xpc_channel.c

linux 内核源代码

	/* disconnect channels associated with the partition going down */

	for (ch_number = 0; ch_number < part->nchannels; ch_number++) {
		ch = &part->channels[ch_number];

		xpc_msgqueue_ref(ch);
		spin_lock_irqsave(&ch->lock, irq_flags);

		XPC_DISCONNECT_CHANNEL(ch, reason, &irq_flags);

		spin_unlock_irqrestore(&ch->lock, irq_flags);
		xpc_msgqueue_deref(ch);
	}

	xpc_wakeup_channel_mgr(part);

	xpc_part_deref(part);
}


/*
 * Teardown the infrastructure necessary to support XPartition Communication
 * between the specified remote partition and the local one.
 */
void
xpc_teardown_infrastructure(struct xpc_partition *part)
{
	partid_t partid = XPC_PARTID(part);


	/*
	 * We start off by making this partition inaccessible to local
	 * processes by marking it as no longer setup. Then we make it
	 * inaccessible to remote processes by clearing the XPC per partition
	 * specific variable's magic # (which indicates that these variables
	 * are no longer valid) and by ignoring all XPC notify IPIs sent to
	 * this partition.
	 */

	DBUG_ON(atomic_read(&part->nchannels_engaged) != 0);
	DBUG_ON(atomic_read(&part->nchannels_active) != 0);
	DBUG_ON(part->setup_state != XPC_P_SETUP);
	part->setup_state = XPC_P_WTEARDOWN;

	xpc_vars_part[partid].magic = 0;


	free_irq(SGI_XPC_NOTIFY, (void *) (u64) partid);


	/*
	 * Before proceeding with the teardown we have to wait until all
	 * existing references cease.
	 */
	wait_event(part->teardown_wq, (atomic_read(&part->references) == 0));


	/* now we can begin tearing down the infrastructure */

	part->setup_state = XPC_P_TORNDOWN;

	/* in case we've still got outstanding timers registered... */
	del_timer_sync(&part->dropped_IPI_timer);

	kfree(part->remote_openclose_args_base);
	part->remote_openclose_args = NULL;
	kfree(part->local_openclose_args_base);
	part->local_openclose_args = NULL;
	kfree(part->remote_GPs_base);
	part->remote_GPs = NULL;
	kfree(part->local_GPs_base);
	part->local_GPs = NULL;
	kfree(part->channels);
	part->channels = NULL;
	part->local_IPI_amo_va = NULL;
}


/*
 * Called by XP at the time of channel connection registration to cause
 * XPC to establish connections to all currently active partitions.
 */
void
xpc_initiate_connect(int ch_number)
{
	partid_t partid;
	struct xpc_partition *part;
	struct xpc_channel *ch;


	DBUG_ON(ch_number < 0 || ch_number >= XPC_NCHANNELS);

	for (partid = 1; partid < XP_MAX_PARTITIONS; partid++) {
		part = &xpc_partitions[partid];

		if (xpc_part_ref(part)) {
			ch = &part->channels[ch_number];

			/*
			 * Initiate the establishment of a connection on the
			 * newly registered channel to the remote partition.
			 */
			xpc_wakeup_channel_mgr(part);
			xpc_part_deref(part);
		}
	}
}


void
xpc_connected_callout(struct xpc_channel *ch)
{
	/* let the registerer know that a connection has been established */

	if (ch->func != NULL) {
		dev_dbg(xpc_chan, "ch->func() called, reason=xpcConnected, "
			"partid=%d, channel=%d\n", ch->partid, ch->number);

		ch->func(xpcConnected, ch->partid, ch->number,
				(void *) (u64) ch->local_nentries, ch->key);

		dev_dbg(xpc_chan, "ch->func() returned, reason=xpcConnected, "
			"partid=%d, channel=%d\n", ch->partid, ch->number);
	}
}


/*
 * Called by XP at the time of channel connection unregistration to cause
 * XPC to teardown all current connections for the specified channel.
 *
 * Before returning xpc_initiate_disconnect() will wait until all connections
 * on the specified channel have been closed/torndown. So the caller can be
 * assured that they will not be receiving any more callouts from XPC to the
 * function they registered via xpc_connect().
 *
 * Arguments:
 *
 *	ch_number - channel # to unregister.
 */
void
xpc_initiate_disconnect(int ch_number)
{
	unsigned long irq_flags;
	partid_t partid;
	struct xpc_partition *part;
	struct xpc_channel *ch;


	DBUG_ON(ch_number < 0 || ch_number >= XPC_NCHANNELS);

	/* initiate the channel disconnect for every active partition */
	for (partid = 1; partid < XP_MAX_PARTITIONS; partid++) {
		part = &xpc_partitions[partid];

		if (xpc_part_ref(part)) {
			ch = &part->channels[ch_number];
			xpc_msgqueue_ref(ch);

			spin_lock_irqsave(&ch->lock, irq_flags);

			if (!(ch->flags & XPC_C_DISCONNECTED)) {
				ch->flags |= XPC_C_WDISCONNECT;

				XPC_DISCONNECT_CHANNEL(ch, xpcUnregistering,
								&irq_flags);
			}

			spin_unlock_irqrestore(&ch->lock, irq_flags);

			xpc_msgqueue_deref(ch);
			xpc_part_deref(part);
		}
	}

	xpc_disconnect_wait(ch_number);
}


/*
 * To disconnect a channel, and reflect it back to all who may be waiting.
 *
 * An OPEN is not allowed until XPC_C_DISCONNECTING is cleared by
 * xpc_process_disconnect(), and if set, XPC_C_WDISCONNECT is cleared by
 * xpc_disconnect_wait().
 *
 * THE CHANNEL IS TO BE LOCKED BY THE CALLER AND WILL REMAIN LOCKED UPON RETURN.
 */
void
xpc_disconnect_channel(const int line, struct xpc_channel *ch,
			enum xpc_retval reason, unsigned long *irq_flags)
{
	u32 channel_was_connected = (ch->flags & XPC_C_CONNECTED);


	DBUG_ON(!spin_is_locked(&ch->lock));

	if (ch->flags & (XPC_C_DISCONNECTING | XPC_C_DISCONNECTED)) {
		return;
	}
	DBUG_ON(!(ch->flags & (XPC_C_CONNECTING | XPC_C_CONNECTED)));

	dev_dbg(xpc_chan, "reason=%d, line=%d, partid=%d, channel=%d\n",
		reason, line, ch->partid, ch->number);

	XPC_SET_REASON(ch, reason, line);

	ch->flags |= (XPC_C_CLOSEREQUEST | XPC_C_DISCONNECTING);
	/* some of these may not have been set */
	ch->flags &= ~(XPC_C_OPENREQUEST | XPC_C_OPENREPLY |
			XPC_C_ROPENREQUEST | XPC_C_ROPENREPLY |
			XPC_C_CONNECTING | XPC_C_CONNECTED);

	xpc_IPI_send_closerequest(ch, irq_flags);

	if (channel_was_connected) {
		ch->flags |= XPC_C_WASCONNECTED;
	}

	spin_unlock_irqrestore(&ch->lock, *irq_flags);

	/* wake all idle kthreads so they can exit */
	if (atomic_read(&ch->kthreads_idle) > 0) {
		wake_up_all(&ch->idle_wq);

	} else if ((ch->flags & XPC_C_CONNECTEDCALLOUT_MADE) &&
			!(ch->flags & XPC_C_DISCONNECTINGCALLOUT)) {
		/* start a kthread that will do the xpcDisconnecting callout */
		xpc_create_kthreads(ch, 1, 1);
	}

	/* wake those waiting to allocate an entry from the local msg queue */
	if (atomic_read(&ch->n_on_msg_allocate_wq) > 0) {
		wake_up(&ch->msg_allocate_wq);
	}

	spin_lock_irqsave(&ch->lock, *irq_flags);
}


void
xpc_disconnect_callout(struct xpc_channel *ch, enum xpc_retval reason)
{
	/*
	 * Let the channel's registerer know that the channel is being
	 * disconnected. We don't want to do this if the registerer was never
	 * informed of a connection being made.
	 */

	if (ch->func != NULL) {
		dev_dbg(xpc_chan, "ch->func() called, reason=%d, partid=%d, "
			"channel=%d\n", reason, ch->partid, ch->number);

		ch->func(reason, ch->partid, ch->number, NULL, ch->key);

		dev_dbg(xpc_chan, "ch->func() returned, reason=%d, partid=%d, "
			"channel=%d\n", reason, ch->partid, ch->number);
	}
}


/*
 * Wait for a message entry to become available for the specified channel,
 * but don't wait any longer than 1 jiffy.
 */
static enum xpc_retval
xpc_allocate_msg_wait(struct xpc_channel *ch)
{
	enum xpc_retval ret;


	if (ch->flags & XPC_C_DISCONNECTING) {
		DBUG_ON(ch->reason == xpcInterrupted);  // >>> Is this true?
		return ch->reason;
	}

	atomic_inc(&ch->n_on_msg_allocate_wq);
	ret = interruptible_sleep_on_timeout(&ch->msg_allocate_wq, 1);
	atomic_dec(&ch->n_on_msg_allocate_wq);

	if (ch->flags & XPC_C_DISCONNECTING) {
		ret = ch->reason;
		DBUG_ON(ch->reason == xpcInterrupted);  // >>> Is this true?
	} else if (ret == 0) {
		ret = xpcTimeout;
	} else {
		ret = xpcInterrupted;
	}

	return ret;
}


/*
 * Allocate an entry for a message from the message queue associated with the
 * specified channel.
 */
static enum xpc_retval
xpc_allocate_msg(struct xpc_channel *ch, u32 flags,
			struct xpc_msg **address_of_msg)
{
	struct xpc_msg *msg;
	enum xpc_retval ret;
	s64 put;


	/* this reference will be dropped in xpc_send_msg() */
	xpc_msgqueue_ref(ch);

	if (ch->flags & XPC_C_DISCONNECTING) {
		xpc_msgqueue_deref(ch);
		return ch->reason;
	}
	if (!(ch->flags & XPC_C_CONNECTED)) {
		xpc_msgqueue_deref(ch);
		return xpcNotConnected;
	}


	/*
	 * Get the next available message entry from the local message queue.
	 * If none are available, we'll make sure that we grab the latest
	 * GP values.
	 */
	ret = xpcTimeout;

	while (1) {

		put = (volatile s64) ch->w_local_GP.put;
		if (put - (volatile s64) ch->w_remote_GP.get <
							ch->local_nentries) {

			/* There are available message entries. We need to try
			 * to secure one for ourselves. We'll do this by trying
			 * to increment w_local_GP.put as long as someone else
			 * doesn't beat us to it. If they do, we'll have to
			 * try again.
		 	 */
			if (cmpxchg(&ch->w_local_GP.put, put, put + 1) ==
									put) {
				/* we got the entry referenced by put */
				break;
			}
			continue;	/* try again */
		}


		/*
		 * There aren't any available msg entries at this time.
		 *
		 * In waiting for a message entry to become available,
		 * we set a timeout in case the other side is not
		 * sending completion IPIs. This lets us fake an IPI
		 * that will cause the IPI handler to fetch the latest
		 * GP values as if an IPI was sent by the other side.
		 */
		if (ret == xpcTimeout) {
			xpc_IPI_send_local_msgrequest(ch);
		}

		if (flags & XPC_NOWAIT) {
			xpc_msgqueue_deref(ch);
			return xpcNoWait;
		}

		ret = xpc_allocate_msg_wait(ch);
		if (ret != xpcInterrupted && ret != xpcTimeout) {
			xpc_msgqueue_deref(ch);
			return ret;
		}
	}


	/* get the message's address and initialize it */
	msg = (struct xpc_msg *) ((u64) ch->local_msgqueue +
				(put % ch->local_nentries) * ch->msg_size);


	DBUG_ON(msg->flags != 0);
	msg->number = put;

	dev_dbg(xpc_chan, "w_local_GP.put changed to %ld; msg=0x%p, "
		"msg_number=%ld, partid=%d, channel=%d\n", put + 1,
		(void *) msg, msg->number, ch->partid, ch->number);

	*address_of_msg = msg;

	return xpcSuccess;
}


/*
 * Allocate an entry for a message from the message queue associated with the
 * specified channel. NOTE that this routine can sleep waiting for a message
 * entry to become available. To not sleep, pass in the XPC_NOWAIT flag.
 *
 * Arguments:
 *
 *	partid - ID of partition to which the channel is connected.
 *	ch_number - channel #.
 *	flags - see xpc.h for valid flags.
 *	payload - address of the allocated payload area pointer (filled in on
 * 	          return) in which the user-defined message is constructed.
 */
enum xpc_retval
xpc_initiate_allocate(partid_t partid, int ch_number, u32 flags, void **payload)
{
	struct xpc_partition *part = &xpc_partitions[partid];
	enum xpc_retval ret = xpcUnknownReason;
	struct xpc_msg *msg = NULL;


	DBUG_ON(partid <= 0 || partid >= XP_MAX_PARTITIONS);
	DBUG_ON(ch_number < 0 || ch_number >= part->nchannels);

	*payload = NULL;

	if (xpc_part_ref(part)) {
		ret = xpc_allocate_msg(&part->channels[ch_number], flags, &msg);
		xpc_part_deref(part);

		if (msg != NULL) {
			*payload = &msg->payload;
		}
	}

	return ret;
}


/*
 * Now we actually send the messages that are ready to be sent by advancing
 * the local message queue's Put value and then send an IPI to the recipient
 * partition.
 */
static void
xpc_send_msgs(struct xpc_channel *ch, s64 initial_put)
{
	struct xpc_msg *msg;
	s64 put = initial_put + 1;
	int send_IPI = 0;


	while (1) {

		while (1) {
			if (put == (volatile s64) ch->w_local_GP.put) {
				break;
			}

			msg = (struct xpc_msg *) ((u64) ch->local_msgqueue +
			       (put % ch->local_nentries) * ch->msg_size);

			if (!(msg->flags & XPC_M_READY)) {
				break;
			}

			put++;
		}

		if (put == initial_put) {
			/* nothing's changed */
			break;
		}

		if (cmpxchg_rel(&ch->local_GP->put, initial_put, put) !=
								initial_put) {
			/* someone else beat us to it */
			DBUG_ON((volatile s64) ch->local_GP->put < initial_put);
			break;
		}

		/* we just set the new value of local_GP->put */

		dev_dbg(xpc_chan, "local_GP->put changed to %ld, partid=%d, "