Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1349 insertions, 0 deletions

diff --git a/drivers/misc/sgi-xp/xpc_main.c b/drivers/misc/sgi-xp/xpc_main.c
new file mode 100644
index 000000000..b2c3c22fc
--- /dev/null
+++ b/drivers/misc/sgi-xp/xpc_main.c
@@ -0,0 +1,1349 @@
+/*
+ * 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.
+ *
+ * (C) Copyright 2020 Hewlett Packard Enterprise Development LP
+ * Copyright (c) 2004-2009 Silicon Graphics, Inc.  All Rights Reserved.
+ */
+
+/*
+ * Cross Partition Communication (XPC) support - standard version.
+ *
+ *	XPC provides a message passing capability that crosses partition
+ *	boundaries. This module is made up of two parts:
+ *
+ *	    partition	This part detects the presence/absence of other
+ *			partitions. It provides a heartbeat and monitors
+ *			the heartbeats of other partitions.
+ *
+ *	    channel	This part manages the channels and sends/receives
+ *			messages across them to/from other partitions.
+ *
+ *	There are a couple of additional functions residing in XP, which
+ *	provide an interface to XPC for its users.
+ *
+ *
+ *	Caveats:
+ *
+ *	  . Currently on sn2, we have no way to determine which nasid an IRQ
+ *	    came from. Thus, xpc_send_IRQ_sn2() does a remote amo write
+ *	    followed by an IPI. The amo indicates where data is to be pulled
+ *	    from, so after the IPI arrives, the remote partition checks the amo
+ *	    word. The IPI can actually arrive before the amo however, so other
+ *	    code must periodically check for this case. Also, remote amo
+ *	    operations do not reliably time out. Thus we do a remote PIO read
+ *	    solely to know whether the remote partition is down and whether we
+ *	    should stop sending IPIs to it. This remote PIO read operation is
+ *	    set up in a special nofault region so SAL knows to ignore (and
+ *	    cleanup) any errors due to the remote amo write, PIO read, and/or
+ *	    PIO write operations.
+ *
+ *	    If/when new hardware solves this IPI problem, we should abandon
+ *	    the current approach.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/sysctl.h>
+#include <linux/device.h>
+#include <linux/delay.h>
+#include <linux/reboot.h>
+#include <linux/kdebug.h>
+#include <linux/kthread.h>
+#include "xpc.h"
+
+#ifdef CONFIG_X86_64
+#include <asm/traps.h>
+#endif
+
+/* define two XPC debug device structures to be used with dev_dbg() et al */
+
+static struct device_driver xpc_dbg_name = {
+	.name = "xpc"
+};
+
+static struct device xpc_part_dbg_subname = {
+	.init_name = "",	/* set to "part" at xpc_init() time */
+	.driver = &xpc_dbg_name
+};
+
+static struct device xpc_chan_dbg_subname = {
+	.init_name = "",	/* set to "chan" at xpc_init() time */
+	.driver = &xpc_dbg_name
+};
+
+struct device *xpc_part = &xpc_part_dbg_subname;
+struct device *xpc_chan = &xpc_chan_dbg_subname;
+
+static int xpc_kdebug_ignore;
+
+/* systune related variables for /proc/sys directories */
+
+static int xpc_hb_interval = XPC_HB_DEFAULT_INTERVAL;
+static int xpc_hb_min_interval = 1;
+static int xpc_hb_max_interval = 10;
+
+static int xpc_hb_check_interval = XPC_HB_CHECK_DEFAULT_INTERVAL;
+static int xpc_hb_check_min_interval = 10;
+static int xpc_hb_check_max_interval = 120;
+
+int xpc_disengage_timelimit = XPC_DISENGAGE_DEFAULT_TIMELIMIT;
+static int xpc_disengage_min_timelimit;	/* = 0 */
+static int xpc_disengage_max_timelimit = 120;
+
+static struct ctl_table xpc_sys_xpc_hb_dir[] = {
+	{
+	 .procname = "hb_interval",
+	 .data = &xpc_hb_interval,
+	 .maxlen = sizeof(int),
+	 .mode = 0644,
+	 .proc_handler = proc_dointvec_minmax,
+	 .extra1 = &xpc_hb_min_interval,
+	 .extra2 = &xpc_hb_max_interval},
+	{
+	 .procname = "hb_check_interval",
+	 .data = &xpc_hb_check_interval,
+	 .maxlen = sizeof(int),
+	 .mode = 0644,
+	 .proc_handler = proc_dointvec_minmax,
+	 .extra1 = &xpc_hb_check_min_interval,
+	 .extra2 = &xpc_hb_check_max_interval},
+	{}
+};
+static struct ctl_table xpc_sys_xpc_dir[] = {
+	{
+	 .procname = "hb",
+	 .mode = 0555,
+	 .child = xpc_sys_xpc_hb_dir},
+	{
+	 .procname = "disengage_timelimit",
+	 .data = &xpc_disengage_timelimit,
+	 .maxlen = sizeof(int),
+	 .mode = 0644,
+	 .proc_handler = proc_dointvec_minmax,
+	 .extra1 = &xpc_disengage_min_timelimit,
+	 .extra2 = &xpc_disengage_max_timelimit},
+	{}
+};
+static struct ctl_table xpc_sys_dir[] = {
+	{
+	 .procname = "xpc",
+	 .mode = 0555,
+	 .child = xpc_sys_xpc_dir},
+	{}
+};
+static struct ctl_table_header *xpc_sysctl;
+
+/* non-zero if any remote partition disengage was timed out */
+int xpc_disengage_timedout;
+
+/* #of activate IRQs received and not yet processed */
+int xpc_activate_IRQ_rcvd;
+DEFINE_SPINLOCK(xpc_activate_IRQ_rcvd_lock);
+
+/* IRQ handler notifies this wait queue on receipt of an IRQ */
+DECLARE_WAIT_QUEUE_HEAD(xpc_activate_IRQ_wq);
+
+static unsigned long xpc_hb_check_timeout;
+static struct timer_list xpc_hb_timer;
+
+/* notification that the xpc_hb_checker thread has exited */
+static DECLARE_COMPLETION(xpc_hb_checker_exited);
+
+/* notification that the xpc_discovery thread has exited */
+static DECLARE_COMPLETION(xpc_discovery_exited);
+
+static void xpc_kthread_waitmsgs(struct xpc_partition *, struct xpc_channel *);
+
+static int xpc_system_reboot(struct notifier_block *, unsigned long, void *);
+static struct notifier_block xpc_reboot_notifier = {
+	.notifier_call = xpc_system_reboot,
+};
+
+static int xpc_system_die(struct notifier_block *, unsigned long, void *);
+static struct notifier_block xpc_die_notifier = {
+	.notifier_call = xpc_system_die,
+};
+
+struct xpc_arch_operations xpc_arch_ops;
+
+/*
+ * Timer function to enforce the timelimit on the partition disengage.
+ */
+static void
+xpc_timeout_partition_disengage(struct timer_list *t)
+{
+	struct xpc_partition *part = from_timer(part, t, disengage_timer);
+
+	DBUG_ON(time_is_after_jiffies(part->disengage_timeout));
+
+	xpc_partition_disengaged_from_timer(part);
+
+	DBUG_ON(part->disengage_timeout != 0);
+	DBUG_ON(xpc_arch_ops.partition_engaged(XPC_PARTID(part)));
+}
+
+/*
+ * Timer to produce the heartbeat.  The timer structures function is
+ * already set when this is initially called.  A tunable is used to
+ * specify when the next timeout should occur.
+ */
+static void
+xpc_hb_beater(struct timer_list *unused)
+{
+	xpc_arch_ops.increment_heartbeat();
+
+	if (time_is_before_eq_jiffies(xpc_hb_check_timeout))
+		wake_up_interruptible(&xpc_activate_IRQ_wq);
+
+	xpc_hb_timer.expires = jiffies + (xpc_hb_interval * HZ);
+	add_timer(&xpc_hb_timer);
+}
+
+static void
+xpc_start_hb_beater(void)
+{
+	xpc_arch_ops.heartbeat_init();
+	timer_setup(&xpc_hb_timer, xpc_hb_beater, 0);
+	xpc_hb_beater(NULL);
+}
+
+static void
+xpc_stop_hb_beater(void)
+{
+	del_timer_sync(&xpc_hb_timer);
+	xpc_arch_ops.heartbeat_exit();
+}
+
+/*
+ * At periodic intervals, scan through all active partitions and ensure
+ * their heartbeat is still active.  If not, the partition is deactivated.
+ */
+static void
+xpc_check_remote_hb(void)
+{
+	struct xpc_partition *part;
+	short partid;
+	enum xp_retval ret;
+
+	for (partid = 0; partid < xp_max_npartitions; partid++) {
+
+		if (xpc_exiting)
+			break;
+
+		if (partid == xp_partition_id)
+			continue;
+
+		part = &xpc_partitions[partid];
+
+		if (part->act_state == XPC_P_AS_INACTIVE ||
+		    part->act_state == XPC_P_AS_DEACTIVATING) {
+			continue;
+		}
+
+		ret = xpc_arch_ops.get_remote_heartbeat(part);
+		if (ret != xpSuccess)
+			XPC_DEACTIVATE_PARTITION(part, ret);
+	}
+}
+
+/*
+ * This thread is responsible for nearly all of the partition
+ * activation/deactivation.
+ */
+static int
+xpc_hb_checker(void *ignore)
+{
+	int force_IRQ = 0;
+
+	/* this thread was marked active by xpc_hb_init() */
+
+	set_cpus_allowed_ptr(current, cpumask_of(XPC_HB_CHECK_CPU));
+
+	/* set our heartbeating to other partitions into motion */
+	xpc_hb_check_timeout = jiffies + (xpc_hb_check_interval * HZ);
+	xpc_start_hb_beater();
+
+	while (!xpc_exiting) {
+
+		dev_dbg(xpc_part, "woke up with %d ticks rem; %d IRQs have "
+			"been received\n",
+			(int)(xpc_hb_check_timeout - jiffies),
+			xpc_activate_IRQ_rcvd);
+
+		/* checking of remote heartbeats is skewed by IRQ handling */
+		if (time_is_before_eq_jiffies(xpc_hb_check_timeout)) {
+			xpc_hb_check_timeout = jiffies +
+			    (xpc_hb_check_interval * HZ);
+
+			dev_dbg(xpc_part, "checking remote heartbeats\n");
+			xpc_check_remote_hb();
+		}
+
+		/* check for outstanding IRQs */
+		if (xpc_activate_IRQ_rcvd > 0 || force_IRQ != 0) {
+			force_IRQ = 0;
+			dev_dbg(xpc_part, "processing activate IRQs "
+				"received\n");
+			xpc_arch_ops.process_activate_IRQ_rcvd();
+		}
+
+		/* wait for IRQ or timeout */
+		(void)wait_event_interruptible(xpc_activate_IRQ_wq,
+					       (time_is_before_eq_jiffies(
+						xpc_hb_check_timeout) ||
+						xpc_activate_IRQ_rcvd > 0 ||
+						xpc_exiting));
+	}
+
+	xpc_stop_hb_beater();
+
+	dev_dbg(xpc_part, "heartbeat checker is exiting\n");
+
+	/* mark this thread as having exited */
+	complete(&xpc_hb_checker_exited);
+	return 0;
+}
+
+/*
+ * This thread will attempt to discover other partitions to activate
+ * based on info provided by SAL. This new thread is short lived and
+ * will exit once discovery is complete.
+ */
+static int
+xpc_initiate_discovery(void *ignore)
+{
+	xpc_discovery();
+
+	dev_dbg(xpc_part, "discovery thread is exiting\n");
+
+	/* mark this thread as having exited */
+	complete(&xpc_discovery_exited);
+	return 0;
+}
+
+/*
+ * The first kthread assigned to a newly activated partition is the one
+ * created by XPC HB with which it calls xpc_activating(). XPC hangs on to
+ * that kthread until the partition is brought down, at which time that kthread
+ * returns back to XPC HB. (The return of that kthread will signify to XPC HB
+ * that XPC has dismantled all communication infrastructure for the associated
+ * partition.) This kthread becomes the channel manager for that partition.
+ *
+ * Each active partition has a channel manager, who, besides connecting and
+ * disconnecting channels, will ensure that each of the partition's connected
+ * channels has the required number of assigned kthreads to get the work done.
+ */
+static void
+xpc_channel_mgr(struct xpc_partition *part)
+{
+	while (part->act_state != XPC_P_AS_DEACTIVATING ||
+	       atomic_read(&part->nchannels_active) > 0 ||
+	       !xpc_partition_disengaged(part)) {
+
+		xpc_process_sent_chctl_flags(part);
+
+		/*
+		 * Wait until we've been requested to activate kthreads or
+		 * all of the channel's message queues have been torn down or
+		 * a signal is pending.
+		 *
+		 * The channel_mgr_requests is set to 1 after being awakened,
+		 * This is done to prevent the channel mgr from making one pass
+		 * through the loop for each request, since he will
+		 * be servicing all the requests in one pass. The reason it's
+		 * set to 1 instead of 0 is so that other kthreads will know
+		 * that the channel mgr is running and won't bother trying to
+		 * wake him up.
+		 */
+		atomic_dec(&part->channel_mgr_requests);
+		(void)wait_event_interruptible(part->channel_mgr_wq,
+				(atomic_read(&part->channel_mgr_requests) > 0 ||
+				 part->chctl.all_flags != 0 ||
+				 (part->act_state == XPC_P_AS_DEACTIVATING &&
+				 atomic_read(&part->nchannels_active) == 0 &&
+				 xpc_partition_disengaged(part))));
+		atomic_set(&part->channel_mgr_requests, 1);
+	}
+}
+
+/*
+ * Guarantee that the kzalloc'd memory is cacheline aligned.
+ */
+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);
+}
+
+/*
+ * Setup the channel structures necessary to support XPartition Communication
+ * between the specified remote partition and the local one.
+ */
+static enum xp_retval
+xpc_setup_ch_structures(struct xpc_partition *part)
+{
+	enum xp_retval ret;
+	int ch_number;
+	struct xpc_channel *ch;
+	short partid = XPC_PARTID(part);
+
+	/*
+	 * Allocate all of the channel structures as a contiguous chunk of
+	 * memory.
+	 */
+	DBUG_ON(part->channels != NULL);
+	part->channels = kcalloc(XPC_MAX_NCHANNELS,
+				 sizeof(struct xpc_channel),
+				 GFP_KERNEL);
+	if (part->channels == NULL) {
+		dev_err(xpc_chan, "can't get memory for channels\n");
+		return xpNoMemory;
+	}
+
+	/* allocate the remote open and close args */
+
+	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");
+		ret = xpNoMemory;
+		goto out_1;
+	}
+
+	part->chctl.all_flags = 0;
+	spin_lock_init(&part->chctl_lock);
+
+	atomic_set(&part->channel_mgr_requests, 1);
+	init_waitqueue_head(&part->channel_mgr_wq);
+
+	part->nchannels = XPC_MAX_NCHANNELS;
+
+	atomic_set(&part->nchannels_active, 0);
+	atomic_set(&part->nchannels_engaged, 0);
+
+	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;
+
+		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);
+		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);
+	}
+
+	ret = xpc_arch_ops.setup_ch_structures(part);
+	if (ret != xpSuccess)
+		goto out_2;
+
+	/*
+	 * With the setting of the partition setup_state to XPC_P_SS_SETUP,
+	 * we're declaring that this partition is ready to go.
+	 */
+	part->setup_state = XPC_P_SS_SETUP;
+
+	return xpSuccess;
+
+	/* setup of ch structures failed */
+out_2:
+	kfree(part->remote_openclose_args_base);
+	part->remote_openclose_args = NULL;
+out_1:
+	kfree(part->channels);
+	part->channels = NULL;
+	return ret;
+}
+
+/*
+ * Teardown the channel structures necessary to support XPartition Communication
+ * between the specified remote partition and the local one.
+ */
+static void
+xpc_teardown_ch_structures(struct xpc_partition *part)
+{
+	DBUG_ON(atomic_read(&part->nchannels_engaged) != 0);
+	DBUG_ON(atomic_read(&part->nchannels_active) != 0);
+
+	/*
+	 * Make this partition inaccessible to local processes by marking it
+	 * as no longer setup. Then wait before proceeding with the teardown
+	 * until all existing references cease.
+	 */
+	DBUG_ON(part->setup_state != XPC_P_SS_SETUP);
+	part->setup_state = XPC_P_SS_WTEARDOWN;
+
+	wait_event(part->teardown_wq, (atomic_read(&part->references) == 0));
+
+	/* now we can begin tearing down the infrastructure */
+
+	xpc_arch_ops.teardown_ch_structures(part);
+
+	kfree(part->remote_openclose_args_base);
+	part->remote_openclose_args = NULL;
+	kfree(part->channels);
+	part->channels = NULL;
+
+	part->setup_state = XPC_P_SS_TORNDOWN;
+}
+
+/*
+ * When XPC HB determines that a partition has come up, it will create a new
+ * kthread and that kthread will call this function to attempt to set up the
+ * basic infrastructure used for Cross Partition Communication with the newly
+ * upped partition.
+ *
+ * The kthread that was created by XPC HB and which setup the XPC
+ * infrastructure will remain assigned to the partition becoming the channel
+ * manager for that partition until the partition is deactivating, at which
+ * time the kthread will teardown the XPC infrastructure and then exit.
+ */
+static int
+xpc_activating(void *__partid)
+{
+	short partid = (u64)__partid;
+	struct xpc_partition *part = &xpc_partitions[partid];
+	unsigned long irq_flags;
+
+	DBUG_ON(partid < 0 || partid >= xp_max_npartitions);
+
+	spin_lock_irqsave(&part->act_lock, irq_flags);
+
+	if (part->act_state == XPC_P_AS_DEACTIVATING) {
+		part->act_state = XPC_P_AS_INACTIVE;
+		spin_unlock_irqrestore(&part->act_lock, irq_flags);
+		part->remote_rp_pa = 0;
+		return 0;
+	}
+
+	/* indicate the thread is activating */
+	DBUG_ON(part->act_state != XPC_P_AS_ACTIVATION_REQ);
+	part->act_state = XPC_P_AS_ACTIVATING;
+
+	XPC_SET_REASON(part, 0, 0);
+	spin_unlock_irqrestore(&part->act_lock, irq_flags);
+
+	dev_dbg(xpc_part, "activating partition %d\n", partid);
+
+	xpc_arch_ops.allow_hb(partid);
+
+	if (xpc_setup_ch_structures(part) == xpSuccess) {
+		(void)xpc_part_ref(part);	/* this will always succeed */
+
+		if (xpc_arch_ops.make_first_contact(part) == xpSuccess) {
+			xpc_mark_partition_active(part);
+			xpc_channel_mgr(part);
+			/* won't return until partition is deactivating */
+		}
+
+		xpc_part_deref(part);
+		xpc_teardown_ch_structures(part);
+	}
+
+	xpc_arch_ops.disallow_hb(partid);
+	xpc_mark_partition_inactive(part);
+
+	if (part->reason == xpReactivating) {
+		/* interrupting ourselves results in activating partition */
+		xpc_arch_ops.request_partition_reactivation(part);
+	}
+
+	return 0;
+}
+
+void
+xpc_activate_partition(struct xpc_partition *part)
+{
+	short partid = XPC_PARTID(part);
+	unsigned long irq_flags;
+	struct task_struct *kthread;
+
+	spin_lock_irqsave(&part->act_lock, irq_flags);
+
+	DBUG_ON(part->act_state != XPC_P_AS_INACTIVE);
+
+	part->act_state = XPC_P_AS_ACTIVATION_REQ;
+	XPC_SET_REASON(part, xpCloneKThread, __LINE__);
+
+	spin_unlock_irqrestore(&part->act_lock, irq_flags);
+
+	kthread = kthread_run(xpc_activating, (void *)((u64)partid), "xpc%02d",
+			      partid);
+	if (IS_ERR(kthread)) {
+		spin_lock_irqsave(&part->act_lock, irq_flags);
+		part->act_state = XPC_P_AS_INACTIVE;
+		XPC_SET_REASON(part, xpCloneKThreadFailed, __LINE__);
+		spin_unlock_irqrestore(&part->act_lock, irq_flags);
+	}
+}
+
+void
+xpc_activate_kthreads(struct xpc_channel *ch, int needed)
+{
+	int idle = atomic_read(&ch->kthreads_idle);
+	int assigned = atomic_read(&ch->kthreads_assigned);
+	int wakeup;
+
+	DBUG_ON(needed <= 0);
+
+	if (idle > 0) {
+		wakeup = (needed > idle) ? idle : needed;
+		needed -= wakeup;
+
+		dev_dbg(xpc_chan, "wakeup %d idle kthreads, partid=%d, "
+			"channel=%d\n", wakeup, ch->partid, ch->number);
+
+		/* only wakeup the requested number of kthreads */
+		wake_up_nr(&ch->idle_wq, wakeup);
+	}
+
+	if (needed <= 0)
+		return;
+
+	if (needed + assigned > ch->kthreads_assigned_limit) {
+		needed = ch->kthreads_assigned_limit - assigned;
+		if (needed <= 0)
+			return;
+	}
+
+	dev_dbg(xpc_chan, "create %d new kthreads, partid=%d, channel=%d\n",
+		needed, ch->partid, ch->number);
+
+	xpc_create_kthreads(ch, needed, 0);
+}
+
+/*
+ * This function is where XPC's kthreads wait for messages to deliver.
+ */
+static void
+xpc_kthread_waitmsgs(struct xpc_partition *part, struct xpc_channel *ch)
+{
+	int (*n_of_deliverable_payloads) (struct xpc_channel *) =
+		xpc_arch_ops.n_of_deliverable_payloads;
+
+	do {
+		/* deliver messages to their intended recipients */
+
+		while (n_of_deliverable_payloads(ch) > 0 &&
+		       !(ch->flags & XPC_C_DISCONNECTING)) {
+			xpc_deliver_payload(ch);
+		}
+
+		if (atomic_inc_return(&ch->kthreads_idle) >
+		    ch->kthreads_idle_limit) {
+			/* too many idle kthreads on this channel */
+			atomic_dec(&ch->kthreads_idle);
+			break;
+		}
+
+		dev_dbg(xpc_chan, "idle kthread calling "
+			"wait_event_interruptible_exclusive()\n");
+
+		(void)wait_event_interruptible_exclusive(ch->idle_wq,
+				(n_of_deliverable_payloads(ch) > 0 ||
+				 (ch->flags & XPC_C_DISCONNECTING)));
+
+		atomic_dec(&ch->kthreads_idle);
+
+	} while (!(ch->flags & XPC_C_DISCONNECTING));
+}
+
+static int
+xpc_kthread_start(void *args)
+{
+	short partid = XPC_UNPACK_ARG1(args);
+	u16 ch_number = XPC_UNPACK_ARG2(args);
+	struct xpc_partition *part = &xpc_partitions[partid];
+	struct xpc_channel *ch;
+	int n_needed;
+	unsigned long irq_flags;
+	int (*n_of_deliverable_payloads) (struct xpc_channel *) =
+		xpc_arch_ops.n_of_deliverable_payloads;
+
+	dev_dbg(xpc_chan, "kthread starting, partid=%d, channel=%d\n",
+		partid, ch_number);
+
+	ch = &part->channels[ch_number];
+
+	if (!(ch->flags & XPC_C_DISCONNECTING)) {
+
+		/* let registerer know that connection has been established */
+
+		spin_lock_irqsave(&ch->lock, irq_flags);
+		if (!(ch->flags & XPC_C_CONNECTEDCALLOUT)) {
+			ch->flags |= XPC_C_CONNECTEDCALLOUT;
+			spin_unlock_irqrestore(&ch->lock, irq_flags);
+
+			xpc_connected_callout(ch);
+
+			spin_lock_irqsave(&ch->lock, irq_flags);
+			ch->flags |= XPC_C_CONNECTEDCALLOUT_MADE;
+			spin_unlock_irqrestore(&ch->lock, irq_flags);
+
+			/*
+			 * It is possible that while the callout was being
+			 * made that the remote partition sent some messages.
+			 * If that is the case, we may need to activate
+			 * additional kthreads to help deliver them. We only
+			 * need one less than total #of messages to deliver.
+			 */
+			n_needed = n_of_deliverable_payloads(ch) - 1;
+			if (n_needed > 0 && !(ch->flags & XPC_C_DISCONNECTING))
+				xpc_activate_kthreads(ch, n_needed);
+
+		} else {
+			spin_unlock_irqrestore(&ch->lock, irq_flags);
+		}
+
+		xpc_kthread_waitmsgs(part, ch);
+	}
+
+	/* let registerer know that connection is disconnecting */
+
+	spin_lock_irqsave(&ch->lock, irq_flags);
+	if ((ch->flags & XPC_C_CONNECTEDCALLOUT_MADE) &&
+	    !(ch->flags & XPC_C_DISCONNECTINGCALLOUT)) {
+		ch->flags |= XPC_C_DISCONNECTINGCALLOUT;
+		spin_unlock_irqrestore(&ch->lock, irq_flags);
+
+		xpc_disconnect_callout(ch, xpDisconnecting);
+
+		spin_lock_irqsave(&ch->lock, irq_flags);
+		ch->flags |= XPC_C_DISCONNECTINGCALLOUT_MADE;
+	}
+	spin_unlock_irqrestore(&ch->lock, irq_flags);
+
+	if (atomic_dec_return(&ch->kthreads_assigned) == 0 &&
+	    atomic_dec_return(&part->nchannels_engaged) == 0) {
+		xpc_arch_ops.indicate_partition_disengaged(part);
+	}
+
+	xpc_msgqueue_deref(ch);
+
+	dev_dbg(xpc_chan, "kthread exiting, partid=%d, channel=%d\n",
+		partid, ch_number);
+
+	xpc_part_deref(part);
+	return 0;
+}
+
+/*
+ * For each partition that XPC has established communications with, there is
+ * a minimum of one kernel thread assigned to perform any operation that
+ * may potentially sleep or block (basically the callouts to the asynchronous
+ * functions registered via xpc_connect()).
+ *
+ * Additional kthreads are created and destroyed by XPC as the workload
+ * demands.
+ *
+ * A kthread is assigned to one of the active channels that exists for a given
+ * partition.
+ */
+void
+xpc_create_kthreads(struct xpc_channel *ch, int needed,
+		    int ignore_disconnecting)
+{
+	unsigned long irq_flags;
+	u64 args = XPC_PACK_ARGS(ch->partid, ch->number);
+	struct xpc_partition *part = &xpc_partitions[ch->partid];
+	struct task_struct *kthread;
+	void (*indicate_partition_disengaged) (struct xpc_partition *) =
+		xpc_arch_ops.indicate_partition_disengaged;
+
+	while (needed-- > 0) {
+
+		/*
+		 * The following is done on behalf of the newly created
+		 * kthread. That kthread is responsible for doing the
+		 * counterpart to the following before it exits.
+		 */
+		if (ignore_disconnecting) {
+			if (!atomic_inc_not_zero(&ch->kthreads_assigned)) {
+				/* kthreads assigned had gone to zero */
+				BUG_ON(!(ch->flags &
+					 XPC_C_DISCONNECTINGCALLOUT_MADE));
+				break;
+			}
+
+		} else if (ch->flags & XPC_C_DISCONNECTING) {
+			break;
+
+		} else if (atomic_inc_return(&ch->kthreads_assigned) == 1 &&
+			   atomic_inc_return(&part->nchannels_engaged) == 1) {
+			xpc_arch_ops.indicate_partition_engaged(part);
+		}
+		(void)xpc_part_ref(part);
+		xpc_msgqueue_ref(ch);
+
+		kthread = kthread_run(xpc_kthread_start, (void *)args,
+				      "xpc%02dc%d", ch->partid, ch->number);
+		if (IS_ERR(kthread)) {
+			/* the fork failed */
+
+			/*
+			 * NOTE: if (ignore_disconnecting &&
+			 * !(ch->flags & XPC_C_DISCONNECTINGCALLOUT)) is true,
+			 * then we'll deadlock if all other kthreads assigned
+			 * to this channel are blocked in the channel's
+			 * registerer, because the only thing that will unblock
+			 * them is the xpDisconnecting callout that this
+			 * failed kthread_run() would have made.
+			 */
+
+			if (atomic_dec_return(&ch->kthreads_assigned) == 0 &&
+			    atomic_dec_return(&part->nchannels_engaged) == 0) {
+				indicate_partition_disengaged(part);
+			}
+			xpc_msgqueue_deref(ch);
+			xpc_part_deref(part);
+
+			if (atomic_read(&ch->kthreads_assigned) <
+			    ch->kthreads_idle_limit) {
+				/*
+				 * Flag this as an error only if we have an
+				 * insufficient #of kthreads for the channel
+				 * to function.
+				 */
+				spin_lock_irqsave(&ch->lock, irq_flags);
+				XPC_DISCONNECT_CHANNEL(ch, xpLackOfResources,
+						       &irq_flags);
+				spin_unlock_irqrestore(&ch->lock, irq_flags);
+			}
+			break;
+		}
+	}
+}
+
+void
+xpc_disconnect_wait(int ch_number)
+{
+	unsigned long irq_flags;
+	short partid;
+	struct xpc_partition *part;
+	struct xpc_channel *ch;
+	int wakeup_channel_mgr;
+
+	/* now wait for all callouts to the caller's function to cease */
+	for (partid = 0; partid < xp_max_npartitions; partid++) {
+		part = &xpc_partitions[partid];
+
+		if (!xpc_part_ref(part))
+			continue;
+
+		ch = &part->channels[ch_number];
+
+		if (!(ch->flags & XPC_C_WDISCONNECT)) {
+			xpc_part_deref(part);
+			continue;
+		}
+
+		wait_for_completion(&ch->wdisconnect_wait);
+
+		spin_lock_irqsave(&ch->lock, irq_flags);
+		DBUG_ON(!(ch->flags & XPC_C_DISCONNECTED));
+		wakeup_channel_mgr = 0;
+
+		if (ch->delayed_chctl_flags) {
+			if (part->act_state != XPC_P_AS_DEACTIVATING) {
+				spin_lock(&part->chctl_lock);
+				part->chctl.flags[ch->number] |=
+				    ch->delayed_chctl_flags;
+				spin_unlock(&part->chctl_lock);
+				wakeup_channel_mgr = 1;
+			}
+			ch->delayed_chctl_flags = 0;
+		}
+
+		ch->flags &= ~XPC_C_WDISCONNECT;
+		spin_unlock_irqrestore(&ch->lock, irq_flags);
+
+		if (wakeup_channel_mgr)
+			xpc_wakeup_channel_mgr(part);
+
+		xpc_part_deref(part);
+	}
+}
+
+static int
+xpc_setup_partitions(void)
+{
+	short partid;
+	struct xpc_partition *part;
+
+	xpc_partitions = kcalloc(xp_max_npartitions,
+				 sizeof(struct xpc_partition),
+				 GFP_KERNEL);
+	if (xpc_partitions == NULL) {
+		dev_err(xpc_part, "can't get memory for partition structure\n");
+		return -ENOMEM;
+	}
+
+	/*
+	 * The first few fields of each entry of xpc_partitions[] need to
+	 * be initialized now so that calls to xpc_connect() and
+	 * xpc_disconnect() can be made prior to the activation of any remote
+	 * partition. NOTE THAT NONE OF THE OTHER FIELDS BELONGING TO THESE
+	 * ENTRIES ARE MEANINGFUL UNTIL AFTER AN ENTRY'S CORRESPONDING
+	 * PARTITION HAS BEEN ACTIVATED.
+	 */
+	for (partid = 0; partid < xp_max_npartitions; partid++) {
+		part = &xpc_partitions[partid];
+
+		DBUG_ON((u64)part != L1_CACHE_ALIGN((u64)part));
+
+		part->activate_IRQ_rcvd = 0;
+		spin_lock_init(&part->act_lock);
+		part->act_state = XPC_P_AS_INACTIVE;
+		XPC_SET_REASON(part, 0, 0);
+
+		timer_setup(&part->disengage_timer,
+			    xpc_timeout_partition_disengage, 0);
+
+		part->setup_state = XPC_P_SS_UNSET;
+		init_waitqueue_head(&part->teardown_wq);
+		atomic_set(&part->references, 0);
+	}
+
+	return xpc_arch_ops.setup_partitions();
+}
+
+static void
+xpc_teardown_partitions(void)
+{
+	xpc_arch_ops.teardown_partitions();
+	kfree(xpc_partitions);
+}
+
+static void
+xpc_do_exit(enum xp_retval reason)
+{
+	short partid;
+	int active_part_count, printed_waiting_msg = 0;
+	struct xpc_partition *part;
+	unsigned long printmsg_time, disengage_timeout = 0;
+
+	/* a 'rmmod XPC' and a 'reboot' cannot both end up here together */
+	DBUG_ON(xpc_exiting == 1);
+
+	/*
+	 * Let the heartbeat checker thread and the discovery thread
+	 * (if one is running) know that they should exit. Also wake up
+	 * the heartbeat checker thread in case it's sleeping.
+	 */
+	xpc_exiting = 1;
+	wake_up_interruptible(&xpc_activate_IRQ_wq);
+
+	/* wait for the discovery thread to exit */
+	wait_for_completion(&xpc_discovery_exited);
+
+	/* wait for the heartbeat checker thread to exit */
+	wait_for_completion(&xpc_hb_checker_exited);
+
+	/* sleep for a 1/3 of a second or so */
+	(void)msleep_interruptible(300);
+
+	/* wait for all partitions to become inactive */
+
+	printmsg_time = jiffies + (XPC_DEACTIVATE_PRINTMSG_INTERVAL * HZ);
+	xpc_disengage_timedout = 0;
+
+	do {
+		active_part_count = 0;
+
+		for (partid = 0; partid < xp_max_npartitions; partid++) {
+			part = &xpc_partitions[partid];
+
+			if (xpc_partition_disengaged(part) &&
+			    part->act_state == XPC_P_AS_INACTIVE) {
+				continue;
+			}
+
+			active_part_count++;
+
+			XPC_DEACTIVATE_PARTITION(part, reason);
+
+			if (part->disengage_timeout > disengage_timeout)
+				disengage_timeout = part->disengage_timeout;
+		}
+
+		if (xpc_arch_ops.any_partition_engaged()) {
+			if (time_is_before_jiffies(printmsg_time)) {
+				dev_info(xpc_part, "waiting for remote "
+					 "partitions to deactivate, timeout in "
+					 "%ld seconds\n", (disengage_timeout -
+					 jiffies) / HZ);
+				printmsg_time = jiffies +
+				    (XPC_DEACTIVATE_PRINTMSG_INTERVAL * HZ);
+				printed_waiting_msg = 1;
+			}
+
+		} else if (active_part_count > 0) {
+			if (printed_waiting_msg) {
+				dev_info(xpc_part, "waiting for local partition"
+					 " to deactivate\n");
+				printed_waiting_msg = 0;
+			}
+
+		} else {
+			if (!xpc_disengage_timedout) {
+				dev_info(xpc_part, "all partitions have "
+					 "deactivated\n");
+			}
+			break;
+		}
+
+		/* sleep for a 1/3 of a second or so */
+		(void)msleep_interruptible(300);
+
+	} while (1);
+
+	DBUG_ON(xpc_arch_ops.any_partition_engaged());
+
+	xpc_teardown_rsvd_page();
+
+	if (reason == xpUnloading) {
+		(void)unregister_die_notifier(&xpc_die_notifier);
+		(void)unregister_reboot_notifier(&xpc_reboot_notifier);
+	}
+
+	/* clear the interface to XPC's functions */
+	xpc_clear_interface();
+
+	if (xpc_sysctl)
+		unregister_sysctl_table(xpc_sysctl);
+
+	xpc_teardown_partitions();
+
+	if (is_uv_system())
+		xpc_exit_uv();
+}
+
+/*
+ * This function is called when the system is being rebooted.
+ */
+static int
+xpc_system_reboot(struct notifier_block *nb, unsigned long event, void *unused)
+{
+	enum xp_retval reason;
+
+	switch (event) {
+	case SYS_RESTART:
+		reason = xpSystemReboot;
+		break;
+	case SYS_HALT:
+		reason = xpSystemHalt;
+		break;
+	case SYS_POWER_OFF:
+		reason = xpSystemPoweroff;
+		break;
+	default:
+		reason = xpSystemGoingDown;
+	}
+
+	xpc_do_exit(reason);
+	return NOTIFY_DONE;
+}
+
+/* Used to only allow one cpu to complete disconnect */
+static unsigned int xpc_die_disconnecting;
+
+/*
+ * Notify other partitions to deactivate from us by first disengaging from all
+ * references to our memory.
+ */
+static void
+xpc_die_deactivate(void)
+{
+	struct xpc_partition *part;
+	short partid;
+	int any_engaged;
+	long keep_waiting;
+	long wait_to_print;
+
+	if (cmpxchg(&xpc_die_disconnecting, 0, 1))
+		return;
+
+	/* keep xpc_hb_checker thread from doing anything (just in case) */
+	xpc_exiting = 1;
+
+	xpc_arch_ops.disallow_all_hbs();   /*indicate we're deactivated */
+
+	for (partid = 0; partid < xp_max_npartitions; partid++) {
+		part = &xpc_partitions[partid];
+
+		if (xpc_arch_ops.partition_engaged(partid) ||
+		    part->act_state != XPC_P_AS_INACTIVE) {
+			xpc_arch_ops.request_partition_deactivation(part);
+			xpc_arch_ops.indicate_partition_disengaged(part);
+		}
+	}
+
+	/*
+	 * Though we requested that all other partitions deactivate from us,
+	 * we only wait until they've all disengaged or we've reached the
+	 * defined timelimit.
+	 *
+	 * Given that one iteration through the following while-loop takes
+	 * approximately 200 microseconds, calculate the #of loops to take
+	 * before bailing and the #of loops before printing a waiting message.
+	 */
+	keep_waiting = xpc_disengage_timelimit * 1000 * 5;
+	wait_to_print = XPC_DEACTIVATE_PRINTMSG_INTERVAL * 1000 * 5;
+
+	while (1) {
+		any_engaged = xpc_arch_ops.any_partition_engaged();
+		if (!any_engaged) {
+			dev_info(xpc_part, "all partitions have deactivated\n");
+			break;
+		}
+
+		if (!keep_waiting--) {
+			for (partid = 0; partid < xp_max_npartitions;
+			     partid++) {
+				if (xpc_arch_ops.partition_engaged(partid)) {
+					dev_info(xpc_part, "deactivate from "
+						 "remote partition %d timed "
+						 "out\n", partid);
+				}
+			}
+			break;
+		}
+
+		if (!wait_to_print--) {
+			dev_info(xpc_part, "waiting for remote partitions to "
+				 "deactivate, timeout in %ld seconds\n",
+				 keep_waiting / (1000 * 5));
+			wait_to_print = XPC_DEACTIVATE_PRINTMSG_INTERVAL *
+			    1000 * 5;
+		}
+
+		udelay(200);
+	}
+}
+
+/*
+ * This function is called when the system is being restarted or halted due
+ * to some sort of system failure. If this is the case we need to notify the
+ * other partitions to disengage from all references to our memory.
+ * This function can also be called when our heartbeater could be offlined
+ * for a time. In this case we need to notify other partitions to not worry
+ * about the lack of a heartbeat.
+ */
+static int
+xpc_system_die(struct notifier_block *nb, unsigned long event, void *_die_args)
+{
+#ifdef CONFIG_IA64		/* !!! temporary kludge */
+	switch (event) {
+	case DIE_MACHINE_RESTART:
+	case DIE_MACHINE_HALT:
+		xpc_die_deactivate();
+		break;
+
+	case DIE_KDEBUG_ENTER:
+		/* Should lack of heartbeat be ignored by other partitions? */
+		if (!xpc_kdebug_ignore)
+			break;
+
+		fallthrough;
+	case DIE_MCA_MONARCH_ENTER:
+	case DIE_INIT_MONARCH_ENTER:
+		xpc_arch_ops.offline_heartbeat();
+		break;
+
+	case DIE_KDEBUG_LEAVE:
+		/* Is lack of heartbeat being ignored by other partitions? */
+		if (!xpc_kdebug_ignore)
+			break;
+
+		fallthrough;
+	case DIE_MCA_MONARCH_LEAVE:
+	case DIE_INIT_MONARCH_LEAVE:
+		xpc_arch_ops.online_heartbeat();
+		break;
+	}
+#else
+	struct die_args *die_args = _die_args;
+
+	switch (event) {
+	case DIE_TRAP:
+		if (die_args->trapnr == X86_TRAP_DF)
+			xpc_die_deactivate();
+
+		if (((die_args->trapnr == X86_TRAP_MF) ||
+		     (die_args->trapnr == X86_TRAP_XF)) &&
+		    !user_mode(die_args->regs))
+			xpc_die_deactivate();
+
+		break;
+	case DIE_INT3:
+	case DIE_DEBUG:
+		break;
+	case DIE_OOPS:
+	case DIE_GPF:
+	default:
+		xpc_die_deactivate();
+	}
+#endif
+
+	return NOTIFY_DONE;
+}
+
+static int __init
+xpc_init(void)
+{
+	int ret;
+	struct task_struct *kthread;
+
+	dev_set_name(xpc_part, "part");
+	dev_set_name(xpc_chan, "chan");
+
+	if (is_uv_system()) {
+		ret = xpc_init_uv();
+
+	} else {
+		ret = -ENODEV;
+	}
+
+	if (ret != 0)
+		return ret;
+
+	ret = xpc_setup_partitions();
+	if (ret != 0) {
+		dev_err(xpc_part, "can't get memory for partition structure\n");
+		goto out_1;
+	}
+
+	xpc_sysctl = register_sysctl_table(xpc_sys_dir);
+
+	/*
+	 * Fill the partition reserved page with the information needed by
+	 * other partitions to discover we are alive and establish initial
+	 * communications.
+	 */
+	ret = xpc_setup_rsvd_page();
+	if (ret != 0) {
+		dev_err(xpc_part, "can't setup our reserved page\n");
+		goto out_2;
+	}
+
+	/* add ourselves to the reboot_notifier_list */
+	ret = register_reboot_notifier(&xpc_reboot_notifier);
+	if (ret != 0)
+		dev_warn(xpc_part, "can't register reboot notifier\n");
+
+	/* add ourselves to the die_notifier list */
+	ret = register_die_notifier(&xpc_die_notifier);
+	if (ret != 0)
+		dev_warn(xpc_part, "can't register die notifier\n");
+
+	/*
+	 * The real work-horse behind xpc.  This processes incoming
+	 * interrupts and monitors remote heartbeats.
+	 */
+	kthread = kthread_run(xpc_hb_checker, NULL, XPC_HB_CHECK_THREAD_NAME);
+	if (IS_ERR(kthread)) {
+		dev_err(xpc_part, "failed while forking hb check thread\n");
+		ret = -EBUSY;
+		goto out_3;
+	}
+
+	/*
+	 * Startup a thread that will attempt to discover other partitions to
+	 * activate based on info provided by SAL. This new thread is short
+	 * lived and will exit once discovery is complete.
+	 */
+	kthread = kthread_run(xpc_initiate_discovery, NULL,
+			      XPC_DISCOVERY_THREAD_NAME);
+	if (IS_ERR(kthread)) {
+		dev_err(xpc_part, "failed while forking discovery thread\n");
+
+		/* mark this new thread as a non-starter */
+		complete(&xpc_discovery_exited);
+
+		xpc_do_exit(xpUnloading);
+		return -EBUSY;
+	}
+
+	/* set the interface to point at XPC's functions */
+	xpc_set_interface(xpc_initiate_connect, xpc_initiate_disconnect,
+			  xpc_initiate_send, xpc_initiate_send_notify,
+			  xpc_initiate_received, xpc_initiate_partid_to_nasids);
+
+	return 0;
+
+	/* initialization was not successful */
+out_3:
+	xpc_teardown_rsvd_page();
+
+	(void)unregister_die_notifier(&xpc_die_notifier);
+	(void)unregister_reboot_notifier(&xpc_reboot_notifier);
+out_2:
+	if (xpc_sysctl)
+		unregister_sysctl_table(xpc_sysctl);
+
+	xpc_teardown_partitions();
+out_1:
+	if (is_uv_system())
+		xpc_exit_uv();
+	return ret;
+}
+
+module_init(xpc_init);
+
+static void __exit
+xpc_exit(void)
+{
+	xpc_do_exit(xpUnloading);
+}
+
+module_exit(xpc_exit);
+
+MODULE_AUTHOR("Silicon Graphics, Inc.");
+MODULE_DESCRIPTION("Cross Partition Communication (XPC) support");
+MODULE_LICENSE("GPL");
+
+module_param(xpc_hb_interval, int, 0);
+MODULE_PARM_DESC(xpc_hb_interval, "Number of seconds between "
+		 "heartbeat increments.");
+
+module_param(xpc_hb_check_interval, int, 0);
+MODULE_PARM_DESC(xpc_hb_check_interval, "Number of seconds between "
+		 "heartbeat checks.");
+
+module_param(xpc_disengage_timelimit, int, 0);
+MODULE_PARM_DESC(xpc_disengage_timelimit, "Number of seconds to wait "
+		 "for disengage to complete.");
+
+module_param(xpc_kdebug_ignore, int, 0);
+MODULE_PARM_DESC(xpc_kdebug_ignore, "Should lack of heartbeat be ignored by "
+		 "other partitions when dropping into kdebug.");