/*
* 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);
}
/** @}
*/