text: /*
   * 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) 2004-2006 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/bte.h>
  #include <asm/sn/sn_sal.h>
  #include <asm/sn/xpc.h>
  
  
  /*
   * Guarantee that the kzalloc'd memory is cacheline aligned.
   */
  static void *
  xpc_kzalloc_cacheline_aligned(size_t size, gfp_t flags, void **base)
  {
  	/* see if kzalloc will give us cachline aligned memory by default */
  	*base = kzalloc(size, flags);
  	if (*base == NULL) {
  		return NULL;
  	}
  	if ((u64) *base == L1_CACHE_ALIGN((u64) *base)) {
  		return *base;
  	}
  	kfree(*base);
  
  	/* nope, we'll have to do it ourselves */
  	*base = kzalloc(size + L1_CACHE_BYTES, flags);
  	if (*base == NULL) {
  		return NULL;
  	}
  	return (void *) L1_CACHE_ALIGN((u64) *base);
  }
  
  
  /*
   * 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);
  		mutex_init(&ch->msg_to_pull_mutex);
  		init_completion(&ch->wdisconnect_wait);
  
  		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, cpuid;
  	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 = kzalloc(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;
  	}
  
  	part->nchannels = XPC_NCHANNELS;
  
  
  	/* allocate all the required GET/PUT values */
  
  	part->local_GPs = xpc_kzalloc_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;
  	}
  
  	part->remote_GPs = xpc_kzalloc_cacheline_aligned(XPC_GP_SIZE,
  					GFP_KERNEL, &part->remote_GPs_base);
  	if (part->remote_GPs == NULL) {
  		dev_err(xpc_chan, "can't get memory for remote get/put "
  			"values\n");
  		kfree(part->local_GPs_base);
  		part->local_GPs = NULL;
  		kfree(part->channels);
  		part->channels = NULL;
  		return xpcNoMemory;
  	}
  
  
  	/* allocate all the required open and close args */
  
  	part->local_openclose_args = xpc_kzalloc_cacheline_aligned(
  					XPC_OPENCLOSE_ARGS_SIZE, GFP_KERNEL,
  					&part->local_openclose_args_base);
  	if (part->local_openclose_args == NULL) {
  		dev_err(xpc_chan, "can't get memory for local connect args\n");
  		kfree(part->remote_GPs_base);
  		part->remote_GPs = NULL;
  		kfree(part->local_GPs_base);
  		part->local_GPs = NULL;
  		kfree(part->channels);
  		part->channels = NULL;
  		return xpcNoMemory;
  	}
  
  	part->remote_openclose_args = xpc_kzalloc_cacheline_aligned(
  					XPC_OPENCLOSE_ARGS_SIZE, GFP_KERNEL,
  					&part->remote_openclose_args_base);
  	if (part->remote_openclose_args == NULL) {
  		dev_err(xpc_chan, "can't get memory for remote connect args\n");
  		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;
  		return xpcNoMemory;
  	}
  
  
  	xpc_initialize_channels(part, partid);
  
  	atomic_set(&part->nchannels_active, 0);
  	atomic_set(&part->nchannels_engaged, 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, IRQF_SHARED,
  				part->IPI_owner, (void *) (u64) partid);
  	if (ret != 0) {
  		dev_err(xpc_chan, "can't register NOTIFY IRQ handler, "
  			"errno=%d\n", -ret);
  		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;
  		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.
  	 */
  	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);
  	cpuid = raw_smp_processor_id();	/* any CPU in this partition will do */
  	xpc_vars_part[partid].IPI_nasid = cpuid_to_nasid(cpuid);
  	xpc_vars_part[partid].IPI_phys_cpuid = cpu_physical_id(cpuid);
  	xpc_vars_part[partid].nchannels = part->nchannels;
  	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) 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 partition 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 */
  
  		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 minimum #of entries? like 4 or 8?
  	for (nentries = ch->local_nentries; nentries > 0; nentries--) {
  
  		nbytes = nentries * ch->msg_size;
  		ch->local_msgqueue = xpc_kzalloc_cacheline_aligned(nbytes,
  						GFP_KERNEL,
  						&ch->local_msgqueue_base);
  		if (ch->local_msgqueue == NULL) {
  			continue;
  		}
  
  		nbytes = nentries * sizeof(struct xpc_notify);
  		ch->notify_queue = kzalloc(nbytes, GFP_KERNEL);
  		if (ch->notify_queue == NULL) {
  			kfree(ch->local_msgqueue_base);
  			ch->local_msgqueue = NULL;
  			continue;
  		}
  
  		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 minimum #of entries? like 4 or 8?
  	for (nentries = ch->remote_nentries; nentries > 0; nentries--) {
  
  		nbytes = nentries * ch->msg_size;
  		ch->remote_msgqueue = xpc_kzalloc_cacheline_aligned(nbytes,
  						GFP_KERNEL,
  						&ch->remote_msgqueue_base);
  		if (ch->remote_msgqueue == NULL) {
  			continue;
  		}
  
  		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;
  	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;
  	}
  
  	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, 0);
  	spin_lock_irqsave(&ch->lock, *irq_flags);
  }
  
  
  /*
   * 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);
  		}
  	}
  }
  
  
  /*
   * 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;
  	}
  }
  
  
  /*
   * 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(1UL << 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_IPI_send_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 */
  		xpc_notify_senders(ch, ch->reason, ch->w_local_GP.put);
  	}
  
  	/* both sides are disconnected now */
  
  	if (ch->flags & XPC_C_DISCONNECTINGCALLOUT_MADE) {
  		spin_unlock_irqrestore(&ch->lock, *irq_flags);
  		xpc_disconnect_callout(ch, xpcDisconnected);
  		spin_lock_irqsave(&ch->lock, *irq_flags);
  	}
  
  	/* it's now safe to free the channel's message queues */
  	xpc_free_msgqueues(ch);
  
  	/* mark disconnected, clear all other flags except XPC_C_WDISCONNECT */
  	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->partid, ch->reason);
  	}
  
  	if (ch->flags & XPC_C_WDISCONNECT) {
  		/* we won't lose the CPU since we're holding ch->lock */
  		complete(&ch->wdisconnect_wait);
  	} else if (ch->delayed_IPI_flags) {
  		if (part->act_state != XPC_P_DEACTIVATING) {
  			/* time to take action on any delayed IPI flags */
  			spin_lock(&part->IPI_lock);
  			XPC_SET_IPI_FLAGS(part->local_IPI_amo, ch->number,
  							ch->delayed_IPI_flags);
  			spin_unlock(&part->IPI_lock);
  		}
  		ch->delayed_IPI_flags = 0;
  	}
  }
  
  
  /*
   * 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);
  
  again:
  
  	if ((ch->flags & XPC_C_DISCONNECTED) &&
  					(ch->flags & XPC_C_WDISCONNECT)) {
  		/*
  		 * Delay processing IPI flags until thread waiting disconnect
  		 * has had a chance to see that the channel is disconnected.
  		 */
  		ch->delayed_IPI_flags |= IPI_flags;
  		spin_unlock_irqrestore(&ch->lock, irq_flags);
  		return;
  	}
  
  
  	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 RCLOSEREQUEST 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);
  			DBUG_ON(!(ch->flags & XPC_C_DISCONNECTED));
  			goto again;
  		}
  
  		if (ch->flags & XPC_C_DISCONNECTED) {
  			if (!(IPI_flags & XPC_IPI_OPENREQUEST)) {
  				if ((XPC_GET_IPI_FLAGS(part->local_IPI_amo,
  					 ch_number) & XPC_IPI_OPENREQUEST)) {
  
  					DBUG_ON(ch->delayed_IPI_flags != 0);
  					spin_lock(&part->IPI_lock);
  					XPC_SET_IPI_FLAGS(part->local_IPI_amo,
  							ch_number,
  							XPC_IPI_CLOSEREQUEST);
  					spin_unlock(&part->IPI_lock);
  				}
  				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);
  
  			DBUG_ON(IPI_flags & XPC_IPI_CLOSEREPLY);
  			spin_unlock_irqrestore(&ch->lock, irq_flags);
  			return;
  		}
  
  		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));
  
  		if (!(ch->flags & XPC_C_RCLOSEREQUEST)) {
  			if ((XPC_GET_IPI_FLAGS(part->local_IPI_amo, ch_number)
  						& XPC_IPI_CLOSEREQUEST)) {
  
  				DBUG_ON(ch->delayed_IPI_flags != 0);
  				spin_lock(&part->IPI_lock);
  				XPC_SET_IPI_FLAGS(part->local_IPI_amo,
  						ch_number, XPC_IPI_CLOSEREPLY);
  				spin_unlock(&part->IPI_lock);
  			}
  			spin_unlock_irqrestore(&ch->lock, irq_flags);
  			return;
  		}
  
  		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 (part->act_state == XPC_P_DEACTIVATING ||
  					(ch->flags & XPC_C_ROPENREQUEST)) {
  			spin_unlock_irqrestore(&ch->lock, irq_flags);
  			return;
  		}
  
  		if (ch->flags & (XPC_C_DISCONNECTING | XPC_C_WDISCONNECT)) {
  			ch->delayed_IPI_flags |= XPC_IPI_OPENREQUEST;
  			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
  		 */
  		if (args->msg_size == 0 || args->local_nentries == 0) {
  			/* assume OPENREQUEST was delayed by mistake */
  			spin_unlock_irqrestore(&ch->lock, irq_flags);
  			return;
  		}
  
  		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;
  		}
  		if (!(ch->flags & XPC_C_OPENREQUEST)) {
  			XPC_DISCONNECT_CHANNEL(ch, xpcOpenCloseError,
  								&irq_flags);
  			spin_unlock_irqrestore(&ch->lock, irq_flags);
  			return;
  		}
  
  		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 (mutex_trylock(&registration->mutex) == 0) {
  		return xpcRetry;
  	}
  
  	if (!XPC_CHANNEL_REGISTERED(ch->number)) {
  		mutex_unlock(&registration->mutex);
  		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);
  		mutex_unlock(&registration->mutex);
  		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.
  			 */
  			mutex_unlock(&registration->mutex);
  			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);
  	}
  
  	mutex_unlock(&registration->mutex);
  
  
  	/* 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;
  }
  
  
  /*
   * 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);
  
  		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);
  
  		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_CONNECTEDCALLOUT_MADE) {
  				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;
  	u32 ch_flags;
  
  
  	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);
  		}
  
  		ch_flags = ch->flags;	/* need an atomic snapshot of 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 is
   * going 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_going_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 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, "
  			"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 = notify;
  	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;
  		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 (mutex_lock_interruptible(&ch->msg_to_pull_mutex) != 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);
  
  			mutex_unlock(&ch->msg_to_pull_mutex);
  			return NULL;
  		}
  
  		mb();	/* >>> this may not be needed, we're not sure */
  
  		ch->next_msg_to_pull += nmsgs;
  	}
  
  	mutex_unlock(&ch->msg_to_pull_mutex);
  
  	/* 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);
  }
  
  