[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)
{
    /* qemu_event_set has release semantics, but because it *loads*
     * ev->value we need a full memory barrier here.
     */
    smp_mb();
    if (atomic_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)
{
    unsigned value;

    value = atomic_read(&ev->value);
    smp_mb_acquire();
    if (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_read(&ev->value);
    smp_mb_acquire();
    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	{
374293ca PB	277	/* qemu_event_set has release semantics, but because it loads
	278	* ev->value we need a full memory barrier here.
	279	*/
	280	smp_mb();
	281	if (atomic_read(&ev->value) != EV_SET) {
7c9b2bf6 PB	282	if (atomic_xchg(&ev->value, EV_SET) == EV_BUSY) {
	283	/* There were waiters, wake them up. */
	284	SetEvent(ev->event);
	285	}
	286	}
c7c4d063 PB	287	}
	288
	289	void qemu_event_reset(QemuEvent *ev)
	290	{
374293ca PB	291	unsigned value;
	292
	293	value = atomic_read(&ev->value);
	294	smp_mb_acquire();
	295	if (value == EV_SET) {
7c9b2bf6 PB	296	/* If there was a concurrent reset (or even reset+wait),
	297	* do nothing. Otherwise change EV_SET->EV_FREE.
	298	*/
	299	atomic_or(&ev->value, EV_FREE);
	300	}
c7c4d063 PB	301	}
	302
	303	void qemu_event_wait(QemuEvent *ev)
	304	{
7c9b2bf6 PB	305	unsigned value;
7c9b2bf6 PB	306
374293ca PB	307	value = atomic_read(&ev->value);
374293ca PB	308	smp_mb_acquire();
7c9b2bf6 PB	309	if (value != EV_SET) {
	310	if (value == EV_FREE) {
	311	/* qemu_event_set is not yet going to call SetEvent, but we are
	312	* going to do another check for EV_SET below when setting EV_BUSY.
	313	* At that point it is safe to call WaitForSingleObject.
	314	*/
	315	ResetEvent(ev->event);
	316
	317	/* Tell qemu_event_set that there are waiters. No need to retry
	318	* because there cannot be a concurent busy->free transition.
	319	* After the CAS, the event will be either set or busy.
	320	*/
	321	if (atomic_cmpxchg(&ev->value, EV_FREE, EV_BUSY) == EV_SET) {
	322	value = EV_SET;
	323	} else {
	324	value = EV_BUSY;
	325	}
	326	}
	327	if (value == EV_BUSY) {
	328	WaitForSingleObject(ev->event, INFINITE);
	329	}
	330	}
c7c4d063 PB	331	}
c7c4d063 PB	332
9257d46d	333	struct QemuThreadData {
403e6331 PB	334	/* Passed to win32_start_routine. */
	335	void (start_routine)(void *);
	336	void *arg;
	337	short mode;
ef57137f	338	NotifierList exit;
403e6331 PB	339
	340	/* Only used for joinable threads. */
	341	bool exited;
	342	void *ret;
	343	CRITICAL_SECTION cs;
9257d46d PB	344	};
9257d46d PB	345
ef57137f PB	346	static bool atexit_registered;
	347	static NotifierList main_thread_exit;
	348
6265e4ff	349	static __thread QemuThreadData *qemu_thread_data;
9257d46d	350
ef57137f PB	351	static void run_main_thread_exit(void)
	352	{
	353	notifier_list_notify(&main_thread_exit, NULL);
	354	}
	355
	356	void qemu_thread_atexit_add(Notifier *notifier)
	357	{
	358	if (!qemu_thread_data) {
	359	if (!atexit_registered) {
	360	atexit_registered = true;
	361	atexit(run_main_thread_exit);
	362	}
	363	notifier_list_add(&main_thread_exit, notifier);
	364	} else {
	365	notifier_list_add(&qemu_thread_data->exit, notifier);
	366	}
	367	}
	368
	369	void qemu_thread_atexit_remove(Notifier *notifier)
	370	{
	371	notifier_remove(notifier);
	372	}
	373
9257d46d PB	374	static unsigned __stdcall win32_start_routine(void *arg)
9257d46d PB	375	{
403e6331 PB	376	QemuThreadData data = (QemuThreadData ) arg;
	377	void (start_routine)(void *) = data->start_routine;
	378	void *thread_arg = data->arg;
	379
6265e4ff	380	qemu_thread_data = data;
403e6331	381	qemu_thread_exit(start_routine(thread_arg));
9257d46d PB	382	abort();
	383	}
	384
	385	void qemu_thread_exit(void *arg)
	386	{
6265e4ff JK	387	QemuThreadData *data = qemu_thread_data;
6265e4ff JK	388
ef57137f PB	389	notifier_list_notify(&data->exit, NULL);
ef57137f PB	390	if (data->mode == QEMU_THREAD_JOINABLE) {
403e6331 PB	391	data->ret = arg;
	392	EnterCriticalSection(&data->cs);
	393	data->exited = true;
	394	LeaveCriticalSection(&data->cs);
ef57137f PB	395	} else {
ef57137f PB	396	g_free(data);
403e6331 PB	397	}
	398	_endthreadex(0);
	399	}
	400
	401	void qemu_thread_join(QemuThread thread)
	402	{
	403	QemuThreadData *data;
	404	void *ret;
	405	HANDLE handle;
	406
	407	data = thread->data;
ef57137f	408	if (data->mode == QEMU_THREAD_DETACHED) {
403e6331 PB	409	return NULL;
403e6331 PB	410	}
ef57137f	411
403e6331 PB	412	/*
	413	* Because multiple copies of the QemuThread can exist via
	414	* qemu_thread_get_self, we need to store a value that cannot
	415	* leak there. The simplest, non racy way is to store the TID,
	416	* discard the handle that _beginthreadex gives back, and
	417	* get another copy of the handle here.
	418	*/
1ecf47bf PB	419	handle = qemu_thread_get_handle(thread);
1ecf47bf PB	420	if (handle) {
403e6331 PB	421	WaitForSingleObject(handle, INFINITE);
403e6331 PB	422	CloseHandle(handle);
403e6331 PB	423	}
	424	ret = data->ret;
	425	DeleteCriticalSection(&data->cs);
	426	g_free(data);
	427	return ret;
9257d46d PB	428	}
9257d46d PB	429
4900116e	430	void qemu_thread_create(QemuThread thread, const char name,
9257d46d	431	void (start_routine)(void *),
cf218714	432	void *arg, int mode)
9257d46d PB	433	{
9257d46d PB	434	HANDLE hThread;
9257d46d	435	struct QemuThreadData *data;
6265e4ff	436
7267c094	437	data = g_malloc(sizeof *data);
9257d46d PB	438	data->start_routine = start_routine;
9257d46d PB	439	data->arg = arg;
403e6331 PB	440	data->mode = mode;
403e6331 PB	441	data->exited = false;
ef57137f	442	notifier_list_init(&data->exit);
9257d46d	443
edc1de97 SW	444	if (data->mode != QEMU_THREAD_DETACHED) {
	445	InitializeCriticalSection(&data->cs);
	446	}
	447
9257d46d	448	hThread = (HANDLE) _beginthreadex(NULL, 0, win32_start_routine,
403e6331	449	data, 0, &thread->tid);
9257d46d PB	450	if (!hThread) {
	451	error_exit(GetLastError(), __func__);
	452	}
	453	CloseHandle(hThread);
ef57137f	454	thread->data = data;
9257d46d PB	455	}
	456
	457	void qemu_thread_get_self(QemuThread *thread)
	458	{
6265e4ff	459	thread->data = qemu_thread_data;
403e6331	460	thread->tid = GetCurrentThreadId();
9257d46d PB	461	}
9257d46d PB	462
1ecf47bf PB	463	HANDLE qemu_thread_get_handle(QemuThread *thread)
	464	{
	465	QemuThreadData *data;
	466	HANDLE handle;
	467
	468	data = thread->data;
ef57137f	469	if (data->mode == QEMU_THREAD_DETACHED) {
1ecf47bf PB	470	return NULL;
	471	}
	472
	473	EnterCriticalSection(&data->cs);
	474	if (!data->exited) {
	475	handle = OpenThread(SYNCHRONIZE \| THREAD_SUSPEND_RESUME, FALSE,
	476	thread->tid);
	477	} else {
	478	handle = NULL;
	479	}
	480	LeaveCriticalSection(&data->cs);
	481	return handle;
	482	}
	483
2d797b65	484	bool qemu_thread_is_self(QemuThread *thread)
9257d46d	485	{
403e6331	486	return GetCurrentThreadId() == thread->tid;
9257d46d	487	}