Merge with master.kernel.org:/pub/scm/linux/kernel/git/torvalds/linux-2.6.git

1 files changed, 2297 insertions, 0 deletions

diff --git a/arch/ia64/sn/kernel/xpc_channel.c b/arch/ia64/sn/kernel/xpc_channel.c
new file mode 100644
index 00000000000..0bf6fbcc46d
--- /dev/null
+++ b/arch/ia64/sn/kernel/xpc_channel.c
@@ -0,0 +1,2297 @@
+/*
+ * 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) 2004-2005 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/slab.h>
+#include <asm/sn/bte.h>
+#include <asm/sn/sn_sal.h>
+#include "xpc.h"
+
+
+/*
+ * Set up the initial values for the XPartition Communication channels.
+ */
+static void
+xpc_initialize_channels(struct xpc_partition *part, partid_t partid)
+{
+	int ch_number;
+	struct xpc_channel *ch;
+
+
+	for (ch_number = 0; ch_number < part->nchannels; ch_number++) {
+		ch = &part->channels[ch_number];
+
+		ch->partid = partid;
+		ch->number = ch_number;
+		ch->flags = XPC_C_DISCONNECTED;
+
+		ch->local_GP = &part->local_GPs[ch_number];
+		ch->local_openclose_args =
+					&part->local_openclose_args[ch_number];
+
+		atomic_set(&ch->kthreads_assigned, 0);
+		atomic_set(&ch->kthreads_idle, 0);
+		atomic_set(&ch->kthreads_active, 0);
+
+		atomic_set(&ch->references, 0);
+		atomic_set(&ch->n_to_notify, 0);
+
+		spin_lock_init(&ch->lock);
+		sema_init(&ch->msg_to_pull_sema, 1);	/* mutex */
+
+		atomic_set(&ch->n_on_msg_allocate_wq, 0);
+		init_waitqueue_head(&ch->msg_allocate_wq);
+		init_waitqueue_head(&ch->idle_wq);
+	}
+}
+
+
+/*
+ * Setup the infrastructure necessary to support XPartition Communication
+ * between the specified remote partition and the local one.
+ */
+enum xpc_retval
+xpc_setup_infrastructure(struct xpc_partition *part)
+{
+	int ret;
+	struct timer_list *timer;
+	partid_t partid = XPC_PARTID(part);
+
+
+	/*
+	 * Zero out MOST of the entry for this partition. Only the fields
+	 * starting with `nchannels' will be zeroed. The preceding fields must
+	 * remain `viable' across partition ups and downs, since they may be
+	 * referenced during this memset() operation.
+	 */
+	memset(&part->nchannels, 0, sizeof(struct xpc_partition) -
+				offsetof(struct xpc_partition, nchannels));
+
+	/*
+	 * Allocate all of the channel structures as a contiguous chunk of
+	 * memory.
+	 */
+	part->channels = kmalloc(sizeof(struct xpc_channel) * XPC_NCHANNELS,
+								GFP_KERNEL);
+	if (part->channels == NULL) {
+		dev_err(xpc_chan, "can't get memory for channels\n");
+		return xpcNoMemory;
+	}
+	memset(part->channels, 0, sizeof(struct xpc_channel) * XPC_NCHANNELS);
+
+	part->nchannels = XPC_NCHANNELS;
+
+
+	/* allocate all the required GET/PUT values */
+
+	part->local_GPs = xpc_kmalloc_cacheline_aligned(XPC_GP_SIZE,
+					GFP_KERNEL, &part->local_GPs_base);
+	if (part->local_GPs == NULL) {
+		kfree(part->channels);
+		part->channels = NULL;
+		dev_err(xpc_chan, "can't get memory for local get/put "
+			"values\n");
+		return xpcNoMemory;
+	}
+	memset(part->local_GPs, 0, XPC_GP_SIZE);
+
+	part->remote_GPs = xpc_kmalloc_cacheline_aligned(XPC_GP_SIZE,
+					GFP_KERNEL, &part->remote_GPs_base);
+	if (part->remote_GPs == NULL) {
+		kfree(part->channels);
+		part->channels = NULL;
+		kfree(part->local_GPs_base);
+		part->local_GPs = NULL;
+		dev_err(xpc_chan, "can't get memory for remote get/put "
+			"values\n");
+		return xpcNoMemory;
+	}
+	memset(part->remote_GPs, 0, XPC_GP_SIZE);
+
+
+	/* allocate all the required open and close args */
+
+	part->local_openclose_args = xpc_kmalloc_cacheline_aligned(
+					XPC_OPENCLOSE_ARGS_SIZE, GFP_KERNEL,
+					&part->local_openclose_args_base);
+	if (part->local_openclose_args == NULL) {
+		kfree(part->channels);
+		part->channels = NULL;
+		kfree(part->local_GPs_base);
+		part->local_GPs = NULL;
+		kfree(part->remote_GPs_base);
+		part->remote_GPs = NULL;
+		dev_err(xpc_chan, "can't get memory for local connect args\n");
+		return xpcNoMemory;
+	}
+	memset(part->local_openclose_args, 0, XPC_OPENCLOSE_ARGS_SIZE);
+
+	part->remote_openclose_args = xpc_kmalloc_cacheline_aligned(
+					XPC_OPENCLOSE_ARGS_SIZE, GFP_KERNEL,
+					&part->remote_openclose_args_base);
+	if (part->remote_openclose_args == NULL) {
+		kfree(part->channels);
+		part->channels = NULL;
+		kfree(part->local_GPs_base);
+		part->local_GPs = NULL;
+		kfree(part->remote_GPs_base);
+		part->remote_GPs = NULL;
+		kfree(part->local_openclose_args_base);
+		part->local_openclose_args = NULL;
+		dev_err(xpc_chan, "can't get memory for remote connect args\n");
+		return xpcNoMemory;
+	}
+	memset(part->remote_openclose_args, 0, XPC_OPENCLOSE_ARGS_SIZE);
+
+
+	xpc_initialize_channels(part, partid);
+
+	atomic_set(&part->nchannels_active, 0);
+
+
+	/* local_IPI_amo were set to 0 by an earlier memset() */
+
+	/* Initialize this partitions AMO_t structure */
+	part->local_IPI_amo_va = xpc_IPI_init(partid);
+
+	spin_lock_init(&part->IPI_lock);
+
+	atomic_set(&part->channel_mgr_requests, 1);
+	init_waitqueue_head(&part->channel_mgr_wq);
+
+	sprintf(part->IPI_owner, "xpc%02d", partid);
+	ret = request_irq(SGI_XPC_NOTIFY, xpc_notify_IRQ_handler, SA_SHIRQ,
+				part->IPI_owner, (void *) (u64) partid);
+	if (ret != 0) {
+		kfree(part->channels);
+		part->channels = NULL;
+		kfree(part->local_GPs_base);
+		part->local_GPs = NULL;
+		kfree(part->remote_GPs_base);
+		part->remote_GPs = NULL;
+		kfree(part->local_openclose_args_base);
+		part->local_openclose_args = NULL;
+		kfree(part->remote_openclose_args_base);
+		part->remote_openclose_args = NULL;
+		dev_err(xpc_chan, "can't register NOTIFY IRQ handler, "
+			"errno=%d\n", -ret);
+		return xpcLackOfResources;
+	}
+
+	/* Setup a timer to check for dropped IPIs */
+	timer = &part->dropped_IPI_timer;
+	init_timer(timer);
+	timer->function = (void (*)(unsigned long)) xpc_dropped_IPI_check;
+	timer->data = (unsigned long) part;
+	timer->expires = jiffies + XPC_P_DROPPED_IPI_WAIT;
+	add_timer(timer);
+
+	/*
+	 * With the setting of the partition setup_state to XPC_P_SETUP, we're
+	 * declaring that this partition is ready to go.
+	 */
+	(volatile u8) part->setup_state = XPC_P_SETUP;
+
+
+	/*
+	 * Setup the per partition specific variables required by the
+	 * remote partition to establish channel connections with us.
+	 *
+	 * The setting of the magic # indicates that these per partition
+	 * specific variables are ready to be used.
+	 */
+	xpc_vars_part[partid].GPs_pa = __pa(part->local_GPs);
+	xpc_vars_part[partid].openclose_args_pa =
+					__pa(part->local_openclose_args);
+	xpc_vars_part[partid].IPI_amo_pa = __pa(part->local_IPI_amo_va);
+	xpc_vars_part[partid].IPI_nasid = cpuid_to_nasid(smp_processor_id());
+	xpc_vars_part[partid].IPI_phys_cpuid =
+					cpu_physical_id(smp_processor_id());
+	xpc_vars_part[partid].nchannels = part->nchannels;
+	(volatile u64) xpc_vars_part[partid].magic = XPC_VP_MAGIC1;
+
+	return xpcSuccess;
+}
+
+
+/*
+ * Create a wrapper that hides the underlying mechanism for pulling a cacheline
+ * (or multiple cachelines) from a remote partition.
+ *
+ * src must be a cacheline aligned physical address on the remote partition.
+ * dst must be a cacheline aligned virtual address on this partition.
+ * cnt must be an cacheline sized
+ */
+static enum xpc_retval
+xpc_pull_remote_cachelines(struct xpc_partition *part, void *dst,
+				const void *src, size_t cnt)
+{
+	bte_result_t bte_ret;
+
+
+	DBUG_ON((u64) src != L1_CACHE_ALIGN((u64) src));
+	DBUG_ON((u64) dst != L1_CACHE_ALIGN((u64) dst));
+	DBUG_ON(cnt != L1_CACHE_ALIGN(cnt));
+
+	if (part->act_state == XPC_P_DEACTIVATING) {
+		return part->reason;
+	}
+
+	bte_ret = xp_bte_copy((u64) src, (u64) ia64_tpa((u64) dst),
+				(u64) cnt, (BTE_NORMAL | BTE_WACQUIRE), NULL);
+	if (bte_ret == BTE_SUCCESS) {
+		return xpcSuccess;
+	}
+
+	dev_dbg(xpc_chan, "xp_bte_copy() from partition %d failed, ret=%d\n",
+		XPC_PARTID(part), bte_ret);
+
+	return xpc_map_bte_errors(bte_ret);
+}
+
+
+/*
+ * Pull the remote per partititon specific variables from the specified
+ * partition.
+ */
+enum xpc_retval
+xpc_pull_remote_vars_part(struct xpc_partition *part)
+{
+	u8 buffer[L1_CACHE_BYTES * 2];
+	struct xpc_vars_part *pulled_entry_cacheline =
+			(struct xpc_vars_part *) L1_CACHE_ALIGN((u64) buffer);
+	struct xpc_vars_part *pulled_entry;
+	u64 remote_entry_cacheline_pa, remote_entry_pa;
+	partid_t partid = XPC_PARTID(part);
+	enum xpc_retval ret;
+
+
+	/* pull the cacheline that contains the variables we're interested in */
+
+	DBUG_ON(part->remote_vars_part_pa !=
+				L1_CACHE_ALIGN(part->remote_vars_part_pa));
+	DBUG_ON(sizeof(struct xpc_vars_part) != L1_CACHE_BYTES / 2);
+
+	remote_entry_pa = part->remote_vars_part_pa +
+			sn_partition_id * sizeof(struct xpc_vars_part);
+
+	remote_entry_cacheline_pa = (remote_entry_pa & ~(L1_CACHE_BYTES - 1));
+
+	pulled_entry = (struct xpc_vars_part *) ((u64) pulled_entry_cacheline +
+				(remote_entry_pa & (L1_CACHE_BYTES - 1)));
+
+	ret = xpc_pull_remote_cachelines(part, pulled_entry_cacheline,
+					(void *) remote_entry_cacheline_pa,
+					L1_CACHE_BYTES);
+	if (ret != xpcSuccess) {
+		dev_dbg(xpc_chan, "failed to pull XPC vars_part from "
+			"partition %d, ret=%d\n", partid, ret);
+		return ret;
+	}
+
+
+	/* see if they've been set up yet */
+
+	if (pulled_entry->magic != XPC_VP_MAGIC1 &&
+				pulled_entry->magic != XPC_VP_MAGIC2) {
+
+		if (pulled_entry->magic != 0) {
+			dev_dbg(xpc_chan, "partition %d's XPC vars_part for "
+				"partition %d has bad magic value (=0x%lx)\n",
+				partid, sn_partition_id, pulled_entry->magic);
+			return xpcBadMagic;
+		}
+
+		/* they've not been initialized yet */
+		return xpcRetry;
+	}
+
+	if (xpc_vars_part[partid].magic == XPC_VP_MAGIC1) {
+
+		/* validate the variables */
+
+		if (pulled_entry->GPs_pa == 0 ||
+				pulled_entry->openclose_args_pa == 0 ||
+					pulled_entry->IPI_amo_pa == 0) {
+
+			dev_err(xpc_chan, "partition %d's XPC vars_part for "
+				"partition %d are not valid\n", partid,
+				sn_partition_id);
+			return xpcInvalidAddress;
+		}
+
+		/* the variables we imported look to be valid */
+
+		part->remote_GPs_pa = pulled_entry->GPs_pa;
+		part->remote_openclose_args_pa =
+					pulled_entry->openclose_args_pa;
+		part->remote_IPI_amo_va =
+				      (AMO_t *) __va(pulled_entry->IPI_amo_pa);
+		part->remote_IPI_nasid = pulled_entry->IPI_nasid;
+		part->remote_IPI_phys_cpuid = pulled_entry->IPI_phys_cpuid;
+
+		if (part->nchannels > pulled_entry->nchannels) {
+			part->nchannels = pulled_entry->nchannels;
+		}
+
+		/* let the other side know that we've pulled their variables */
+
+		(volatile u64) xpc_vars_part[partid].magic = XPC_VP_MAGIC2;
+	}
+
+	if (pulled_entry->magic == XPC_VP_MAGIC1) {
+		return xpcRetry;
+	}
+
+	return xpcSuccess;
+}
+
+
+/*
+ * Get the IPI flags and pull the openclose args and/or remote GPs as needed.
+ */
+static u64
+xpc_get_IPI_flags(struct xpc_partition *part)
+{
+	unsigned long irq_flags;
+	u64 IPI_amo;
+	enum xpc_retval ret;
+
+
+	/*
+	 * See if there are any IPI flags to be handled.
+	 */
+
+	spin_lock_irqsave(&part->IPI_lock, irq_flags);
+	if ((IPI_amo = part->local_IPI_amo) != 0) {
+		part->local_IPI_amo = 0;
+	}
+	spin_unlock_irqrestore(&part->IPI_lock, irq_flags);
+
+
+	if (XPC_ANY_OPENCLOSE_IPI_FLAGS_SET(IPI_amo)) {
+		ret = xpc_pull_remote_cachelines(part,
+					part->remote_openclose_args,
+					(void *) part->remote_openclose_args_pa,
+					XPC_OPENCLOSE_ARGS_SIZE);
+		if (ret != xpcSuccess) {
+			XPC_DEACTIVATE_PARTITION(part, ret);
+
+			dev_dbg(xpc_chan, "failed to pull openclose args from "
+				"partition %d, ret=%d\n", XPC_PARTID(part),
+				ret);
+
+			/* don't bother processing IPIs anymore */
+			IPI_amo = 0;
+		}
+	}
+
+	if (XPC_ANY_MSG_IPI_FLAGS_SET(IPI_amo)) {
+		ret = xpc_pull_remote_cachelines(part, part->remote_GPs,
+						(void *) part->remote_GPs_pa,
+						XPC_GP_SIZE);
+		if (ret != xpcSuccess) {
+			XPC_DEACTIVATE_PARTITION(part, ret);
+
+			dev_dbg(xpc_chan, "failed to pull GPs from partition "
+				"%d, ret=%d\n", XPC_PARTID(part), ret);
+
+			/* don't bother processing IPIs anymore */
+			IPI_amo = 0;
+		}
+	}
+
+	return IPI_amo;
+}
+
+
+/*
+ * Allocate the local message queue and the notify queue.
+ */
+static enum xpc_retval
+xpc_allocate_local_msgqueue(struct xpc_channel *ch)
+{
+	unsigned long irq_flags;
+	int nentries;
+	size_t nbytes;
+
+
+	// >>> may want to check for ch->flags & XPC_C_DISCONNECTING between
+	// >>> iterations of the for-loop, bail if set?
+
+	// >>> should we impose a minumum #of entries? like 4 or 8?
+	for (nentries = ch->local_nentries; nentries > 0; nentries--) {
+
+		nbytes = nentries * ch->msg_size;
+		ch->local_msgqueue = xpc_kmalloc_cacheline_aligned(nbytes,
+						(GFP_KERNEL | GFP_DMA),
+						&ch->local_msgqueue_base);
+		if (ch->local_msgqueue == NULL) {
+			continue;
+		}
+		memset(ch->local_msgqueue, 0, nbytes);
+
+		nbytes = nentries * sizeof(struct xpc_notify);
+		ch->notify_queue = kmalloc(nbytes, (GFP_KERNEL | GFP_DMA));
+		if (ch->notify_queue == NULL) {
+			kfree(ch->local_msgqueue_base);
+			ch->local_msgqueue = NULL;
+			continue;
+		}
+		memset(ch->notify_queue, 0, nbytes);
+
+		spin_lock_irqsave(&ch->lock, irq_flags);
+		if (nentries < ch->local_nentries) {
+			dev_dbg(xpc_chan, "nentries=%d local_nentries=%d, "
+				"partid=%d, channel=%d\n", nentries,
+				ch->local_nentries, ch->partid, ch->number);
+
+			ch->local_nentries = nentries;
+		}
+		spin_unlock_irqrestore(&ch->lock, irq_flags);
+		return xpcSuccess;
+	}
+
+	dev_dbg(xpc_chan, "can't get memory for local message queue and notify "
+		"queue, partid=%d, channel=%d\n", ch->partid, ch->number);
+	return xpcNoMemory;
+}
+
+
+/*
+ * Allocate the cached remote message queue.
+ */
+static enum xpc_retval
+xpc_allocate_remote_msgqueue(struct xpc_channel *ch)
+{
+	unsigned long irq_flags;
+	int nentries;
+	size_t nbytes;
+
+
+	DBUG_ON(ch->remote_nentries <= 0);
+
+	// >>> may want to check for ch->flags & XPC_C_DISCONNECTING between
+	// >>> iterations of the for-loop, bail if set?
+
+	// >>> should we impose a minumum #of entries? like 4 or 8?
+	for (nentries = ch->remote_nentries; nentries > 0; nentries--) {
+
+		nbytes = nentries * ch->msg_size;
+		ch->remote_msgqueue = xpc_kmalloc_cacheline_aligned(nbytes,
+						(GFP_KERNEL | GFP_DMA),
+						&ch->remote_msgqueue_base);
+		if (ch->remote_msgqueue == NULL) {
+			continue;
+		}
+		memset(ch->remote_msgqueue, 0, nbytes);
+
+		spin_lock_irqsave(&ch->lock, irq_flags);
+		if (nentries < ch->remote_nentries) {
+			dev_dbg(xpc_chan, "nentries=%d remote_nentries=%d, "
+				"partid=%d, channel=%d\n", nentries,
+				ch->remote_nentries, ch->partid, ch->number);
+
+			ch->remote_nentries = nentries;
+		}
+		spin_unlock_irqrestore(&ch->lock, irq_flags);
+		return xpcSuccess;
+	}
+
+	dev_dbg(xpc_chan, "can't get memory for cached remote message queue, "
+		"partid=%d, channel=%d\n", ch->partid, ch->number);
+	return xpcNoMemory;
+}
+
+
+/*
+ * Allocate message queues and other stuff associated with a channel.
+ *
+ * Note: Assumes all of the channel sizes are filled in.
+ */
+static enum xpc_retval
+xpc_allocate_msgqueues(struct xpc_channel *ch)
+{
+	unsigned long irq_flags;
+	int i;
+	enum xpc_retval ret;
+
+
+	DBUG_ON(ch->flags & XPC_C_SETUP);
+
+	if ((ret = xpc_allocate_local_msgqueue(ch)) != xpcSuccess) {
+		return ret;
+	}
+
+	if ((ret = xpc_allocate_remote_msgqueue(ch)) != xpcSuccess) {
+		kfree(ch->local_msgqueue_base);
+		ch->local_msgqueue = NULL;
+		kfree(ch->notify_queue);
+		ch->notify_queue = NULL;
+		return ret;
+	}
+
+	for (i = 0; i < ch->local_nentries; i++) {
+		/* use a semaphore as an event wait queue */
+		sema_init(&ch->notify_queue[i].sema, 0);
+	}
+
+	sema_init(&ch->teardown_sema, 0);	/* event wait */
+
+	spin_lock_irqsave(&ch->lock, irq_flags);
+	ch->flags |= XPC_C_SETUP;
+	spin_unlock_irqrestore(&ch->lock, irq_flags);
+
+	return xpcSuccess;
+}
+
+
+/*
+ * 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 xpc_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 != xpcSuccess) {
+			XPC_DISCONNECT_CHANNEL(ch, ret, irq_flags);
+		}
+		if (ch->flags & (XPC_C_CONNECTED | XPC_C_DISCONNECTING)) {
+			return;
+		}
+
+		DBUG_ON(!(ch->flags & XPC_C_SETUP));
+		DBUG_ON(ch->local_msgqueue == NULL);
+		DBUG_ON(ch->remote_msgqueue == NULL);
+	}
+
+	if (!(ch->flags & XPC_C_OPENREPLY)) {
+		ch->flags |= XPC_C_OPENREPLY;
+		xpc_IPI_send_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);
+	spin_lock_irqsave(&ch->lock, *irq_flags);
+}
+
+
+/*
+ * Free up message queues and other stuff that were allocated for the specified
+ * channel.
+ *
+ * Note: ch->reason and ch->reason_line are left set for debugging purposes,
+ * they're cleared when XPC_C_DISCONNECTED is cleared.
+ */
+static void
+xpc_free_msgqueues(struct xpc_channel *ch)
+{
+	DBUG_ON(!spin_is_locked(&ch->lock));
+	DBUG_ON(atomic_read(&ch->n_to_notify) != 0);
+
+	ch->remote_msgqueue_pa = 0;
+	ch->func = NULL;
+	ch->key = NULL;
+	ch->msg_size = 0;
+	ch->local_nentries = 0;
+	ch->remote_nentries = 0;
+	ch->kthreads_assigned_limit = 0;
+	ch->kthreads_idle_limit = 0;
+
+	ch->local_GP->get = 0;
+	ch->local_GP->put = 0;
+	ch->remote_GP.get = 0;
+	ch->remote_GP.put = 0;
+	ch->w_local_GP.get = 0;
+	ch->w_local_GP.put = 0;
+	ch->w_remote_GP.get = 0;
+	ch->w_remote_GP.put = 0;
+	ch->next_msg_to_pull = 0;
+
+	if (ch->flags & XPC_C_SETUP) {
+		ch->flags &= ~XPC_C_SETUP;
+
+		dev_dbg(xpc_chan, "ch->flags=0x%x, partid=%d, channel=%d\n",
+			ch->flags, ch->partid, ch->number);
+
+		kfree(ch->local_msgqueue_base);
+		ch->local_msgqueue = NULL;
+		kfree(ch->remote_msgqueue_base);
+		ch->remote_msgqueue = NULL;
+		kfree(ch->notify_queue);
+		ch->notify_queue = NULL;
+
+		/* in case someone is waiting for the teardown to complete */
+		up(&ch->teardown_sema);
+	}
+}
+
+
+/*
+ * 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 ch_flags = ch->flags;
+
+
+	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->references) > 0) {
+		return;
+	}
+	DBUG_ON(atomic_read(&ch->kthreads_assigned) != 0);
+
+	/* it's now safe to free the channel's message queues */
+
+	xpc_free_msgqueues(ch);
+	DBUG_ON(ch->flags & XPC_C_SETUP);
+
+	if (part->act_state != XPC_P_DEACTIVATING) {
+
+		/* 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_IPI_send_closereply(ch, irq_flags);
+		}
+
+		if (!(ch->flags & XPC_C_RCLOSEREPLY)) {
+			return;
+		}
+	}
+
+	/* both sides are disconnected now */
+
+	ch->flags = XPC_C_DISCONNECTED;	/* clear all flags, but this one */
+
+	atomic_dec(&part->nchannels_active);
+
+	if (ch_flags & XPC_C_WASCONNECTED) {
+		dev_info(xpc_chan, "channel %d to partition %d disconnected, "
+			"reason=%d\n", ch->number, ch->partid, ch->reason);
+	}
+}
+
+
+/*
+ * Process a change in the channel's remote connection state.
+ */
+static void
+xpc_process_openclose_IPI(struct xpc_partition *part, int ch_number,
+				u8 IPI_flags)
+{
+	unsigned long irq_flags;
+	struct xpc_openclose_args *args =
+				&part->remote_openclose_args[ch_number];
+	struct xpc_channel *ch = &part->channels[ch_number];
+	enum xpc_retval reason;
+
+
+
+	spin_lock_irqsave(&ch->lock, irq_flags);
+
+
+	if (IPI_flags & XPC_IPI_CLOSEREQUEST) {
+
+		dev_dbg(xpc_chan, "XPC_IPI_CLOSEREQUEST (reason=%d) received "
+			"from partid=%d, channel=%d\n", args->reason,
+			ch->partid, ch->number);
+
+		/*
+		 * If RCLOSEREQUEST is set, we're probably waiting for
+		 * RCLOSEREPLY. We should find it and a ROPENREQUEST packed
+		 * with this RCLOSEQREUQEST in the IPI_flags.
+		 */
+
+		if (ch->flags & XPC_C_RCLOSEREQUEST) {
+			DBUG_ON(!(ch->flags & XPC_C_DISCONNECTING));
+			DBUG_ON(!(ch->flags & XPC_C_CLOSEREQUEST));
+			DBUG_ON(!(ch->flags & XPC_C_CLOSEREPLY));
+			DBUG_ON(ch->flags & XPC_C_RCLOSEREPLY);
+
+			DBUG_ON(!(IPI_flags & XPC_IPI_CLOSEREPLY));
+			IPI_flags &= ~XPC_IPI_CLOSEREPLY;
+			ch->flags |= XPC_C_RCLOSEREPLY;
+
+			/* both sides have finished disconnecting */
+			xpc_process_disconnect(ch, &irq_flags);
+		}
+
+		if (ch->flags & XPC_C_DISCONNECTED) {
+			// >>> explain this section
+
+			if (!(IPI_flags & XPC_IPI_OPENREQUEST)) {
+				DBUG_ON(part->act_state !=
+							XPC_P_DEACTIVATING);
+				spin_unlock_irqrestore(&ch->lock, irq_flags);
+				return;
+			}
+
+			XPC_SET_REASON(ch, 0, 0);
+			ch->flags &= ~XPC_C_DISCONNECTED;
+
+			atomic_inc(&part->nchannels_active);
+			ch->flags |= (XPC_C_CONNECTING | XPC_C_ROPENREQUEST);
+		}
+
+		IPI_flags &= ~(XPC_IPI_OPENREQUEST | XPC_IPI_OPENREPLY);
+
+		/*
+		 * The meaningful CLOSEREQUEST connection state fields are:
+		 *      reason = reason connection is to be closed
+		 */
+
+		ch->flags |= XPC_C_RCLOSEREQUEST;
+
+		if (!(ch->flags & XPC_C_DISCONNECTING)) {
+			reason = args->reason;
+			if (reason <= xpcSuccess || reason > xpcUnknownReason) {
+				reason = xpcUnknownReason;
+			} else if (reason == xpcUnregistering) {
+				reason = xpcOtherUnregistering;
+			}
+
+			XPC_DISCONNECT_CHANNEL(ch, reason, &irq_flags);
+		} else {
+			xpc_process_disconnect(ch, &irq_flags);
+		}
+	}
+
+
+	if (IPI_flags & XPC_IPI_CLOSEREPLY) {
+
+		dev_dbg(xpc_chan, "XPC_IPI_CLOSEREPLY received from partid=%d,"
+			" channel=%d\n", ch->partid, ch->number);
+
+		if (ch->flags & XPC_C_DISCONNECTED) {
+			DBUG_ON(part->act_state != XPC_P_DEACTIVATING);
+			spin_unlock_irqrestore(&ch->lock, irq_flags);
+			return;
+		}
+
+		DBUG_ON(!(ch->flags & XPC_C_CLOSEREQUEST));
+		DBUG_ON(!(ch->flags & XPC_C_RCLOSEREQUEST));
+
+		ch->flags |= XPC_C_RCLOSEREPLY;
+
+		if (ch->flags & XPC_C_CLOSEREPLY) {
+			/* both sides have finished disconnecting */
+			xpc_process_disconnect(ch, &irq_flags);
+		}
+	}
+
+
+	if (IPI_flags & XPC_IPI_OPENREQUEST) {
+
+		dev_dbg(xpc_chan, "XPC_IPI_OPENREQUEST (msg_size=%d, "
+			"local_nentries=%d) received from partid=%d, "
+			"channel=%d\n", args->msg_size, args->local_nentries,
+			ch->partid, ch->number);
+
+		if ((ch->flags & XPC_C_DISCONNECTING) ||
+					part->act_state == XPC_P_DEACTIVATING) {
+			spin_unlock_irqrestore(&ch->lock, irq_flags);
+			return;
+		}
+		DBUG_ON(!(ch->flags & (XPC_C_DISCONNECTED |
+							XPC_C_OPENREQUEST)));
+		DBUG_ON(ch->flags & (XPC_C_ROPENREQUEST | XPC_C_ROPENREPLY |
+					XPC_C_OPENREPLY | XPC_C_CONNECTED));
+
+		/*
+		 * The meaningful OPENREQUEST connection state fields are:
+		 *      msg_size = size of channel's messages in bytes
+		 *      local_nentries = remote partition's local_nentries
+		 */
+		DBUG_ON(args->msg_size == 0);
+		DBUG_ON(args->local_nentries == 0);
+
+		ch->flags |= (XPC_C_ROPENREQUEST | XPC_C_CONNECTING);
+		ch->remote_nentries = args->local_nentries;
+
+
+		if (ch->flags & XPC_C_OPENREQUEST) {
+			if (args->msg_size != ch->msg_size) {
+				XPC_DISCONNECT_CHANNEL(ch, xpcUnequalMsgSizes,
+								&irq_flags);
+				spin_unlock_irqrestore(&ch->lock, irq_flags);
+				return;
+			}
+		} else {
+			ch->msg_size = args->msg_size;
+
+			XPC_SET_REASON(ch, 0, 0);
+			ch->flags &= ~XPC_C_DISCONNECTED;
+
+			atomic_inc(&part->nchannels_active);
+		}
+
+		xpc_process_connect(ch, &irq_flags);
+	}
+
+
+	if (IPI_flags & XPC_IPI_OPENREPLY) {
+
+		dev_dbg(xpc_chan, "XPC_IPI_OPENREPLY (local_msgqueue_pa=0x%lx, "
+			"local_nentries=%d, remote_nentries=%d) received from "
+			"partid=%d, channel=%d\n", args->local_msgqueue_pa,
+			args->local_nentries, args->remote_nentries,
+			ch->partid, ch->number);
+
+		if (ch->flags & (XPC_C_DISCONNECTING | XPC_C_DISCONNECTED)) {
+			spin_unlock_irqrestore(&ch->lock, irq_flags);
+			return;
+		}
+		DBUG_ON(!(ch->flags & XPC_C_OPENREQUEST));
+		DBUG_ON(!(ch->flags & XPC_C_ROPENREQUEST));
+		DBUG_ON(ch->flags & XPC_C_CONNECTED);
+
+		/*
+		 * The meaningful OPENREPLY connection state fields are:
+		 *      local_msgqueue_pa = physical address of remote
+		 *			    partition's local_msgqueue
+		 *      local_nentries = remote partition's local_nentries
+		 *      remote_nentries = remote partition's remote_nentries
+		 */
+		DBUG_ON(args->local_msgqueue_pa == 0);
+		DBUG_ON(args->local_nentries == 0);
+		DBUG_ON(args->remote_nentries == 0);
+
+		ch->flags |= XPC_C_ROPENREPLY;
+		ch->remote_msgqueue_pa = args->local_msgqueue_pa;
+
+		if (args->local_nentries < ch->remote_nentries) {
+			dev_dbg(xpc_chan, "XPC_IPI_OPENREPLY: new "
+				"remote_nentries=%d, old remote_nentries=%d, "
+				"partid=%d, channel=%d\n",
+				args->local_nentries, ch->remote_nentries,
+				ch->partid, ch->number);
+
+			ch->remote_nentries = args->local_nentries;
+		}
+		if (args->remote_nentries < ch->local_nentries) {
+			dev_dbg(xpc_chan, "XPC_IPI_OPENREPLY: new "
+				"local_nentries=%d, old local_nentries=%d, "
+				"partid=%d, channel=%d\n",
+				args->remote_nentries, ch->local_nentries,
+				ch->partid, ch->number);
+
+			ch->local_nentries = args->remote_nentries;
+		}
+
+		xpc_process_connect(ch, &irq_flags);
+	}
+
+	spin_unlock_irqrestore(&ch->lock, irq_flags);
+}
+
+
+/*
+ * Attempt to establish a channel connection to a remote partition.
+ */
+static enum xpc_retval
+xpc_connect_channel(struct xpc_channel *ch)
+{
+	unsigned long irq_flags;
+	struct xpc_registration *registration = &xpc_registrations[ch->number];
+
+
+	if (down_interruptible(&registration->sema) != 0) {
+		return xpcInterrupted;
+	}
+
+	if (!XPC_CHANNEL_REGISTERED(ch->number)) {
+		up(&registration->sema);
+		return xpcUnregistered;
+	}
+
+	spin_lock_irqsave(&ch->lock, irq_flags);
+
+	DBUG_ON(ch->flags & XPC_C_CONNECTED);
+	DBUG_ON(ch->flags & XPC_C_OPENREQUEST);
+
+	if (ch->flags & XPC_C_DISCONNECTING) {
+		spin_unlock_irqrestore(&ch->lock, irq_flags);
+		up(&registration->sema);
+		return ch->reason;
+	}
+
+
+	/* add info from the channel connect registration to the channel */
+
+	ch->kthreads_assigned_limit = registration->assigned_limit;
+	ch->kthreads_idle_limit = registration->idle_limit;
+	DBUG_ON(atomic_read(&ch->kthreads_assigned) != 0);
+	DBUG_ON(atomic_read(&ch->kthreads_idle) != 0);
+	DBUG_ON(atomic_read(&ch->kthreads_active) != 0);
+
+	ch->func = registration->func;
+	DBUG_ON(registration->func == NULL);
+	ch->key = registration->key;
+
+	ch->local_nentries = registration->nentries;
+
+	if (ch->flags & XPC_C_ROPENREQUEST) {
+		if (registration->msg_size != ch->msg_size) {
+			/* the local and remote sides aren't the same */
+
+			/*
+			 * Because XPC_DISCONNECT_CHANNEL() can block we're
+			 * forced to up the registration sema before we unlock
+			 * the channel lock. But that's okay here because we're
+			 * done with the part that required the registration
+			 * sema. XPC_DISCONNECT_CHANNEL() requires that the
+			 * channel lock be locked and will unlock and relock
+			 * the channel lock as needed.
+			 */
+			up(&registration->sema);
+			XPC_DISCONNECT_CHANNEL(ch, xpcUnequalMsgSizes,
+								&irq_flags);
+			spin_unlock_irqrestore(&ch->lock, irq_flags);
+			return xpcUnequalMsgSizes;
+		}
+	} else {
+		ch->msg_size = registration->msg_size;
+
+		XPC_SET_REASON(ch, 0, 0);
+		ch->flags &= ~XPC_C_DISCONNECTED;
+
+		atomic_inc(&xpc_partitions[ch->partid].nchannels_active);
+	}
+
+	up(&registration->sema);
+
+
+	/* initiate the connection */
+
+	ch->flags |= (XPC_C_OPENREQUEST | XPC_C_CONNECTING);
+	xpc_IPI_send_openrequest(ch, &irq_flags);
+
+	xpc_process_connect(ch, &irq_flags);
+
+	spin_unlock_irqrestore(&ch->lock, irq_flags);
+
+	return xpcSuccess;
+}
+
+
+/*
+ * Notify those who wanted to be notified upon delivery of their message.
+ */
+static void
+xpc_notify_senders(struct xpc_channel *ch, enum xpc_retval reason, s64 put)
+{
+	struct xpc_notify *notify;
+	u8 notify_type;
+	s64 get = ch->w_remote_GP.get - 1;
+
+
+	while (++get < put && atomic_read(&ch->n_to_notify) > 0) {
+
+		notify = &ch->notify_queue[get % ch->local_nentries];
+
+		/*
+		 * See if the notify entry indicates it was associated with
+		 * a message who's sender wants to be notified. It is possible
+		 * that it is, but someone else is doing or has done the
+		 * notification.
+		 */
+		notify_type = notify->type;
+		if (notify_type == 0 ||
+				cmpxchg(&notify->type, notify_type, 0) !=
+								notify_type) {
+			continue;
+		}
+
+		DBUG_ON(notify_type != XPC_N_CALL);
+
+		atomic_dec(&ch->n_to_notify);
+
+		if (notify->func != NULL) {
+			dev_dbg(xpc_chan, "notify->func() called, notify=0x%p, "
+				"msg_number=%ld, partid=%d, channel=%d\n",
+				(void *) notify, get, ch->partid, ch->number);
+
+			notify->func(reason, ch->partid, ch->number,
+								notify->key);
+
+			dev_dbg(xpc_chan, "notify->func() returned, "
+				"notify=0x%p, msg_number=%ld, partid=%d, "
+				"channel=%d\n", (void *) notify, get,
+				ch->partid, ch->number);
+		}
+	}
+}
+
+
+/*
+ * Clear some of the msg flags in the local message queue.
+ */
+static inline void
+xpc_clear_local_msgqueue_flags(struct xpc_channel *ch)
+{
+	struct xpc_msg *msg;
+	s64 get;
+
+
+	get = ch->w_remote_GP.get;
+	do {
+		msg = (struct xpc_msg *) ((u64) ch->local_msgqueue +
+				(get % ch->local_nentries) * ch->msg_size);
+		msg->flags = 0;
+	} while (++get < (volatile s64) ch->remote_GP.get);
+}
+
+
+/*
+ * Clear some of the msg flags in the remote message queue.
+ */
+static inline void
+xpc_clear_remote_msgqueue_flags(struct xpc_channel *ch)
+{
+	struct xpc_msg *msg;
+	s64 put;
+
+
+	put = ch->w_remote_GP.put;
+	do {
+		msg = (struct xpc_msg *) ((u64) ch->remote_msgqueue +
+				(put % ch->remote_nentries) * ch->msg_size);
+		msg->flags = 0;
+	} while (++put < (volatile s64) ch->remote_GP.put);
+}
+
+
+static void
+xpc_process_msg_IPI(struct xpc_partition *part, int ch_number)
+{
+	struct xpc_channel *ch = &part->channels[ch_number];
+	int nmsgs_sent;
+
+
+	ch->remote_GP = part->remote_GPs[ch_number];
+
+
+	/* See what, if anything, has changed for each connected channel */
+
+	xpc_msgqueue_ref(ch);
+
+	if (ch->w_remote_GP.get == ch->remote_GP.get &&
+				ch->w_remote_GP.put == ch->remote_GP.put) {
+		/* nothing changed since GPs were last pulled */
+		xpc_msgqueue_deref(ch);
+		return;
+	}
+
+	if (!(ch->flags & XPC_C_CONNECTED)){
+		xpc_msgqueue_deref(ch);
+		return;
+	}
+
+
+	/*
+	 * First check to see if messages recently sent by us have been
+	 * received by the other side. (The remote GET value will have
+	 * changed since we last looked at it.)
+	 */
+
+	if (ch->w_remote_GP.get != ch->remote_GP.get) {
+
+		/*
+		 * We need to notify any senders that want to be notified
+		 * that their sent messages have been received by their
+		 * intended recipients. We need to do this before updating
+		 * w_remote_GP.get so that we don't allocate the same message
+		 * queue entries prematurely (see xpc_allocate_msg()).
+		 */
+		if (atomic_read(&ch->n_to_notify) > 0) {
+			/*
+			 * Notify senders that messages sent have been
+			 * received and delivered by the other side.
+			 */
+			xpc_notify_senders(ch, xpcMsgDelivered,
+							ch->remote_GP.get);
+		}
+
+		/*
+		 * Clear msg->flags in previously sent messages, so that
+		 * they're ready for xpc_allocate_msg().
+		 */
+		xpc_clear_local_msgqueue_flags(ch);
+
+		(volatile s64) ch->w_remote_GP.get = ch->remote_GP.get;
+
+		dev_dbg(xpc_chan, "w_remote_GP.get changed to %ld, partid=%d, "
+			"channel=%d\n", ch->w_remote_GP.get, ch->partid,
+			ch->number);
+
+		/*
+		 * If anyone was waiting for message queue entries to become
+		 * available, wake them up.
+		 */
+		if (atomic_read(&ch->n_on_msg_allocate_wq) > 0) {
+			wake_up(&ch->msg_allocate_wq);
+		}
+	}
+
+
+	/*
+	 * Now check for newly sent messages by the other side. (The remote
+	 * PUT value will have changed since we last looked at it.)
+	 */
+
+	if (ch->w_remote_GP.put != ch->remote_GP.put) {
+		/*
+		 * Clear msg->flags in previously received messages, so that
+		 * they're ready for xpc_get_deliverable_msg().
+		 */
+		xpc_clear_remote_msgqueue_flags(ch);
+
+		(volatile s64) ch->w_remote_GP.put = ch->remote_GP.put;
+
+		dev_dbg(xpc_chan, "w_remote_GP.put changed to %ld, partid=%d, "
+			"channel=%d\n", ch->w_remote_GP.put, ch->partid,
+			ch->number);
+
+		nmsgs_sent = ch->w_remote_GP.put - ch->w_local_GP.get;
+		if (nmsgs_sent > 0) {
+			dev_dbg(xpc_chan, "msgs waiting to be copied and "
+				"delivered=%d, partid=%d, channel=%d\n",
+				nmsgs_sent, ch->partid, ch->number);
+
+			if (ch->flags & XPC_C_CONNECTCALLOUT) {
+				xpc_activate_kthreads(ch, nmsgs_sent);
+			}
+		}
+	}
+
+	xpc_msgqueue_deref(ch);
+}
+
+
+void
+xpc_process_channel_activity(struct xpc_partition *part)
+{
+	unsigned long irq_flags;
+	u64 IPI_amo, IPI_flags;
+	struct xpc_channel *ch;
+	int ch_number;
+
+
+	IPI_amo = xpc_get_IPI_flags(part);
+
+	/*
+	 * Initiate channel connections for registered channels.
+	 *
+	 * For each connected channel that has pending messages activate idle
+	 * kthreads and/or create new kthreads as needed.
+	 */
+
+	for (ch_number = 0; ch_number < part->nchannels; ch_number++) {
+		ch = &part->channels[ch_number];
+
+
+		/*
+		 * Process any open or close related IPI flags, and then deal
+		 * with connecting or disconnecting the channel as required.
+		 */
+
+		IPI_flags = XPC_GET_IPI_FLAGS(IPI_amo, ch_number);
+
+		if (XPC_ANY_OPENCLOSE_IPI_FLAGS_SET(IPI_flags)) {
+			xpc_process_openclose_IPI(part, ch_number, IPI_flags);
+		}
+
+
+		if (ch->flags & XPC_C_DISCONNECTING) {
+			spin_lock_irqsave(&ch->lock, irq_flags);
+			xpc_process_disconnect(ch, &irq_flags);
+			spin_unlock_irqrestore(&ch->lock, irq_flags);
+			continue;
+		}
+
+		if (part->act_state == XPC_P_DEACTIVATING) {
+			continue;
+		}
+
+		if (!(ch->flags & XPC_C_CONNECTED)) {
+			if (!(ch->flags & XPC_C_OPENREQUEST)) {
+				DBUG_ON(ch->flags & XPC_C_SETUP);
+				(void) xpc_connect_channel(ch);
+			} else {
+				spin_lock_irqsave(&ch->lock, irq_flags);
+				xpc_process_connect(ch, &irq_flags);
+				spin_unlock_irqrestore(&ch->lock, irq_flags);
+			}
+			continue;
+		}
+
+
+		/*
+		 * Process any message related IPI flags, this may involve the
+		 * activation of kthreads to deliver any pending messages sent
+		 * from the other partition.
+		 */
+
+		if (XPC_ANY_MSG_IPI_FLAGS_SET(IPI_flags)) {
+			xpc_process_msg_IPI(part, ch_number);
+		}
+	}
+}
+
+
+/*
+ * XPC's heartbeat code calls this function to inform XPC that a partition has
+ * gone down.  XPC responds by tearing down the XPartition Communication
+ * infrastructure used for the just downed partition.
+ *
+ * XPC's heartbeat code will never call this function and xpc_partition_up()
+ * at the same time. Nor will it ever make multiple calls to either function
+ * at the same time.
+ */
+void
+xpc_partition_down(struct xpc_partition *part, enum xpc_retval reason)
+{
+	unsigned long irq_flags;
+	int ch_number;
+	struct xpc_channel *ch;
+
+
+	dev_dbg(xpc_chan, "deactivating partition %d, reason=%d\n",
+		XPC_PARTID(part), reason);
+
+	if (!xpc_part_ref(part)) {
+		/* infrastructure for this partition isn't currently set up */
+		return;
+	}
+
+
+	/* disconnect all channels associated with the downed partition */
+
+	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_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 proceding 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];
+
+			if (!(ch->flags & XPC_C_DISCONNECTING)) {
+				DBUG_ON(ch->flags & XPC_C_OPENREQUEST);
+				DBUG_ON(ch->flags & XPC_C_CONNECTED);
+				DBUG_ON(ch->flags & XPC_C_SETUP);
+
+				/*
+				 * 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)
+{
+	unsigned long irq_flags;
+
+
+	/* 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);
+	}
+
+	spin_lock_irqsave(&ch->lock, irq_flags);
+	ch->flags |= XPC_C_CONNECTCALLOUT;
+	spin_unlock_irqrestore(&ch->lock, irq_flags);
+}
+
+
+/*
+ * 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);
+
+			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_free_msgqueues().
+ *
+ * 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 flags;
+
+
+	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);
+
+	flags = ch->flags;
+	/* 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);
+
+	ch->flags |= (XPC_C_CLOSEREQUEST | XPC_C_DISCONNECTING);
+	xpc_IPI_send_closerequest(ch, irq_flags);
+
+	if (flags & XPC_C_CONNECTED) {
+		ch->flags |= XPC_C_WASCONNECTED;
+	}
+
+	if (atomic_read(&ch->kthreads_idle) > 0) {
+		/* wake all idle kthreads so they can exit */
+		wake_up_all(&ch->idle_wq);
+	}
+
+	spin_unlock_irqrestore(&ch->lock, *irq_flags);
+
+
+	/* 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);
+	}
+
+	/* wake those waiting for notify completion */
+
+	if (atomic_read(&ch->n_to_notify) > 0) {
+		xpc_notify_senders(ch, reason, ch->w_local_GP.put);
+	}
+
+	spin_lock_irqsave(&ch->lock, *irq_flags);
+}
+
+
+void
+xpc_disconnected_callout(struct xpc_channel *ch)
+{
+	/*
+	 * Let the channel's registerer know that the channel is now
+	 * disconnected. We don't want to do this if the registerer was never
+	 * informed of a connection being made, unless the disconnect was for
+	 * abnormal reasons.
+	 */
+
+	if (ch->func != NULL) {
+		dev_dbg(xpc_chan, "ch->func() called, reason=%d, partid=%d, "
+			"channel=%d\n", ch->reason, ch->partid, ch->number);
+
+		ch->func(ch->reason, ch->partid, ch->number, NULL, ch->key);
+
+		dev_dbg(xpc_chan, "ch->func() returned, reason=%d, partid=%d, "
+			"channel=%d\n", ch->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;
+
+
+	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, "
+			"channel=%d\n", put, ch->partid, ch->number);
+
+		send_IPI = 1;
+
+		/*
+		 * We need to ensure that the message referenced by
+		 * local_GP->put is not XPC_M_READY or that local_GP->put
+		 * equals w_local_GP.put, so we'll go have a look.
+		 */
+		initial_put = put;
+	}
+
+	if (send_IPI) {
+		xpc_IPI_send_msgrequest(ch);
+	}
+}
+
+
+/*
+ * Common code that does the actual sending of the message by advancing the
+ * local message queue's Put value and sends an IPI to the partition the
+ * message is being sent to.
+ */
+static enum xpc_retval
+xpc_send_msg(struct xpc_channel *ch, struct xpc_msg *msg, u8 notify_type,
+			xpc_notify_func func, void *key)
+{
+	enum xpc_retval ret = xpcSuccess;
+	struct xpc_notify *notify = NULL;   // >>> to keep the compiler happy!!
+	s64 put, msg_number = msg->number;
+
+
+	DBUG_ON(notify_type == XPC_N_CALL && func == NULL);
+	DBUG_ON((((u64) msg - (u64) ch->local_msgqueue) / ch->msg_size) !=
+					msg_number % ch->local_nentries);
+	DBUG_ON(msg->flags & XPC_M_READY);
+
+	if (ch->flags & XPC_C_DISCONNECTING) {
+		/* drop the reference grabbed in xpc_allocate_msg() */
+		xpc_msgqueue_deref(ch);
+		return ch->reason;
+	}
+
+	if (notify_type != 0) {
+		/*
+		 * Tell the remote side to send an ACK interrupt when the
+		 * message has been delivered.
+		 */
+		msg->flags |= XPC_M_INTERRUPT;
+
+		atomic_inc(&ch->n_to_notify);
+
+		notify = &ch->notify_queue[msg_number % ch->local_nentries];
+		notify->func = func;
+		notify->key = key;
+		(volatile u8) notify->type = notify_type;
+
+		// >>> is a mb() needed here?
+
+		if (ch->flags & XPC_C_DISCONNECTING) {
+			/*
+			 * An error occurred between our last error check and
+			 * this one. We will try to clear the type field from
+			 * the notify entry. If we succeed then
+			 * xpc_disconnect_channel() didn't already process
+			 * the notify entry.
+			 */
+			if (cmpxchg(&notify->type, notify_type, 0) ==
+								notify_type) {
+				atomic_dec(&ch->n_to_notify);
+				ret = ch->reason;
+			}
+
+			/* drop the reference grabbed in xpc_allocate_msg() */
+			xpc_msgqueue_deref(ch);
+			return ret;
+		}
+	}
+
+	msg->flags |= XPC_M_READY;
+
+	/*
+	 * The preceding store of msg->flags must occur before the following
+	 * load of ch->local_GP->put.
+	 */
+	mb();
+
+	/* see if the message is next in line to be sent, if so send it */
+
+	put = ch->local_GP->put;
+	if (put == msg_number) {
+		xpc_send_msgs(ch, put);
+	}
+
+	/* drop the reference grabbed in xpc_allocate_msg() */
+	xpc_msgqueue_deref(ch);
+	return ret;
+}
+
+
+/*
+ * Send a message previously allocated using xpc_initiate_allocate() on the
+ * specified channel connected to the specified partition.
+ *
+ * This routine will not wait for the message to be received, nor will
+ * notification be given when it does happen. Once this routine has returned
+ * the message entry allocated via xpc_initiate_allocate() is no longer
+ * accessable to the caller.
+ *
+ * This routine, although called by users, does not call xpc_part_ref() to
+ * ensure that the partition infrastructure is in place. It relies on the
+ * fact that we called xpc_msgqueue_ref() in xpc_allocate_msg().
+ *
+ * Arguments:
+ *
+ *	partid - ID of partition to which the channel is connected.
+ *	ch_number - channel # to send message on.
+ *	payload - pointer to the payload area allocated via
+ *			xpc_initiate_allocate().
+ */
+enum xpc_retval
+xpc_initiate_send(partid_t partid, int ch_number, void *payload)
+{
+	struct xpc_partition *part = &xpc_partitions[partid];
+	struct xpc_msg *msg = XPC_MSG_ADDRESS(payload);
+	enum xpc_retval ret;
+
+
+	dev_dbg(xpc_chan, "msg=0x%p, partid=%d, channel=%d\n", (void *) msg,
+		partid, ch_number);
+
+	DBUG_ON(partid <= 0 || partid >= XP_MAX_PARTITIONS);
+	DBUG_ON(ch_number < 0 || ch_number >= part->nchannels);
+	DBUG_ON(msg == NULL);
+
+	ret = xpc_send_msg(&part->channels[ch_number], msg, 0, NULL, NULL);
+
+	return ret;
+}
+
+
+/*
+ * Send a message previously allocated using xpc_initiate_allocate on the
+ * specified channel connected to the specified partition.
+ *
+ * This routine will not wait for the message to be sent. Once this routine
+ * has returned the message entry allocated via xpc_initiate_allocate() is no
+ * longer accessable to the caller.
+ *
+ * Once the remote end of the channel has received the message, the function
+ * passed as an argument to xpc_initiate_send_notify() will be called. This
+ * allows the sender to free up or re-use any buffers referenced by the
+ * message, but does NOT mean the message has been processed at the remote
+ * end by a receiver.
+ *
+ * If this routine returns an error, the caller's function will NOT be called.
+ *
+ * This routine, although called by users, does not call xpc_part_ref() to
+ * ensure that the partition infrastructure is in place. It relies on the
+ * fact that we called xpc_msgqueue_ref() in xpc_allocate_msg().
+ *
+ * Arguments:
+ *
+ *	partid - ID of partition to which the channel is connected.
+ *	ch_number - channel # to send message on.
+ *	payload - pointer to the payload area allocated via
+ *			xpc_initiate_allocate().
+ *	func - function to call with asynchronous notification of message
+ *		  receipt. THIS FUNCTION MUST BE NON-BLOCKING.
+ *	key - user-defined key to be passed to the function when it's called.
+ */
+enum xpc_retval
+xpc_initiate_send_notify(partid_t partid, int ch_number, void *payload,
+				xpc_notify_func func, void *key)
+{
+	struct xpc_partition *part = &xpc_partitions[partid];
+	struct xpc_msg *msg = XPC_MSG_ADDRESS(payload);
+	enum xpc_retval ret;
+
+
+	dev_dbg(xpc_chan, "msg=0x%p, partid=%d, channel=%d\n", (void *) msg,
+		partid, ch_number);
+
+	DBUG_ON(partid <= 0 || partid >= XP_MAX_PARTITIONS);
+	DBUG_ON(ch_number < 0 || ch_number >= part->nchannels);
+	DBUG_ON(msg == NULL);
+	DBUG_ON(func == NULL);
+
+	ret = xpc_send_msg(&part->channels[ch_number], msg, XPC_N_CALL,
+								func, key);
+	return ret;
+}
+
+
+static struct xpc_msg *
+xpc_pull_remote_msg(struct xpc_channel *ch, s64 get)
+{
+	struct xpc_partition *part = &xpc_partitions[ch->partid];
+	struct xpc_msg *remote_msg, *msg;
+	u32 msg_index, nmsgs;
+	u64 msg_offset;
+	enum xpc_retval ret;
+
+
+	if (down_interruptible(&ch->msg_to_pull_sema) != 0) {
+		/* we were interrupted by a signal */
+		return NULL;
+	}
+
+	while (get >= ch->next_msg_to_pull) {
+
+		/* pull as many messages as are ready and able to be pulled */
+
+		msg_index = ch->next_msg_to_pull % ch->remote_nentries;
+
+		DBUG_ON(ch->next_msg_to_pull >=
+					(volatile s64) ch->w_remote_GP.put);
+		nmsgs =  (volatile s64) ch->w_remote_GP.put -
+						ch->next_msg_to_pull;
+		if (msg_index + nmsgs > ch->remote_nentries) {
+			/* ignore the ones that wrap the msg queue for now */
+			nmsgs = ch->remote_nentries - msg_index;
+		}
+
+		msg_offset = msg_index * ch->msg_size;
+		msg = (struct xpc_msg *) ((u64) ch->remote_msgqueue +
+								msg_offset);
+		remote_msg = (struct xpc_msg *) (ch->remote_msgqueue_pa +
+								msg_offset);
+
+		if ((ret = xpc_pull_remote_cachelines(part, msg, remote_msg,
+				nmsgs * ch->msg_size)) != xpcSuccess) {
+
+			dev_dbg(xpc_chan, "failed to pull %d msgs starting with"
+				" msg %ld from partition %d, channel=%d, "
+				"ret=%d\n", nmsgs, ch->next_msg_to_pull,
+				ch->partid, ch->number, ret);
+
+			XPC_DEACTIVATE_PARTITION(part, ret);
+
+			up(&ch->msg_to_pull_sema);
+			return NULL;
+		}
+
+		mb();	/* >>> this may not be needed, we're not sure */
+
+		ch->next_msg_to_pull += nmsgs;
+	}
+
+	up(&ch->msg_to_pull_sema);
+
+	/* return the message we were looking for */
+	msg_offset = (get % ch->remote_nentries) * ch->msg_size;
+	msg = (struct xpc_msg *) ((u64) ch->remote_msgqueue + msg_offset);
+
+	return msg;
+}
+
+
+/*
+ * Get a message to be delivered.
+ */
+static struct xpc_msg *
+xpc_get_deliverable_msg(struct xpc_channel *ch)
+{
+	struct xpc_msg *msg = NULL;
+	s64 get;
+
+
+	do {
+		if ((volatile u32) ch->flags & XPC_C_DISCONNECTING) {
+			break;
+		}
+
+		get = (volatile s64) ch->w_local_GP.get;
+		if (get == (volatile s64) ch->w_remote_GP.put) {
+			break;
+		}
+
+		/* There are messages waiting to be pulled and delivered.
+		 * We need to try to secure one for ourselves. We'll do this
+		 * by trying to increment w_local_GP.get and hope that no one
+		 * else beats us to it. If they do, we'll we'll simply have
+		 * to try again for the next one.
+	 	 */
+
+		if (cmpxchg(&ch->w_local_GP.get, get, get + 1) == get) {
+			/* we got the entry referenced by get */
+
+			dev_dbg(xpc_chan, "w_local_GP.get changed to %ld, "
+				"partid=%d, channel=%d\n", get + 1,
+				ch->partid, ch->number);
+
+			/* pull the message from the remote partition */
+
+			msg = xpc_pull_remote_msg(ch, get);
+
+			DBUG_ON(msg != NULL && msg->number != get);
+			DBUG_ON(msg != NULL && (msg->flags & XPC_M_DONE));
+			DBUG_ON(msg != NULL && !(msg->flags & XPC_M_READY));
+
+			break;
+		}
+
+	} while (1);
+
+	return msg;
+}
+
+
+/*
+ * Deliver a message to its intended recipient.
+ */
+void
+xpc_deliver_msg(struct xpc_channel *ch)
+{
+	struct xpc_msg *msg;
+
+
+	if ((msg = xpc_get_deliverable_msg(ch)) != NULL) {
+
+		/*
+		 * This ref is taken to protect the payload itself from being
+		 * freed before the user is finished with it, which the user
+		 * indicates by calling xpc_initiate_received().
+		 */
+		xpc_msgqueue_ref(ch);
+
+		atomic_inc(&ch->kthreads_active);
+
+		if (ch->func != NULL) {
+			dev_dbg(xpc_chan, "ch->func() called, msg=0x%p, "
+				"msg_number=%ld, partid=%d, channel=%d\n",
+				(void *) msg, msg->number, ch->partid,
+				ch->number);
+
+			/* deliver the message to its intended recipient */
+			ch->func(xpcMsgReceived, ch->partid, ch->number,
+					&msg->payload, ch->key);
+
+			dev_dbg(xpc_chan, "ch->func() returned, msg=0x%p, "
+				"msg_number=%ld, partid=%d, channel=%d\n",
+				(void *) msg, msg->number, ch->partid,
+				ch->number);
+		}
+
+		atomic_dec(&ch->kthreads_active);
+	}
+}
+
+
+/*
+ * Now we actually acknowledge the messages that have been delivered and ack'd
+ * by advancing the cached remote message queue's Get value and if requested
+ * send an IPI to the message sender's partition.
+ */
+static void
+xpc_acknowledge_msgs(struct xpc_channel *ch, s64 initial_get, u8 msg_flags)
+{
+	struct xpc_msg *msg;
+	s64 get = initial_get + 1;
+	int send_IPI = 0;
+
+
+	while (1) {
+
+		while (1) {
+			if (get == (volatile s64) ch->w_local_GP.get) {
+				break;
+			}
+
+			msg = (struct xpc_msg *) ((u64) ch->remote_msgqueue +
+			       (get % ch->remote_nentries) * ch->msg_size);
+
+			if (!(msg->flags & XPC_M_DONE)) {
+				break;
+			}
+
+			msg_flags |= msg->flags;
+			get++;
+		}
+
+		if (get == initial_get) {
+			/* nothing's changed */
+			break;
+		}
+
+		if (cmpxchg_rel(&ch->local_GP->get, initial_get, get) !=
+								initial_get) {
+			/* someone else beat us to it */
+			DBUG_ON((volatile s64) ch->local_GP->get <=
+								initial_get);
+			break;
+		}
+
+		/* we just set the new value of local_GP->get */
+
+		dev_dbg(xpc_chan, "local_GP->get changed to %ld, partid=%d, "
+			"channel=%d\n", get, ch->partid, ch->number);
+
+		send_IPI = (msg_flags & XPC_M_INTERRUPT);
+
+		/*
+		 * We need to ensure that the message referenced by
+		 * local_GP->get is not XPC_M_DONE or that local_GP->get
+		 * equals w_local_GP.get, so we'll go have a look.
+		 */
+		initial_get = get;
+	}
+
+	if (send_IPI) {
+		xpc_IPI_send_msgrequest(ch);
+	}
+}
+
+
+/*
+ * Acknowledge receipt of a delivered message.
+ *
+ * If a message has XPC_M_INTERRUPT set, send an interrupt to the partition
+ * that sent the message.
+ *
+ * This function, although called by users, does not call xpc_part_ref() to
+ * ensure that the partition infrastructure is in place. It relies on the
+ * fact that we called xpc_msgqueue_ref() in xpc_deliver_msg().
+ *
+ * Arguments:
+ *
+ *	partid - ID of partition to which the channel is connected.
+ *	ch_number - channel # message received on.
+ *	payload - pointer to the payload area allocated via
+ *			xpc_initiate_allocate().
+ */
+void
+xpc_initiate_received(partid_t partid, int ch_number, void *payload)
+{
+	struct xpc_partition *part = &xpc_partitions[partid];
+	struct xpc_channel *ch;
+	struct xpc_msg *msg = XPC_MSG_ADDRESS(payload);
+	s64 get, msg_number = msg->number;
+
+
+	DBUG_ON(partid <= 0 || partid >= XP_MAX_PARTITIONS);
+	DBUG_ON(ch_number < 0 || ch_number >= part->nchannels);
+
+	ch = &part->channels[ch_number];
+
+	dev_dbg(xpc_chan, "msg=0x%p, msg_number=%ld, partid=%d, channel=%d\n",
+		(void *) msg, msg_number, ch->partid, ch->number);
+
+	DBUG_ON((((u64) msg - (u64) ch->remote_msgqueue) / ch->msg_size) !=
+					msg_number % ch->remote_nentries);
+	DBUG_ON(msg->flags & XPC_M_DONE);
+
+	msg->flags |= XPC_M_DONE;
+
+	/*
+	 * The preceding store of msg->flags must occur before the following
+	 * load of ch->local_GP->get.
+	 */
+	mb();
+
+	/*
+	 * See if this message is next in line to be acknowledged as having
+	 * been delivered.
+	 */
+	get = ch->local_GP->get;
+	if (get == msg_number) {
+		xpc_acknowledge_msgs(ch, get, msg->flags);
+	}
+
+	/* the call to xpc_msgqueue_ref() was done by xpc_deliver_msg()  */
+	xpc_msgqueue_deref(ch);
+}
+