[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-common.h"
#include "qemu/thread.h"
#include "qemu/notify.h"
#include <process.h>
#include <assert.h>
#include <limits.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	*/
	13	#include "qemu-common.h"
1de7afc9	14	#include "qemu/thread.h"
ef57137f	15	#include "qemu/notify.h"
9257d46d PB	16	#include <process.h>
	17	#include <assert.h>
	18	#include <limits.h>
	19
8f480de0 DDAG	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;
5c312079 DDAG	26
5c312079 DDAG	27	fprintf(stderr, "qemu: thread naming not supported on this host\n");
8f480de0 DDAG	28	}
8f480de0 DDAG	29
9257d46d PB	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);
53380ac3	38	abort();
9257d46d PB	39	}
	40
	41	void qemu_mutex_init(QemuMutex *mutex)
	42	{
	43	mutex->owner = 0;
	44	InitializeCriticalSection(&mutex->lock);
	45	}
	46
1a290aea SW	47	void qemu_mutex_destroy(QemuMutex *mutex)
	48	{
	49	assert(mutex->owner == 0);
	50	DeleteCriticalSection(&mutex->lock);
	51	}
	52
9257d46d PB	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
1a290aea SW	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
9257d46d PB	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
38b14db3 PB	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
7c9b2bf6 PB	241	/* Wrap a Win32 manual-reset event with a fast userspace path. The idea
	242	* is to reset the Win32 event lazily, as part of a test-reset-test-wait
	243	* sequence. Such a sequence is, indeed, how QemuEvents are used by
	244	* RCU and other subsystems!
	245	*
	246	* Valid transitions:
	247	* - free->set, when setting the event
	248	* - busy->set, when setting the event, followed by futex_wake
	249	* - set->free, when resetting the event
	250	* - free->busy, when waiting
	251	*
	252	* set->busy does not happen (it can be observed from the outside but
	253	* it really is set->free->busy).
	254	*
	255	* busy->free provably cannot happen; to enforce it, the set->free transition
	256	* is done with an OR, which becomes a no-op if the event has concurrently
	257	* transitioned to free or busy (and is faster than cmpxchg).
	258	*/
	259
	260	#define EV_SET 0
	261	#define EV_FREE 1
	262	#define EV_BUSY -1
	263
c7c4d063 PB	264	void qemu_event_init(QemuEvent *ev, bool init)
	265	{
	266	/* Manual reset. */
7c9b2bf6 PB	267	ev->event = CreateEvent(NULL, TRUE, TRUE, NULL);
7c9b2bf6 PB	268	ev->value = (init ? EV_SET : EV_FREE);
c7c4d063 PB	269	}
	270
	271	void qemu_event_destroy(QemuEvent *ev)
	272	{
	273	CloseHandle(ev->event);
	274	}
	275
	276	void qemu_event_set(QemuEvent *ev)
	277	{
7c9b2bf6 PB	278	if (atomic_mb_read(&ev->value) != EV_SET) {
	279	if (atomic_xchg(&ev->value, EV_SET) == EV_BUSY) {
	280	/* There were waiters, wake them up. */
	281	SetEvent(ev->event);
	282	}
	283	}
c7c4d063 PB	284	}
	285
	286	void qemu_event_reset(QemuEvent *ev)
	287	{
7c9b2bf6 PB	288	if (atomic_mb_read(&ev->value) == EV_SET) {
	289	/* If there was a concurrent reset (or even reset+wait),
	290	* do nothing. Otherwise change EV_SET->EV_FREE.
	291	*/
	292	atomic_or(&ev->value, EV_FREE);
	293	}
c7c4d063 PB	294	}
	295
	296	void qemu_event_wait(QemuEvent *ev)
	297	{
7c9b2bf6 PB	298	unsigned value;
	299
	300	value = atomic_mb_read(&ev->value);
	301	if (value != EV_SET) {
	302	if (value == EV_FREE) {
	303	/* qemu_event_set is not yet going to call SetEvent, but we are
	304	* going to do another check for EV_SET below when setting EV_BUSY.
	305	* At that point it is safe to call WaitForSingleObject.
	306	*/
	307	ResetEvent(ev->event);
	308
	309	/* Tell qemu_event_set that there are waiters. No need to retry
	310	* because there cannot be a concurent busy->free transition.
	311	* After the CAS, the event will be either set or busy.
	312	*/
	313	if (atomic_cmpxchg(&ev->value, EV_FREE, EV_BUSY) == EV_SET) {
	314	value = EV_SET;
	315	} else {
	316	value = EV_BUSY;
	317	}
	318	}
	319	if (value == EV_BUSY) {
	320	WaitForSingleObject(ev->event, INFINITE);
	321	}
	322	}
c7c4d063 PB	323	}
c7c4d063 PB	324
9257d46d	325	struct QemuThreadData {
403e6331 PB	326	/* Passed to win32_start_routine. */
	327	void (start_routine)(void *);
	328	void *arg;
	329	short mode;
ef57137f	330	NotifierList exit;
403e6331 PB	331
	332	/* Only used for joinable threads. */
	333	bool exited;
	334	void *ret;
	335	CRITICAL_SECTION cs;
9257d46d PB	336	};
9257d46d PB	337
ef57137f PB	338	static bool atexit_registered;
	339	static NotifierList main_thread_exit;
	340
6265e4ff	341	static __thread QemuThreadData *qemu_thread_data;
9257d46d	342
ef57137f PB	343	static void run_main_thread_exit(void)
	344	{
	345	notifier_list_notify(&main_thread_exit, NULL);
	346	}
	347
	348	void qemu_thread_atexit_add(Notifier *notifier)
	349	{
	350	if (!qemu_thread_data) {
	351	if (!atexit_registered) {
	352	atexit_registered = true;
	353	atexit(run_main_thread_exit);
	354	}
	355	notifier_list_add(&main_thread_exit, notifier);
	356	} else {
	357	notifier_list_add(&qemu_thread_data->exit, notifier);
	358	}
	359	}
	360
	361	void qemu_thread_atexit_remove(Notifier *notifier)
	362	{
	363	notifier_remove(notifier);
	364	}
	365
9257d46d PB	366	static unsigned __stdcall win32_start_routine(void *arg)
9257d46d PB	367	{
403e6331 PB	368	QemuThreadData data = (QemuThreadData ) arg;
	369	void (start_routine)(void *) = data->start_routine;
	370	void *thread_arg = data->arg;
	371
6265e4ff	372	qemu_thread_data = data;
403e6331	373	qemu_thread_exit(start_routine(thread_arg));
9257d46d PB	374	abort();
	375	}
	376
	377	void qemu_thread_exit(void *arg)
	378	{
6265e4ff JK	379	QemuThreadData *data = qemu_thread_data;
6265e4ff JK	380
ef57137f PB	381	notifier_list_notify(&data->exit, NULL);
ef57137f PB	382	if (data->mode == QEMU_THREAD_JOINABLE) {
403e6331 PB	383	data->ret = arg;
	384	EnterCriticalSection(&data->cs);
	385	data->exited = true;
	386	LeaveCriticalSection(&data->cs);
ef57137f PB	387	} else {
ef57137f PB	388	g_free(data);
403e6331 PB	389	}
	390	_endthreadex(0);
	391	}
	392
	393	void qemu_thread_join(QemuThread thread)
	394	{
	395	QemuThreadData *data;
	396	void *ret;
	397	HANDLE handle;
	398
	399	data = thread->data;
ef57137f	400	if (data->mode == QEMU_THREAD_DETACHED) {
403e6331 PB	401	return NULL;
403e6331 PB	402	}
ef57137f	403
403e6331 PB	404	/*
	405	* Because multiple copies of the QemuThread can exist via
	406	* qemu_thread_get_self, we need to store a value that cannot
	407	* leak there. The simplest, non racy way is to store the TID,
	408	* discard the handle that _beginthreadex gives back, and
	409	* get another copy of the handle here.
	410	*/
1ecf47bf PB	411	handle = qemu_thread_get_handle(thread);
1ecf47bf PB	412	if (handle) {
403e6331 PB	413	WaitForSingleObject(handle, INFINITE);
403e6331 PB	414	CloseHandle(handle);
403e6331 PB	415	}
	416	ret = data->ret;
	417	DeleteCriticalSection(&data->cs);
	418	g_free(data);
	419	return ret;
9257d46d PB	420	}
9257d46d PB	421
4900116e	422	void qemu_thread_create(QemuThread thread, const char name,
9257d46d	423	void (start_routine)(void *),
cf218714	424	void *arg, int mode)
9257d46d PB	425	{
9257d46d PB	426	HANDLE hThread;
9257d46d	427	struct QemuThreadData *data;
6265e4ff	428
7267c094	429	data = g_malloc(sizeof *data);
9257d46d PB	430	data->start_routine = start_routine;
9257d46d PB	431	data->arg = arg;
403e6331 PB	432	data->mode = mode;
403e6331 PB	433	data->exited = false;
ef57137f	434	notifier_list_init(&data->exit);
9257d46d	435
edc1de97 SW	436	if (data->mode != QEMU_THREAD_DETACHED) {
	437	InitializeCriticalSection(&data->cs);
	438	}
	439
9257d46d	440	hThread = (HANDLE) _beginthreadex(NULL, 0, win32_start_routine,
403e6331	441	data, 0, &thread->tid);
9257d46d PB	442	if (!hThread) {
	443	error_exit(GetLastError(), __func__);
	444	}
	445	CloseHandle(hThread);
ef57137f	446	thread->data = data;
9257d46d PB	447	}
	448
	449	void qemu_thread_get_self(QemuThread *thread)
	450	{
6265e4ff	451	thread->data = qemu_thread_data;
403e6331	452	thread->tid = GetCurrentThreadId();
9257d46d PB	453	}
9257d46d PB	454
1ecf47bf PB	455	HANDLE qemu_thread_get_handle(QemuThread *thread)
	456	{
	457	QemuThreadData *data;
	458	HANDLE handle;
	459
	460	data = thread->data;
ef57137f	461	if (data->mode == QEMU_THREAD_DETACHED) {
1ecf47bf PB	462	return NULL;
	463	}
	464
	465	EnterCriticalSection(&data->cs);
	466	if (!data->exited) {
	467	handle = OpenThread(SYNCHRONIZE \| THREAD_SUSPEND_RESUME, FALSE,
	468	thread->tid);
	469	} else {
	470	handle = NULL;
	471	}
	472	LeaveCriticalSection(&data->cs);
	473	return handle;
	474	}
	475
2d797b65	476	bool qemu_thread_is_self(QemuThread *thread)
9257d46d	477	{
403e6331	478	return GetCurrentThreadId() == thread->tid;
9257d46d	479	}