cond->sema) {
	88	error_exit(GetLastError(), __func__);
	89	}
	90	cond->continue_event = CreateEvent(NULL, /* security */
	91	FALSE, /* auto-reset */
	92	FALSE, /* not signaled */
	93	NULL); /* name */
	94	if (!cond->continue_event) {
	95	error_exit(GetLastError(), __func__);
	96	}
	97	}
	98
1a290aea SW	99	void qemu_cond_destroy(QemuCond *cond)
	100	{
	101	BOOL result;
	102	result = CloseHandle(cond->continue_event);
	103	if (!result) {
	104	error_exit(GetLastError(), __func__);
	105	}
	106	cond->continue_event = 0;
	107	result = CloseHandle(cond->sema);
	108	if (!result) {
	109	error_exit(GetLastError(), __func__);
	110	}
	111	cond->sema = 0;
	112	}
	113
9257d46d PB	114	void qemu_cond_signal(QemuCond *cond)
	115	{
	116	DWORD result;
	117
	118	/*
	119	* Signal only when there are waiters. cond->waiters is
	120	* incremented by pthread_cond_wait under the external lock,
	121	* so we are safe about that.
	122	*/
	123	if (cond->waiters == 0) {
	124	return;
	125	}
	126
	127	/*
	128	* Waiting threads decrement it outside the external lock, but
	129	* only if another thread is executing pthread_cond_broadcast and
	130	* has the mutex. So, it also cannot be decremented concurrently
	131	* with this particular access.
	132	*/
	133	cond->target = cond->waiters - 1;
	134	result = SignalObjectAndWait(cond->sema, cond->continue_event,
	135	INFINITE, FALSE);
	136	if (result == WAIT_ABANDONED \|\| result == WAIT_FAILED) {
	137	error_exit(GetLastError(), __func__);
	138	}
	139	}
	140
	141	void qemu_cond_broadcast(QemuCond *cond)
	142	{
	143	BOOLEAN result;
	144	/*
	145	* As in pthread_cond_signal, access to cond->waiters and
	146	* cond->target is locked via the external mutex.
	147	*/
	148	if (cond->waiters == 0) {
	149	return;
	150	}
	151
	152	cond->target = 0;
	153	result = ReleaseSemaphore(cond->sema, cond->waiters, NULL);
	154	if (!result) {
	155	error_exit(GetLastError(), __func__);
	156	}
	157
	158	/*
	159	* At this point all waiters continue. Each one takes its
	160	* slice of the semaphore. Now it's our turn to wait: Since
	161	* the external mutex is held, no thread can leave cond_wait,
	162	* yet. For this reason, we can be sure that no thread gets
	163	* a chance to eat more than one slice. OTOH, it means
	164	* that the last waiter must send us a wake-up.
	165	*/
	166	WaitForSingleObject(cond->continue_event, INFINITE);
	167	}
	168
	169	void qemu_cond_wait(QemuCond cond, QemuMutex mutex)
	170	{
	171	/*
	172	* This access is protected under the mutex.
	173	*/
	174	cond->waiters++;
	175
	176	/*
	177	* Unlock external mutex and wait for signal.
178	* NOTE: we've held mutex locked long enough to increment
179	* waiters count above, so there's no problem with
180	* leaving mutex unlocked before we wait on semaphore.
181	*/
182	qemu_mutex_unlock(mutex);
183	WaitForSingleObject(cond->sema, INFINITE);
184
185	/* Now waiters must rendez-vous with the signaling thread and
186	* let it continue. For cond_broadcast this has heavy contention
187	* and triggers thundering herd. So goes life.
188	*
189	* Decrease waiters count. The mutex is not taken, so we have
190	* to do this atomically.
191	*
192	* All waiters contend for the mutex at the end of this function
193	* until the signaling thread relinquishes it. To ensure
194	* each waiter consumes exactly one slice of the semaphore,
195	* the signaling thread stops until it is told by the last
196	* waiter that it can go on.
197	*/
198	if (InterlockedDecrement(&cond->waiters) == cond->target) {
199	SetEvent(cond->continue_event);
200	}
201
202	qemu_mutex_lock(mutex);
203	}
204
38b14db3 PB	205	void qemu_sem_init(QemuSemaphore *sem, int init)
	206	{
	207	/* Manual reset. */
	208	sem->sema = CreateSemaphore(NULL, init, LONG_MAX, NULL);
	209	}
	210
	211	void qemu_sem_destroy(QemuSemaphore *sem)
	212	{
	213	CloseHandle(sem->sema);
	214	}
	215
	216	void qemu_sem_post(QemuSemaphore *sem)
	217	{
	218	ReleaseSemaphore(sem->sema, 1, NULL);
	219	}
	220
	221	int qemu_sem_timedwait(QemuSemaphore *sem, int ms)
	222	{
	223	int rc = WaitForSingleObject(sem->sema, ms);
	224	if (rc == WAIT_OBJECT_0) {
	225	return 0;
	226	}
	227	if (rc != WAIT_TIMEOUT) {
	228	error_exit(GetLastError(), __func__);
	229	}
	230	return -1;
	231	}
	232
	233	void qemu_sem_wait(QemuSemaphore *sem)
	234	{
	235	if (WaitForSingleObject(sem->sema, INFINITE) != WAIT_OBJECT_0) {
	236	error_exit(GetLastError(), __func__);
	237	}
	238	}
	239
7c9b2bf6 PB	240	/* Wrap a Win32 manual-reset event with a fast userspace path. The idea
	241	* is to reset the Win32 event lazily, as part of a test-reset-test-wait
	242	* sequence. Such a sequence is, indeed, how QemuEvents are used by
	243	* RCU and other subsystems!
	244	*
	245	* Valid transitions:
	246	* - free->set, when setting the event
	247	* - busy->set, when setting the event, followed by futex_wake
	248	* - set->free, when resetting the event
	249	* - free->busy, when waiting
	250	*
	251	* set->busy does not happen (it can be observed from the outside but
	252	* it really is set->free->busy).
	253	*
	254	* busy->free provably cannot happen; to enforce it, the set->free transition
	255	* is done with an OR, which becomes a no-op if the event has concurrently
	256	* transitioned to free or busy (and is faster than cmpxchg).
	257	*/
	258
	259	#define EV_SET 0
	260	#define EV_FREE 1
	261	#define EV_BUSY -1
	262
c7c4d063 PB	263	void qemu_event_init(QemuEvent *ev, bool init)
	264	{
	265	/* Manual reset. */
7c9b2bf6 PB	266	ev->event = CreateEvent(NULL, TRUE, TRUE, NULL);
7c9b2bf6 PB	267	ev->value = (init ? EV_SET : EV_FREE);
c7c4d063 PB	268	}
	269
	270	void qemu_event_destroy(QemuEvent *ev)
	271	{
	272	CloseHandle(ev->event);
	273	}
	274
	275	void qemu_event_set(QemuEvent *ev)
	276	{
7c9b2bf6 PB	277	if (atomic_mb_read(&ev->value) != EV_SET) {
	278	if (atomic_xchg(&ev->value, EV_SET) == EV_BUSY) {
	279	/* There were waiters, wake them up. */
	280	SetEvent(ev->event);
	281	}
	282	}
c7c4d063 PB	283	}
	284
	285	void qemu_event_reset(QemuEvent *ev)
	286	{
7c9b2bf6 PB	287	if (atomic_mb_read(&ev->value) == EV_SET) {
	288	/* If there was a concurrent reset (or even reset+wait),
	289	* do nothing. Otherwise change EV_SET->EV_FREE.
	290	*/
	291	atomic_or(&ev->value, EV_FREE);
	292	}
c7c4d063 PB	293	}
	294
	295	void qemu_event_wait(QemuEvent *ev)
	296	{
7c9b2bf6 PB	297	unsigned value;
	298
	299	value = atomic_mb_read(&ev->value);
	300	if (value != EV_SET) {
	301	if (value == EV_FREE) {
	302	/* qemu_event_set is not yet going to call SetEvent, but we are
	303	* going to do another check for EV_SET below when setting EV_BUSY.
	304	* At that point it is safe to call WaitForSingleObject.
	305	*/
	306	ResetEvent(ev->event);
	307
	308	/* Tell qemu_event_set that there are waiters. No need to retry
	309	* because there cannot be a concurent busy->free transition.
	310	* After the CAS, the event will be either set or busy.
	311	*/
	312	if (atomic_cmpxchg(&ev->value, EV_FREE, EV_BUSY) == EV_SET) {
	313	value = EV_SET;
	314	} else {
	315	value = EV_BUSY;
	316	}
	317	}
	318	if (value == EV_BUSY) {
	319	WaitForSingleObject(ev->event, INFINITE);
	320	}
	321	}
c7c4d063 PB	322	}
c7c4d063 PB	323
9257d46d	324	struct QemuThreadData {
403e6331 PB	325	/* Passed to win32_start_routine. */
	326	void (start_routine)(void *);
	327	void *arg;
	328	short mode;
ef57137f	329	NotifierList exit;
403e6331 PB	330
	331	/* Only used for joinable threads. */
	332	bool exited;
	333	void *ret;
	334	CRITICAL_SECTION cs;
9257d46d PB	335	};
9257d46d PB	336
ef57137f PB	337	static bool atexit_registered;
	338	static NotifierList main_thread_exit;
	339
6265e4ff	340	static __thread QemuThreadData *qemu_thread_data;
9257d46d	341
ef57137f PB	342	static void run_main_thread_exit(void)
	343	{
	344	notifier_list_notify(&main_thread_exit, NULL);
	345	}
	346
	347	void qemu_thread_atexit_add(Notifier *notifier)
	348	{
	349	if (!qemu_thread_data) {
	350	if (!atexit_registered) {
	351	atexit_registered = true;
	352	atexit(run_main_thread_exit);
	353	}
	354	notifier_list_add(&main_thread_exit, notifier);
	355	} else {
	356	notifier_list_add(&qemu_thread_data->exit, notifier);
	357	}
	358	}
	359
	360	void qemu_thread_atexit_remove(Notifier *notifier)
	361	{
	362	notifier_remove(notifier);
	363	}
	364
9257d46d PB	365	static unsigned __stdcall win32_start_routine(void *arg)
9257d46d PB	366	{
403e6331 PB	367	QemuThreadData data = (QemuThreadData ) arg;
	368	void (start_routine)(void *) = data->start_routine;
	369	void *thread_arg = data->arg;
	370
6265e4ff	371	qemu_thread_data = data;
403e6331	372	qemu_thread_exit(start_routine(thread_arg));
9257d46d PB	373	abort();
	374	}
	375
	376	void qemu_thread_exit(void *arg)
	377	{
6265e4ff JK	378	QemuThreadData *data = qemu_thread_data;
6265e4ff JK	379
ef57137f PB	380	notifier_list_notify(&data->exit, NULL);
ef57137f PB	381	if (data->mode == QEMU_THREAD_JOINABLE) {
403e6331 PB	382	data->ret = arg;
	383	EnterCriticalSection(&data->cs);
	384	data->exited = true;
	385	LeaveCriticalSection(&data->cs);
ef57137f PB	386	} else {
ef57137f PB	387	g_free(data);
403e6331 PB	388	}
	389	_endthreadex(0);
	390	}
	391
	392	void qemu_thread_join(QemuThread thread)
	393	{
	394	QemuThreadData *data;
	395	void *ret;
	396	HANDLE handle;
	397
	398	data = thread->data;
ef57137f	399	if (data->mode == QEMU_THREAD_DETACHED) {
403e6331 PB	400	return NULL;
403e6331 PB	401	}
ef57137f	402
403e6331 PB	403	/*
	404	* Because multiple copies of the QemuThread can exist via
	405	* qemu_thread_get_self, we need to store a value that cannot
	406	* leak there. The simplest, non racy way is to store the TID,
	407	* discard the handle that _beginthreadex gives back, and
	408	* get another copy of the handle here.
	409	*/
1ecf47bf PB	410	handle = qemu_thread_get_handle(thread);
1ecf47bf PB	411	if (handle) {
403e6331 PB	412	WaitForSingleObject(handle, INFINITE);
403e6331 PB	413	CloseHandle(handle);
403e6331 PB	414	}
	415	ret = data->ret;
	416	DeleteCriticalSection(&data->cs);
	417	g_free(data);
	418	return ret;
9257d46d PB	419	}
9257d46d PB	420
4900116e	421	void qemu_thread_create(QemuThread thread, const char name,
9257d46d	422	void (start_routine)(void *),
cf218714	423	void *arg, int mode)
9257d46d PB	424	{
9257d46d PB	425	HANDLE hThread;
9257d46d	426	struct QemuThreadData *data;
6265e4ff	427
7267c094	428	data = g_malloc(sizeof *data);
9257d46d PB	429	data->start_routine = start_routine;
9257d46d PB	430	data->arg = arg;
403e6331 PB	431	data->mode = mode;
403e6331 PB	432	data->exited = false;
ef57137f	433	notifier_list_init(&data->exit);
9257d46d	434
edc1de97 SW	435	if (data->mode != QEMU_THREAD_DETACHED) {
	436	InitializeCriticalSection(&data->cs);
	437	}
	438
9257d46d	439	hThread = (HANDLE) _beginthreadex(NULL, 0, win32_start_routine,
403e6331	440	data, 0, &thread->tid);
9257d46d PB	441	if (!hThread) {
	442	error_exit(GetLastError(), __func__);
	443	}
	444	CloseHandle(hThread);
ef57137f	445	thread->data = data;
9257d46d PB	446	}
	447
	448	void qemu_thread_get_self(QemuThread *thread)
	449	{
6265e4ff	450	thread->data = qemu_thread_data;
403e6331	451	thread->tid = GetCurrentThreadId();
9257d46d PB	452	}
9257d46d PB	453
1ecf47bf PB	454	HANDLE qemu_thread_get_handle(QemuThread *thread)
	455	{
	456	QemuThreadData *data;
	457	HANDLE handle;
	458
	459	data = thread->data;
ef57137f	460	if (data->mode == QEMU_THREAD_DETACHED) {
1ecf47bf PB	461	return NULL;
	462	}
	463
	464	EnterCriticalSection(&data->cs);
	465	if (!data->exited) {
	466	handle = OpenThread(SYNCHRONIZE \| THREAD_SUSPEND_RESUME, FALSE,
	467	thread->tid);
	468	} else {
	469	handle = NULL;
	470	}
	471	LeaveCriticalSection(&data->cs);
	472	return handle;
	473	}
	474
2d797b65	475	bool qemu_thread_is_self(QemuThread *thread)
9257d46d	476	{
403e6331	477	return GetCurrentThreadId() == thread->tid;
9257d46d	478	}