/*
 * threads.c:  Thread handles
 *
 * Author:
 *	Dick Porter (dick@ximian.com)
 *
 * (C) 2002-2006 Ximian, Inc.
 * Copyright 2003-2011 Novell, Inc (http://www.novell.com)
 * Copyright 2011 Xamarin, Inc (http://www.xamarin.com)
 */

#include <config.h>
#include <stdio.h>
#include <glib.h>
#include <string.h>
#include <pthread.h>
#include <signal.h>
#include <sched.h>
#include <sys/time.h>
#include <errno.h>
#include <sys/types.h>
#include <unistd.h>

#include <mono/io-layer/wapi.h>
#include <mono/io-layer/wapi-private.h>
#include <mono/io-layer/handles-private.h>
#include <mono/io-layer/misc-private.h>
#include <mono/io-layer/thread-private.h>
#include <mono/io-layer/mutex-private.h>

#include <mono/utils/mono-threads.h>
#include <mono/utils/gc_wrapper.h>
#include <mono/utils/atomic.h>
#include <mono/utils/mono-mutex.h>

#ifdef HAVE_VALGRIND_MEMCHECK_H
#include <valgrind/memcheck.h>
#endif

#if 0
#define DEBUG(...) g_message(__VA_ARGS__)
#else
#define DEBUG(...)
#endif

#if 0
#define WAIT_DEBUG(code) do { code } while (0)
#else
#define WAIT_DEBUG(code) do { } while (0)
#endif

/* Hash threads with tids. I thought of using TLS for this, but that
 * would have to set the data in the new thread, which is more hassle
 */
static mono_once_t thread_hash_once = MONO_ONCE_INIT;
static pthread_key_t thread_hash_key;

/* This key is used with attached threads and a destructor to signal
 * when attached threads exit, as they don't have the thread_exit()
 * infrastructure
 */
static pthread_key_t thread_attached_key;

struct _WapiHandleOps _wapi_thread_ops = {
	NULL,				/* close */
	NULL,				/* signal */
	NULL,				/* own */
	NULL,				/* is_owned */
	NULL,				/* special_wait */
	NULL				/* prewait */
};

static mono_once_t thread_ops_once=MONO_ONCE_INIT;

static void thread_ops_init (void)
{
	_wapi_handle_register_capabilities (WAPI_HANDLE_THREAD,
					    WAPI_HANDLE_CAP_WAIT);
}

void _wapi_thread_cleanup (void)
{
	int ret;
	
	ret = pthread_key_delete (thread_hash_key);
	g_assert (ret == 0);
	
	ret = pthread_key_delete (thread_attached_key);
	g_assert (ret == 0);
}

/* Called by thread_exit(), but maybe indirectly by
 * mono_thread_manage() via mono_thread_signal_self() too
 */
static void _wapi_thread_abandon_mutexes (gpointer handle)
{
	struct _WapiHandle_thread *thread_handle;
	gboolean ok;
	int i;
	pid_t pid = _wapi_getpid ();
	pthread_t tid = pthread_self ();
	
	DEBUG ("%s: Thread %p abandoning held mutexes", __func__, handle);

	if (handle == NULL) {
		handle = _wapi_thread_handle_from_id (pthread_self ());
		if (handle == NULL) {
			/* Something gone badly wrong... */
			return;
		}
	}
	
	ok = _wapi_lookup_handle (handle, WAPI_HANDLE_THREAD,
				  (gpointer *)&thread_handle);
	if (ok == FALSE) {
		g_warning ("%s: error looking up thread handle %p", __func__,
			   handle);
		return;
	}
	
	if (!pthread_equal (thread_handle->id, tid)) {
		return;
	}
	
	for (i = 0; i < thread_handle->owned_mutexes->len; i++) {
		gpointer mutex = g_ptr_array_index (thread_handle->owned_mutexes, i);
		
		_wapi_mutex_abandon (mutex, pid, tid);
		_wapi_thread_disown_mutex (mutex);
	}
}

void _wapi_thread_set_termination_details (gpointer handle,
					   guint32 exitstatus)
{
	struct _WapiHandle_thread *thread_handle;
	gboolean ok;
	int thr_ret;
	
	if (_wapi_handle_issignalled (handle) ||
	    _wapi_handle_type (handle) == WAPI_HANDLE_UNUSED) {
		/* We must have already deliberately finished with
		 * this thread, so don't do any more now
		 */
		return;
	}

	DEBUG ("%s: Thread %p terminating", __func__, handle);

	_wapi_thread_abandon_mutexes (handle);
	
	ok = _wapi_lookup_handle (handle, WAPI_HANDLE_THREAD,
				  (gpointer *)&thread_handle);
	if (ok == FALSE) {
		g_warning ("%s: error looking up thread handle %p", __func__,
			   handle);

		return;
	}
	
	pthread_cleanup_push ((void(*)(void *))_wapi_handle_unlock_handle,
			      handle);
	thr_ret = _wapi_handle_lock_handle (handle);
	g_assert (thr_ret == 0);
	
	thread_handle->exitstatus = exitstatus;
	thread_handle->state = THREAD_STATE_EXITED;
	g_ptr_array_free (thread_handle->owned_mutexes, TRUE);

	_wapi_handle_set_signal_state (handle, TRUE, TRUE);

	thr_ret = _wapi_handle_unlock_handle (handle);
	g_assert (thr_ret == 0);
	pthread_cleanup_pop (0);
	
	DEBUG("%s: Recording thread handle %p id %ld status as %d",
		  __func__, handle, thread_handle->id, exitstatus);
	
	/* The thread is no longer active, so unref it */
	_wapi_handle_unref (handle);
}

void _wapi_thread_signal_self (guint32 exitstatus)
{
	gpointer handle;
	
	handle = _wapi_thread_handle_from_id (pthread_self ());
	if (handle == NULL) {
		/* Something gone badly wrong... */
		return;
	}
	
	_wapi_thread_set_termination_details (handle, exitstatus);
}

/* Called by the thread creation code as a thread is finishing up, and
 * by ExitThread()
*/
static void thread_exit (guint32 exitstatus, gpointer handle) G_GNUC_NORETURN;
#if defined(__native_client__)
void nacl_shutdown_gc_thread(void);
#endif
static void thread_exit (guint32 exitstatus, gpointer handle)
{
#if defined(__native_client__)
	nacl_shutdown_gc_thread();
#endif
	_wapi_thread_set_termination_details (handle, exitstatus);
	
	/* Call pthread_exit() to call destructors and really exit the
	 * thread
	 */
	mono_gc_pthread_exit (NULL);
}

void
wapi_thread_set_exit_code (guint32 exitstatus, gpointer handle)
{
	_wapi_thread_set_termination_details (handle, exitstatus);
}

static void thread_attached_exit (gpointer handle)
{
	/* Drop the extra reference we take in thread_attach, now this
	 * thread is dead
	 */
	
	_wapi_thread_set_termination_details (handle, 0);
}

static void thread_hash_init(void)
{
	int thr_ret;
	
	thr_ret = pthread_key_create (&thread_hash_key, NULL);
	g_assert (thr_ret == 0);

	thr_ret = pthread_key_create (&thread_attached_key,
				      thread_attached_exit);
	g_assert (thr_ret == 0);
}

/*
 * wapi_create_thread_handle:
 *
 *   Create a thread handle for the current thread.
 */
gpointer
wapi_create_thread_handle (void)
{
	struct _WapiHandle_thread thread_handle = {0}, *thread;
	gpointer handle;
	int res;

	mono_once (&thread_hash_once, thread_hash_init);
	mono_once (&thread_ops_once, thread_ops_init);

	thread_handle.state = THREAD_STATE_START;
	thread_handle.owned_mutexes = g_ptr_array_new ();

	handle = _wapi_handle_new (WAPI_HANDLE_THREAD, &thread_handle);
	if (handle == _WAPI_HANDLE_INVALID) {
		g_warning ("%s: error creating thread handle", __func__);
		SetLastError (ERROR_GEN_FAILURE);
		
		return NULL;
	}

	res = _wapi_lookup_handle (handle, WAPI_HANDLE_THREAD,
							   (gpointer *)&thread);
	g_assert (res);

	thread->handle = handle;

	res = pthread_setspecific (thread_hash_key, handle);
	if (res)
		mono_gc_pthread_exit (NULL);

	thread->id = pthread_self ();

	/*
	 * Hold a reference while the thread is active, because we use
	 * the handle to store thread exit information
	 */
	_wapi_handle_ref (handle);

	DEBUG ("%s: started thread id %ld", __func__, thread->id);
	
	return handle;
}

/* The only time this function is called when tid != pthread_self ()
 * is from OpenThread (), so we can fast-path most cases by just
 * looking up the handle in TLS.  OpenThread () must cope with a NULL
 * return and do a handle search in that case.
 */
gpointer _wapi_thread_handle_from_id (pthread_t tid)
{
	gpointer ret;

	if (pthread_equal (tid, pthread_self ()) &&
	    (ret = pthread_getspecific (thread_hash_key)) != NULL) {
		/* We know the handle */

		DEBUG ("%s: Returning %p for self thread %ld from TLS",
			   __func__, ret, tid);
		
		return(ret);
	}
	
	DEBUG ("%s: Returning NULL for unknown or non-self thread %ld",
		   __func__, tid);
		

	return(NULL);
}

static gboolean find_thread_by_id (gpointer handle, gpointer user_data)
{
	pthread_t tid = (pthread_t)user_data;
	struct _WapiHandle_thread *thread_handle;
	gboolean ok;
	
	/* Ignore threads that have already exited (ie they are signalled) */
	if (_wapi_handle_issignalled (handle) == FALSE) {
		ok = _wapi_lookup_handle (handle, WAPI_HANDLE_THREAD,
					  (gpointer *)&thread_handle);
		if (ok == FALSE) {
			/* It's possible that the handle has vanished
			 * during the _wapi_search_handle before it
			 * gets here, so don't spam the console with
			 * warnings.
			 */
			return(FALSE);
		}
		
		DEBUG ("%s: looking at thread %ld from process %d", __func__, thread_handle->id, 0);

		if (pthread_equal (thread_handle->id, tid)) {
			DEBUG ("%s: found the thread we are looking for",
				   __func__);
			return(TRUE);
		}
	}
	
	DEBUG ("%s: not found %ld, returning FALSE", __func__, tid);
	
	return(FALSE);
}

/* NB tid is 32bit in MS API, but we need 64bit on amd64 and s390x
 * (and probably others)
 */
gpointer OpenThread (guint32 access G_GNUC_UNUSED, gboolean inherit G_GNUC_UNUSED, gsize tid)
{
	gpointer ret=NULL;
	
	mono_once (&thread_hash_once, thread_hash_init);
	mono_once (&thread_ops_once, thread_ops_init);
	
	DEBUG ("%s: looking up thread %"G_GSIZE_FORMAT, __func__, tid);

	ret = _wapi_thread_handle_from_id ((pthread_t)tid);
	if (ret == NULL) {
		/* We need to search for this thread */
		ret = _wapi_search_handle (WAPI_HANDLE_THREAD, find_thread_by_id, (gpointer)tid, NULL, FALSE/*TRUE*/);	/* FIXME: have a proper look at this, me might not need to set search_shared = TRUE */
	} else {
		/* if _wapi_search_handle() returns a found handle, it
		 * refs it itself
		 */
		_wapi_handle_ref (ret);
	}
	
	DEBUG ("%s: returning thread handle %p", __func__, ret);
	
	return(ret);
}

/**
 * ExitThread:
 * @exitcode: Sets the thread's exit code, which can be read from
 * another thread with GetExitCodeThread().
 *
 * Terminates the calling thread.  A thread can also exit by returning
 * from its start function. When the last thread in a process
 * terminates, the process itself terminates.
 */
void ExitThread(guint32 exitcode)
{
	gpointer thread = _wapi_thread_handle_from_id (pthread_self ());
	
	if (thread != NULL) {
		thread_exit(exitcode, thread);
	} else {
		/* Just blow this thread away */
		mono_gc_pthread_exit (NULL);
	}
}

/**
 * GetExitCodeThread:
 * @handle: The thread handle to query
 * @exitcode: The thread @handle exit code is stored here
 *
 * Finds the exit code of @handle, and stores it in @exitcode.  If the
 * thread @handle is still running, the value stored is %STILL_ACTIVE.
 *
 * Return value: %TRUE, or %FALSE on error.
 */
gboolean GetExitCodeThread(gpointer handle, guint32 *exitcode)
{
	struct _WapiHandle_thread *thread_handle;
	gboolean ok;
	
	ok = _wapi_lookup_handle (handle, WAPI_HANDLE_THREAD,
				  (gpointer *)&thread_handle);
	if (ok == FALSE) {
		g_warning ("%s: error looking up thread handle %p", __func__,
			   handle);
		return (FALSE);
	}
	
	DEBUG ("%s: Finding exit status for thread handle %p id %ld",
		   __func__, handle, thread_handle->id);

	if (exitcode == NULL) {
		DEBUG ("%s: Nowhere to store exit code", __func__);
		return(FALSE);
	}
	
	if (thread_handle->state != THREAD_STATE_EXITED) {
		DEBUG ("%s: Thread still active (state %d, exited is %d)",
			   __func__, thread_handle->state,
			   THREAD_STATE_EXITED);
		*exitcode = STILL_ACTIVE;
		return(TRUE);
	}
	
	*exitcode = thread_handle->exitstatus;
	
	return(TRUE);
}

/**
 * GetCurrentThreadId:
 *
 * Looks up the thread ID of the current thread.  This ID can be
 * passed to OpenThread() to create a new handle on this thread.
 *
 * Return value: the thread ID.  NB this is defined as DWORD (ie 32
 * bit) in the MS API, but we need to cope with 64 bit IDs for s390x
 * and amd64.  This doesn't really break the API, it just embraces and
 * extends it on 64bit platforms :)
 */
gsize GetCurrentThreadId(void)
{
	pthread_t tid = pthread_self();
	
#ifdef PTHREAD_POINTER_ID
	/* Don't use GPOINTER_TO_UINT here, it can't cope with
	 * sizeof(void *) > sizeof(uint) when a cast to uint would
	 * overflow
	 */
	return((gsize)tid);
#else
	return(tid);
#endif
}

static gpointer thread_attach(gsize *tid)
{
	struct _WapiHandle_thread thread_handle = {0}, *thread_handle_p;
	gpointer handle;
	gboolean ok;
	int thr_ret;
	
	mono_once (&thread_hash_once, thread_hash_init);
	mono_once (&thread_ops_once, thread_ops_init);

	thread_handle.state = THREAD_STATE_START;
	thread_handle.owned_mutexes = g_ptr_array_new ();

	handle = _wapi_handle_new (WAPI_HANDLE_THREAD, &thread_handle);
	if (handle == _WAPI_HANDLE_INVALID) {
		g_warning ("%s: error creating thread handle", __func__);
		
		SetLastError (ERROR_GEN_FAILURE);
		return (NULL);
	}

	pthread_cleanup_push ((void(*)(void *))_wapi_handle_unlock_handle,
			      handle);
	thr_ret = _wapi_handle_lock_handle (handle);
	g_assert (thr_ret == 0);
	
	ok = _wapi_lookup_handle (handle, WAPI_HANDLE_THREAD,
				  (gpointer *)&thread_handle_p);
	if (ok == FALSE) {
		g_warning ("%s: error looking up thread handle %p", __func__,
			   handle);
		
		SetLastError (ERROR_GEN_FAILURE);
		goto cleanup;
	}

	/* Hold a reference while the thread is active, because we use
	 * the handle to store thread exit information
	 */
	_wapi_handle_ref (handle);

	thread_handle_p->handle = handle;
	thread_handle_p->id = pthread_self ();

	thr_ret = pthread_setspecific (thread_hash_key, (void *)handle);
	g_assert (thr_ret == 0);

	thr_ret = pthread_setspecific (thread_attached_key, (void *)handle);
	g_assert (thr_ret == 0);
	
	DEBUG("%s: Attached thread handle %p ID %ld", __func__, handle,
		  thread_handle_p->id);

	if (tid != NULL) {
#ifdef PTHREAD_POINTER_ID
		/* Don't use GPOINTER_TO_UINT here, it can't cope with
		 * sizeof(void *) > sizeof(uint) when a cast to uint
		 * would overflow
		 */
		*tid = (gsize)(thread_handle_p->id);
#else
		*tid = thread_handle_p->id;
#endif
	}

cleanup:
	thr_ret = _wapi_handle_unlock_handle (handle);
	g_assert (thr_ret == 0);
	pthread_cleanup_pop (0);
	
	return(handle);
}

gpointer _wapi_thread_duplicate ()
{
	gpointer ret = NULL;
	
	mono_once (&thread_hash_once, thread_hash_init);
	mono_once (&thread_ops_once, thread_ops_init);
	
	ret = _wapi_thread_handle_from_id (pthread_self ());
	if (!ret) {
		ret = thread_attach (NULL);
	} else {
		_wapi_handle_ref (ret);
	}
	
	return(ret);
}

/**
 * GetCurrentThread:
 *
 * Looks up the handle associated with the current thread.  Under
 * Windows this is a pseudohandle, and must be duplicated with
 * DuplicateHandle() for some operations.
 *
 * Return value: The current thread handle, or %NULL on failure.
 * (Unknown whether Windows has a possible failure here.  It may be
 * necessary to implement the pseudohandle-constant behaviour).
 */
gpointer GetCurrentThread(void)
{
	mono_once(&thread_hash_once, thread_hash_init);
	mono_once (&thread_ops_once, thread_ops_init);
	
	return(_WAPI_THREAD_CURRENT);
}

/**
 * SleepEx:
 * @ms: The time in milliseconds to suspend for
 * @alertable: if TRUE, the wait can be interrupted by an APC call
 *
 * Suspends execution of the current thread for @ms milliseconds.  A
 * value of zero causes the thread to relinquish its time slice.  A
 * value of %INFINITE causes an infinite delay.
 */
guint32 SleepEx(guint32 ms, gboolean alertable)
{
	struct timespec req, rem;
	int ms_quot, ms_rem;
	int ret;
	gpointer current_thread = NULL;
	
	DEBUG("%s: Sleeping for %d ms", __func__, ms);

	if (alertable) {
		current_thread = _wapi_thread_handle_from_id (pthread_self ());
		if (current_thread == NULL) {
			SetLastError (ERROR_INVALID_HANDLE);
			return(WAIT_FAILED);
		}
		
		if (_wapi_thread_apc_pending (current_thread)) {
			_wapi_thread_dispatch_apc_queue (current_thread);
			return WAIT_IO_COMPLETION;
		}
	}
	
	if(ms==0) {
		sched_yield();
		return 0;
	}
	
	/* FIXME: check for INFINITE and sleep forever */
	ms_quot = ms / 1000;
	ms_rem = ms % 1000;
	
	req.tv_sec=ms_quot;
	req.tv_nsec=ms_rem*1000000;
	
again:
	memset (&rem, 0, sizeof (rem));
	ret=nanosleep(&req, &rem);

	if (alertable && _wapi_thread_apc_pending (current_thread)) {
		_wapi_thread_dispatch_apc_queue (current_thread);
		return WAIT_IO_COMPLETION;
	}
	
	if(ret==-1) {
		/* Sleep interrupted with rem time remaining */
#ifdef DEBUG_ENABLED
		guint32 rems=rem.tv_sec*1000 + rem.tv_nsec/1000000;
		
		g_message("%s: Still got %d ms to go", __func__, rems);
#endif
		req=rem;
		goto again;
	}

	return 0;
}

void Sleep(guint32 ms)
{
	SleepEx(ms, FALSE);
}

gboolean _wapi_thread_cur_apc_pending (void)
{
	gpointer thread = _wapi_thread_handle_from_id (pthread_self ());
	
	if (thread == NULL) {
		SetLastError (ERROR_INVALID_HANDLE);
		return(FALSE);
	}
	
	return(_wapi_thread_apc_pending (thread));
}

gboolean _wapi_thread_apc_pending (gpointer handle)
{
	struct _WapiHandle_thread *thread;
	gboolean ok;
	
	ok = _wapi_lookup_handle (handle, WAPI_HANDLE_THREAD,
				  (gpointer *)&thread);
	if (ok == FALSE) {
		/* This might happen at process shutdown, as all
		 * thread handles are forcibly closed.  If a thread
		 * still has an alertable wait the final
		 * _wapi_thread_apc_pending check will probably fail
		 * to find the handle
		 */
		DEBUG ("%s: error looking up thread handle %p", __func__,
			   handle);
		return (FALSE);
	}
	
	return(thread->has_apc || thread->wait_handle == INTERRUPTION_REQUESTED_HANDLE);
}

gboolean _wapi_thread_dispatch_apc_queue (gpointer handle)
{
	/* We don't support calling APC functions */
	struct _WapiHandle_thread *thread;
	gboolean ok;
	
	ok = _wapi_lookup_handle (handle, WAPI_HANDLE_THREAD,
				  (gpointer *)&thread);
	g_assert (ok);

	thread->has_apc = FALSE;

	return(TRUE);
}

/*
 * wapi_interrupt_self:
 *
 * If this function called from a signal handler, and the thread was waiting when receiving
 * the signal, the wait will be broken after the signal handler returns.
 * This function is async-signal-safe.
 */
void
wapi_thread_interrupt_self (void)
{
	HANDLE handle;
	struct _WapiHandle_thread *thread_handle;
	gboolean ok;
	
	handle = _wapi_thread_handle_from_id (pthread_self ());
	g_assert (handle);

	ok = _wapi_lookup_handle (handle, WAPI_HANDLE_THREAD,
				  (gpointer *)&thread_handle);
	if (ok == FALSE) {
		g_warning ("%s: error looking up thread handle %p", __func__,
			   handle);
		return;
	}

	/* No locking/memory barriers are needed here */
	thread_handle->has_apc = TRUE;
}

/*
 * wapi_interrupt_thread:
 *
 *   This is not part of the WIN32 API.
 * The state of the thread handle HANDLE is set to 'interrupted' which means that
 * if the thread calls one of the WaitFor functions, the function will return with 
 * WAIT_IO_COMPLETION instead of waiting. Also, if the thread was waiting when
 * this function was called, the wait will be broken.
 * It is possible that the wait functions return WAIT_IO_COMPLETION, but the
 * target thread didn't receive the interrupt signal yet, in this case it should
 * call the wait function again. This essentially means that the target thread will
 * busy wait until it is ready to process the interruption.
 * FIXME: get rid of QueueUserAPC and thread->has_apc, SleepEx seems to require it.
 */
void wapi_interrupt_thread (gpointer thread_handle)
{
	struct _WapiHandle_thread *thread;
	gboolean ok;
	gpointer prev_handle, wait_handle;
	guint32 idx;
	pthread_cond_t *cond;
	mono_mutex_t *mutex;
	
	ok = _wapi_lookup_handle (thread_handle, WAPI_HANDLE_THREAD,
				  (gpointer *)&thread);
	g_assert (ok);

	while (TRUE) {
		wait_handle = thread->wait_handle;

		/* 
		 * Atomically obtain the handle the thread is waiting on, and
		 * change it to a flag value.
		 */
		prev_handle = InterlockedCompareExchangePointer (&thread->wait_handle,
														 INTERRUPTION_REQUESTED_HANDLE, wait_handle);
		if (prev_handle == INTERRUPTION_REQUESTED_HANDLE)
			/* Already interrupted */
			return;
		if (prev_handle == wait_handle)
			break;

		/* Try again */
	}

	WAIT_DEBUG (printf ("%p: state -> INTERRUPTED.\n", thread->id););

	if (!wait_handle)
		/* Not waiting */
		return;

	/* If we reach here, then wait_handle is set to the flag value, 
	 * which means that the target thread is either
	 * - before the first CAS in timedwait, which means it won't enter the
	 * wait.
	 * - it is after the first CAS, so it is already waiting, or it will 
	 * enter the wait, and it will be interrupted by the broadcast.
	 */
	idx = GPOINTER_TO_UINT(wait_handle);
	cond = &_WAPI_PRIVATE_HANDLES(idx).signal_cond;
	mutex = &_WAPI_PRIVATE_HANDLES(idx).signal_mutex;

	mono_mutex_lock (mutex);
	mono_cond_broadcast (cond);
	mono_mutex_unlock (mutex);

	/* ref added by set_wait_handle */
	_wapi_handle_unref (wait_handle);
}


gpointer wapi_prepare_interrupt_thread (gpointer thread_handle)
{
	struct _WapiHandle_thread *thread;
	gboolean ok;
	gpointer prev_handle, wait_handle;
	
	ok = _wapi_lookup_handle (thread_handle, WAPI_HANDLE_THREAD,
				  (gpointer *)&thread);
	g_assert (ok);

	while (TRUE) {
		wait_handle = thread->wait_handle;

		/* 
		 * Atomically obtain the handle the thread is waiting on, and
		 * change it to a flag value.
		 */
		prev_handle = InterlockedCompareExchangePointer (&thread->wait_handle,
														 INTERRUPTION_REQUESTED_HANDLE, wait_handle);
		if (prev_handle == INTERRUPTION_REQUESTED_HANDLE)
			/* Already interrupted */
			return 0;
		if (prev_handle == wait_handle)
			break;

		/* Try again */
	}

	WAIT_DEBUG (printf ("%p: state -> INTERRUPTED.\n", thread->id););

	return wait_handle;
}

void wapi_finish_interrupt_thread (gpointer wait_handle)
{
	pthread_cond_t *cond;
	mono_mutex_t *mutex;
	guint32 idx;

	if (!wait_handle)
		/* Not waiting */
		return;

	/* If we reach here, then wait_handle is set to the flag value, 
	 * which means that the target thread is either
	 * - before the first CAS in timedwait, which means it won't enter the
	 * wait.
	 * - it is after the first CAS, so it is already waiting, or it will 
	 * enter the wait, and it will be interrupted by the broadcast.
	 */
	idx = GPOINTER_TO_UINT(wait_handle);
	cond = &_WAPI_PRIVATE_HANDLES(idx).signal_cond;
	mutex = &_WAPI_PRIVATE_HANDLES(idx).signal_mutex;

	mono_mutex_lock (mutex);
	mono_cond_broadcast (cond);
	mono_mutex_unlock (mutex);

	/* ref added by set_wait_handle */
	_wapi_handle_unref (wait_handle);
}


/*
 * wapi_self_interrupt:
 *
 *   This is not part of the WIN32 API.
 * Set the 'interrupted' state of the calling thread if it's NULL.
 */
void wapi_self_interrupt (void)
{
	struct _WapiHandle_thread *thread;
	gboolean ok;
	gpointer prev_handle, wait_handle;
	gpointer thread_handle;


	thread_handle = OpenThread (0, 0, GetCurrentThreadId ());
	ok = _wapi_lookup_handle (thread_handle, WAPI_HANDLE_THREAD,
							  (gpointer *)&thread);
	g_assert (ok);

	while (TRUE) {
		wait_handle = thread->wait_handle;

		/*
		 * Atomically obtain the handle the thread is waiting on, and
		 * change it to a flag value.
		 */
		prev_handle = InterlockedCompareExchangePointer (&thread->wait_handle,
														 INTERRUPTION_REQUESTED_HANDLE, wait_handle);
		if (prev_handle == INTERRUPTION_REQUESTED_HANDLE)
			/* Already interrupted */
			goto cleanup;
		/*We did not get interrupted*/
		if (prev_handle == wait_handle)
			break;

		/* Try again */
	}

	if (wait_handle) {
		/* ref added by set_wait_handle */
		_wapi_handle_unref (wait_handle);
	}

cleanup:
	_wapi_handle_unref (thread_handle);
}

/*
 * wapi_clear_interruption:
 *
 *   This is not part of the WIN32 API. 
 * Clear the 'interrupted' state of the calling thread.
 * This function is signal safe
 */
void wapi_clear_interruption (void)
{
	struct _WapiHandle_thread *thread;
	gboolean ok;
	gpointer prev_handle;
	gpointer thread_handle;

	thread_handle = OpenThread (0, 0, GetCurrentThreadId ());
	ok = _wapi_lookup_handle (thread_handle, WAPI_HANDLE_THREAD,
							  (gpointer *)&thread);
	g_assert (ok);

	prev_handle = InterlockedCompareExchangePointer (&thread->wait_handle,
													 NULL, INTERRUPTION_REQUESTED_HANDLE);
	if (prev_handle == INTERRUPTION_REQUESTED_HANDLE)
		WAIT_DEBUG (printf ("%p: state -> NORMAL.\n", GetCurrentThreadId ()););

	_wapi_handle_unref (thread_handle);
}

char* wapi_current_thread_desc ()
{
	struct _WapiHandle_thread *thread;
	int i;
	gboolean ok;
	gpointer handle;
	gpointer thread_handle;
	GString* text;
	char *res;

	thread_handle = OpenThread (0, 0, GetCurrentThreadId ());
	ok = _wapi_lookup_handle (thread_handle, WAPI_HANDLE_THREAD,
							  (gpointer *)&thread);
	if (!ok)
		return g_strdup_printf ("thread handle %p state : lookup failure", thread_handle);

	handle = thread->wait_handle;
	text = g_string_new (0);
	g_string_append_printf (text, "thread handle %p state : ", thread_handle);

	if (!handle)
		g_string_append_printf (text, "not waiting");
	else if (handle == INTERRUPTION_REQUESTED_HANDLE)
		g_string_append_printf (text, "interrupted state");
	else
		g_string_append_printf (text, "waiting on %p : %s ", handle, _wapi_handle_typename[_wapi_handle_type (handle)]);
	g_string_append_printf (text, " owns (");
	for (i = 0; i < thread->owned_mutexes->len; i++) {
		gpointer mutex = g_ptr_array_index (thread->owned_mutexes, i);
		if (i > 0)
			g_string_append_printf (text, ", %p", mutex);
		else
			g_string_append_printf (text, "%p", mutex);
	}
	g_string_append_printf (text, ")");

	res = text->str;
	g_string_free (text, FALSE);
	return res;
}

/**
 * wapi_thread_set_wait_handle:
 *
 *   Set the wait handle for the current thread to HANDLE. Return TRUE on success, FALSE
 * if the thread is in interrupted state, and cannot start waiting.
 */
gboolean wapi_thread_set_wait_handle (gpointer handle)
{
	struct _WapiHandle_thread *thread;
	gboolean ok;
	gpointer prev_handle;
	gpointer thread_handle;

	thread_handle = OpenThread (0, 0, GetCurrentThreadId ());
	ok = _wapi_lookup_handle (thread_handle, WAPI_HANDLE_THREAD,
							  (gpointer *)&thread);
	g_assert (ok);

	prev_handle = InterlockedCompareExchangePointer (&thread->wait_handle,
													 handle, NULL);
	_wapi_handle_unref (thread_handle);

	if (prev_handle == NULL) {
		/* thread->wait_handle acts as an additional reference to the handle */
		_wapi_handle_ref (handle);

		WAIT_DEBUG (printf ("%p: state -> WAITING.\n", GetCurrentThreadId ()););
	} else {
		g_assert (prev_handle == INTERRUPTION_REQUESTED_HANDLE);
		WAIT_DEBUG (printf ("%p: unable to set state to WAITING.\n", GetCurrentThreadId ()););
	}

	return prev_handle == NULL;
}

/**
 * wapi_thread_clear_wait_handle:
 *
 *   Clear the wait handle of the current thread.
 */
void wapi_thread_clear_wait_handle (gpointer handle)
{
	struct _WapiHandle_thread *thread;
	gboolean ok;
	gpointer prev_handle;
	gpointer thread_handle;

	thread_handle = OpenThread (0, 0, GetCurrentThreadId ());
	ok = _wapi_lookup_handle (thread_handle, WAPI_HANDLE_THREAD,
							  (gpointer *)&thread);
	g_assert (ok);

	prev_handle = InterlockedCompareExchangePointer (&thread->wait_handle,
													 NULL, handle);

	if (prev_handle == handle) {
		_wapi_handle_unref (handle);
		WAIT_DEBUG (printf ("%p: state -> NORMAL.\n", GetCurrentThreadId ()););
	} else {
		/*It can be NULL if it was asynchronously cleared*/
		g_assert (prev_handle == INTERRUPTION_REQUESTED_HANDLE || prev_handle == NULL);
		WAIT_DEBUG (printf ("%p: finished waiting.\n", GetCurrentThreadId ()););
	}

	_wapi_handle_unref (thread_handle);
}

void _wapi_thread_own_mutex (gpointer mutex)
{
	struct _WapiHandle_thread *thread_handle;
	gboolean ok;
	gpointer thread;
	
	thread = _wapi_thread_handle_from_id (pthread_self ());
	if (thread == NULL) {
		g_warning ("%s: error looking up thread by ID", __func__);
		return;
	}

	ok = _wapi_lookup_handle (thread, WAPI_HANDLE_THREAD,
				  (gpointer *)&thread_handle);
	if (ok == FALSE) {
		g_warning ("%s: error looking up thread handle %p", __func__,
			   thread);
		return;
	}

	_wapi_handle_ref (mutex);
	
	g_ptr_array_add (thread_handle->owned_mutexes, mutex);
}

void _wapi_thread_disown_mutex (gpointer mutex)
{
	struct _WapiHandle_thread *thread_handle;
	gboolean ok;
	gpointer thread;

	thread = _wapi_thread_handle_from_id (pthread_self ());
	if (thread == NULL) {
		g_warning ("%s: error looking up thread by ID", __func__);
		return;
	}

	ok = _wapi_lookup_handle (thread, WAPI_HANDLE_THREAD,
				  (gpointer *)&thread_handle);
	if (ok == FALSE) {
		g_warning ("%s: error looking up thread handle %p", __func__,
			   thread);
		return;
	}

	_wapi_handle_unref (mutex);
	
	g_ptr_array_remove (thread_handle->owned_mutexes, mutex);
}