--- /dev/null
+From 09358972bff5ce99de496bbba97c85d417b3c054 Mon Sep 17 00:00:00 2001
+From: Robin Holt <holt@sgi.com>
+Date: Tue, 26 Oct 2010 14:21:15 -0700
+Subject: sgi-xp: incoming XPC channel messages can come in after the channel's partition structures have been torn down
+
+From: Robin Holt <holt@sgi.com>
+
+commit 09358972bff5ce99de496bbba97c85d417b3c054 upstream.
+
+Under some workloads, some channel messages have been observed being
+delayed on the sending side past the point where the receiving side has
+been able to tear down its partition structures.
+
+This condition is already detected in xpc_handle_activate_IRQ_uv(), but
+that information is not given to xpc_handle_activate_mq_msg_uv(). As a
+result, xpc_handle_activate_mq_msg_uv() assumes the structures still exist
+and references them, causing a NULL-pointer deref.
+
+Signed-off-by: Robin Holt <holt@sgi.com>
+Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
+Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
+
+---
+ drivers/misc/sgi-xp/xpc_uv.c | 17 +++++++++++++++++
+ 1 file changed, 17 insertions(+)
+
+--- a/drivers/misc/sgi-xp/xpc_uv.c
++++ b/drivers/misc/sgi-xp/xpc_uv.c
+@@ -409,6 +409,7 @@ xpc_process_activate_IRQ_rcvd_uv(void)
+ static void
+ xpc_handle_activate_mq_msg_uv(struct xpc_partition *part,
+ struct xpc_activate_mq_msghdr_uv *msg_hdr,
++ int part_setup,
+ int *wakeup_hb_checker)
+ {
+ unsigned long irq_flags;
+@@ -473,6 +474,9 @@ xpc_handle_activate_mq_msg_uv(struct xpc
+ case XPC_ACTIVATE_MQ_MSG_CHCTL_CLOSEREQUEST_UV: {
+ struct xpc_activate_mq_msg_chctl_closerequest_uv *msg;
+
++ if (!part_setup)
++ break;
++
+ msg = container_of(msg_hdr, struct
+ xpc_activate_mq_msg_chctl_closerequest_uv,
+ hdr);
+@@ -489,6 +493,9 @@ xpc_handle_activate_mq_msg_uv(struct xpc
+ case XPC_ACTIVATE_MQ_MSG_CHCTL_CLOSEREPLY_UV: {
+ struct xpc_activate_mq_msg_chctl_closereply_uv *msg;
+
++ if (!part_setup)
++ break;
++
+ msg = container_of(msg_hdr, struct
+ xpc_activate_mq_msg_chctl_closereply_uv,
+ hdr);
+@@ -503,6 +510,9 @@ xpc_handle_activate_mq_msg_uv(struct xpc
+ case XPC_ACTIVATE_MQ_MSG_CHCTL_OPENREQUEST_UV: {
+ struct xpc_activate_mq_msg_chctl_openrequest_uv *msg;
+
++ if (!part_setup)
++ break;
++
+ msg = container_of(msg_hdr, struct
+ xpc_activate_mq_msg_chctl_openrequest_uv,
+ hdr);
+@@ -520,6 +530,9 @@ xpc_handle_activate_mq_msg_uv(struct xpc
+ case XPC_ACTIVATE_MQ_MSG_CHCTL_OPENREPLY_UV: {
+ struct xpc_activate_mq_msg_chctl_openreply_uv *msg;
+
++ if (!part_setup)
++ break;
++
+ msg = container_of(msg_hdr, struct
+ xpc_activate_mq_msg_chctl_openreply_uv, hdr);
+ args = &part->remote_openclose_args[msg->ch_number];
+@@ -537,6 +550,9 @@ xpc_handle_activate_mq_msg_uv(struct xpc
+ case XPC_ACTIVATE_MQ_MSG_CHCTL_OPENCOMPLETE_UV: {
+ struct xpc_activate_mq_msg_chctl_opencomplete_uv *msg;
+
++ if (!part_setup)
++ break;
++
+ msg = container_of(msg_hdr, struct
+ xpc_activate_mq_msg_chctl_opencomplete_uv, hdr);
+ spin_lock_irqsave(&part->chctl_lock, irq_flags);
+@@ -613,6 +629,7 @@ xpc_handle_activate_IRQ_uv(int irq, void
+
+ part_referenced = xpc_part_ref(part);
+ xpc_handle_activate_mq_msg_uv(part, msg_hdr,
++ part_referenced,
+ &wakeup_hb_checker);
+ if (part_referenced)
+ xpc_part_deref(part);