[apple/xnu.git] / iokit / Kernel / IOWorkLoop.cpp

/*
 * Copyright (c) 1998-2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This Original Code and all software distributed under the License are
 * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/*
Copyright (c) 1998 Apple Computer, Inc.  All rights reserved.

HISTORY
    1998-7-13	Godfrey van der Linden(gvdl)
        Created.
*/
#include <IOKit/IOWorkLoop.h>
#include <IOKit/IOEventSource.h>
#include <IOKit/IOInterruptEventSource.h>
#include <IOKit/IOCommandGate.h>
#include <IOKit/IOTimeStamp.h>

#define super OSObject

OSDefineMetaClassAndStructors(IOWorkLoop, OSObject);

// Block of unused functions intended for future use
OSMetaClassDefineReservedUnused(IOWorkLoop, 0);
OSMetaClassDefineReservedUnused(IOWorkLoop, 1);
OSMetaClassDefineReservedUnused(IOWorkLoop, 2);
OSMetaClassDefineReservedUnused(IOWorkLoop, 3);
OSMetaClassDefineReservedUnused(IOWorkLoop, 4);
OSMetaClassDefineReservedUnused(IOWorkLoop, 5);
OSMetaClassDefineReservedUnused(IOWorkLoop, 6);
OSMetaClassDefineReservedUnused(IOWorkLoop, 7);

enum IOWorkLoopState { kLoopRestart = 0x1, kLoopTerminate = 0x2 };
static inline void SETP(void *addr, unsigned int flag)
    { unsigned int *num = (unsigned int *) addr; *num |= flag; }
static inline void CLRP(void *addr, unsigned int flag)
    { unsigned int *num = (unsigned int *) addr; *num &= ~flag; }
static inline bool ISSETP(void *addr, unsigned int flag)
    { unsigned int *num = (unsigned int *) addr; return (*num & flag) != 0; }

#define fFlags loopRestart

void IOWorkLoop::launchThreadMain(void *self)
{
    register thread_t mythread = current_thread();

    // Make sure that this thread always has a kernel stack
    stack_privilege(mythread);
    thread_set_cont_arg((int) self);
    threadMainContinuation();
}

bool IOWorkLoop::init()
{
    // The super init and gateLock allocation MUST be done first
    if ( !super::init() )
        return false;

    if ( !(gateLock = IORecursiveLockAlloc()) )
        return false;

    if ( !(workToDoLock = IOSimpleLockAlloc()) )
        return false;

    controlG = IOCommandGate::
	commandGate(this, (IOCommandGate::Action) &IOWorkLoop::_maintRequest);
    if ( !controlG )
        return false;

    IOSimpleLockInit(workToDoLock);
    workToDo = false;

    // Point the controlGate at the workLoop.  Usually addEventSource
    // does this automatically.  The problem is in this case addEventSource
    // uses the control gate and it has to be bootstrapped.
    controlG->setWorkLoop(this);
    if (addEventSource(controlG) != kIOReturnSuccess)
        return false;

    workThread = IOCreateThread(launchThreadMain, (void *) this);
    if (!workThread)
        return false;

    return true;
}

IOWorkLoop *
IOWorkLoop::workLoop()
{
    IOWorkLoop *me = new IOWorkLoop;

    if (me && !me->init()) {
        me->free();
        return 0;
    }

    return me;
}

// Free is called twice:
// First when the atomic retainCount transitions from 1 -> 0
// Secondly when the work loop itself is commiting hari kari
// Hence the each leg of the free must be single threaded.
void IOWorkLoop::free()
{
    if (workThread) {
	IOInterruptState is;

	// If we are here then we must be trying to shut down this work loop
	// in this case disable all of the event source, mark the loop for
	// as terminating and wakeup the work thread itself and return
	// Note: we hold the gate across the entire operation mainly for the 
	// benefit of our event sources so we can disable them cleanly.
	closeGate();

	disableAllEventSources();

        is = IOSimpleLockLockDisableInterrupt(workToDoLock);
	SETP(&fFlags, kLoopTerminate);
        thread_wakeup_one((void *) &workToDo);
        IOSimpleLockUnlockEnableInterrupt(workToDoLock, is);

	openGate();
    }
    else /* !workThread */ {
        IOEventSource *event, *next;

        for (event = eventChain; event; event = next) {
            next = event->getNext();
            event->setWorkLoop(0);
            event->setNext(0);
            event->release();
        }
        eventChain = 0;

	// Either we have a partial initialisation to clean up
	// or we the workThread itself is performing hari-kari.
	// either way clean up all of our resources and return.
	
	if (controlG) {
	    controlG->release();
	    controlG = 0;
	}

	if (workToDoLock) {
	    IOSimpleLockFree(workToDoLock);
	    workToDoLock = 0;
	}

	if (gateLock) {
	    IORecursiveLockFree(gateLock);
	    gateLock = 0;
	}

	super::free();
    }
}

IOReturn IOWorkLoop::addEventSource(IOEventSource *newEvent)
{
    return controlG->runCommand((void *) mAddEvent, (void *) newEvent);
}
    
IOReturn IOWorkLoop::removeEventSource(IOEventSource *toRemove)
{
    return controlG->runCommand((void *) mRemoveEvent, (void *) toRemove);
}

void IOWorkLoop::enableAllEventSources() const
{
    IOEventSource *event;

    for (event = eventChain; event; event = event->getNext())
        event->enable();
}

void IOWorkLoop::disableAllEventSources() const
{
    IOEventSource *event;

    for (event = eventChain; event; event = event->getNext())
        if (event != controlG)	// Don't disable the control gate
            event->disable();
}

void IOWorkLoop::enableAllInterrupts() const
{
    IOEventSource *event;

    for (event = eventChain; event; event = event->getNext())
        if (OSDynamicCast(IOInterruptEventSource, event))
            event->enable();
}

void IOWorkLoop::disableAllInterrupts() const
{
    IOEventSource *event;

    for (event = eventChain; event; event = event->getNext())
        if (OSDynamicCast(IOInterruptEventSource, event))
            event->disable();
}

#if KDEBUG
#define IOTimeClientS()							\
do {									\
    IOTimeStampStart(IODBG_WORKLOOP(IOWL_CLIENT),			\
                     (unsigned int) this, (unsigned int) event);	\
} while(0)

#define IOTimeClientE()							\
do {									\
    IOTimeStampEnd(IODBG_WORKLOOP(IOWL_CLIENT),				\
                   (unsigned int) this, (unsigned int) event);		\
} while(0)

#define IOTimeWorkS()							\
do {									\
    IOTimeStampStart(IODBG_WORKLOOP(IOWL_WORK),	(unsigned int) this);	\
} while(0)

#define IOTimeWorkE()							\
do {									\
    IOTimeStampEnd(IODBG_WORKLOOP(IOWL_WORK),(unsigned int) this);	\
} while(0)

#else /* !KDEBUG */

#define IOTimeClientS()
#define IOTimeClientE()
#define IOTimeWorkS()
#define IOTimeWorkE()

#endif /* KDEBUG */

void IOWorkLoop::threadMainContinuation()
{
  IOWorkLoop* self;
  self = (IOWorkLoop *) thread_get_cont_arg();

  self->threadMain();
}

void IOWorkLoop::threadMain()
{
    CLRP(&fFlags, kLoopRestart);

    for (;;) {
        bool more;
	IOInterruptState is;

    IOTimeWorkS();

        closeGate();
        if (ISSETP(&fFlags, kLoopTerminate))
	    goto exitThread;

        do {
            workToDo = more = false;
            for (IOEventSource *event = eventChain; event; event = event->getNext()) {

            IOTimeClientS();
                more |= event->checkForWork();
            IOTimeClientE();

		if (ISSETP(&fFlags, kLoopTerminate))
		    goto exitThread;
                else if (fFlags & kLoopRestart) {
		    CLRP(&fFlags, kLoopRestart);
                    continue;
                }
            }
        } while (more);

    IOTimeWorkE();

        openGate();

	is = IOSimpleLockLockDisableInterrupt(workToDoLock);
        if ( !ISSETP(&fFlags, kLoopTerminate) && !workToDo) {
	    assert_wait((void *) &workToDo, false);
	    IOSimpleLockUnlockEnableInterrupt(workToDoLock, is);

#if defined (__i386__)
	    thread_block(0);
	    continue;
#else
	    thread_set_cont_arg((int) this);
	    thread_block(&threadMainContinuation);
#endif
	    /* NOTREACHED */
	}

	// At this point we either have work to do or we need
	// to commit suicide.  But no matter 
	// Clear the simple lock and retore the interrupt state
	IOSimpleLockUnlockEnableInterrupt(workToDoLock, is);
	if (workToDo)
	    continue;
	else
	    break;
    }

exitThread:
    workThread = 0;	// Say we don't have a loop and free ourselves
    free();
    IOExitThread(0);
}

IOThread IOWorkLoop::getThread() const
{
    return workThread;
}

bool IOWorkLoop::onThread() const
{
    return (IOThreadSelf() == workThread);
}

bool IOWorkLoop::inGate() const
{
    return IORecursiveLockHaveLock(gateLock);
}

// Internal APIs used by event sources to control the thread
void IOWorkLoop::signalWorkAvailable()
{
    if (workToDoLock) {
        IOInterruptState is = IOSimpleLockLockDisableInterrupt(workToDoLock);
        workToDo = true;
        thread_wakeup_one((void *) &workToDo);
        IOSimpleLockUnlockEnableInterrupt(workToDoLock, is);
    }
}

void IOWorkLoop::openGate()
{
    IORecursiveLockUnlock(gateLock);
}

void IOWorkLoop::closeGate()
{
    IORecursiveLockLock(gateLock);
}

bool IOWorkLoop::tryCloseGate()
{
    return IORecursiveLockTryLock(gateLock) != 0;
}

int IOWorkLoop::sleepGate(void *event, UInt32 interuptibleType)
{
    return IORecursiveLockSleep(gateLock, event, interuptibleType);
}

void IOWorkLoop::wakeupGate(void *event, bool oneThread)
{
    IORecursiveLockWakeup(gateLock, event, oneThread);
}

IOReturn IOWorkLoop::_maintRequest(void *inC, void *inD, void *, void *)
{
    maintCommandEnum command = (maintCommandEnum) (vm_address_t) inC;
    IOEventSource *inEvent = (IOEventSource *) inD;
    IOReturn res = kIOReturnSuccess;

    switch (command)
    {
    case mAddEvent:
	SETP(&fFlags, kLoopRestart);
        inEvent->retain();
        inEvent->setWorkLoop(this);
        inEvent->setNext(0);

        if (!eventChain)
            eventChain = inEvent;
        else {
            IOEventSource *event, *next;

            for (event = eventChain; (next = event->getNext()); event = next)
                ;
            event->setNext(inEvent);
        }
        break;

    case mRemoveEvent:
        if (eventChain == inEvent)
            eventChain = inEvent->getNext();
        else {
            IOEventSource *event, *next;

            event = eventChain;
            while ((next = event->getNext()) && next != inEvent)
                event = next;

            if (!next) {
                res = kIOReturnBadArgument;
                break;
            }
            event->setNext(inEvent->getNext());
        }

        inEvent->setWorkLoop(0);
        inEvent->setNext(0);
        inEvent->release();
	SETP(&fFlags, kLoopRestart);
        break;

    default:
        return kIOReturnUnsupported;
    }

    return res;
}
Commit	Line	Data
1c79356b A	1	/*
	2	* Copyright (c) 1998-2000 Apple Computer, Inc. All rights reserved.
	3	*
	4	* @APPLE_LICENSE_HEADER_START@
	5	*
	6	* The contents of this file constitute Original Code as defined in and
	7	* are subject to the Apple Public Source License Version 1.1 (the
	8	* "License"). You may not use this file except in compliance with the
	9	* License. Please obtain a copy of the License at
	10	* http://www.apple.com/publicsource and read it before using this file.
	11	*
	12	* This Original Code and all software distributed under the License are
	13	* distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
	14	* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
	15	* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
	16	* FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT. Please see the
	17	* License for the specific language governing rights and limitations
	18	* under the License.
	19	*
	20	* @APPLE_LICENSE_HEADER_END@
	21	*/
	22	/*
	23	Copyright (c) 1998 Apple Computer, Inc. All rights reserved.
	24
	25	HISTORY
	26	1998-7-13 Godfrey van der Linden(gvdl)
	27	Created.
	28	*/
	29	#include <IOKit/IOWorkLoop.h>
	30	#include <IOKit/IOEventSource.h>
	31	#include <IOKit/IOInterruptEventSource.h>
	32	#include <IOKit/IOCommandGate.h>
	33	#include <IOKit/IOTimeStamp.h>
	34
	35	#define super OSObject
	36
	37	OSDefineMetaClassAndStructors(IOWorkLoop, OSObject);
	38
	39	// Block of unused functions intended for future use
	40	OSMetaClassDefineReservedUnused(IOWorkLoop, 0);
	41	OSMetaClassDefineReservedUnused(IOWorkLoop, 1);
	42	OSMetaClassDefineReservedUnused(IOWorkLoop, 2);
	43	OSMetaClassDefineReservedUnused(IOWorkLoop, 3);
	44	OSMetaClassDefineReservedUnused(IOWorkLoop, 4);
	45	OSMetaClassDefineReservedUnused(IOWorkLoop, 5);
	46	OSMetaClassDefineReservedUnused(IOWorkLoop, 6);
	47	OSMetaClassDefineReservedUnused(IOWorkLoop, 7);
	48
	49	enum IOWorkLoopState { kLoopRestart = 0x1, kLoopTerminate = 0x2 };
	50	static inline void SETP(void *addr, unsigned int flag)
	51	{ unsigned int num = (unsigned int ) addr; *num \|= flag; }
	52	static inline void CLRP(void *addr, unsigned int flag)
	53	{ unsigned int num = (unsigned int ) addr; *num &= ~flag; }
	54	static inline bool ISSETP(void *addr, unsigned int flag)
	55	{ unsigned int num = (unsigned int ) addr; return (*num & flag) != 0; }
	56
	57	#define fFlags loopRestart
	58
	59	void IOWorkLoop::launchThreadMain(void *self)
	60	{
	61	register thread_t mythread = current_thread();
	62
	63	// Make sure that this thread always has a kernel stack
	64	stack_privilege(mythread);
65	thread_set_cont_arg((int) self);
66	threadMainContinuation();
67	}
68
69	bool IOWorkLoop::init()
70	{
71	// The super init and gateLock allocation MUST be done first
72	if ( !super::init() )
73	return false;
74
75	if ( !(gateLock = IORecursiveLockAlloc()) )
76	return false;
77
78	if ( !(workToDoLock = IOSimpleLockAlloc()) )
79	return false;
80
81	controlG = IOCommandGate::
82	commandGate(this, (IOCommandGate::Action) &IOWorkLoop::_maintRequest);
83	if ( !controlG )
84	return false;
85
86	IOSimpleLockInit(workToDoLock);
87	workToDo = false;
88
89	// Point the controlGate at the workLoop. Usually addEventSource
90	// does this automatically. The problem is in this case addEventSource
91	// uses the control gate and it has to be bootstrapped.
92	controlG->setWorkLoop(this);
93	if (addEventSource(controlG) != kIOReturnSuccess)
94	return false;
95
96	workThread = IOCreateThread(launchThreadMain, (void *) this);
97	if (!workThread)
98	return false;
99
100	return true;
101	}
102
103	IOWorkLoop *
104	IOWorkLoop::workLoop()
105	{
106	IOWorkLoop *me = new IOWorkLoop;
107
108	if (me && !me->init()) {
109	me->free();
110	return 0;
111	}
112
113	return me;
114	}
115
116	// Free is called twice:
117	// First when the atomic retainCount transitions from 1 -> 0
118	// Secondly when the work loop itself is commiting hari kari
119	// Hence the each leg of the free must be single threaded.
120	void IOWorkLoop::free()
121	{
122	if (workThread) {
123	IOInterruptState is;
124
125	// If we are here then we must be trying to shut down this work loop
126	// in this case disable all of the event source, mark the loop for
127	// as terminating and wakeup the work thread itself and return
128	// Note: we hold the gate across the entire operation mainly for the
129	// benefit of our event sources so we can disable them cleanly.
130	closeGate();
131
132	disableAllEventSources();
133
134	is = IOSimpleLockLockDisableInterrupt(workToDoLock);
135	SETP(&fFlags, kLoopTerminate);
136	thread_wakeup_one((void *) &workToDo);
137	IOSimpleLockUnlockEnableInterrupt(workToDoLock, is);
138
139	openGate();
140	}
141	else /* !workThread */ {
142	IOEventSource event, next;
143
144	for (event = eventChain; event; event = next) {
145	next = event->getNext();
146	event->setWorkLoop(0);
147	event->setNext(0);
148	event->release();
149	}
150	eventChain = 0;
151
152	// Either we have a partial initialisation to clean up
153	// or we the workThread itself is performing hari-kari.
154	// either way clean up all of our resources and return.
155
156	if (controlG) {
157	controlG->release();
158	controlG = 0;
159	}
160
161	if (workToDoLock) {
162	IOSimpleLockFree(workToDoLock);
163	workToDoLock = 0;
164	}
165
166	if (gateLock) {
167	IORecursiveLockFree(gateLock);
168	gateLock = 0;
169	}
170
171	super::free();
172	}
173	}
174
175	IOReturn IOWorkLoop::addEventSource(IOEventSource *newEvent)
176	{
177	return controlG->runCommand((void ) mAddEvent, (void ) newEvent);
178	}
179
180	IOReturn IOWorkLoop::removeEventSource(IOEventSource *toRemove)
181	{
182	return controlG->runCommand((void ) mRemoveEvent, (void ) toRemove);
183	}
184
185	void IOWorkLoop::enableAllEventSources() const
186	{
187	IOEventSource *event;
188
189	for (event = eventChain; event; event = event->getNext())
190	event->enable();
191	}
192
193	void IOWorkLoop::disableAllEventSources() const
194	{
195	IOEventSource *event;
196
197	for (event = eventChain; event; event = event->getNext())
198	if (event != controlG) // Don't disable the control gate
199	event->disable();
200	}
201
202	void IOWorkLoop::enableAllInterrupts() const
203	{
204	IOEventSource *event;
205
206	for (event = eventChain; event; event = event->getNext())
207	if (OSDynamicCast(IOInterruptEventSource, event))
208	event->enable();
209	}
210
211	void IOWorkLoop::disableAllInterrupts() const
212	{
213	IOEventSource *event;
214
215	for (event = eventChain; event; event = event->getNext())
216	if (OSDynamicCast(IOInterruptEventSource, event))
217	event->disable();
218	}
219
220	#if KDEBUG
221	#define IOTimeClientS() \
222	do { \
223	IOTimeStampStart(IODBG_WORKLOOP(IOWL_CLIENT), \
224	(unsigned int) this, (unsigned int) event); \
225	} while(0)
226
227	#define IOTimeClientE() \
228	do { \
229	IOTimeStampEnd(IODBG_WORKLOOP(IOWL_CLIENT), \
230	(unsigned int) this, (unsigned int) event); \
231	} while(0)
232
233	#define IOTimeWorkS() \
234	do { \
235	IOTimeStampStart(IODBG_WORKLOOP(IOWL_WORK), (unsigned int) this); \
236	} while(0)
237
238	#define IOTimeWorkE() \
239	do { \
240	IOTimeStampEnd(IODBG_WORKLOOP(IOWL_WORK),(unsigned int) this); \
241	} while(0)
242
243	#else /* !KDEBUG */
244
245	#define IOTimeClientS()
246	#define IOTimeClientE()
247	#define IOTimeWorkS()
248	#define IOTimeWorkE()
249
250	#endif /* KDEBUG */
251
252	void IOWorkLoop::threadMainContinuation()
253	{
254	IOWorkLoop* self;
255	self = (IOWorkLoop *) thread_get_cont_arg();
256
257	self->threadMain();
258	}
259
260	void IOWorkLoop::threadMain()
261	{
262	CLRP(&fFlags, kLoopRestart);
263
264	for (;;) {
265	bool more;
266	IOInterruptState is;
267
268	IOTimeWorkS();
269
270	closeGate();
271	if (ISSETP(&fFlags, kLoopTerminate))
272	goto exitThread;
273
274	do {
275	workToDo = more = false;
276	for (IOEventSource *event = eventChain; event; event = event->getNext()) {
277
278	IOTimeClientS();
279	more \|= event->checkForWork();
280	IOTimeClientE();
281
282	if (ISSETP(&fFlags, kLoopTerminate))
283	goto exitThread;
284	else if (fFlags & kLoopRestart) {
285	CLRP(&fFlags, kLoopRestart);
286	continue;
287	}
288	}
289	} while (more);
290
291	IOTimeWorkE();
292
293	openGate();
294
295	is = IOSimpleLockLockDisableInterrupt(workToDoLock);
296	if ( !ISSETP(&fFlags, kLoopTerminate) && !workToDo) {
297	assert_wait((void *) &workToDo, false);
298	IOSimpleLockUnlockEnableInterrupt(workToDoLock, is);
299
300	#if defined (__i386__)
301	thread_block(0);
302	continue;
303	#else
304	thread_set_cont_arg((int) this);
305	thread_block(&threadMainContinuation);
306	#endif
307	/* NOTREACHED */
308	}
309
310	// At this point we either have work to do or we need
311	// to commit suicide. But no matter
312	// Clear the simple lock and retore the interrupt state
313	IOSimpleLockUnlockEnableInterrupt(workToDoLock, is);
314	if (workToDo)
315	continue;
316	else
317	break;
318	}
319
320	exitThread:
321	workThread = 0; // Say we don't have a loop and free ourselves
322	free();
323	IOExitThread(0);
324	}
325
326	IOThread IOWorkLoop::getThread() const
327	{
328	return workThread;
329	}
330
331	bool IOWorkLoop::onThread() const
332	{
333	return (IOThreadSelf() == workThread);
334	}
335
336	bool IOWorkLoop::inGate() const
337	{
338	return IORecursiveLockHaveLock(gateLock);
339	}
340
341	// Internal APIs used by event sources to control the thread
342	void IOWorkLoop::signalWorkAvailable()
343	{
344	if (workToDoLock) {
345	IOInterruptState is = IOSimpleLockLockDisableInterrupt(workToDoLock);
346	workToDo = true;
347	thread_wakeup_one((void *) &workToDo);
348	IOSimpleLockUnlockEnableInterrupt(workToDoLock, is);
349	}
350	}
351
352	void IOWorkLoop::openGate()
353	{
354	IORecursiveLockUnlock(gateLock);
355	}
356
357	void IOWorkLoop::closeGate()
358	{
359	IORecursiveLockLock(gateLock);
360	}
361
362	bool IOWorkLoop::tryCloseGate()
363	{
364	return IORecursiveLockTryLock(gateLock) != 0;
365	}
366
367	int IOWorkLoop::sleepGate(void *event, UInt32 interuptibleType)
368	{
369	return IORecursiveLockSleep(gateLock, event, interuptibleType);
370	}
371
372	void IOWorkLoop::wakeupGate(void *event, bool oneThread)
373	{
374	IORecursiveLockWakeup(gateLock, event, oneThread);
375	}
376
377	IOReturn IOWorkLoop::_maintRequest(void inC, void inD, void , void )
378	{
379	maintCommandEnum command = (maintCommandEnum) (vm_address_t) inC;
380	IOEventSource inEvent = (IOEventSource ) inD;
381	IOReturn res = kIOReturnSuccess;
382
383	switch (command)
384	{
385	case mAddEvent:
386	SETP(&fFlags, kLoopRestart);
387	inEvent->retain();
388	inEvent->setWorkLoop(this);
389	inEvent->setNext(0);
390
391	if (!eventChain)
392	eventChain = inEvent;
393	else {
394	IOEventSource event, next;
395
396	for (event = eventChain; (next = event->getNext()); event = next)
397	;
398	event->setNext(inEvent);
399	}
400	break;
401
402	case mRemoveEvent:
403	if (eventChain == inEvent)
404	eventChain = inEvent->getNext();
405	else {
406	IOEventSource event, next;
407
408	event = eventChain;
409	while ((next = event->getNext()) && next != inEvent)
410	event = next;
411
412	if (!next) {
413	res = kIOReturnBadArgument;
414	break;
415	}
416	event->setNext(inEvent->getNext());
417	}
418
419	inEvent->setWorkLoop(0);
420	inEvent->setNext(0);
421	inEvent->release();
422	SETP(&fFlags, kLoopRestart);
423	break;
424
425	default:
426	return kIOReturnUnsupported;
427	}
428
429	return res;
430	}