/*
* 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.
*/
/* 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
*
* 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.
*
* - There may be objection that a race may occur when the syscall finds
* an appropriate call and before executing ipc_send, the phone call might
* be disconnected and connected elsewhere. As there is no easy solution,
* the application will be notified by an 'PHONE_DISCONNECTED' message
* and the phone will not be allocated before the application notifies
* the kernel subsystem that it does not have any pending calls regarding
* this phone call.
*
* Locking order
*
* There are 2 possibilities
* - 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.
*
* - first answerbox, then phone(s)
* + Easy phone disconnect
* - Multiple checks needed when sending message
*
* Because the answerbox destroyal is much less frequent operation,
* the first method is chosen.
*
* Cleanup strategy
*
* 1) Disconnect all phones.
* * Send message 'PHONE_DISCONNECTED' to the target application
* - Once all phones are disconnected, no further calls can arrive
*
* 2) Answer all messages in 'calls' and 'dispatched_calls' queues with
* appropriate error code.
*
* 3) Wait for all async answers to arrive
* Alternatively - we might try to invalidate all messages by setting some
* flag, that would dispose of the message once it is answered. This
* would need to link all calls in one big list, which we don't currently
* do.
*
*
*/
#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
*
* @return NULL on not found, otherwise pointer to call structure
*/
call_t * get_call(__native callid)
{
/* TODO: Traverse list of dispatched calls and find one */
/* TODO: locking of call, ripping it from dispatched calls etc. */
return (call_t *) callid;
}
/** Allocate new phone slot in current TASK structure */
int phone_alloc(void)
{
int i;
spinlock_lock(&TASK->lock);
for (i=0; i < IPC_MAX_PHONES; i++) {
if (!TASK->phones[i].busy) {
TASK->phones[i].busy = 1;
break;
}
}
spinlock_unlock(&TASK->lock);
if (i >= IPC_MAX_PHONES)
return -1;
return i;
}
/** Disconnect phone */
void phone_dealloc(int phoneid)
{
spinlock_lock(&TASK->lock);
ASSERT(TASK->phones[phoneid].busy);
if (TASK->phones[phoneid].callee)
ipc_phone_destroy(&TASK->phones[phoneid]);
TASK->phones[phoneid].busy = 0;
spinlock_unlock(&TASK->lock);
}
/** Connect phone to a given answerbox
*
* @param phoneid The slot that will be connected
*
* 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->busy);
ipc_phone_connect(phone, box);
}