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/*

 * 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

 */

/* IPC resources management

 *

 * The goal of this source code is to properly manage IPC resources and allow

 * straight and clean clean-up procedure upon task termination.

 *

 * The pattern of usage of the resources is:

 * - allocate empty phone slot, connect | deallocate slot

 * - disconnect connected phone (some messages might be on the fly)

 * - find phone in slot and send a message using phone

 * - answer message to phone

 * - hangup phone (the caller has hung up)

 * - hangup phone (the answerbox is exiting)

 *

 * Locking strategy

 *

 * - To use a phone, disconnect a phone etc., the phone must be first locked and

 *   then checked that it is connected

 * - To connect an allocated phone it need not be locked (assigning pointer is

 *   atomic on all platforms)

 *

 * - To find an empty phone slot, the TASK must be locked

 * - To answer a message, the answerbox must be locked

 * - The locking of phone and answerbox is done at the ipc_ level.

 *   It is perfectly correct to pass unconnected phone to these functions and

 *   proper reply will be generated.

 *

 * Locking order

 *

 * - first phone, then answerbox

 *   + Easy locking on calls

 *   - Very hard traversing list of phones when disconnecting because the phones

 *     may disconnect during traversal of list of connected phones. The only

 *     possibility is try_lock with restart of list traversal.

 *

 * Destroying is less frequent, this approach is taken.

 *

 * Phone call

 *

 * *** Connect_me_to ***

 * The caller sends IPC_M_CONNECT_ME_TO to an answerbox. The server receives

 * 'phoneid' of the connecting phone as an ARG5. If it answers with RETVAL=0,

 * the phonecall is accepted, otherwise it is refused.

 *

 * *** Connect_to_me ***

 * The caller sends IPC_M_CONNECT_TO_ME.

 * The server receives an automatically opened phoneid. If it accepts

 * (RETVAL=0), it can use the phoneid immediately.

 * Possible race condition can arise, when the client receives messages from new

 * connection before getting response for connect_to_me message. Userspace

 * should implement handshake protocol that would control it.

 *

 * Phone hangup

 *

 * *** The caller hangs up (sys_ipc_hangup) ***

 * - The phone is disconnected (no more messages can be sent over this phone),

 *   all in-progress messages are correctly handled. The answerbox receives

 *   IPC_M_PHONE_HUNGUP call from the phone that hung up. When all async

 *   calls are answered, the phone is deallocated.

 *

 * *** The answerbox hangs up (ipc_answer(EHANGUP))

 * - The phone is disconnected. EHANGUP response code is sent

 *   to the calling task. All new calls through this phone

 *   get a EHUNGUP error code, the task is expected to

 *   send an sys_ipc_hangup after cleaning up its internal structures.

 *

 * Call forwarding

 *

 * The call can be forwarded, so that the answer to call is passed directly

 * to the original sender. However, this poses special problems regarding

 * routing of hangup messages.

 *

 * sys_ipc_hangup -> IPC_M_PHONE_HUNGUP

 * - this message CANNOT be forwarded

 *

 * EHANGUP during forward

 * - The *forwarding* phone will be closed, EFORWARD is sent to receiver.

 *

 * EHANGUP, ENOENT during forward

 * - EFORWARD is sent to the receiver, ipc_forward returns error code EFORWARD

 *

 * Cleanup strategy

 *

 * 1) Disconnect all our phones ('ipc_phone_hangup').

 *

 * 2) Disconnect all phones connected to answerbox.

 *

 * 3) Answer all messages in 'calls' and 'dispatched_calls' queues with

 *    appropriate error code (EHANGUP, EFORWARD).

 *

 * 4) Wait for all async answers to arrive and dispose of them.

 *

 */

#include <synch/spinlock.h>

#include <ipc/ipc.h>

#include <arch.h>

#include <proc/task.h>

#include <ipc/ipcrsc.h>

#include <debug.h>

/** Find call_t * in call table according to callid.

 *

 * @todo Some speedup (hash table?)

 *

 * @param callid    Userspace hash of the call. Currently it is the call

 *          structure kernel address.

 *

 * @return      NULL on not found, otherwise pointer to the call

 *          structure.

 */

call_t *get_call(unative_t callid)

{

    link_t *lst;

    call_t *call, *result = NULL;

    spinlock_lock(&TASK->answerbox.lock);

    for (lst = TASK->answerbox.dispatched_calls.next;

        lst != &TASK->answerbox.dispatched_calls; lst = lst->next) {

        call = list_get_instance(lst, call_t, link);

        if ((unative_t) call == callid) {

            result = call;

            break;

        }

    }

    spinlock_unlock(&TASK->answerbox.lock);

    return result;

}

/** Allocate new phone slot in the specified task.

 *

 * @param t     Task for which to allocate a new phone.

 *

 * @return      New phone handle or -1 if the phone handle limit is

 *          exceeded.

 */

int phone_alloc(task_t *t)

{

    int i;

    spinlock_lock(&t->lock);

    for (i = 0; i < IPC_MAX_PHONES; i++) {

        if (t->phones[i].state == IPC_PHONE_HUNGUP &&

            atomic_get(&t->phones[i].active_calls) == 0)

            t->phones[i].state = IPC_PHONE_FREE;

        if (t->phones[i].state == IPC_PHONE_FREE) {

            t->phones[i].state = IPC_PHONE_CONNECTING;

            break;

        }

    }

    spinlock_unlock(&t->lock);

    if (i == IPC_MAX_PHONES)

        return -1;

    return i;

}

/** Mark a phone structure free.

 *

 * @param phone     Phone structure to be marked free.

 */

static void phone_deallocp(phone_t *phone)

{

    ASSERT(phone->state == IPC_PHONE_CONNECTING);

    /* atomic operation */

    phone->state = IPC_PHONE_FREE;

}

/** Free slot from a disconnected phone.

 *

 * All already sent messages will be correctly processed.

 *

 * @param phoneid   Phone handle of the phone to be freed.

 */

void phone_dealloc(int phoneid)

{

    phone_deallocp(&TASK->phones[phoneid]);

}

/** Connect phone to a given answerbox.

 *

 * @param phoneid   Phone handle to be connected.

 * @param box       Answerbox to which to connect the phone handle.

 *

 * The procedure _enforces_ that the user first marks the phone

 * busy (e.g. via phone_alloc) and then connects the phone, otherwise

 * race condition may appear.

 */

void phone_connect(int phoneid, answerbox_t *box)

{

    phone_t *phone = &TASK->phones[phoneid];

    ASSERT(phone->state == IPC_PHONE_CONNECTING);

    ipc_phone_connect(phone, box);

}

/** @}

 */