source: mainline/kernel/generic/src/ipc/ipc.c@ 02667d9

/*
 * 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 <assert.h>
#include <synch/spinlock.h>
#include <synch/mutex.h>
#include <synch/waitq.h>
#include <ipc/ipc.h>
#include <ipc/ipcrsc.h>
#include <abi/ipc/methods.h>
#include <ipc/kbox.h>
#include <ipc/event.h>
#include <ipc/sysipc_ops.h>
#include <ipc/sysipc_priv.h>
#include <errno.h>
#include <mm/slab.h>
#include <arch.h>
#include <proc/task.h>
#include <mem.h>
#include <print.h>
#include <console/console.h>
#include <proc/thread.h>
#include <arch/interrupt.h>
#include <ipc/irq.h>
#include <cap/cap.h>

static void ipc_forget_call(call_t *);

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

static slab_cache_t *call_slab;
static slab_cache_t *answerbox_slab;

slab_cache_t *phone_slab = NULL; 

/** Initialize a call structure.
 *
 * @param call Call structure to be initialized.
 *
 */
static void _ipc_call_init(call_t *call)
{
        memsetb(call, sizeof(*call), 0);
        spinlock_initialize(&call->forget_lock, "forget_lock");
        call->active = false;
        call->forget = false;
        call->sender = NULL;
        call->callerbox = NULL;
        call->buffer = NULL;
}

void ipc_call_hold(call_t *call)
{
        atomic_inc(&call->refcnt);
}

void ipc_call_release(call_t *call)
{
        if (atomic_predec(&call->refcnt) == 0) {
                if (call->buffer)
                        free(call->buffer);
                slab_free(call_slab, call);
        }
}

/** 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 with one reference.
 *
 */
call_t *ipc_call_alloc(unsigned int flags)
{
        call_t *call = slab_alloc(call_slab, flags);
        if (call) {
                _ipc_call_init(call);
                ipc_call_hold(call);
        }
        
        return call;
}

/** Deallocate a call structure.
 *
 * @param call Call structure to be freed.
 *
 */
void ipc_call_free(call_t *call)
{
        ipc_call_release(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)
{
        irq_spinlock_initialize(&box->lock, "ipc.box.lock");
        irq_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);
        box->task = task;
}

/** Connect a phone to an answerbox.
 *
 * This function must be passed a reference to phone->kobject.
 *
 * @param phone  Initialized phone structure.
 * @param box    Initialized answerbox structure.
 * @return       True if the phone was connected, false otherwise.
 */
bool ipc_phone_connect(phone_t *phone, answerbox_t *box)
{
        bool active;

        mutex_lock(&phone->lock);
        irq_spinlock_lock(&box->lock, true);

        active = box->active;
        if (active) {
                phone->state = IPC_PHONE_CONNECTED;
                phone->callee = box;
                /* Pass phone->kobject reference to box->connected_phones */
                list_append(&phone->link, &box->connected_phones);
        }

        irq_spinlock_unlock(&box->lock, true);
        mutex_unlock(&phone->lock);

        if (!active) {
                /* We still have phone->kobject's reference; drop it */
                kobject_put(phone->kobject);
        }

        return active;
}

/** Initialize a phone structure.
 *
 * @param phone Phone structure to be initialized.
 * @param caller Owning task.
 *
 */
void ipc_phone_init(phone_t *phone, task_t *caller)
{
        mutex_initialize(&phone->lock, MUTEX_PASSIVE);
        phone->caller = caller;
        phone->callee = NULL;
        phone->state = IPC_PHONE_FREE;
        atomic_set(&phone->active_calls, 0);
        phone->kobject = NULL;
}

/** Helper function to facilitate synchronous calls.
 *
 * @param phone   Destination kernel phone structure.
 * @param request Call structure with request.
 *
 * @return EOK on success or a negative error code.
 *
 */
int ipc_call_sync(phone_t *phone, call_t *request)
{
        answerbox_t *mybox = slab_alloc(answerbox_slab, 0);
        ipc_answerbox_init(mybox, TASK);
        
        /* We will receive data in a special box. */
        request->callerbox = mybox;
        
        int rc = ipc_call(phone, request);
        if (rc != EOK) {
                slab_free(answerbox_slab, mybox);
                return rc;
        }

        call_t *answer = ipc_wait_for_call(mybox, SYNCH_NO_TIMEOUT,
            SYNCH_FLAGS_INTERRUPTIBLE);
        if (!answer) {

                /*
                 * The sleep was interrupted.
                 *
                 * There are two possibilities now:
                 * 1) the call gets answered before we manage to forget it
                 * 2) we manage to forget the call before it gets answered
                 */

                spinlock_lock(&request->forget_lock);
                spinlock_lock(&TASK->active_calls_lock);

                assert(!request->forget);

                bool answered = !request->active;
                if (!answered) {
                        /*
                         * The call is not yet answered and we won the race to
                         * forget it.
                         */
                        ipc_forget_call(request);       /* releases locks */
                        rc = EINTR;
                        
                } else {
                        spinlock_unlock(&TASK->active_calls_lock);
                        spinlock_unlock(&request->forget_lock);
                }

                if (answered) {
                        /*
                         * The other side won the race to answer the call.
                         * It is safe to wait for the answer uninterruptibly
                         * now.
                         */
                        answer = ipc_wait_for_call(mybox, SYNCH_NO_TIMEOUT,
                            SYNCH_FLAGS_NONE);
                }
        }
        assert(!answer || request == answer);
        
        slab_free(answerbox_slab, mybox);
        return rc;
}

/** Answer a message which was not dispatched and is not listed in any queue.
 *
 * @param call       Call structure to be answered.
 * @param selflocked If true, then TASK->answebox is locked.
 *
 */
void _ipc_answer_free_call(call_t *call, bool selflocked)
{
        /* Count sent answer */
        irq_spinlock_lock(&TASK->lock, true);
        TASK->ipc_info.answer_sent++;
        irq_spinlock_unlock(&TASK->lock, true);

        spinlock_lock(&call->forget_lock);
        if (call->forget) {
                /* This is a forgotten call and call->sender is not valid. */
                spinlock_unlock(&call->forget_lock);
                ipc_call_free(call);
                return;
        } else {
                /*
                 * If the call is still active, i.e. it was answered
                 * in a non-standard way, remove the call from the
                 * sender's active call list.
                 */
                if (call->active) {
                        spinlock_lock(&call->sender->active_calls_lock);
                        list_remove(&call->ta_link);
                        spinlock_unlock(&call->sender->active_calls_lock);
                }
        }
        spinlock_unlock(&call->forget_lock);

        answerbox_t *callerbox = call->callerbox ? call->callerbox :
            &call->sender->answerbox;
        bool do_lock = ((!selflocked) || (callerbox != &TASK->answerbox));
        
        call->flags |= IPC_CALL_ANSWERED;
        
        call->data.task_id = TASK->taskid;
        
        if (do_lock)
                irq_spinlock_lock(&callerbox->lock, true);
        
        list_append(&call->ab_link, &callerbox->answers);
        
        if (do_lock)
                irq_spinlock_unlock(&callerbox->lock, true);
        
        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 */
        irq_spinlock_lock(&box->lock, true);
        list_remove(&call->ab_link);
        irq_spinlock_unlock(&box->lock, true);
        
        /* Send back answer */
        _ipc_answer_free_call(call, false);
}

static void _ipc_call_actions_internal(phone_t *phone, call_t *call,
    bool preforget)
{
        task_t *caller = phone->caller;

        call->caller_phone = phone;

        if (preforget) {
                call->forget = true;
        } else {
                atomic_inc(&phone->active_calls);
                call->sender = caller;
                call->active = true;
                spinlock_lock(&caller->active_calls_lock);
                list_append(&call->ta_link, &caller->active_calls);
                spinlock_unlock(&caller->active_calls_lock);
        }

        call->data.phone = phone;
        call->data.task_id = caller->taskid;
}

/** 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, sysarg_t err)
{
        _ipc_call_actions_internal(phone, call, false);
        IPC_SET_RETVAL(call->data, err);
        _ipc_answer_free_call(call, false);
}

/** 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.
 * @param preforget If true, the call will be delivered already forgotten.
 *
 */
static void _ipc_call(phone_t *phone, answerbox_t *box, call_t *call,
    bool preforget)
{
        task_t *caller = phone->caller;

        /* Count sent ipc call */
        irq_spinlock_lock(&caller->lock, true);
        caller->ipc_info.call_sent++;
        irq_spinlock_unlock(&caller->lock, true);
        
        if (!(call->flags & IPC_CALL_FORWARDED))
                _ipc_call_actions_internal(phone, call, preforget);
        
        irq_spinlock_lock(&box->lock, true);
        list_append(&call->ab_link, &box->calls);
        irq_spinlock_unlock(&box->lock, true);
        
        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)
{
        mutex_lock(&phone->lock);
        if (phone->state != IPC_PHONE_CONNECTED) {
                mutex_unlock(&phone->lock);
                if (!(call->flags & IPC_CALL_FORWARDED)) {
                        if (phone->state == IPC_PHONE_HUNGUP)
                                ipc_backsend_err(phone, call, EHANGUP);
                        else
                                ipc_backsend_err(phone, call, ENOENT);
                }
                
                return ENOENT;
        }
        
        answerbox_t *box = phone->callee;
        _ipc_call(phone, box, call, false);
        
        mutex_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 0 if the phone is disconnected.
 * @return -1 if the phone was already disconnected.
 *
 */
int ipc_phone_hangup(phone_t *phone)
{
        mutex_lock(&phone->lock);
        if (phone->state == IPC_PHONE_FREE ||
            phone->state == IPC_PHONE_HUNGUP ||
            phone->state == IPC_PHONE_CONNECTING) {
                mutex_unlock(&phone->lock);
                return -1;
        }
        
        answerbox_t *box = phone->callee;
        if (phone->state != IPC_PHONE_SLAMMED) {
                /* Remove myself from answerbox */
                irq_spinlock_lock(&box->lock, true);
                list_remove(&phone->link);
                irq_spinlock_unlock(&box->lock, true);

                /* Drop the answerbox reference */
                kobject_put(phone->kobject);
                
                call_t *call = ipc_call_alloc(0);
                IPC_SET_IMETHOD(call->data, IPC_M_PHONE_HUNGUP);
                call->request_method = IPC_M_PHONE_HUNGUP;
                call->flags |= IPC_CALL_DISCARD_ANSWER;
                _ipc_call(phone, box, call, false);
        }
        
        phone->state = IPC_PHONE_HUNGUP;
        mutex_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 0 if forwarding succeeded or an error code if
 *         there was an 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,
    unsigned int mode)
{
        /* Count forwarded calls */
        irq_spinlock_lock(&TASK->lock, true);
        TASK->ipc_info.forwarded++;
        irq_spinlock_pass(&TASK->lock, &oldbox->lock);
        list_remove(&call->ab_link);
        irq_spinlock_unlock(&oldbox->lock, true);
        
        if (mode & IPC_FF_ROUTE_FROM_ME) {
                call->data.phone = newphone;
                call->data.task_id = TASK->taskid;
        }
        
        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, unsigned int flags)
{
        call_t *request;
        uint64_t irq_cnt = 0;
        uint64_t answer_cnt = 0;
        uint64_t call_cnt = 0;
        int rc;
        
restart:
        rc = waitq_sleep_timeout(&box->wq, usec, flags);
        if (SYNCH_FAILED(rc))
                return NULL;
        
        irq_spinlock_lock(&box->lock, true);
        if (!list_empty(&box->irq_notifs)) {
                /* Count received IRQ notification */
                irq_cnt++;
                
                irq_spinlock_lock(&box->irq_lock, false);
                
                request = list_get_instance(list_first(&box->irq_notifs),
                    call_t, ab_link);
                list_remove(&request->ab_link);
                
                irq_spinlock_unlock(&box->irq_lock, false);
        } else if (!list_empty(&box->answers)) {
                /* Count received answer */
                answer_cnt++;
                
                /* Handle asynchronous answers */
                request = list_get_instance(list_first(&box->answers),
                    call_t, ab_link);
                list_remove(&request->ab_link);
                atomic_dec(&request->caller_phone->active_calls);
        } else if (!list_empty(&box->calls)) {
                /* Count received call */
                call_cnt++;
                
                /* Handle requests */
                request = list_get_instance(list_first(&box->calls),
                    call_t, ab_link);
                list_remove(&request->ab_link);
                
                /* Append request to dispatch queue */
                list_append(&request->ab_link, &box->dispatched_calls);
        } else {
                /* This can happen regularly after ipc_cleanup */
                irq_spinlock_unlock(&box->lock, true);
                goto restart;
        }
        
        irq_spinlock_pass(&box->lock, &TASK->lock);
        
        TASK->ipc_info.irq_notif_received += irq_cnt;
        TASK->ipc_info.answer_received += answer_cnt;
        TASK->ipc_info.call_received += call_cnt;
        
        irq_spinlock_unlock(&TASK->lock, true);
        
        return request;
}

/** Answer all calls from list with EHANGUP answer.
 *
 * @param box Answerbox with the list.
 * @param lst Head of the list to be cleaned up.
 */
void ipc_cleanup_call_list(answerbox_t *box, list_t *lst)
{
        irq_spinlock_lock(&box->lock, true);
        while (!list_empty(lst)) {
                call_t *call = list_get_instance(list_first(lst), call_t,
                    ab_link);
                
                list_remove(&call->ab_link);

                irq_spinlock_unlock(&box->lock, true);

                if (lst == &box->calls)
                        SYSIPC_OP(request_process, call, box);

                ipc_data_t old = call->data;
                IPC_SET_RETVAL(call->data, EHANGUP);
                answer_preprocess(call, &old);
                _ipc_answer_free_call(call, true);

                irq_spinlock_lock(&box->lock, true);
        }
        irq_spinlock_unlock(&box->lock, true);
}

/** 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.
 *
 */
void ipc_answerbox_slam_phones(answerbox_t *box, bool notify_box)
{
        phone_t *phone;
        DEADLOCK_PROBE_INIT(p_phonelck);
        
        /* Disconnect all phones connected to our answerbox */
restart_phones:
        irq_spinlock_lock(&box->lock, true);
        while (!list_empty(&box->connected_phones)) {
                phone = list_get_instance(list_first(&box->connected_phones),
                    phone_t, link);
                if (SYNCH_FAILED(mutex_trylock(&phone->lock))) {
                        irq_spinlock_unlock(&box->lock, true);
                        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) {
                        task_hold(phone->caller);
                        mutex_unlock(&phone->lock);
                        irq_spinlock_unlock(&box->lock, true);

                        /*
                         * Send one call to the answerbox for each phone.
                         * Used to make sure the kbox thread wakes up after
                         * the last phone has been disconnected. The call is
                         * forgotten upon sending, so the "caller" may cease
                         * to exist as soon as we release it.
                         */
                        call_t *call = ipc_call_alloc(0);
                        IPC_SET_IMETHOD(call->data, IPC_M_PHONE_HUNGUP);
                        call->request_method = IPC_M_PHONE_HUNGUP;
                        call->flags |= IPC_CALL_DISCARD_ANSWER;
                        _ipc_call(phone, box, call, true);

                        task_release(phone->caller);

                        kobject_put(phone->kobject);
                        
                        /* Must start again */
                        goto restart_phones;
                }
                
                mutex_unlock(&phone->lock);
                kobject_put(phone->kobject);
        }
        
        irq_spinlock_unlock(&box->lock, true);
}

static void ipc_forget_call(call_t *call)
{
        assert(spinlock_locked(&TASK->active_calls_lock));
        assert(spinlock_locked(&call->forget_lock));

        /*
         * Forget the call and donate it to the task which holds up the answer.
         */

        call->forget = true;
        call->sender = NULL;
        list_remove(&call->ta_link);

        /*
         * The call may be freed by _ipc_answer_free_call() before we are done
         * with it; to avoid working with a destroyed call_t structure, we
         * must hold a reference to it.
         */
        ipc_call_hold(call);

        spinlock_unlock(&call->forget_lock);
        spinlock_unlock(&TASK->active_calls_lock);

        atomic_dec(&call->caller_phone->active_calls);

        SYSIPC_OP(request_forget, call);

        ipc_call_release(call);
}

static void ipc_forget_all_active_calls(void)
{
        call_t *call;

restart:
        spinlock_lock(&TASK->active_calls_lock);
        if (list_empty(&TASK->active_calls)) {
                /*
                 * We are done, there are no more active calls.
                 * Nota bene: there may still be answers waiting for pick up.
                 */
                spinlock_unlock(&TASK->active_calls_lock);
                return; 
        }
        
        call = list_get_instance(list_first(&TASK->active_calls), call_t,
            ta_link);

        if (!spinlock_trylock(&call->forget_lock)) {
                /*
                 * Avoid deadlock and let async_answer() or
                 *  _ipc_answer_free_call() win the race to dequeue the first
                 * call on the list.
                 */
                spinlock_unlock(&TASK->active_calls_lock);
                goto restart;
        }

        ipc_forget_call(call);

        goto restart;
}

static bool phone_cap_wait_cb(cap_t *cap, void *arg)
{
        phone_t *phone = cap->kobject->phone;
        bool *restart = (bool *) arg;

        mutex_lock(&phone->lock);
        if ((phone->state == IPC_PHONE_HUNGUP) &&
            (atomic_get(&phone->active_calls) == 0)) {
                phone->state = IPC_PHONE_FREE;
                phone->callee = NULL;
        }

        /*
         * We might have had some IPC_PHONE_CONNECTING phones at the beginning
         * of ipc_cleanup(). Depending on whether these were forgotten or
         * answered, they will eventually enter the IPC_PHONE_FREE or
         * IPC_PHONE_CONNECTED states, respectively.  In the latter case, the
         * other side may slam the open phones at any time, in which case we
         * will get an IPC_PHONE_SLAMMED phone.
         */
        if ((phone->state == IPC_PHONE_CONNECTED) ||
            (phone->state == IPC_PHONE_SLAMMED)) {
                mutex_unlock(&phone->lock);
                ipc_phone_hangup(phone);
                /*
                 * Now there may be one extra active call, which needs to be
                 * forgotten.
                 */
                ipc_forget_all_active_calls();
                *restart = true;
                return false;
        }

        /*
         * 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 (phone->state != IPC_PHONE_FREE) {
                mutex_unlock(&phone->lock);
                return false;
        }

        mutex_unlock(&phone->lock);
        return true;
}

/** Wait for all answers to asynchronous calls to arrive. */
static void ipc_wait_for_all_answered_calls(void)
{
        call_t *call;
        bool restart;

restart:
        /*
         * Go through all phones, until they are all free.
         * Locking is needed as there may be connection handshakes in progress.
         */
        restart = false;
        if (caps_apply_to_kobject_type(TASK, KOBJECT_TYPE_PHONE,
            phone_cap_wait_cb, &restart)) {
                /* Got into cleanup */
                return;
        }
        if (restart)
                goto restart;
        
        call = ipc_wait_for_call(&TASK->answerbox, SYNCH_NO_TIMEOUT,
            SYNCH_FLAGS_NONE);
        assert(call->flags & (IPC_CALL_ANSWERED | IPC_CALL_NOTIF));

        SYSIPC_OP(answer_process, call);

        ipc_call_free(call);
        goto restart;
}

static bool phone_cap_cleanup_cb(cap_t *cap, void *arg)
{
        ipc_phone_hangup(cap->kobject->phone);
        return true;
}

static bool irq_cap_cleanup_cb(cap_t *cap, void *arg)
{
        ipc_irq_unsubscribe(&TASK->answerbox, cap->handle);
        return true;
}

/** Clean 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)
{
        /*
         * Mark the answerbox as inactive.
         *
         * The main purpose for doing this is to prevent any pending callback
         * connections from getting established beyond this point.
         */
        irq_spinlock_lock(&TASK->answerbox.lock, true);
        TASK->answerbox.active = false;
        irq_spinlock_unlock(&TASK->answerbox.lock, true);

        /* Disconnect all our phones ('ipc_phone_hangup') */
        caps_apply_to_kobject_type(TASK, KOBJECT_TYPE_PHONE,
            phone_cap_cleanup_cb, NULL);
        
        /* Unsubscribe from any event notifications. */
        event_cleanup_answerbox(&TASK->answerbox);
        
        /* Disconnect all connected IRQs */
        caps_apply_to_kobject_type(TASK, KOBJECT_TYPE_IRQ, irq_cap_cleanup_cb,
            NULL);
        
        /* Disconnect all phones connected to our regular answerbox */
        ipc_answerbox_slam_phones(&TASK->answerbox, false);
        
#ifdef CONFIG_UDEBUG
        /* Clean up kbox thread and communications */
        ipc_kbox_cleanup();
#endif
        
        /* Answer all messages in 'calls' and 'dispatched_calls' queues */
        ipc_cleanup_call_list(&TASK->answerbox, &TASK->answerbox.calls);
        ipc_cleanup_call_list(&TASK->answerbox,
            &TASK->answerbox.dispatched_calls);
        
        ipc_forget_all_active_calls();
        ipc_wait_for_all_answered_calls();
}

/** Initilize IPC subsystem
 *
 */
void ipc_init(void)
{
        call_slab = slab_cache_create("call_t", sizeof(call_t), 0, NULL,
            NULL, 0);
        phone_slab = slab_cache_create("phone_t", sizeof(phone_t), 0, NULL,
            NULL, 0);
        answerbox_slab = slab_cache_create("answerbox_t", sizeof(answerbox_t),
            0, NULL, NULL, 0);
}


static void ipc_print_call_list(list_t *list)
{
        list_foreach(*list, ab_link, call_t, call) {
#ifdef __32_BITS__
                printf("%10p ", call);
#endif
                
#ifdef __64_BITS__
                printf("%18p ", call);
#endif
                
                spinlock_lock(&call->forget_lock);

                printf("%-8" PRIun " %-6" PRIun " %-6" PRIun " %-6" PRIun
                    " %-6" PRIun " %-6" PRIun " %-7x",
                    IPC_GET_IMETHOD(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);

                if (call->forget) {
                        printf(" ? (call forgotten)\n");
                } else {
                        printf(" %" PRIu64 " (%s)\n",
                            call->sender->taskid, call->sender->name);
                }

                spinlock_unlock(&call->forget_lock);
        }
}

static bool print_task_phone_cb(cap_t *cap, void *arg)
{
        phone_t *phone = cap->kobject->phone;

        mutex_lock(&phone->lock);
        if (phone->state != IPC_PHONE_FREE) {
                printf("%-11d %7" PRIun " ", cap->handle,
                    atomic_get(&phone->active_calls));
                
                switch (phone->state) {
                case IPC_PHONE_CONNECTING:
                        printf("connecting");
                        break;
                case IPC_PHONE_CONNECTED:
                        printf("connected to %" PRIu64 " (%s)",
                            phone->callee->task->taskid,
                            phone->callee->task->name);
                        break;
                case IPC_PHONE_SLAMMED:
                        printf("slammed by %p", phone->callee);
                        break;
                case IPC_PHONE_HUNGUP:
                        printf("hung up by %p", phone->callee);
                        break;
                default:
                        break;
                }
                
                printf("\n");
        }
        mutex_unlock(&phone->lock);

        return true;
}

/** List answerbox contents.
 *
 * @param taskid Task ID.
 *
 */
void ipc_print_task(task_id_t taskid)
{
        irq_spinlock_lock(&tasks_lock, true);
        task_t *task = task_find_by_id(taskid);
        if (!task) {
                irq_spinlock_unlock(&tasks_lock, true);
                return;
        }
        task_hold(task);
        irq_spinlock_unlock(&tasks_lock, true);
        
        printf("[phone cap] [calls] [state\n");
        
        caps_apply_to_kobject_type(task, KOBJECT_TYPE_PHONE,
            print_task_phone_cb, NULL);
        
        irq_spinlock_lock(&task->lock, true);
        irq_spinlock_lock(&task->answerbox.lock, false);
        
#ifdef __32_BITS__
        printf("[call id ] [method] [arg1] [arg2] [arg3] [arg4] [arg5]"
            " [flags] [sender\n");
#endif
        
#ifdef __64_BITS__
        printf("[call id         ] [method] [arg1] [arg2] [arg3] [arg4]"
            " [arg5] [flags] [sender\n");
#endif
        
        printf(" --- incomming calls ---\n");
        ipc_print_call_list(&task->answerbox.calls);
        printf(" --- dispatched calls ---\n");
        ipc_print_call_list(&task->answerbox.dispatched_calls);
        printf(" --- incoming answers ---\n");
        ipc_print_call_list(&task->answerbox.answers);
        
        irq_spinlock_unlock(&task->answerbox.lock, false);
        irq_spinlock_unlock(&task->lock, true);

        task_release(task);
}

/** @}
 */