/*
 * Copyright (c) 1998-2010 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The 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, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */

#include <pexpert/pexpert.h>
#include <IOKit/IOWorkLoop.h>
#include <IOKit/IOEventSource.h>
#include <IOKit/IOInterruptEventSource.h>
#include <IOKit/IOCommandGate.h>
#include <IOKit/IOTimeStamp.h>
#include <IOKit/IOKitDebug.h>
#include <libkern/OSDebug.h>
#include <kern/thread.h>

#define super OSObject

OSDefineMetaClassAndStructors(IOWorkLoop, OSObject);

// Block of unused functions intended for future use
#if __LP64__
OSMetaClassDefineReservedUnused(IOWorkLoop, 0);
OSMetaClassDefineReservedUnused(IOWorkLoop, 1);
OSMetaClassDefineReservedUnused(IOWorkLoop, 2);
#else
OSMetaClassDefineReservedUsed(IOWorkLoop, 0);
OSMetaClassDefineReservedUsed(IOWorkLoop, 1);
OSMetaClassDefineReservedUsed(IOWorkLoop, 2);
#endif
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 char *num = (unsigned char *) addr; *num |= flag; }
static inline void CLRP(void *addr, unsigned int flag)
    { unsigned char *num = (unsigned char *) addr; *num &= ~flag; }
static inline bool ISSETP(void *addr, unsigned int flag)
    { unsigned char *num = (unsigned char *) addr; return (*num & flag) != 0; }

#define fFlags loopRestart

#define passiveEventChain	reserved->passiveEventChain

#if IOKITSTATS

#define IOStatisticsRegisterCounter() \
do { \
	reserved->counter = IOStatistics::registerWorkLoop(this); \
} while(0)

#define IOStatisticsUnregisterCounter() \
do { \
	if (reserved) \
		IOStatistics::unregisterWorkLoop(reserved->counter); \
} while(0)

#define IOStatisticsOpenGate() \
do { \
	IOStatistics::countWorkLoopOpenGate(reserved->counter); \
} while(0)

#define IOStatisticsCloseGate() \
do { \
	IOStatistics::countWorkLoopCloseGate(reserved->counter); \
} while(0)

#define IOStatisticsAttachEventSource() \
do { \
	IOStatistics::attachWorkLoopEventSource(reserved->counter, inEvent->reserved->counter); \
} while(0)

#define IOStatisticsDetachEventSource() \
do { \
	IOStatistics::detachWorkLoopEventSource(reserved->counter, inEvent->reserved->counter); \
} while(0)

#else

#define IOStatisticsRegisterCounter()
#define IOStatisticsUnregisterCounter()
#define IOStatisticsOpenGate()
#define IOStatisticsCloseGate()
#define IOStatisticsAttachEventSource()
#define IOStatisticsDetachEventSource()

#endif /* IOKITSTATS */

bool IOWorkLoop::init()
{
    // The super init and gateLock allocation MUST be done first.
    if ( !super::init() )
        return false;
	
	// Allocate our ExpansionData if it hasn't been allocated already.
	if ( !reserved )
	{
		reserved = IONew(ExpansionData,1);
		if ( !reserved )
			return false;
		
		bzero(reserved,sizeof(ExpansionData));
	}
	
#if DEBUG
	OSBacktrace ( reserved->allocationBacktrace, sizeof ( reserved->allocationBacktrace ) / sizeof ( reserved->allocationBacktrace[0] ) );
#endif
	
    if ( gateLock == NULL ) {
        if ( !( gateLock = IORecursiveLockAlloc()) )
            return false;
    }
	
    if ( workToDoLock == NULL ) {
        if ( !(workToDoLock = IOSimpleLockAlloc()) )
            return false;
        IOSimpleLockInit(workToDoLock);
        workToDo = false;
    }

    IOStatisticsRegisterCounter();

    if ( controlG == NULL ) {
        controlG = IOCommandGate::commandGate(
            this,
            OSMemberFunctionCast(
                IOCommandGate::Action,
                this,
                &IOWorkLoop::_maintRequest));

        if ( !controlG )
            return 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;
    }

    if ( workThread == NULL ) {
        thread_continue_t cptr = OSMemberFunctionCast(
            thread_continue_t,
            this,
            &IOWorkLoop::threadMain);
        if (KERN_SUCCESS != kernel_thread_start(cptr, this, &workThread))
            return false;
    }

    (void) thread_set_tag(workThread, THREAD_TAG_IOWORKLOOP);
    return true;
}

IOWorkLoop *
IOWorkLoop::workLoop()
{
    return IOWorkLoop::workLoopWithOptions(0);
}

IOWorkLoop *
IOWorkLoop::workLoopWithOptions(IOOptionBits options)
{
	IOWorkLoop *me = new IOWorkLoop;
	
	if (me && options) {
		me->reserved = IONew(ExpansionData,1);
		if (!me->reserved) {
			me->release();
			return 0;
		}
		bzero(me->reserved,sizeof(ExpansionData));
		me->reserved->options = options;
	}
	
	if (me && !me->init()) {
		me->release();
		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
	// 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;

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

	// Either we have a partial initialization to clean up
	// or 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;
	}
	
	IOStatisticsUnregisterCounter();
	
	if (reserved) {
	    IODelete(reserved, ExpansionData, 1);
	    reserved = 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();

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

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

    for (event = eventChain; event; event = event->getNext())
		event->disable();
	
	/* NOTE: controlG is in passiveEventChain since it's an IOCommandGate */
    for (event = passiveEventChain; 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();
}


/* virtual */ bool IOWorkLoop::runEventSources()
{
    bool res = false;
    bool traceWL = (gIOKitTrace & kIOTraceWorkLoops) ? true : false;
    bool traceES = (gIOKitTrace & kIOTraceEventSources) ? true : false;
    
    closeGate();
    if (ISSETP(&fFlags, kLoopTerminate))
		goto abort;
	
    if (traceWL)
    	IOTimeStampStartConstant(IODBG_WORKLOOP(IOWL_WORK), (uintptr_t) this);
	
    bool more;
    do {
		CLRP(&fFlags, kLoopRestart);
		more = false;
		IOInterruptState is = IOSimpleLockLockDisableInterrupt(workToDoLock);
		workToDo = false;
		IOSimpleLockUnlockEnableInterrupt(workToDoLock, is);
		/* NOTE: only loop over event sources in eventChain. Bypass "passive" event sources for performance */
		for (IOEventSource *evnt = eventChain; evnt; evnt = evnt->getNext()) {
			
			if (traceES)
				IOTimeStampStartConstant(IODBG_WORKLOOP(IOWL_CLIENT), (uintptr_t) this, (uintptr_t) evnt);
			
			more |= evnt->checkForWork();
			
			if (traceES)
				IOTimeStampEndConstant(IODBG_WORKLOOP(IOWL_CLIENT), (uintptr_t) this, (uintptr_t) evnt);
			
			if (ISSETP(&fFlags, kLoopTerminate))
				goto abort;
			else if (fFlags & kLoopRestart) {
				more = true;
				break;
			}
		}
    } while (more);
	
    res = true;
	
    if (traceWL)
    	IOTimeStampEndConstant(IODBG_WORKLOOP(IOWL_WORK), (uintptr_t) this);
	
abort:
    openGate();
    return res;
}

/* virtual */ void IOWorkLoop::threadMain()
{
restartThread:
    do {
	if ( !runEventSources() )
	    goto exitThread;

	IOInterruptState is = IOSimpleLockLockDisableInterrupt(workToDoLock);
        if ( !ISSETP(&fFlags, kLoopTerminate) && !workToDo) {
	    assert_wait((void *) &workToDo, false);
	    IOSimpleLockUnlockEnableInterrupt(workToDoLock, is);
	    thread_continue_t cptr = NULL;
	    if (!reserved || !(kPreciousStack & reserved->options))
		cptr = OSMemberFunctionCast(
			thread_continue_t, this, &IOWorkLoop::threadMain);
	    thread_block_parameter(cptr, this);
	    goto restartThread;
	    /* 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);
    } while(workToDo);

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

	thread_deallocate(thread);
    (void) thread_terminate(thread);
}

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()
{
    IOStatisticsOpenGate();
    IORecursiveLockUnlock(gateLock);
}

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

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

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

int IOWorkLoop::sleepGate(void *event, AbsoluteTime deadline, UInt32 interuptibleType)
{
    int res; 
    IOStatisticsOpenGate();
    res = IORecursiveLockSleepDeadline(gateLock, event, deadline, interuptibleType);
    IOStatisticsCloseGate();
    return res;
}

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

IOReturn IOWorkLoop::runAction(Action inAction, OSObject *target,
                                  void *arg0, void *arg1,
                                  void *arg2, void *arg3)
{
    IOReturn res;

    // closeGate is recursive so don't worry if we already hold the lock.
    closeGate();
    res = (*inAction)(target, arg0, arg1, arg2, arg3);
    openGate();

    return res;
}

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

    switch (command)
    {
    case mAddEvent:
        if (!inEvent->getWorkLoop()) {
            SETP(&fFlags, kLoopRestart);

            inEvent->retain();
            inEvent->setWorkLoop(this);
            inEvent->setNext(0);

    		/* Check if this is a passive or active event source being added */
    		if (eventSourcePerformsWork(inEvent)) {
    		
	            if (!eventChain)
    	            eventChain = inEvent;
        	    else {
            	    IOEventSource *event, *next;
    
                	for (event = eventChain; (next = event->getNext()); event = next)
                    	;
                	event->setNext(inEvent);
                	
            	}
            	
            }
            else {
    		
	            if (!passiveEventChain)
    	            passiveEventChain = inEvent;
        	    else {
            	    IOEventSource *event, *next;
    
                	for (event = passiveEventChain; (next = event->getNext()); event = next)
                    	;
                	event->setNext(inEvent);
                	
            	}
            	
            }
            IOStatisticsAttachEventSource();
        }
        break;

    case mRemoveEvent:
        if (inEvent->getWorkLoop()) {
        	IOStatisticsDetachEventSource();
    		
        	if (eventSourcePerformsWork(inEvent)) {
				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());
				}
    		}
    		else {
				if (passiveEventChain == inEvent)
					passiveEventChain = inEvent->getNext();
				else {
					IOEventSource *event, *next;
		
					event = passiveEventChain;
					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;
}

bool
IOWorkLoop::eventSourcePerformsWork(IOEventSource *inEventSource)
{
	bool	result = true;

	/*
	 * The idea here is to see if the subclass of IOEventSource has overridden checkForWork().
	 * The assumption is that if you override checkForWork(), you need to be
	 * active and not passive.
	 *
	 * We picked a known quantity controlG that does not override
	 * IOEventSource::checkForWork(), namely the IOCommandGate associated with
	 * the workloop to which this event source is getting attached.
	 * 
	 * We do a pointer comparison on the offset in the vtable for inNewEvent against
	 * the offset in the vtable for inReferenceEvent. This works because
	 * IOCommandGate's slot for checkForWork() has the address of
	 * IOEventSource::checkForWork() in it.
	 * 
	 * Think of OSMemberFunctionCast yielding the value at the vtable offset for
	 * checkForWork() here. We're just testing to see if it's the same or not.
	 *
	 */
	if (controlG) {
		void *	ptr1;
		void *	ptr2;
		
		ptr1 = OSMemberFunctionCast(void*, inEventSource, &IOEventSource::checkForWork);
		ptr2 = OSMemberFunctionCast(void*, controlG, &IOEventSource::checkForWork);
		
		if (ptr1 == ptr2)
			result = false;
	}
	
    return result;
}