path: root/drivers/misc/sgi-xp/xpc_channel.c

/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (c) 2004-2008 Silicon Graphics, Inc.  All Rights Reserved.
 */

/*
 * Cross Partition Communication (XPC) channel support.
 *
 *	This is the part of XPC that manages the channels and
 *	sends/receives messages across them to/from other partitions.
 *
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/cache.h>
#include <linux/interrupt.h>
#include <linux/mutex.h>
#include <linux/completion.h>
#include <asm/sn/sn_sal.h>
#include "xpc.h"

/*
 * Process a connect message from a remote partition.
 *
 * Note: xpc_process_connect() is expecting to be called with the
 * spin_lock_irqsave held and will leave it locked upon return.
 */
static void
xpc_process_connect(struct xpc_channel *ch, unsigned long *irq_flags)
{
	enum xp_retval ret;

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

	if (!(ch->flags & XPC_C_OPENREQUEST) ||
	    !(ch->flags & XPC_C_ROPENREQUEST)) {
		/* nothing more to do for now */
		return;
	}
	DBUG_ON(!(ch->flags & XPC_C_CONNECTING));

	if (!(ch->flags & XPC_C_SETUP)) {
		spin_unlock_irqrestore(&ch->lock, *irq_flags);
		ret = xpc_allocate_msgqueues(ch);
		spin_lock_irqsave(&ch->lock, *irq_flags);

		if (ret != xpSuccess)
			XPC_DISCONNECT_CHANNEL(ch, ret, irq_flags);

		ch->flags |= XPC_C_SETUP;

		if (ch->flags & (XPC_C_CONNECTED | XPC_C_DISCONNECTING))
			return;

		DBUG_ON(ch->local_msgqueue == NULL);
		DBUG_ON(ch->remote_msgqueue == NULL);
	}

	if (!(ch->flags & XPC_C_OPENREPLY)) {
		ch->flags |= XPC_C_OPENREPLY;
		xpc_send_chctl_openreply(ch, irq_flags);
	}

	if (!(ch->flags & XPC_C_ROPENREPLY))
		return;

	DBUG_ON(ch->remote_msgqueue_pa == 0);

	ch->flags = (XPC_C_CONNECTED | XPC_C_SETUP);	/* clear all else */

	dev_info(xpc_chan, "channel %d to partition %d connected\n",
		 ch->number, ch->partid);

	spin_unlock_irqrestore(&ch->lock, *irq_flags);
	xpc_create_kthreads(ch, 1, 0);
	spin_lock_irqsave(&ch->lock, *irq_flags);
}

/*
 * spin_lock_irqsave() is expected to be held on entry.
 */
static void
xpc_process_disconnect(struct xpc_channel *ch, unsigned long *irq_flags)
{
	struct xpc_partition *part = &xpc_partitions[ch->partid];
	u32 channel_was_connected = (ch->flags & XPC_C_WASCONNECTED);

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

	if (!(ch->flags & XPC_C_DISCONNECTING))
		return;

	DBUG_ON(!(ch->flags & XPC_C_CLOSEREQUEST));

	/* make sure all activity has settled down first */

	if (atomic_read(&ch->kthreads_assigned) > 0 ||
	    atomic_read(&ch->references) > 0) {
		return;
	}
	DBUG_ON((ch->flags & XPC_C_CONNECTEDCALLOUT_MADE) &&
		!(ch->flags & XPC_C_DISCONNECTINGCALLOUT_MADE));

	if (part->act_state == XPC_P_DEACTIVATING) {
		/* can't proceed until the other side disengages from us */
		if (xpc_partition_engaged(ch->partid))
			return;

	} else {

		/* as long as the other side is up do the full protocol */

		if (!(ch->flags & XPC_C_RCLOSEREQUEST))
			return;

		if (!(ch->flags & XPC_C_CLOSEREPLY)) {
			ch->flags |= XPC_C_CLOSEREPLY;
			xpc_send_chctl_closereply(ch, irq_flags);
		}

		if (!(ch->flags & XPC_C_RCLOSEREPLY))
			return;
	}

	/* wake those waiting for notify completion */
	if (atomic_read(&ch->n_to_notify) > 0) {
		/* we do callout while holding ch->lock, callout can't block */
		xpc_notify_senders_of_disconnect(ch);
	}

	/* both sides are disconnected now */

	if (ch->flags & XPC_C_DISCONNECTINGCALLOUT_MADE) {
		spin_unlock_irqrestore(&ch->lock, *irq_flags);
		xpc_disconnect_callout(ch, xpDisconnected);
		spin_lock_irqsave(&ch->lock, *irq_flags);
	}

	/* it's now safe to free the channel's message queues */
	xpc_free_msgqueues(ch);

	/*
	 * Mark the channel disconnected and clear all other flags, including
	 * XPC_C_SETUP (because of call to xpc_free_msgqueues()) but not
	 * including XPC_C_WDISCONNECT (if it was set).
	 */
	ch->flags = (XPC_C_DISCONNECTED | (ch->flags & XPC_C_WDISCONNECT));

	atomic_dec(&part->nchannels_active);

	if (channel_was_connected) {
		dev_info(xpc_chan, "channel %d to partition %d disconnected, "
			 "reason=%d\n", ch->number, ch->