1 files changed, 1323 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 000000000000..f673ba90eb0e
--- /dev/null
+++ b/drivers/misc/sgi-xp/xpc_main.c
@@ -0,0 +1,1323 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (c) 2004-2008 Silicon Graphics, Inc.  All Rights Reserved.
+ */
+
+/*
+ * Cross Partition Communication (XPC) 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:
+ *
+ *        . We currently have no way to determine which nasid an IPI came
+ *          from. Thus, xpc_IPI_send() 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/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/cache.h>
+#include <linux/interrupt.h>
+#include <linux/delay.h>
+#include <linux/reboot.h>
+#include <linux/completion.h>
+#include <linux/kdebug.h>
+#include <linux/kthread.h>
+#include <linux/uaccess.h>
+#include <asm/sn/intr.h>
+#include <asm/sn/sn_sal.h>
+#include "xpc.h"
+
+/* define two XPC debug device structures to be used with dev_dbg() et al */
+
+struct device_driver xpc_dbg_name = {
+        .name = "xpc"
+};
+
+struct device xpc_part_dbg_subname = {
+        .bus_id = {0},          /* set to "part" at xpc_init() time */
+        .driver = &xpc_dbg_name
+};
+
+struct device xpc_chan_dbg_subname = {
+        .bus_id = {0},          /* 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_request_timelimit = XPC_DISENGAGE_REQUEST_DEFAULT_TIMELIMIT;
+static int xpc_disengage_request_min_timelimit; /* = 0 */
+static int xpc_disengage_request_max_timelimit = 120;
+
+static ctl_table xpc_sys_xpc_hb_dir[] = {
+        {
+         .ctl_name = CTL_UNNUMBERED,
+         .procname = "hb_interval",
+         .data = &xpc_hb_interval,
+         .maxlen = sizeof(int),
+         .mode = 0644,
+         .proc_handler = &proc_dointvec_minmax,
+         .strategy = &sysctl_intvec,
+         .extra1 = &xpc_hb_min_interval,
+         .extra2 = &xpc_hb_max_interval},
+        {
+         .ctl_name = CTL_UNNUMBERED,
+         .procname = "hb_check_interval",
+         .data = &xpc_hb_check_interval,
+         .maxlen = sizeof(int),
+         .mode = 0644,
+         .proc_handler = &proc_dointvec_minmax,
+         .strategy = &sysctl_intvec,
+         .extra1 = &xpc_hb_check_min_interval,
+         .extra2 = &xpc_hb_check_max_interval},
+        {}
+};
+static ctl_table xpc_sys_xpc_dir[] = {
+        {
+         .ctl_name = CTL_UNNUMBERED,
+         .procname = "hb",
+         .mode = 0555,
+         .child = xpc_sys_xpc_hb_dir},
+        {
+         .ctl_name = CTL_UNNUMBERED,
+         .procname = "disengage_request_timelimit",
+         .data = &xpc_disengage_request_timelimit,
+         .maxlen = sizeof(int),
+         .mode = 0644,
+         .proc_handler = &proc_dointvec_minmax,
+         .strategy = &sysctl_intvec,
+         .extra1 = &xpc_disengage_request_min_timelimit,
+         .extra2 = &xpc_disengage_request_max_timelimit},
+        {}
+};
+static ctl_table xpc_sys_dir[] = {
+        {
+         .ctl_name = CTL_UNNUMBERED,
+         .procname = "xpc",
+         .mode = 0555,
+         .child = xpc_sys_xpc_dir},
+        {}
+};
+static struct ctl_table_header *xpc_sysctl;
+
+/* non-zero if any remote partition disengage request was timed out */
+int xpc_disengage_request_timedout;
+
+/* #of IRQs received */
+static atomic_t xpc_act_IRQ_rcvd;
+
+/* IRQ handler notifies this wait queue on receipt of an IRQ */
+static DECLARE_WAIT_QUEUE_HEAD(xpc_act_IRQ_wq);
+
+static unsigned long xpc_hb_check_timeout;
+
+/* 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 struct timer_list xpc_hb_timer;
+
+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,
+};
+
+/*
+ * Timer function to enforce the timelimit on the partition disengage request.
+ */
+static void
+xpc_timeout_partition_disengage_request(unsigned long data)
+{
+        struct xpc_partition *part = (struct xpc_partition *)data;
+
+        DBUG_ON(time_before(jiffies, part->disengage_request_timeout));
+
+        (void)xpc_partition_disengaged(part);
+
+        DBUG_ON(part->disengage_request_timeout != 0);
+        DBUG_ON(xpc_partition_engaged(1UL << XPC_PARTID(part)) != 0);
+}
+
+/*
+ * Notify the heartbeat check thread that an IRQ has been received.
+ */
+static irqreturn_t
+xpc_act_IRQ_handler(int irq, void *dev_id)
+{
+        atomic_inc(&xpc_act_IRQ_rcvd);
+        wake_up_interruptible(&xpc_act_IRQ_wq);
+        return IRQ_HANDLED;
+}
+
+/*
+ * 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(unsigned long dummy)
+{
+        xpc_vars->heartbeat++;
+
+        if (time_after_eq(jiffies, xpc_hb_check_timeout))
+                wake_up_interruptible(&xpc_act_IRQ_wq);
+
+        xpc_hb_timer.expires = jiffies + (xpc_hb_interval * HZ);
+        add_timer(&xpc_hb_timer);
+}
+
+/*
+ * This thread is responsible for nearly all of the partition
+ * activation/deactivation.
+ */
+static int
+xpc_hb_checker(void *ignore)
+{
+        int last_IRQ_count = 0;
+        int new_IRQ_count;
+        int force_IRQ = 0;
+
+        /* this thread was marked active by xpc_hb_init() */
+
+        set_cpus_allowed(current, cpumask_of_cpu(XPC_HB_CHECK_CPU));
+
+        /* set our heartbeating to other partitions into motion */
+        xpc_hb_check_timeout = jiffies + (xpc_hb_check_interval * HZ);
+        xpc_hb_beater(0);
+
+        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),
+                        atomic_read(&xpc_act_IRQ_rcvd) - last_IRQ_count);
+
+                /* checking of remote heartbeats is skewed by IRQ handling */
+                if (time_after_eq(jiffies, xpc_hb_check_timeout)) {
+                        dev_dbg(xpc_part, "checking remote heartbeats\n");
+                        xpc_check_remote_hb();
+
+                        /*
+                         * We need to periodically recheck to ensure no
+                         * IPI/AMO pairs have been missed.  That check
+                         * must always reset xpc_hb_check_timeout.
+                         */
+                        force_IRQ = 1;
+                }
+
+                /* check for outstanding IRQs */
+                new_IRQ_count = atomic_read(&xpc_act_IRQ_rcvd);
+                if (last_IRQ_count < new_IRQ_count || force_IRQ != 0) {
+                        force_IRQ = 0;
+
+                        dev_dbg(xpc_part, "found an IRQ to process; will be "
+                                "resetting xpc_hb_check_timeout\n");
+
+                        last_IRQ_count += xpc_identify_act_IRQ_sender();
+                        if (last_IRQ_count < new_IRQ_count) {
+                                /* retry once to help avoid missing AMO */
+                                (void)xpc_identify_act_IRQ_sender();
+                        }
+                        last_IRQ_count = new_IRQ_count;
+
+                        xpc_hb_check_timeout = jiffies +
+                            (xpc_hb_check_interval * HZ);
+                }
+
+                /* wait for IRQ or timeout */
+                (void)wait_event_interruptible(xpc_act_IRQ_wq,
+                                               (last_IRQ_count <
+                                                atomic_read(&xpc_act_IRQ_rcvd)
+                                                || time_after_eq(jiffies,
+                                                        xpc_hb_check_timeout) ||
+                                                xpc_exiting));
+        }
+
+        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;
+}
+
+/*
+ * Establish first contact with the remote partititon. This involves pulling
+ * the XPC per partition variables from the remote partition and waiting for
+ * the remote partition to pull ours.
+ */
+static enum xpc_retval
+xpc_make_first_contact(struct xpc_partition *part)
+{
+        enum xpc_retval ret;
+
+        while ((ret = xpc_pull_remote_vars_part(part)) != xpcSuccess) {
+                if (ret != xpcRetry) {
+                        XPC_DEACTIVATE_PARTITION(part, ret);
+                        return ret;
+                }
+
+                dev_dbg(xpc_chan, "waiting to make first contact with "
+                        "partition %d\n", XPC_PARTID(part));
+
+                /* wait a 1/4 of a second or so */
+                (void)msleep_interruptible(250);
+
+                if (part->act_state == XPC_P_DEACTIVATING)
+                        return part->reason;
+        }
+
+        return xpc_mark_partition_active(part);
+}
+
+/*
+ * The first kthread assigned to a newly activated partition is the one
+ * created by XPC HB with which it calls xpc_partition_up(). 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_DEACTIVATING ||
+               atomic_read(&part->nchannels_active) > 0 ||
+               !xpc_partition_disengaged(part)) {
+
+                xpc_process_channel_activity(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->local_IPI_amo != 0 ||
+                                 (part->act_state == XPC_P_DEACTIVATING &&
+                                 atomic_read(&part->nchannels_active) == 0 &&
+                                 xpc_partition_disengaged(part))));
+                atomic_set(&part->channel_mgr_requests, 1);
+        }
+}
+
+/*
+ * 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 until the partition
+ * goes down. At which time the kthread will teardown the XPC infrastructure
+ * and then exit.
+ *
+ * XPC HB will put the remote partition's XPC per partition specific variables
+ * physical address into xpc_partitions[partid].remote_vars_part_pa prior to
+ * calling xpc_partition_up().
+ */
+static void
+xpc_partition_up(struct xpc_partition *part)
+{
+        DBUG_ON(part->channels != NULL);
+
+        dev_dbg(xpc_chan, "activating partition %d\n", XPC_PARTID(part));
+
+        if (xpc_setup_infrastructure(part) != xpcSuccess)
+                return;
+
+        /*
+         * The kthread that XPC HB called us with will become the
+         * channel manager for this partition. It will not return
+         * back to XPC HB until the partition's XPC infrastructure
+         * has been dismantled.
+         */
+
+        (void)xpc_part_ref(part);       /* this will always succeed */
+
+        if (xpc_make_first_contact(part) == xpcSuccess)
+                xpc_channel_mgr(part);
+
+        xpc_part_deref(part);
+
+        xpc_teardown_infrastructure(part);
+}
+
+static int
+xpc_activating(void *__partid)
+{
+        partid_t partid = (u64)__partid;
+        struct xpc_partition *part = &xpc_partitions[partid];
+        unsigned long irq_flags;
+
+        DBUG_ON(partid <= 0 || partid >= XP_MAX_PARTITIONS);
+
+        spin_lock_irqsave(&part->act_lock, irq_flags);
+
+        if (part->act_state == XPC_P_DEACTIVATING) {
+                part->act_state = XPC_P_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_ACTIVATION_REQ);
+        part->act_state = XPC_P_ACTIVATING;
+
+        XPC_SET_REASON(part, 0, 0);
+        spin_unlock_irqrestore(&part->act_lock, irq_flags);
+
+        dev_dbg(xpc_part, "bringing partition %d up\n", partid);
+
+        /*
+         * Register the remote partition's AMOs with SAL so it can handle
+         * and cleanup errors within that address range should the remote
+         * partition go down. We don't unregister this range because it is
+         * difficult to tell when outstanding writes to the remote partition
+         * are finished and thus when it is safe to unregister. This should
+         * not result in wasted space in the SAL xp_addr_region table because
+         * we should get the same page for remote_amos_page_pa after module
+         * reloads and system reboots.
+         */
+        if (sn_register_xp_addr_region(part->remote_amos_page_pa,
+                                       PAGE_SIZE, 1) < 0) {
+                dev_warn(xpc_part, "xpc_partition_up(%d) failed to register "
+                         "xp_addr region\n", partid);
+
+                spin_lock_irqsave(&part->act_lock, irq_flags);
+                part->act_state = XPC_P_INACTIVE;
+                XPC_SET_REASON(part, xpcPhysAddrRegFailed, __LINE__);
+                spin_unlock_irqrestore(&part->act_lock, irq_flags);
+                part->remote_rp_pa = 0;
+                return 0;
+        }
+
+        xpc_allow_hb(partid, xpc_vars);
+        xpc_IPI_send_activated(part);
+
+        /*
+         * xpc_partition_up() holds this thread and marks this partition as
+         * XPC_P_ACTIVE by calling xpc_hb_mark_active().
+         */
+        (void)xpc_partition_up(part);
+
+        xpc_disallow_hb(partid, xpc_vars);
+        xpc_mark_partition_inactive(part);
+
+        if (part->reason == xpcReactivating) {
+                /* interrupting ourselves results in activating partition */
+                xpc_IPI_send_reactivate(part);
+        }
+
+        return 0;
+}
+
+void
+xpc_activate_partition(struct xpc_partition *part)
+{
+        partid_t 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_INACTIVE);
+
+        part->act_state = XPC_P_ACTIVATION_REQ;
+        XPC_SET_REASON(part, xpcCloneKThread, __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_INACTIVE;
+                XPC_SET_REASON(part, xpcCloneKThreadFailed, __LINE__);
+                spin_unlock_irqrestore(&part->act_lock, irq_flags);
+        }
+}
+
+/*
+ * Handle the receipt of a SGI_XPC_NOTIFY IRQ by seeing whether the specified
+ * partition actually sent it. Since SGI_XPC_NOTIFY IRQs may be shared by more
+ * than one partition, we use an AMO_t structure per partition to indicate
+ * whether a partition has sent an IPI or not.  If it has, then wake up the
+ * associated kthread to handle it.
+ *
+ * All SGI_XPC_NOTIFY IRQs received by XPC are the result of IPIs sent by XPC
+ * running on other partitions.
+ *
+ * Noteworthy Arguments:
+ *
+ *      irq - Interrupt ReQuest number. NOT USED.
+ *
+ *      dev_id - partid of IPI's potential sender.
+ */
+irqreturn_t
+xpc_notify_IRQ_handler(int irq, void *dev_id)
+{
+        partid_t partid = (partid_t) (u64)dev_id;
+        struct xpc_partition *part = &xpc_partitions[partid];
+
+        DBUG_ON(partid <= 0 || partid >= XP_MAX_PARTITIONS);
+
+        if (xpc_part_ref(part)) {
+                xpc_check_for_channel_activity(part);
+
+                xpc_part_deref(part);
+        }
+        return IRQ_HANDLED;
+}
+
+/*
+ * Check to see if xpc_notify_IRQ_handler() dropped any IPIs on the floor
+ * because the write to their associated IPI amo completed after the IRQ/IPI
+ * was received.
+ */
+void
+xpc_dropped_IPI_check(struct xpc_partition *part)
+{
+        if (xpc_part_ref(part)) {
+                xpc_check_for_channel_activity(part);
+
+                part->dropped_IPI_timer.expires = jiffies +
+                    XPC_P_DROPPED_IPI_WAIT;
+                add_timer(&part->dropped_IPI_timer);
+                xpc_part_deref(part);
+        }
+}
+
+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)
+{
+        do {
+                /* deliver messages to their intended recipients */
+
+                while (ch->w_local_GP.get < ch->w_remote_GP.put &&
+                       !(ch->flags & XPC_C_DISCONNECTING)) {
+                        xpc_deliver_msg(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,
+                                (ch->w_local_GP.get < ch->w_remote_GP.put ||
+                                 (ch->flags & XPC_C_DISCONNECTING)));
+
+                atomic_dec(&ch->kthreads_idle);
+
+        } while (!(ch->flags & XPC_C_DISCONNECTING));
+}
+
+static int
+xpc_kthread_start(void *args)
+{
+        partid_t 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;
+
+        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 = ch->w_remote_GP.put - ch->w_local_GP.get - 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, xpcDisconnecting);
+
+                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) {
+                if (atomic_dec_return(&part->nchannels_engaged) == 0) {
+                        xpc_mark_partition_disengaged(part);
+                        xpc_IPI_send_disengage(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;
+
+        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) {
+                        if (atomic_inc_return(&part->nchannels_engaged) == 1)
+                                xpc_mark_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 xpcDisconnecting callout that this
+                         * failed kthread_run() would have made.
+                         */
+
+                        if (atomic_dec_return(&ch->kthreads_assigned) == 0 &&
+                            atomic_dec_return(&part->nchannels_engaged) == 0) {
+                                xpc_mark_partition_disengaged(part);
+                                xpc_IPI_send_disengage(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, xpcLackOfResources,
+                                                       &irq_flags);
+                                spin_unlock_irqrestore(&ch->lock, irq_flags);
+                        }
+                        break;
+                }
+        }
+}
+
+void
+xpc_disconnect_wait(int ch_number)
+{
+        unsigned long irq_flags;
+        partid_t 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 = 1; partid < XP_MAX_PARTITIONS; 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_IPI_flags) {
+                        if (part->act_state != XPC_P_DEACTIVATING) {
+                                spin_lock(&part->IPI_lock);
+                                XPC_SET_IPI_FLAGS(part->local_IPI_amo,
+                                                  ch->number,
+                                                  ch->delayed_IPI_flags);
+                                spin_unlock(&part->IPI_lock);
+                                wakeup_channel_mgr = 1;
+                        }
+                        ch->delayed_IPI_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 void
+xpc_do_exit(enum xpc_retval reason)
+{
+        partid_t partid;
+        int active_part_count, printed_waiting_msg = 0;
+        struct xpc_partition *part;
+        unsigned long printmsg_time, disengage_request_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_act_IRQ_wq);
+
+        /* ignore all incoming interrupts */
+        free_irq(SGI_XPC_ACTIVATE, NULL);
+
+        /* 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_DISENGAGE_PRINTMSG_INTERVAL * HZ);
+        xpc_disengage_request_timedout = 0;
+
+        do {
+                active_part_count = 0;
+
+                for (partid = 1; partid < XP_MAX_PARTITIONS; partid++) {
+                        part = &xpc_partitions[partid];
+
+                        if (xpc_partition_disengaged(part) &&
+                            part->act_state == XPC_P_INACTIVE) {
+                                continue;
+                        }
+
+                        active_part_count++;
+
+                        XPC_DEACTIVATE_PARTITION(part, reason);
+
+                        if (part->disengage_request_timeout >
+                            disengage_request_timeout) {
+                                disengage_request_timeout =
+                                    part->disengage_request_timeout;
+                        }
+                }
+
+                if (xpc_partition_engaged(-1UL)) {
+                        if (time_after(jiffies, printmsg_time)) {
+                                dev_info(xpc_part, "waiting for remote "
+                                         "partitions to disengage, timeout in "
+                                         "%ld seconds\n",
+                                         (disengage_request_timeout - jiffies)
+                                         / HZ);
+                                printmsg_time = jiffies +
+                                    (XPC_DISENGAGE_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 disengage\n");
+                                printed_waiting_msg = 0;
+                        }
+
+                } else {
+                        if (!xpc_disengage_request_timedout) {
+                                dev_info(xpc_part, "all partitions have "
+                                         "disengaged\n");
+                        }
+                        break;
+                }
+
+                /* sleep for a 1/3 of a second or so */
+                (void)msleep_interruptible(300);
+
+        } while (1);
+
+        DBUG_ON(xpc_partition_engaged(-1UL));
+
+        /* indicate to others that our reserved page is uninitialized */
+        xpc_rsvd_page->vars_pa = 0;
+
+        /* now it's time to eliminate our heartbeat */
+        del_timer_sync(&xpc_hb_timer);
+        DBUG_ON(xpc_vars->heartbeating_to_mask != 0);
+
+        if (reason == xpcUnloading) {
+                /* take ourselves off of the reboot_notifier_list */
+                (void)unregister_reboot_notifier(&xpc_reboot_notifier);
+
+                /* take ourselves off of the die_notifier list */
+                (void)unregister_die_notifier(&xpc_die_notifier);
+        }
+
+        /* close down protections for IPI operations */
+        xpc_restrict_IPI_ops();
+
+        /* clear the interface to XPC's functions */
+        xpc_clear_interface();
+
+        if (xpc_sysctl)
+                unregister_sysctl_table(xpc_sysctl);
+
+        kfree(xpc_remote_copy_buffer_base);
+}
+
+/*
+ * 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 xpc_retval reason;
+
+        switch (event) {
+        case SYS_RESTART:
+                reason = xpcSystemReboot;
+                break;
+        case SYS_HALT:
+                reason = xpcSystemHalt;
+                break;
+        case SYS_POWER_OFF:
+                reason = xpcSystemPoweroff;
+                break;
+        default:
+                reason = xpcSystemGoingDown;
+        }
+
+        xpc_do_exit(reason);
+        return NOTIFY_DONE;
+}
+
+/*
+ * Notify other partitions to disengage from all references to our memory.
+ */
+static void
+xpc_die_disengage(void)
+{
+        struct xpc_partition *part;
+        partid_t partid;
+        unsigned long engaged;
+        long time, printmsg_time, disengage_request_timeout;
+
+        /* keep xpc_hb_checker thread from doing anything (just in case) */
+        xpc_exiting = 1;
+
+        xpc_vars->heartbeating_to_mask = 0;     /* indicate we're deactivated */
+
+        for (partid = 1; partid < XP_MAX_PARTITIONS; partid++) {
+                part = &xpc_partitions[partid];
+
+                if (!XPC_SUPPORTS_DISENGAGE_REQUEST(part->
+                    remote_vars_version)) {
+
+                        /* just in case it was left set by an earlier XPC */
+                        xpc_clear_partition_engaged(1UL << partid);
+                        continue;
+                }
+
+                if (xpc_partition_engaged(1UL << partid) ||
+                    part->act_state != XPC_P_INACTIVE) {
+                        xpc_request_partition_disengage(part);
+                        xpc_mark_partition_disengaged(part);
+                        xpc_IPI_send_disengage(part);
+                }
+        }
+
+        time = rtc_time();
+        printmsg_time = time +
+            (XPC_DISENGAGE_PRINTMSG_INTERVAL * sn_rtc_cycles_per_second);
+        disengage_request_timeout = time +
+            (xpc_disengage_request_timelimit * sn_rtc_cycles_per_second);
+
+        /* wait for all other partitions to disengage from us */
+
+        while (1) {
+                engaged = xpc_partition_engaged(-1UL);
+                if (!engaged) {
+                        dev_info(xpc_part, "all partitions have disengaged\n");
+                        break;
+                }
+
+                time = rtc_time();
+                if (time >= disengage_request_timeout) {
+                        for (partid = 1; partid < XP_MAX_PARTITIONS; partid++) {
+                                if (engaged & (1UL << partid)) {
+                                        dev_info(xpc_part, "disengage from "
+                                                 "remote partition %d timed "
+                                                 "out\n", partid);
+                                }
+                        }
+                        break;
+                }
+
+                if (time >= printmsg_time) {
+                        dev_info(xpc_part, "waiting for remote partitions to "
+                                 "disengage, timeout in %ld seconds\n",
+                                 (disengage_request_timeout - time) /
+                                 sn_rtc_cycles_per_second);
+                        printmsg_time = time +
+                            (XPC_DISENGAGE_PRINTMSG_INTERVAL *
+                             sn_rtc_cycles_per_second);
+                }
+        }
+}
+
+/*
+ * 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 *unused)
+{
+        switch (event) {
+        case DIE_MACHINE_RESTART:
+        case DIE_MACHINE_HALT:
+                xpc_die_disengage();
+                break;
+
+        case DIE_KDEBUG_ENTER:
+                /* Should lack of heartbeat be ignored by other partitions? */
+                if (!xpc_kdebug_ignore)
+                        break;
+
+                /* fall through */
+        case DIE_MCA_MONARCH_ENTER:
+        case DIE_INIT_MONARCH_ENTER:
+                xpc_vars->heartbeat++;
+                xpc_vars->heartbeat_offline = 1;
+                break;
+
+        case DIE_KDEBUG_LEAVE:
+                /* Is lack of heartbeat being ignored by other partitions? */
+                if (!xpc_kdebug_ignore)
+                        break;
+
+                /* fall through */
+        case DIE_MCA_MONARCH_LEAVE:
+        case DIE_INIT_MONARCH_LEAVE:
+                xpc_vars->heartbeat++;
+                xpc_vars->heartbeat_offline = 0;
+                break;
+        }
+
+        return NOTIFY_DONE;
+}
+
+int __init
+xpc_init(void)
+{
+        int ret;
+        partid_t partid;
+        struct xpc_partition *part;
+        struct task_struct *kthread;
+        size_t buf_size;
+
+        if (!ia64_platform_is("sn2"))
+                return -ENODEV;
+
+        buf_size = max(XPC_RP_VARS_SIZE,
+                       XPC_RP_HEADER_SIZE + XP_NASID_MASK_BYTES);
+        xpc_remote_copy_buffer = xpc_kmalloc_cacheline_aligned(buf_size,
+                                                               GFP_KERNEL,
+                                                  &xpc_remote_copy_buffer_base);
+        if (xpc_remote_copy_buffer == NULL)
+                return -ENOMEM;
+
+        snprintf(xpc_part->bus_id, BUS_ID_SIZE, "part");
+        snprintf(xpc_chan->bus_id, BUS_ID_SIZE, "chan");
+
+        xpc_sysctl = register_sysctl_table(xpc_sys_dir);
+
+        /*
+         * 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 = 1; partid < XP_MAX_PARTITIONS; partid++) {
+                part = &xpc_partitions[partid];
+
+                DBUG_ON((u64)part != L1_CACHE_ALIGN((u64)part));
+
+                part->act_IRQ_rcvd = 0;
+                spin_lock_init(&part->act_lock);
+                part->act_state = XPC_P_INACTIVE;
+                XPC_SET_REASON(part, 0, 0);
+
+                init_timer(&part->disengage_request_timer);
+                part->disengage_request_timer.function =
+                    xpc_timeout_partition_disengage_request;
+                part->disengage_request_timer.data = (unsigned long)part;
+
+                part->setup_state = XPC_P_UNSET;
+                init_waitqueue_head(&part->teardown_wq);
+                atomic_set(&part->references, 0);
+        }
+
+        /*
+         * Open up protections for IPI operations (and AMO operations on
+         * Shub 1.1 systems).
+         */
+        xpc_allow_IPI_ops();
+
+        /*
+         * Interrupts being processed will increment this atomic variable and
+         * awaken the heartbeat thread which will process the interrupts.
+         */
+        atomic_set(&xpc_act_IRQ_rcvd, 0);
+
+        /*
+         * This is safe to do before the xpc_hb_checker thread has started
+         * because the handler releases a wait queue.  If an interrupt is
+         * received before the thread is waiting, it will not go to sleep,
+         * but rather immediately process the interrupt.
+         */
+        ret = request_irq(SGI_XPC_ACTIVATE, xpc_act_IRQ_handler, 0,
+                          "xpc hb", NULL);
+        if (ret != 0) {
+                dev_err(xpc_part, "can't register ACTIVATE IRQ handler, "
+                        "errno=%d\n", -ret);
+
+                xpc_restrict_IPI_ops();
+
+                if (xpc_sysctl)
+                        unregister_sysctl_table(xpc_sysctl);
+
+                kfree(xpc_remote_copy_buffer_base);
+                return -EBUSY;
+        }
+
+        /*
+         * Fill the partition reserved page with the information needed by
+         * other partitions to discover we are alive and establish initial
+         * communications.
+         */
+        xpc_rsvd_page = xpc_rsvd_page_init();
+        if (xpc_rsvd_page == NULL) {
+                dev_err(xpc_part, "could not setup our reserved page\n");
+
+                free_irq(SGI_XPC_ACTIVATE, NULL);
+                xpc_restrict_IPI_ops();
+
+                if (xpc_sysctl)
+                        unregister_sysctl_table(xpc_sysctl);
+
+                kfree(xpc_remote_copy_buffer_base);
+                return -EBUSY;
+        }
+
+        /* 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");
+
+        init_timer(&xpc_hb_timer);
+        xpc_hb_timer.function = xpc_hb_beater;
+
+        /*
+         * 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");
+
+                /* indicate to others that our reserved page is uninitialized */
+                xpc_rsvd_page->vars_pa = 0;
+
+                /* take ourselves off of the reboot_notifier_list */
+                (void)unregister_reboot_notifier(&xpc_reboot_notifier);
+
+                /* take ourselves off of the die_notifier list */
+                (void)unregister_die_notifier(&xpc_die_notifier);
+
+                del_timer_sync(&xpc_hb_timer);
+                free_irq(SGI_XPC_ACTIVATE, NULL);
+                xpc_restrict_IPI_ops();
+
+                if (xpc_sysctl)
+                        unregister_sysctl_table(xpc_sysctl);
+
+                kfree(xpc_remote_copy_buffer_base);
+                return -EBUSY;
+        }
+
+        /*
+         * 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(xpcUnloading);
+                return -EBUSY;
+        }
+
+        /* set the interface to point at XPC's functions */
+        xpc_set_interface(xpc_initiate_connect, xpc_initiate_disconnect,
+                          xpc_initiate_allocate, xpc_initiate_send,
+                          xpc_initiate_send_notify, xpc_initiate_received,
+                          xpc_initiate_partid_to_nasids);
+
+        return 0;
+}
+
+module_init(xpc_init);
+
+void __exit
+xpc_exit(void)
+{
+        xpc_do_exit(xpcUnloading);
+}
+
+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_request_timelimit, int, 0);
+MODULE_PARM_DESC(xpc_disengage_request_timelimit, "Number of seconds to wait "
+                 "for disengage request 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.");