/*
 * Copyright (c) 2006 Ondrej Palkovsky
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup genericipc
 * @{
 */
/** @file
 */

/* Lock ordering
 *
 * First the answerbox, then the phone.
 */

#include <synch/spinlock.h>
#include <synch/waitq.h>
#include <synch/synch.h>
#include <ipc/ipc.h>
#include <errno.h>
#include <mm/slab.h>
#include <arch.h>
#include <proc/task.h>
#include <memstr.h>
#include <debug.h>

#include <print.h>
#include <console/klog.h>
#include <proc/thread.h>
#include <arch/interrupt.h>
#include <ipc/irq.h>

/** Open channel that is assigned automatically to new tasks */
answerbox_t *ipc_phone_0 = NULL;

static slab_cache_t *ipc_call_slab;

/** Initialize a call structure.
 *
 * @param call		Call structure to be initialized.
 */
static void _ipc_call_init(call_t *call)
{
	memsetb((uintptr_t) call, sizeof(*call), 0);
	call->callerbox = &TASK->answerbox;
	call->sender = TASK;
	call->buffer = NULL;
}

/** Allocate and initialize a call structure.
 * 
 * The call is initialized, so that the reply will be directed to
 * TASK->answerbox.
 *
 * @param flags		Parameters for slab_alloc (e.g FRAME_ATOMIC).
 *
 * @return		If flags permit it, return NULL, or initialized kernel
 *			call structure.
 */
call_t *ipc_call_alloc(int flags)
{
	call_t *call;

	call = slab_alloc(ipc_call_slab, flags);
	_ipc_call_init(call);

	return call;
}

/** Initialize a statically allocated call structure.
 *
 * @param call		Statically allocated kernel call structure to be
 *			initialized.
 */
void ipc_call_static_init(call_t *call)
{
	_ipc_call_init(call);
	call->flags |= IPC_CALL_STATIC_ALLOC;
}

/** Deallocate a call structure.
 *
 * @param call		Call structure to be freed.
 */
void ipc_call_free(call_t *call)
{
	ASSERT(!(call->flags & IPC_CALL_STATIC_ALLOC));
	/* Check to see if we have data in the IPC_M_DATA_SEND buffer. */
	if (call->buffer)
		free(call->buffer);
	slab_free(ipc_call_slab, call);
}

/** Initialize an answerbox structure.
 *
 * @param box		Answerbox structure to be initialized.
 * @param task		Task to which the answerbox belongs.
 */
void ipc_answerbox_init(answerbox_t *box, task_t *task)
{
	spinlock_initialize(&box->lock, "ipc_box_lock");
	spinlock_initialize(&box->irq_lock, "ipc_box_irqlock");
	waitq_initialize(&box->wq);
	list_initialize(&box->connected_phones);
	list_initialize(&box->calls);
	list_initialize(&box->dispatched_calls);
	list_initialize(&box->answers);
	list_initialize(&box->irq_notifs);
	list_initialize(&box->irq_head);
	box->task = task;
}

/** Connect a phone to an answerbox.
 *
 * @param phone		Initialized phone structure.
 * @param box		Initialized answerbox structure.
 */
void ipc_phone_connect(phone_t *phone, answerbox_t *box)
{
	spinlock_lock(&phone->lock);

	phone->state = IPC_PHONE_CONNECTED;
	phone->callee = box;

	spinlock_lock(&box->lock);
	list_append(&phone->link, &box->connected_phones);
	spinlock_unlock(&box->lock);

	spinlock_unlock(&phone->lock);
}

/** Initialize a phone structure.
 *
 * @param phone		Phone structure to be initialized.
 */
void ipc_phone_init(phone_t *phone)
{
	spinlock_initialize(&phone->lock, "phone_lock");
	phone->callee = NULL;
	phone->state = IPC_PHONE_FREE;
	atomic_set(&phone->active_calls, 0);
}

/** Helper function to facilitate synchronous calls.
 *
 * @param phone		Destination kernel phone structure.
 * @param request	Call structure with request.
 */
void ipc_call_sync(phone_t *phone, call_t *request)
{
	answerbox_t sync_box; 

	ipc_answerbox_init(&sync_box, TASK);

	/* We will receive data in a special box. */
	request->callerbox = &sync_box;

	ipc_call(phone, request);
	ipc_wait_for_call(&sync_box, SYNCH_NO_TIMEOUT, SYNCH_FLAGS_NONE);
}

/** Answer a message which was not dispatched and is not listed in any queue.
 *
 * @param call		Call structure to be answered.
 */
static void _ipc_answer_free_call(call_t *call)
{
	answerbox_t *callerbox = call->callerbox;

	call->flags |= IPC_CALL_ANSWERED;

	spinlock_lock(&callerbox->lock);
	list_append(&call->link, &callerbox->answers);
	spinlock_unlock(&callerbox->lock);
	waitq_wakeup(&callerbox->wq, WAKEUP_FIRST);
}

/** Answer a message which is in a callee queue.
 *
 * @param box		Answerbox that is answering the message.
 * @param call		Modified request that is being sent back.
 */
void ipc_answer(answerbox_t *box, call_t *call)
{
	/* Remove from active box */
	spinlock_lock(&box->lock);
	list_remove(&call->link);
	spinlock_unlock(&box->lock);
	/* Send back answer */
	_ipc_answer_free_call(call);
}

/** Simulate sending back a message.
 *
 * Most errors are better handled by forming a normal backward
 * message and sending it as a normal answer.
 *
 * @param phone		Phone structure the call should appear to come from.
 * @param call		Call structure to be answered.
 * @param err		Return value to be used for the answer.
 */
void ipc_backsend_err(phone_t *phone, call_t *call, unative_t err)
{
	call->data.phone = phone;
	atomic_inc(&phone->active_calls);
	IPC_SET_RETVAL(call->data, err);
	_ipc_answer_free_call(call);
}

/** Unsafe unchecking version of ipc_call.
 *
 * @param phone		Phone structure the call comes from.
 * @param box		Destination answerbox structure.
 * @param call		Call structure with request.
 */
static void _ipc_call(phone_t *phone, answerbox_t *box, call_t *call)
{
	if (!(call->flags & IPC_CALL_FORWARDED)) {
		atomic_inc(&phone->active_calls);
		call->data.phone = phone;
	}

	spinlock_lock(&box->lock);
	list_append(&call->link, &box->calls);
	spinlock_unlock(&box->lock);
	waitq_wakeup(&box->wq, WAKEUP_FIRST);
}

/** Send an asynchronous request using a phone to an answerbox.
 *
 * @param phone		Phone structure the call comes from and which is
 *			connected to the destination answerbox.
 * @param call		Call structure with request.
 *
 * @return		Return 0 on success, ENOENT on error.
 */
int ipc_call(phone_t *phone, call_t *call)
{
	answerbox_t *box;

	spinlock_lock(&phone->lock);
	if (phone->state != IPC_PHONE_CONNECTED) {
		spinlock_unlock(&phone->lock);
		if (call->flags & IPC_CALL_FORWARDED) {
			IPC_SET_RETVAL(call->data, EFORWARD);
			_ipc_answer_free_call(call);
		} else {
			if (phone->state == IPC_PHONE_HUNGUP)
				ipc_backsend_err(phone, call, EHANGUP);
			else
				ipc_backsend_err(phone, call, ENOENT);
		}
		return ENOENT;
	}
	box = phone->callee;
	_ipc_call(phone, box, call);
	
	spinlock_unlock(&phone->lock);
	return 0;
}

/** Disconnect phone from answerbox.
 *
 * This call leaves the phone in the HUNGUP state. The change to 'free' is done
 * lazily later.
 *
 * @param phone		Phone structure to be hung up.
 *              
 * @return		Return 0 if the phone is disconnected.
 *			Return -1 if the phone was already disconnected.
 */
int ipc_phone_hangup(phone_t *phone)
{
	answerbox_t *box;
	call_t *call;
	
	spinlock_lock(&phone->lock);
	if (phone->state == IPC_PHONE_FREE ||
	    phone->state == IPC_PHONE_HUNGUP ||
	    phone->state == IPC_PHONE_CONNECTING) {
		spinlock_unlock(&phone->lock);
		return -1;
	}
	box = phone->callee;
	if (phone->state != IPC_PHONE_SLAMMED) {
		/* Remove myself from answerbox */
		spinlock_lock(&box->lock);
		list_remove(&phone->link);
		spinlock_unlock(&box->lock);

		if (phone->state != IPC_PHONE_SLAMMED) {
			call = ipc_call_alloc(0);
			IPC_SET_METHOD(call->data, IPC_M_PHONE_HUNGUP);
			call->flags |= IPC_CALL_DISCARD_ANSWER;
			_ipc_call(phone, box, call);
		}
	}

	phone->state = IPC_PHONE_HUNGUP;
	spinlock_unlock(&phone->lock);

	return 0;
}

/** Forwards call from one answerbox to another one.
 *
 * @param call		Call structure to be redirected.
 * @param newphone	Phone structure to target answerbox.
 * @param oldbox	Old answerbox structure.
 * @param mode		Flags that specify mode of the forward operation.
 *
 * @return		Return 0 if forwarding succeeded or an error code if
 *			there was error.
 * 
 * The return value serves only as an information for the forwarder,
 * the original caller is notified automatically with EFORWARD.
 */
int ipc_forward(call_t *call, phone_t *newphone, answerbox_t *oldbox, int mode)
{
	spinlock_lock(&oldbox->lock);
	list_remove(&call->link);
	spinlock_unlock(&oldbox->lock);

	if (mode & IPC_FF_ROUTE_FROM_ME)
		call->data.phone = newphone;

	return ipc_call(newphone, call);
}


/** Wait for a phone call.
 *
 * @param box		Answerbox expecting the call.
 * @param usec		Timeout in microseconds. See documentation for
 *			waitq_sleep_timeout() for decription of its special
 *			meaning.
 * @param flags		Select mode of sleep operation. See documentation for
 *			waitq_sleep_timeout() for description of its special
 *			meaning.
 * @return 		Recived call structure or NULL.
 * 
 * To distinguish between a call and an answer, have a look at call->flags.
 */
call_t *ipc_wait_for_call(answerbox_t *box, uint32_t usec, int flags)
{
	call_t *request;
	ipl_t ipl;
	int rc;

restart:
	rc = waitq_sleep_timeout(&box->wq, usec, flags);
	if (SYNCH_FAILED(rc))
		return NULL;
	
	spinlock_lock(&box->lock);
	if (!list_empty(&box->irq_notifs)) {
		ipl = interrupts_disable();
		spinlock_lock(&box->irq_lock);

		request = list_get_instance(box->irq_notifs.next, call_t, link);
		list_remove(&request->link);

		spinlock_unlock(&box->irq_lock);
		interrupts_restore(ipl);
	} else if (!list_empty(&box->answers)) {
		/* Handle asynchronous answers */
		request = list_get_instance(box->answers.next, call_t, link);
		list_remove(&request->link);
		atomic_dec(&request->data.phone->active_calls);
	} else if (!list_empty(&box->calls)) {
		/* Handle requests */
		request = list_get_instance(box->calls.next, call_t, link);
		list_remove(&request->link);
		/* Append request to dispatch queue */
		list_append(&request->link, &box->dispatched_calls);
	} else {
		/* This can happen regularly after ipc_cleanup */
		spinlock_unlock(&box->lock);
		goto restart;
	}
	spinlock_unlock(&box->lock);
	return request;
}

/** Answer all calls from list with EHANGUP answer.
 *
 * @param lst		Head of the list to be cleaned up.
 */
static void ipc_cleanup_call_list(link_t *lst)
{
	call_t *call;

	while (!list_empty(lst)) {
		call = list_get_instance(lst->next, call_t, link);
		if (call->buffer)
			free(call->buffer);
		list_remove(&call->link);

		IPC_SET_RETVAL(call->data, EHANGUP);
		_ipc_answer_free_call(call);
	}
}

/** Disconnects all phones connected to an answerbox.
 *
 * @param box		Answerbox to disconnect phones from.
 * @param notify_box	If true, the answerbox will get a hangup message for
 *			each disconnected phone.
 */
static void ipc_answerbox_slam_phones(answerbox_t *box, bool notify_box)
{
	phone_t *phone;
	DEADLOCK_PROBE_INIT(p_phonelck);
	ipl_t ipl;
	call_t *call;

	call = ipc_call_alloc(0);

	/* Disconnect all phones connected to our answerbox */
restart_phones:
	ipl = interrupts_disable();
	spinlock_lock(&box->lock);
	while (!list_empty(&box->connected_phones)) {
		phone = list_get_instance(box->connected_phones.next,
		    phone_t, link);
		if (!spinlock_trylock(&phone->lock)) {
			spinlock_unlock(&box->lock);
			interrupts_restore(ipl);
			DEADLOCK_PROBE(p_phonelck, DEADLOCK_THRESHOLD);
			goto restart_phones;
		}
		
		/* Disconnect phone */
		ASSERT(phone->state == IPC_PHONE_CONNECTED);

		list_remove(&phone->link);
		phone->state = IPC_PHONE_SLAMMED;

		if (notify_box) {
			spinlock_unlock(&phone->lock);
			spinlock_unlock(&box->lock);
			interrupts_restore(ipl);

			/*
			 * Send one message to the answerbox for each
			 * phone. Used to make sure the kbox thread
			 * wakes up after the last phone has been
			 * disconnected.
			 */
			IPC_SET_METHOD(call->data, IPC_M_PHONE_HUNGUP);
			call->flags |= IPC_CALL_DISCARD_ANSWER;
			_ipc_call(phone, box, call);

			/* Allocate another call in advance */
			call = ipc_call_alloc(0);

			/* Must start again */
			goto restart_phones;
		}

		spinlock_unlock(&phone->lock);
	}

	spinlock_unlock(&box->lock);
	interrupts_restore(ipl);

	/* Free unused call */
	if (call) ipc_call_free(call);
}

static void ipc_kbox_cleanup()
{
	ipl_t ipl;
	bool have_kb_thread;

	/* Only hold kb_cleanup_lock while setting kb_finished - this is enough */
	ipl = interrupts_disable();
	spinlock_lock(&TASK->kb_cleanup_lock);

	TASK->kb_finished = true;

	spinlock_unlock(&TASK->kb_cleanup_lock);
	interrupts_restore(ipl);

	have_kb_thread = (TASK->kb_thread != NULL);

	/* From now on nobody will try to connect phones or attach kbox threads */

	/*
	 * Disconnect all phones connected to our kbox. Passing true for
	 * notify_box causes a HANGUP message to be inserted for each
	 * disconnected phone. This ensures the kbox thread is going to
	 * wake up and terminate.
	 */
	ipc_answerbox_slam_phones(&TASK->kernel_box, have_kb_thread);
	
	/* TODO: Wait for kbox thread to terminate */
	if (have_kb_thread) {
		klog_printf("ipc_kbox_cleanup - wait for kbox thread to finish");
		waitq_sleep(&TASK->kb_thread_shutdown_wq);
	}

	/* Answer all messages in 'calls' and 'dispatched_calls' queues */
	spinlock_lock(&TASK->kernel_box.lock);
	ipc_cleanup_call_list(&TASK->kernel_box.dispatched_calls);
	ipc_cleanup_call_list(&TASK->kernel_box.calls);
	spinlock_unlock(&TASK->kernel_box.lock);
}


/** Cleans up all IPC communication of the current task.
 *
 * Note: ipc_hangup sets returning answerbox to TASK->answerbox, you
 * have to change it as well if you want to cleanup other tasks than TASK.
 */
void ipc_cleanup(void)
{
	int i;
	call_t *call;

	/* Disconnect all our phones ('ipc_phone_hangup') */
	for (i = 0; i < IPC_MAX_PHONES; i++)
		ipc_phone_hangup(&TASK->phones[i]);

	/* Disconnect all connected irqs */
	ipc_irq_cleanup(&TASK->answerbox);

	/* Disconnect all phones connected to our regular answerbox */
	ipc_answerbox_slam_phones(&TASK->answerbox, false);

	/* Clean up kbox thread and communications */
	ipc_kbox_cleanup();

	/* Answer all messages in 'calls' and 'dispatched_calls' queues */
	spinlock_lock(&TASK->answerbox.lock);
	ipc_cleanup_call_list(&TASK->answerbox.dispatched_calls);
	ipc_cleanup_call_list(&TASK->answerbox.calls);
	spinlock_unlock(&TASK->answerbox.lock);
	
	/* Wait for all async answers to arrive */
	while (1) {
		/* Go through all phones, until all are FREE... */
		/* Locking not needed, no one else should modify
		 * it, when we are in cleanup */
		for (i = 0; i < IPC_MAX_PHONES; i++) {
			if (TASK->phones[i].state == IPC_PHONE_HUNGUP &&
			    atomic_get(&TASK->phones[i].active_calls) == 0)
				TASK->phones[i].state = IPC_PHONE_FREE;
			
			/* Just for sure, we might have had some 
			 * IPC_PHONE_CONNECTING phones */
			if (TASK->phones[i].state == IPC_PHONE_CONNECTED)
				ipc_phone_hangup(&TASK->phones[i]);
			/* If the hangup succeeded, it has sent a HANGUP 
			 * message, the IPC is now in HUNGUP state, we
			 * wait for the reply to come */
			
			if (TASK->phones[i].state != IPC_PHONE_FREE)
				break;
		}
		/* Voila, got into cleanup */
		if (i == IPC_MAX_PHONES)
			break;
		
		call = ipc_wait_for_call(&TASK->answerbox, SYNCH_NO_TIMEOUT,
		    SYNCH_FLAGS_NONE);
		ASSERT((call->flags & IPC_CALL_ANSWERED) ||
		    (call->flags & IPC_CALL_NOTIF));
		ASSERT(!(call->flags & IPC_CALL_STATIC_ALLOC));
		
		atomic_dec(&TASK->active_calls);
		ipc_call_free(call);
	}
}


/** Initilize IPC subsystem */
void ipc_init(void)
{
	ipc_call_slab = slab_cache_create("ipc_call", sizeof(call_t), 0, NULL,
	    NULL, 0);
}


/** List answerbox contents.
 *
 * @param taskid	Task ID.
 */
void ipc_print_task(task_id_t taskid)
{
	task_t *task;
	int i;
	call_t *call;
	link_t *tmp;
	
	spinlock_lock(&tasks_lock);
	task = task_find_by_id(taskid);
	if (task) 
		spinlock_lock(&task->lock);
	spinlock_unlock(&tasks_lock);
	if (!task)
		return;

	/* Print opened phones & details */
	printf("PHONE:\n");
	for (i = 0; i < IPC_MAX_PHONES; i++) {
		spinlock_lock(&task->phones[i].lock);
		if (task->phones[i].state != IPC_PHONE_FREE) {
			printf("%d: ", i);
			switch (task->phones[i].state) {
			case IPC_PHONE_CONNECTING:
				printf("connecting ");
				break;
			case IPC_PHONE_CONNECTED:
				printf("connected to: %p ", 
				       task->phones[i].callee);
				break;
			case IPC_PHONE_SLAMMED:
				printf("slammed by: %p ", 
				       task->phones[i].callee);
				break;
			case IPC_PHONE_HUNGUP:
				printf("hung up - was: %p ", 
				       task->phones[i].callee);
				break;
			default:
				break;
			}
			printf("active: %d\n",
			    atomic_get(&task->phones[i].active_calls));
		}
		spinlock_unlock(&task->phones[i].lock);
	}


	/* Print answerbox - calls */
	spinlock_lock(&task->answerbox.lock);
	printf("ABOX - CALLS:\n");
	for (tmp = task->answerbox.calls.next; tmp != &task->answerbox.calls;
	    tmp = tmp->next) {
		call = list_get_instance(tmp, call_t, link);
		printf("Callid: %p Srctask:%llu M:%d A1:%d A2:%d A3:%d "
		    "A4:%d A5:%d Flags:%x\n", call, call->sender->taskid,
		    IPC_GET_METHOD(call->data), IPC_GET_ARG1(call->data),
		    IPC_GET_ARG2(call->data), IPC_GET_ARG3(call->data),
		    IPC_GET_ARG4(call->data), IPC_GET_ARG5(call->data),
		    call->flags);
	}
	/* Print answerbox - calls */
	printf("ABOX - DISPATCHED CALLS:\n");
	for (tmp=task->answerbox.dispatched_calls.next; 
	     tmp != &task->answerbox.dispatched_calls; 
	     tmp = tmp->next) {
		call = list_get_instance(tmp, call_t, link);
		printf("Callid: %p Srctask:%llu M:%d A1:%d A2:%d A3:%d "
		    "A4:%d A5:%d Flags:%x\n", call, call->sender->taskid,
		    IPC_GET_METHOD(call->data), IPC_GET_ARG1(call->data),
		    IPC_GET_ARG2(call->data), IPC_GET_ARG3(call->data),
		    IPC_GET_ARG4(call->data), IPC_GET_ARG5(call->data),
		    call->flags);
	}
	/* Print answerbox - calls */
	printf("ABOX - ANSWERS:\n");
	for (tmp = task->answerbox.answers.next; tmp != &task->answerbox.answers;
	    tmp = tmp->next) {
		call = list_get_instance(tmp, call_t, link);
		printf("Callid:%p M:%d A1:%d A2:%d A3:%d A4:%d A5:%d Flags:%x\n", 
		    call, IPC_GET_METHOD(call->data), IPC_GET_ARG1(call->data),
		    IPC_GET_ARG2(call->data), IPC_GET_ARG3(call->data),
		    IPC_GET_ARG4(call->data), IPC_GET_ARG5(call->data),
		    call->flags);
	}

	spinlock_unlock(&task->answerbox.lock);
	spinlock_unlock(&task->lock);
}

#include <ipc/ipcrsc.h>
#include <console/klog.h>
#include <udebug/udebug_ipc.h>

static void kbox_thread_proc(void *arg)
{
	call_t *call;
	int method;
	bool done;
	ipl_t ipl;

	(void)arg;
	klog_printf("kbox_thread_proc()");
	done = false;

	while (!done) {
		//klog_printf("kbox: wait for call");
		call = ipc_wait_for_call(&TASK->kernel_box, SYNCH_NO_TIMEOUT,
			SYNCH_FLAGS_NONE);

		if (call != NULL) {
			method = IPC_GET_METHOD(call->data);

			if (method == IPC_M_DEBUG_ALL) {
				udebug_call_receive(call);
			}

			if (method == IPC_M_PHONE_HUNGUP) {
				klog_printf("kbox: handle hangup message");

				/* Was it our debugger, who hung up? */
				if (call->sender == TASK->udebug.debugger) {
					/* Terminate debugging session (if any) */
					klog_printf("kbox: terminate debug session");
					ipl = interrupts_disable();
					spinlock_lock(&TASK->lock);
					udebug_task_cleanup(TASK);
					spinlock_unlock(&TASK->lock);
					interrupts_restore(ipl);
				} else {
					klog_printf("kbox: was not debugger");
				}

				klog_printf("kbox: continue with hangup message");
				IPC_SET_RETVAL(call->data, 0);
				ipc_answer(&TASK->kernel_box, call);

				ipl = interrupts_disable();
				spinlock_lock(&TASK->lock);
				spinlock_lock(&TASK->answerbox.lock);
				if (list_empty(&TASK->answerbox.connected_phones)) {
					/* Last phone has been disconnected */
					TASK->kb_thread = NULL;
					done = true;
					klog_printf("phone list is empty");
				}
				spinlock_unlock(&TASK->answerbox.lock);
				spinlock_unlock(&TASK->lock);
				interrupts_restore(ipl);
			}
		}
	}

	klog_printf("kbox: done, waking up possible shutdown routine");
	waitq_wakeup(&TASK->kb_thread_shutdown_wq, WAKEUP_ALL);
	klog_printf("kbox: finished");
}


/**
 * Connect phone to a task kernel-box specified by id.
 *
 * Note that this is not completely atomic. For optimisation reasons,
 * The task might start cleaning up kbox after the phone has been connected
 * and before a kbox thread has been created. This must be taken into account
 * in the cleanup code.
 *
 * @return 		Phone id on success, or negative error code.
 */
int ipc_connect_kbox(task_id_t taskid)
{
	int newphid;
	task_t *ta;
	thread_t *kb_thread;
	ipl_t ipl;
	bool had_kb_thread;

	newphid = phone_alloc();
	if (newphid < 0)
		return ELIMIT;

	ipl = interrupts_disable();
	spinlock_lock(&tasks_lock);

	ta = task_find_by_id(taskid);
	if (ta == NULL) {
		spinlock_unlock(&tasks_lock);
		interrupts_restore(ipl);
		return ENOENT;
	}

	spinlock_lock(&ta->kb_cleanup_lock);
	spinlock_unlock(&tasks_lock);

	/*
	 * Only ta->kb_cleanup_lock left. Since we checked the value
	 * of ta->kb_finished, this suffices to ensure the task's exitence.
	 * (And that it didn't start kbox cleanup yet). It also ensures
	 * mutual exclusion with other threads running this function.
	 */

	if (ta->kb_finished != false) {
		spinlock_unlock(&ta->kb_cleanup_lock);
		interrupts_restore(ipl);
		return EINVAL;
	}

	/* Connect the newly allocated phone to the kbox */
	ipc_phone_connect(&TASK->phones[newphid], &ta->kernel_box);

	had_kb_thread = (ta->kb_thread != NULL);
	
	/*
	 * Release all locks. This is an optimisation, that makes
	 * unnecessary thread creation very unlikely.
	 */
	spinlock_unlock(&ta->kb_cleanup_lock);
	interrupts_restore(ipl);

	/* Create a kbox thread */

	kb_thread = thread_create(kbox_thread_proc,
		NULL, ta, THREAD_FLAG_NOATTACH, "kbox", false);
	if (!kb_thread)
		return ENOMEM;

	/*
	 * It might happen that someone else has attached a kbox thread.
	 * in the meantime. Also, the task might have gone or shut down.
	 * Let's try from the beginning.
	 */

	ipl = interrupts_disable();
	spinlock_lock(&tasks_lock);

	ta = task_find_by_id(taskid);
	if (ta == NULL) {
		spinlock_unlock(&tasks_lock);
		return ENOENT;
	}

	spinlock_lock(&ta->kb_cleanup_lock);
	spinlock_unlock(&tasks_lock);

	if (ta->kb_finished != false || ta->kb_thread != NULL) {
		spinlock_unlock(&ta->kb_cleanup_lock);
		interrupts_restore(ipl);

		/*
		 * Release the allocated thread struct. This won't
		 * happen too often, only if two CPUs raced for
		 * connecting to the kbox.
		 */
		thread_unattached_free(kb_thread);
		return EINVAL;
	}

	/* Attach thread */
	ta->kb_thread = kb_thread;
	thread_attach(kb_thread, ta);

	thread_detach(kb_thread);
	thread_ready(kb_thread);

	spinlock_unlock(&ta->kb_cleanup_lock);
	interrupts_restore(ipl);

	return newphid;
}

/** @}
 */