[patch 1/3] V2 sgi-xpc: ensure flags are updated before bte_copy

[Robin Holt]

From: Robin Holt <holt@xxxxxxx>

The clearing of the msg->flags needs a barrier between it and the notify
of the channel threads that the messages are cleaned and ready for use.

I also modified all the *mb() operations to be prefixed with smp_ as
they all are really only needed when running with multiple cpus.

Signed-off-by: Robin Holt <holt@xxxxxxx>
Signed-off-by: Dean Nelson <dcn@xxxxxxx>
Cc: <stable@xxxxxxxxxx>

---

 drivers/misc/sgi-xp/xpc_sn2.c |    9 +++++----
 drivers/misc/sgi-xp/xpc_uv.c  |    2 +-
 2 files changed, 6 insertions(+), 5 deletions(-)
Index: xpc-fixes-20090115/drivers/misc/sgi-xp/xpc_sn2.c
===================================================================
--- xpc-fixes-20090115.orig/drivers/misc/sgi-xp/xpc_sn2.c	2009-01-21 09:32:18.601506191 -0600
+++ xpc-fixes-20090115/drivers/misc/sgi-xp/xpc_sn2.c	2009-01-21 09:44:14.930207605 -0600
@@ -1836,6 +1836,7 @@ xpc_process_msg_chctl_flags_sn2(struct x
 		 */
 		xpc_clear_remote_msgqueue_flags_sn2(ch);
 
+		smp_wmb(); /* ensure flags have been cleared before bte_copy */
 		ch_sn2->w_remote_GP.put = ch_sn2->remote_GP.put;
 
 		dev_dbg(xpc_chan, "w_remote_GP.put changed to %ld, partid=%d, "
@@ -1934,7 +1935,7 @@ xpc_get_deliverable_payload_sn2(struct x
 			break;
 
 		get = ch_sn2->w_local_GP.get;
-		rmb();	/* guarantee that .get loads before .put */
+		smp_rmb();	/* guarantee that .get loads before .put */
 		if (get == ch_sn2->w_remote_GP.put)
 			break;
 
@@ -2053,7 +2054,7 @@ xpc_allocate_msg_sn2(struct xpc_channel 
 	while (1) {
 
 		put = ch_sn2->w_local_GP.put;
-		rmb();	/* guarantee that .put loads before .get */
+		smp_rmb();	/* guarantee that .put loads before .get */
 		if (put - ch_sn2->w_remote_GP.get < ch->local_nentries) {
 
 			/* There are available message entries. We need to try
@@ -2186,7 +2187,7 @@ xpc_send_payload_sn2(struct xpc_channel 
 	 * The preceding store of msg->flags must occur before the following
 	 * load of local_GP->put.
 	 */
-	mb();
+	smp_mb();
 
 	/* see if the message is next in line to be sent, if so send it */
 
@@ -2287,7 +2288,7 @@ xpc_received_payload_sn2(struct xpc_chan
 	 * The preceding store of msg->flags must occur before the following
 	 * load of local_GP->get.
 	 */
-	mb();
+	smp_mb();
 
 	/*
 	 * See if this message is next in line to be acknowledged as having
Index: xpc-fixes-20090115/drivers/misc/sgi-xp/xpc_uv.c
===================================================================
--- xpc-fixes-20090115.orig/drivers/misc/sgi-xp/xpc_uv.c	2009-01-15 09:55:59.000000000 -0600
+++ xpc-fixes-20090115/drivers/misc/sgi-xp/xpc_uv.c	2009-01-21 09:44:34.296607895 -0600
@@ -1423,7 +1423,7 @@ xpc_send_payload_uv(struct xpc_channel *
 		atomic_inc(&ch->n_to_notify);
 
 		msg_slot->key = key;
-		wmb(); /* a non-NULL func must hit memory after the key */
+		smp_wmb(); /* a non-NULL func must hit memory after the key */
 		msg_slot->func = func;
 
 		if (ch->flags & XPC_C_DISCONNECTING) {

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