ClabureDB: Classified Bug-Reports Database

   /*
    * 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:
   *
   *          . 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/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"
  
  /* 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_timelimit = XPC_DISENGAGE_DEFAULT_TIMELIMIT;
  static int xpc_disengage_min_timelimit;        /* = 0 */
  static int xpc_disengage_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_timelimit",
          .data = &xpc_disengage_timelimit,
          .maxlen = sizeof(int),
          .mode = 0644,
          .proc_handler = &proc_dointvec_minmax,
          .strategy = &sysctl_intvec,
          .extra1 = &xpc_disengage_min_timelimit,
          .extra2 = &xpc_disengage_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 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;
 void *xpc_heartbeating_to_mask;
 
 /* 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,
 };
 
 int (*xpc_setup_partitions_sn) (void);
 enum xp_retval (*xpc_get_partition_rsvd_page_pa) (void *buf, u64 *cookie,
                                                   unsigned long *rp_pa,
                                                   size_t *len);
 int (*xpc_setup_rsvd_page_sn) (struct xpc_rsvd_page *rp);
 void (*xpc_heartbeat_init) (void);
 void (*xpc_heartbeat_exit) (void);
 void (*xpc_increment_heartbeat) (void);
 void (*xpc_offline_heartbeat) (void);
 void (*xpc_online_heartbeat) (void);
 enum xp_retval (*xpc_get_remote_heartbeat) (struct xpc_partition *part);
 
 enum xp_retval (*xpc_make_first_contact) (struct xpc_partition *part);
 void (*xpc_notify_senders_of_disconnect) (struct xpc_channel *ch);
 u64 (*xpc_get_chctl_all_flags) (struct xpc_partition *part);
 enum xp_retval (*xpc_setup_msg_structures) (struct xpc_channel *ch);
 void (*xpc_teardown_msg_structures) (struct xpc_channel *ch);
 void (*xpc_process_msg_chctl_flags) (struct xpc_partition *part, int ch_number);
 int (*xpc_n_of_deliverable_payloads) (struct xpc_channel *ch);
 void *(*xpc_get_deliverable_payload) (struct xpc_channel *ch);
 
 void (*xpc_request_partition_activation) (struct xpc_rsvd_page *remote_rp,
                                           unsigned long remote_rp_pa,
                                           int nasid);
 void (*xpc_request_partition_reactivation) (struct xpc_partition *part);
 void (*xpc_request_partition_deactivation) (struct xpc_partition *part);
 void (*xpc_cancel_partition_deactivation_request) (struct xpc_partition *part);
 
 void (*xpc_process_activate_IRQ_rcvd) (void);
 enum xp_retval (*xpc_setup_ch_structures_sn) (struct xpc_partition *part);
 void (*xpc_teardown_ch_structures_sn) (struct xpc_partition *part);
 
 void (*xpc_indicate_partition_engaged) (struct xpc_partition *part);
 int (*xpc_partition_engaged) (short partid);
 int (*xpc_any_partition_engaged) (void);
 void (*xpc_indicate_partition_disengaged) (struct xpc_partition *part);
 void (*xpc_assume_partition_disengaged) (short partid);
 
 void (*xpc_send_chctl_closerequest) (struct xpc_channel *ch,
                                      unsigned long *irq_flags);
 void (*xpc_send_chctl_closereply) (struct xpc_channel *ch,
                                    unsigned long *irq_flags);
 void (*xpc_send_chctl_openrequest) (struct xpc_channel *ch,
                                     unsigned long *irq_flags);
 void (*xpc_send_chctl_openreply) (struct xpc_channel *ch,
                                   unsigned long *irq_flags);
 
 void (*xpc_save_remote_msgqueue_pa) (struct xpc_channel *ch,
                                      unsigned long msgqueue_pa);
 
 enum xp_retval (*xpc_send_payload) (struct xpc_channel *ch, u32 flags,
                                     void *payload, u16 payload_size,
                                     u8 notify_type, xpc_notify_func func,
                                     void *key);
 void (*xpc_received_payload) (struct xpc_channel *ch, void *payload);
 
 /*
  * Timer function to enforce the timelimit on the partition disengage.
  */
 static void
 xpc_timeout_partition_disengage(unsigned long data)
 {
         struct xpc_partition *part = (struct xpc_partition *)data;
 
         DBUG_ON(time_is_after_jiffies(part->disengage_timeout));
 
         (void)xpc_partition_disengaged(part);
 
         DBUG_ON(part->disengage_timeout != 0);
         DBUG_ON(xpc_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(unsigned long dummy)
 {
         xpc_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_heartbeat_init();
         init_timer(&xpc_hb_timer);
         xpc_hb_timer.function = xpc_hb_beater;
         xpc_hb_beater(0);
 }
 
 static void
 xpc_stop_hb_beater(void)
 {
         del_timer_sync(&xpc_hb_timer);
         xpc_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_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_cpu(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();
 
                         /*
                          * On sn2 we need to periodically recheck to ensure no
                          * IRQ/amo pairs have been missed.
                          */
                         if (is_shub())
                                 force_IRQ = 1;
                 }
 
                 /* 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_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 = kzalloc(sizeof(struct xpc_channel) * XPC_MAX_NCHANNELS,
                                  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_setup_ch_structures_sn(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_teardown_ch_structures_sn(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_allow_hb(partid);
 
         if (xpc_setup_ch_structures(part) == xpSuccess) {
                 (void)xpc_part_ref(part);        /* this will always succeed */
 
                 if (xpc_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_disallow_hb(partid);
         xpc_mark_partition_inactive(part);
 
         if (part->reason == xpReactivating) {
                 /* interrupting ourselves results in activating partition */
                 xpc_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)
 {
         do {
                 /* deliver messages to their intended recipients */
 
                 while (xpc_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,
                                 (xpc_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;
 
         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 = xpc_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_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;
 
         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_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) {
                                 xpc_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 = kzalloc(sizeof(struct xpc_partition) *
                                  xp_max_npartitions, 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);
 
                 init_timer(&part->disengage_timer);
                 part->disengage_timer.function =
                     xpc_timeout_partition_disengage;
                 part->disengage_timer.data = (unsigned long)part;
 
                 part->setup_state = XPC_P_SS_UNSET;
                 init_waitqueue_head(&part->teardown_wq);
                 atomic_set(&part->references, 0);
         }
 
         return xpc_setup_partitions_sn();
 }
 
 static void
 xpc_teardown_partitions(void)
{
        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_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_any_partition_engaged());
        DBUG_ON(xpc_any_hbs_allowed() != 0);

        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_shub())
                xpc_exit_sn2();
        else if (is_uv())
                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;
}

/*
 * 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;

        /* keep xpc_hb_checker thread from doing anything (just in case) */
        xpc_exiting = 1;

        xpc_disallow_all_hbs();        /*indicate we're deactivated */

        for (partid = 0; partid < xp_max_npartitions; partid++) {
                part = &xpc_partitions[partid];

                if (xpc_partition_engaged(partid) ||
                    part->act_state != XPC_P_AS_INACTIVE) {
                        xpc_request_partition_deactivation(part);
                        xpc_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_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_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 *unused)
{
#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;

                /* fall through */
        case DIE_MCA_MONARCH_ENTER:
        case DIE_INIT_MONARCH_ENTER:
                xpc_offline_heartbeat();
                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_online_heartbeat();
                break;
        }
#else
        xpc_die_deactivate();
#endif

        return NOTIFY_DONE;
}

int __init
xpc_init(void)
{
        int ret;
        struct task_struct *kthread;

        snprintf(xpc_part->bus_id, BUS_ID_SIZE, "part");
        snprintf(xpc_chan->bus_id, BUS_ID_SIZE, "chan");

        if (is_shub()) {
                /*
                 * The ia64-sn2 architecture supports at most 64 partitions.
                 * And the inability to unregister remote amos restricts us
                 * further to only support exactly 64 partitions on this
                 * architecture, no less.
                 */
                if (xp_max_npartitions != 64) {
                        dev_err(xpc_part, "max #of partitions not set to 64\n");
                        ret = -EINVAL;
                } else {
                        ret = xpc_init_sn2();
                }

        } else if (is_uv()) {
                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_shub())
                xpc_exit_sn2();
        else if (is_uv())
                xpc_exit_uv();
        return ret;
}

module_init(xpc_init);

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.");