[IA64-SGI] get XPC to cleanly disengage from remote memory references

When XPC is being shutdown (i.e., rmmod, reboot) it doesn't ensure that
other partitions with whom it was connected have completely disengaged
from any attempt at cross-partition memory references. This can lead to
MCAs in any of these other partitions when the partition is reset.

Signed-off-by: Dean Nelson <dcn@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

1 files changed, 179 insertions, 63 deletions

diff --git a/arch/ia64/sn/kernel/xpc_main.c b/arch/ia64/sn/kernel/xpc_main.c
index bb1d5cf..feece20 100644
--- a/arch/ia64/sn/kernel/xpc_main.c
+++ b/arch/ia64/sn/kernel/xpc_main.c
@@ -54,6 +54,7 @@
 #include <linux/interrupt.h>
 #include <linux/slab.h>
 #include <linux/delay.h>
+#include <linux/reboot.h>
 #include <asm/sn/intr.h>
 #include <asm/sn/sn_sal.h>
 #include <asm/uaccess.h>
@@ -82,11 +83,13 @@ struct device *xpc_chan = &xpc_chan_dbg_subname;
 
 /* systune related variables for /proc/sys directories */
 
-static int xpc_hb_min = 1;
-static int xpc_hb_max = 10;
+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_min = 10;
-static int xpc_hb_check_max = 120;
+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;
 
 static ctl_table xpc_sys_xpc_hb_dir[] = {
 	{
@@ -99,7 +102,8 @@ static ctl_table xpc_sys_xpc_hb_dir[] = {
 		&proc_dointvec_minmax,
 		&sysctl_intvec,
 		NULL,
-		&xpc_hb_min, &xpc_hb_max
+		&xpc_hb_min_interval,
+		&xpc_hb_max_interval
 	},
 	{
 		2,
@@ -111,7 +115,8 @@ static ctl_table xpc_sys_xpc_hb_dir[] = {
 		&proc_dointvec_minmax,
 		&sysctl_intvec,
 		NULL,
-		&xpc_hb_check_min, &xpc_hb_check_max
+		&xpc_hb_check_min_interval,
+		&xpc_hb_check_max_interval
 	},
 	{0}
 };
@@ -148,11 +153,11 @@ static DECLARE_WAIT_QUEUE_HEAD(xpc_act_IRQ_wq);
 
 static unsigned long xpc_hb_check_timeout;
 
-/* xpc_hb_checker thread exited notification */
-static DECLARE_MUTEX_LOCKED(xpc_hb_checker_exited);
+/* used as an indication of when the xpc_hb_checker thread is inactive */
+static DECLARE_MUTEX_LOCKED(xpc_hb_checker_inactive);
 
-/* xpc_discovery thread exited notification */
-static DECLARE_MUTEX_LOCKED(xpc_discovery_exited);
+/* used as an indication of when the xpc_discovery thread is inactive */
+static DECLARE_MUTEX_LOCKED(xpc_discovery_inactive);
 
 
 static struct timer_list xpc_hb_timer;
@@ -161,6 +166,30 @@ static struct timer_list xpc_hb_timer;
 static void xpc_kthread_waitmsgs(struct xpc_partition *, struct xpc_channel *);
 
 
+static int xpc_system_reboot(struct notifier_block *, unsigned long, void *);
+static struct notifier_block xpc_reboot_notifier = {
+	.notifier_call = xpc_system_reboot,
+};
+
+
+/*
+ * Timer function to enforce the timelimit on the partition disengage request.
+ */
+static void
+xpc_timeout_partition_disengage_request(unsigned long data)
+{
+	struct xpc_partition *part = (struct xpc_partition *) data;
+
+
+	DBUG_ON(XPC_TICKS < part->disengage_request_timeout);
+
+	(void) xpc_partition_disengaged(part);
+
+	DBUG_ON(part->disengage_request_timeout != 0);
+	DBUG_ON(xpc_partition_engaged(1UL << XPC_PARTID(part)) != 0);
+}
+
+
 /*
  * Notify the heartbeat check thread that an IRQ has been received.
  */
@@ -214,12 +243,6 @@ xpc_hb_checker(void *ignore)
 
 	while (!(volatile int) xpc_exiting) {
 
-		/* wait for IRQ or timeout */
-		(void) wait_event_interruptible(xpc_act_IRQ_wq,
-			    (last_IRQ_count < atomic_read(&xpc_act_IRQ_rcvd) ||
-					jiffies >= xpc_hb_check_timeout ||
-						(volatile int) xpc_exiting));
-
 		dev_dbg(xpc_part, "woke up with %d ticks rem; %d IRQs have "
 			"been received\n",
 			(int) (xpc_hb_check_timeout - jiffies),
@@ -240,6 +263,7 @@ xpc_hb_checker(void *ignore)
 		}
 
 
+		/* check for outstanding IRQs */
 		new_IRQ_count = atomic_read(&xpc_act_IRQ_rcvd);
 		if (last_IRQ_count < new_IRQ_count || force_IRQ != 0) {
 			force_IRQ = 0;
@@ -257,13 +281,19 @@ xpc_hb_checker(void *ignore)
 			xpc_hb_check_timeout = jiffies +
 					   (xpc_hb_check_interval * HZ);
 		}
+
+		/* wait for IRQ or timeout */
+		(void) wait_event_interruptible(xpc_act_IRQ_wq,
+			    (last_IRQ_count < atomic_read(&xpc_act_IRQ_rcvd) ||
+					jiffies >= xpc_hb_check_timeout ||
+						(volatile int) xpc_exiting));
 	}
 
 	dev_dbg(xpc_part, "heartbeat checker is exiting\n");
 
 
 	/* mark this thread as inactive */
-	up(&xpc_hb_checker_exited);
+	up(&xpc_hb_checker_inactive);
 	return 0;
 }
 
@@ -283,7 +313,7 @@ xpc_initiate_discovery(void *ignore)
 	dev_dbg(xpc_part, "discovery thread is exiting\n");
 
 	/* mark this thread as inactive */
-	up(&xpc_discovery_exited);
+	up(&xpc_discovery_inactive);
 	return 0;
 }
 
@@ -309,7 +339,7 @@ xpc_make_first_contact(struct xpc_partition *part)
 			"partition %d\n", XPC_PARTID(part));
 
 		/* wait a 1/4 of a second or so */
-		msleep_interruptible(250);
+		(void) msleep_interruptible(250);
 
 		if (part->act_state == XPC_P_DEACTIVATING) {
 			return part->reason;
@@ -336,7 +366,8 @@ static void
 xpc_channel_mgr(struct xpc_partition *part)
 {
 	while (part->act_state != XPC_P_DEACTIVATING ||
-				atomic_read(&part->nchannels_active) > 0) {
+			atomic_read(&part->nchannels_active) > 0 ||
+					!xpc_partition_disengaged(part)) {
 
 		xpc_process_channel_activity(part);
 
@@ -360,7 +391,8 @@ xpc_channel_mgr(struct xpc_partition *part)
 				(volatile u64) part->local_IPI_amo != 0 ||
 				((volatile u8) part->act_state ==
 							XPC_P_DEACTIVATING &&
-				atomic_read(&part->nchannels_active) == 0)));
+				atomic_read(&part->nchannels_active) == 0 &&
+				xpc_partition_disengaged(part))));
 		atomic_set(&part->channel_mgr_requests, 1);
 
 		// >>> Does it need to wakeup periodically as well? In case we
@@ -482,7 +514,7 @@ xpc_activating(void *__partid)
 		return 0;
 	}
 
-	XPC_ALLOW_HB(partid, xpc_vars);
+	xpc_allow_hb(partid, xpc_vars);
 	xpc_IPI_send_activated(part);
 
 
@@ -492,6 +524,7 @@ xpc_activating(void *__partid)
 	 */
 	(void) xpc_partition_up(part);
 
+	xpc_disallow_hb(partid, xpc_vars);
 	xpc_mark_partition_inactive(part);
 
 	if (part->reason == xpcReactivating) {
@@ -704,11 +737,14 @@ xpc_daemonize_kthread(void *args)
 		xpc_kthread_waitmsgs(part, ch);
 	}
 
-	if (atomic_dec_return(&ch->kthreads_assigned) == 0 &&
-			((ch->flags & XPC_C_CONNECTCALLOUT) ||
-				(ch->reason != xpcUnregistering &&
-					ch->reason != xpcOtherUnregistering))) {
-		xpc_disconnected_callout(ch);
+	if (atomic_dec_return(&ch->kthreads_assigned) == 0) {
+		if (ch->flags & XPC_C_CONNECTCALLOUT) {
+			xpc_disconnecting_callout(ch);
+		}
+		if (atomic_dec_return(&part->nchannels_engaged) == 0) {
+			xpc_mark_partition_disengaged(part);
+			xpc_IPI_send_disengage(part);
+		}
 	}
 
 
@@ -740,6 +776,7 @@ xpc_create_kthreads(struct xpc_channel *ch, int needed)
 	unsigned long irq_flags;
 	pid_t pid;
 	u64 args = XPC_PACK_ARGS(ch->partid, ch->number);
+	struct xpc_partition *part = &xpc_partitions[ch->partid];
 
 
 	while (needed-- > 0) {
@@ -770,9 +807,13 @@ xpc_create_kthreads(struct xpc_channel *ch, int needed)
 		 * kthread. That kthread is responsible for doing the
 		 * counterpart to the following before it exits.
 		 */
-		(void) xpc_part_ref(&xpc_partitions[ch->partid]);
+		(void) xpc_part_ref(part);
 		xpc_msgqueue_ref(ch);
-		atomic_inc(&ch->kthreads_assigned);
+		if (atomic_inc_return(&ch->kthreads_assigned) == 1) {
+			if (atomic_inc_return(&part->nchannels_engaged) == 1) {
+				xpc_mark_partition_engaged(part);
+			}
+		}
 		ch->kthreads_created++;	// >>> temporary debug only!!!
 	}
 }
@@ -781,6 +822,7 @@ xpc_create_kthreads(struct xpc_channel *ch, int needed)
 void
 xpc_disconnect_wait(int ch_number)
 {
+	unsigned long irq_flags;
 	partid_t partid;
 	struct xpc_partition *part;
 	struct xpc_channel *ch;
@@ -793,10 +835,13 @@ xpc_disconnect_wait(int ch_number)
 		if (xpc_part_ref(part)) {
 			ch = &part->channels[ch_number];
 
-// >>> how do we keep from falling into the window between our check and going
-// >>> down and coming back up where sema is re-inited?
-			if (ch->flags & XPC_C_SETUP) {
-				(void) down(&ch->teardown_sema);
+			if (ch->flags & XPC_C_WDISCONNECT) {
+				if (!(ch->flags & XPC_C_DISCONNECTED)) {
+					(void) down(&ch->wdisconnect_sema);
+				}
+				spin_lock_irqsave(&ch->lock, irq_flags);
+				ch->flags &= ~XPC_C_WDISCONNECT;
+				spin_unlock_irqrestore(&ch->lock, irq_flags);
 			}
 
 			xpc_part_deref(part);
@@ -806,62 +851,89 @@ xpc_disconnect_wait(int ch_number)
 
 
 static void
-xpc_do_exit(void)
+xpc_do_exit(enum xpc_retval reason)
 {
 	partid_t partid;
 	int active_part_count;
 	struct xpc_partition *part;
+	unsigned long printmsg_time;
 
 
-	/* now it's time to eliminate our heartbeat */
-	del_timer_sync(&xpc_hb_timer);
-	xpc_vars->heartbeating_to_mask = 0;
-
-	/* indicate to others that our reserved page is uninitialized */
-	xpc_rsvd_page->vars_pa = 0;
+	/* a 'rmmod XPC' and a 'reboot' cannot both end up here together */
+	DBUG_ON(xpc_exiting == 1);
 
 	/*
-	 * Ignore all incoming interrupts. Without interupts the heartbeat
-	 * checker won't activate any new partitions that may come up.
-	 */
-	free_irq(SGI_XPC_ACTIVATE, NULL);
-
-	/*
-	 * Cause the heartbeat checker and the discovery threads to exit.
-	 * We don't want them attempting to activate new partitions as we
-	 * try to deactivate the existing ones.
+	 * Let the heartbeat checker thread and the discovery thread
+	 * (if one is running) know that they should exit. Also wake up
+	 * the heartbeat checker thread in case it's sleeping.
 	 */
 	xpc_exiting = 1;
 	wake_up_interruptible(&xpc_act_IRQ_wq);
 
-	/* wait for the heartbeat checker thread to mark itself inactive */
-	down(&xpc_hb_checker_exited);
+	/* ignore all incoming interrupts */
+	free_irq(SGI_XPC_ACTIVATE, NULL);
 
 	/* wait for the discovery thread to mark itself inactive */
-	down(&xpc_discovery_exited);
+	down(&xpc_discovery_inactive);
+
+	/* wait for the heartbeat checker thread to mark itself inactive */
+	down(&xpc_hb_checker_inactive);
 
 
-	msleep_interruptible(300);
+	/* sleep for a 1/3 of a second or so */
+	(void) msleep_interruptible(300);
 
 
 	/* wait for all partitions to become inactive */
 
+	printmsg_time = jiffies;
+
 	do {
 		active_part_count = 0;
 
 		for (partid = 1; partid < XP_MAX_PARTITIONS; partid++) {
 			part = &xpc_partitions[partid];
-			if (part->act_state != XPC_P_INACTIVE) {
-				active_part_count++;
-
-				XPC_DEACTIVATE_PARTITION(part, xpcUnloading);
+			if (xpc_partition_disengaged(part) &&
+					part->act_state == XPC_P_INACTIVE) {
+				continue;
 			}
+
+			active_part_count++;
+
+			XPC_DEACTIVATE_PARTITION(part, reason);
+		}
+
+		if (active_part_count == 0) {
+			break;
+		}
+
+		if (jiffies >= printmsg_time) {
+			dev_info(xpc_part, "waiting for partitions to "
+				"deactivate/disengage, active count=%d, remote "
+				"engaged=0x%lx\n", active_part_count,
+				xpc_partition_engaged(1UL << partid));
+
+			printmsg_time = jiffies +
+					(XPC_DISENGAGE_PRINTMSG_INTERVAL * HZ);
 		}
 
-		if (active_part_count)
-			msleep_interruptible(300);
-	} while (active_part_count > 0);
+		/* sleep for a 1/3 of a second or so */
+		(void) msleep_interruptible(300);
+
+	} while (1);
+
+	DBUG_ON(xpc_partition_engaged(-1UL));
+
+
+	/* indicate to others that our reserved page is uninitialized */
+	xpc_rsvd_page->vars_pa = 0;
+
+	/* now it's time to eliminate our heartbeat */
+	del_timer_sync(&xpc_hb_timer);
+	DBUG_ON(xpc_vars->heartbeating_to_mask == 0);
 
+	/* take ourselves off of the reboot_notifier_list */
+	(void) unregister_reboot_notifier(&xpc_reboot_notifier);
 
 	/* close down protections for IPI operations */
 	xpc_restrict_IPI_ops();
@@ -876,6 +948,34 @@ xpc_do_exit(void)
 }
 
 
+/*
+ * This function is called when the system is being rebooted.
+ */
+static int
+xpc_system_reboot(struct notifier_block *nb, unsigned long event, void *unused)
+{
+	enum xpc_retval reason;
+
+
+	switch (event) {
+	case SYS_RESTART:
+		reason = xpcSystemReboot;
+		break;
+	case SYS_HALT:
+		reason = xpcSystemHalt;
+		break;
+	case SYS_POWER_OFF:
+		reason = xpcSystemPoweroff;
+		break;
+	default:
+		reason = xpcSystemGoingDown;
+	}
+
+	xpc_do_exit(reason);
+	return NOTIFY_DONE;
+}
+
+
 int __init
 xpc_init(void)
 {
@@ -920,6 +1020,12 @@ xpc_init(void)
 		spin_lock_init(&part->act_lock);
 		part->act_state = XPC_P_INACTIVE;
 		XPC_SET_REASON(part, 0, 0);
+
+		init_timer(&part->disengage_request_timer);
+		part->disengage_request_timer.function =
+				xpc_timeout_partition_disengage_request;
+		part->disengage_request_timer.data = (unsigned long) part;
+
 		part->setup_state = XPC_P_UNSET;
 		init_waitqueue_head(&part->teardown_wq);
 		atomic_set(&part->references, 0);
@@ -976,6 +1082,13 @@ xpc_init(void)
 	}
 
 
+	/* 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");
+	}
+
+
 	/*
 	 * Set the beating to other partitions into motion.  This is
 	 * the last requirement for other partitions' discovery to
@@ -997,6 +1110,9 @@ xpc_init(void)
 		/* indicate to others that our reserved page is uninitialized */
 		xpc_rsvd_page->vars_pa = 0;
 
+		/* take ourselves off of the reboot_notifier_list */
+		(void) unregister_reboot_notifier(&xpc_reboot_notifier);
+
 		del_timer_sync(&xpc_hb_timer);
 		free_irq(SGI_XPC_ACTIVATE, NULL);
 		xpc_restrict_IPI_ops();
@@ -1018,9 +1134,9 @@ xpc_init(void)
 		dev_err(xpc_part, "failed while forking discovery thread\n");
 
 		/* mark this new thread as a non-starter */
-		up(&xpc_discovery_exited);
+		up(&xpc_discovery_inactive);
 
-		xpc_do_exit();
+		xpc_do_exit(xpcUnloading);
 		return -EBUSY;
 	}
 
@@ -1039,7 +1155,7 @@ module_init(xpc_init);
 void __exit
 xpc_exit(void)
 {
-	xpc_do_exit();
+	xpc_do_exit(xpcUnloading);
 }
 module_exit(xpc_exit);