scoutos / prex-0.9.0 / sys / ipc / msg.c @ 03e9c04a
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/*-
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* Copyright (c) 2005-2007, Kohsuke Ohtani
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the author nor the names of any co-contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* msg.c - routines to transmit a message.
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*/
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/**
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* IPC transmission:
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*
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* Messages are sent to the specific object by using msg_send. The
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* transmission of a message is completely synchronous with this
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* kernel. This means the thread which sent a message is blocked until
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* it receives a response from another thread. msg_receive performs
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* reception of a message. msg_receive is also blocked when no message
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* is reached to the target object. The receiver thread must answer the
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* message using msg_reply after processing the message.
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*
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* The receiver thread can not receive an additional message until it
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* replies to the sender. In short, a thread can receive only one
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* message at once. In other hand, once the thread receives a message,
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* it can send another message to different object. This mechanism
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* allows threads to redirect the sender's request to another thread.
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*
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* A message is copied from thread to thread directly without any kernel
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* buffering. The message buffer in sender's memory space is automatically
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* mapped to the receiver's memory by kernel. Since there is no page
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* out of memory in this system, we can copy the message data via physical
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* memory at anytime.
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*/
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#include <kernel.h> |
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#include <sched.h> |
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#include <task.h> |
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#include <kmem.h> |
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#include <thread.h> |
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#include <task.h> |
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#include <event.h> |
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#include <ipc.h> |
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/* forward declarations */
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static thread_t msg_dequeue(queue_t);
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static void msg_enqueue(queue_t, thread_t); |
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static struct event ipc_event; /* event for IPC operation */ |
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/*
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* Send a message.
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*
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* The current thread will be blocked until any other thread
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* receives and reply the message. A thread can send a
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* message to any object if it knows the object id.
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*/
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int
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msg_send(object_t obj, void *msg, size_t size)
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{ |
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struct msg_header *hdr;
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thread_t t; |
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void *kmsg;
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int rc;
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if (!user_area(msg))
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return EFAULT;
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if (size < sizeof(struct msg_header)) |
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return EINVAL;
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sched_lock(); |
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if (!object_valid(obj)) {
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sched_unlock(); |
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return EINVAL;
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} |
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/*
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* A thread can not send a message when it is
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* already receiving from the target object.
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* It will obviously cause a deadlock.
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*/
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if (obj == curthread->recvobj) {
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sched_unlock(); |
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return EDEADLK;
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} |
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/*
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* Translate message address to the kernel linear
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* address. So that a receiver thread can access
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* the message via kernel pointer. We can catch
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* the page fault here.
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*/
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if ((kmsg = kmem_map(msg, size)) == NULL) { |
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sched_unlock(); |
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return EFAULT;
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} |
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curthread->msgaddr = kmsg; |
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curthread->msgsize = size; |
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/*
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* The sender ID is filled in the message header
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* by the kernel. So, the receiver can trust it.
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*/
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hdr = (struct msg_header *)kmsg;
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hdr->task = curtask; |
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/*
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* If receiver already exists, wake it up.
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* The highest priority thread can get the message.
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*/
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if (!queue_empty(&obj->recvq)) {
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t = msg_dequeue(&obj->recvq); |
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sched_unsleep(t, 0);
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} |
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/*
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* Sleep until we get a reply message.
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* Note: Do not touch any data in the object
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* structure after we wakeup. This is because the
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* target object may be deleted while we are sleeping.
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*/
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curthread->sendobj = obj; |
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msg_enqueue(&obj->sendq, curthread); |
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rc = sched_sleep(&ipc_event); |
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if (rc == SLP_INTR)
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queue_remove(&curthread->ipc_link); |
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curthread->sendobj = NULL;
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sched_unlock(); |
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/*
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* Check sleep result.
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*/
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switch (rc) {
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case SLP_BREAK:
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return EAGAIN; /* Receiver has been terminated */ |
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case SLP_INVAL:
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return EINVAL; /* Object has been deleted */ |
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case SLP_INTR:
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return EINTR; /* Exception */ |
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default:
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/* DO NOTHING */
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break;
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} |
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return 0; |
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} |
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/*
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* Receive a message.
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*
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* A thread can receive a message from the object which was
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* created by any thread belongs to same task. If the message
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* has not reached yet, it blocks until any message comes in.
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*
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* The size argument specifies the "maximum" size of the message
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* buffer to receive. If the sent message is larger than this
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* size, the kernel will automatically clip the message to this
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* maximum buffer size.
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*
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* When a message is received, the sender thread is removed from
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* object's send queue. So, another thread can receive the
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* subsequent message from that object. This is important for
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* the multi-thread server which must receive multiple messages
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* simultaneously.
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*/
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int
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msg_receive(object_t obj, void *msg, size_t size)
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{ |
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thread_t t; |
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size_t len; |
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int rc, error = 0; |
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if (!user_area(msg))
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return EFAULT;
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sched_lock(); |
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if (!object_valid(obj)) {
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sched_unlock(); |
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return EINVAL;
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} |
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if (obj->owner != curtask) {
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sched_unlock(); |
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return EACCES;
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} |
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/*
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* Check if this thread finished previous receive
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* operation. A thread can not receive different
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* messages at once.
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*/
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if (curthread->recvobj) {
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sched_unlock(); |
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return EBUSY;
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} |
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curthread->recvobj = obj; |
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/*
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* If no message exists, wait until message arrives.
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*/
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while (queue_empty(&obj->sendq)) {
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/*
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* Block until someone sends a message.
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*/
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msg_enqueue(&obj->recvq, curthread); |
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rc = sched_sleep(&ipc_event); |
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if (rc != 0) { |
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/*
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* Receive is failed due to some reasons.
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*/
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switch (rc) {
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case SLP_INVAL:
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error = EINVAL; /* Object has been deleted */
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break;
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case SLP_INTR:
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queue_remove(&curthread->ipc_link); |
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error = EINTR; /* Got exception */
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break;
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default:
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panic("msg_receive");
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break;
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} |
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curthread->recvobj = NULL;
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sched_unlock(); |
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return error;
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} |
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/*
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* Check the existence of the sender thread again.
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* Even if this thread is woken by the sender thread,
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* the message may be received by another thread.
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* This may happen when another high priority thread
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* becomes runnable before we receive the message.
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*/
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} |
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t = msg_dequeue(&obj->sendq); |
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/*
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* Copy out the message to the user-space.
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*/
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len = MIN(size, t->msgsize); |
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if (len > 0) { |
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if (copyout(t->msgaddr, msg, len)) {
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msg_enqueue(&obj->sendq, t); |
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curthread->recvobj = NULL;
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sched_unlock(); |
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return EFAULT;
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} |
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} |
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/*
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* Detach the message from the target object.
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*/
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curthread->sender = t; |
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t->receiver = curthread; |
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sched_unlock(); |
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return error;
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} |
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/*
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* Send a reply message.
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*
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* The target object must be the object that we are receiving.
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* Otherwise, this function will be failed.
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*/
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int
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msg_reply(object_t obj, void *msg, size_t size)
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{ |
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thread_t t; |
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size_t len; |
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if (!user_area(msg))
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return EFAULT;
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sched_lock(); |
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if (!object_valid(obj) || obj != curthread->recvobj) {
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sched_unlock(); |
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return EINVAL;
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} |
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/*
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* Check if sender still exists
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*/
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if (curthread->sender == NULL) { |
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/* Clear receive state */
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curthread->recvobj = NULL;
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sched_unlock(); |
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return EINVAL;
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} |
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/*
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* Copy a message to the sender's buffer.
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*/
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t = curthread->sender; |
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len = MIN(size, t->msgsize); |
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if (len > 0) { |
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if (copyin(msg, t->msgaddr, len)) {
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sched_unlock(); |
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return EFAULT;
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} |
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} |
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/*
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* Wakeup sender with no error.
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*/
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sched_unsleep(t, 0);
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t->receiver = NULL;
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/* Clear transmit state */
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curthread->sender = NULL;
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curthread->recvobj = NULL;
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sched_unlock(); |
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return 0; |
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} |
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/*
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* Cancel pending message operation of the specified thread.
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* This is called when the thread is terminated.
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*
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* We have to handle the following conditions to prevent deadlock.
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*
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* If the terminated thread is sending a message:
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* 1. A message is already received.
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* -> The receiver thread will reply to the invalid thread.
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*
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* 2. A message is not received yet.
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* -> The thread remains in send queue of the object.
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*
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* When the terminated thread is receiving a message.
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* 3. A message is already sent.
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* -> The sender thread will wait for reply forever.
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*
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* 4. A message is not sent yet.
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* -> The thread remains in receive queue of the object.
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*/
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void
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msg_cancel(thread_t t) |
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{ |
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sched_lock(); |
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if (t->sendobj != NULL) { |
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if (t->receiver != NULL) |
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t->receiver->sender = NULL;
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else
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queue_remove(&t->ipc_link); |
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} |
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if (t->recvobj != NULL) { |
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if (t->sender != NULL) { |
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sched_unsleep(t->sender, SLP_BREAK); |
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t->sender->receiver = NULL;
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} else
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queue_remove(&t->ipc_link); |
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} |
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sched_unlock(); |
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} |
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/*
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* Abort all message operations relevant to the specified object.
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* This is called when the target object is deleted.
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*/
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void
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msg_abort(object_t obj) |
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{ |
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queue_t q; |
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thread_t t; |
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sched_lock(); |
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/*
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* Force wakeup all threads in the send queue.
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*/
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while (!queue_empty(&obj->sendq)) {
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q = dequeue(&obj->sendq); |
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t = queue_entry(q, struct thread, ipc_link);
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sched_unsleep(t, SLP_INVAL); |
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} |
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/*
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* Force wakeup all threads waiting for receive.
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*/
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while (!queue_empty(&obj->recvq)) {
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q = dequeue(&obj->recvq); |
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t = queue_entry(q, struct thread, ipc_link);
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sched_unsleep(t, SLP_INVAL); |
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} |
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sched_unlock(); |
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} |
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/*
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* Dequeue thread from the IPC queue.
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* The most highest priority thread will be chosen.
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*/
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static thread_t
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msg_dequeue(queue_t head) |
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{ |
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queue_t q; |
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thread_t t, top; |
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q = queue_first(head); |
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top = queue_entry(q, struct thread, ipc_link);
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while (!queue_end(head, q)) {
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t = queue_entry(q, struct thread, ipc_link);
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if (t->priority < top->priority)
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top = t; |
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q = queue_next(q); |
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} |
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queue_remove(&top->ipc_link); |
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return top;
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} |
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static void |
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msg_enqueue(queue_t head, thread_t t) |
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{ |
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enqueue(head, &t->ipc_link); |
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} |
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void
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msg_init(void)
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{ |
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event_init(&ipc_event, "ipc");
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} |