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 /*
  * 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.");

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