lkml.org 
[lkml]   [2010]   [Dec]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[125/127] x86: uv: XPC receive message reuse triggers invalid BUG_ON()
2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Robin Holt <holt@sgi.com>

commit 046d6c563b1c6226bbf0f84e5b2413ad8ab921a1 upstream.

This was a difficult bug to trip. XPC was in the middle of sending an
acknowledgement for a received message.

In xpc_received_payload_uv():
.
ret = xpc_send_gru_msg(ch->sn.uv.cached_notify_gru_mq_desc, msg,
sizeof(struct xpc_notify_mq_msghdr_uv));
if (ret != xpSuccess)
XPC_DEACTIVATE_PARTITION(&xpc_partitions[ch->partid], ret);
msg->hdr.msg_slot_number += ch->remote_nentries;

at the point in xpc_send_gru_msg() where the hardware has dispatched the
acknowledgement, the remote side is able to reuse the message structure
and send a message with a different slot number. This problem is made
worse by interrupts.

The adjustment of msg_slot_number and the BUG_ON in
xpc_handle_notify_mq_msg_uv() which verifies the msg_slot_number is
consistent are only used for debug purposes. Since a fix for this that
preserves the debug functionality would either have to infringe upon the
payload or allocate another structure just for debug, I decided to remove
it entirely.

Signed-off-by: Robin Holt <holt@sgi.com>
Cc: Jack Steiner <steiner@sgi.com>
Cc: Ingo Molnar <mingo@elte.hu>
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 | 3 ---
1 file changed, 3 deletions(-)
--- a/drivers/misc/sgi-xp/xpc_uv.c
+++ b/drivers/misc/sgi-xp/xpc_uv.c
@@ -1441,7 +1441,6 @@ xpc_handle_notify_mq_msg_uv(struct xpc_p
msg_slot = ch_uv->recv_msg_slots +
(msg->hdr.msg_slot_number % ch->remote_nentries) * ch->entry_size;

- BUG_ON(msg->hdr.msg_slot_number != msg_slot->hdr.msg_slot_number);
BUG_ON(msg_slot->hdr.size != 0);

memcpy(msg_slot, msg, msg->hdr.size);
@@ -1665,8 +1664,6 @@ xpc_received_payload_uv(struct xpc_chann
sizeof(struct xpc_notify_mq_msghdr_uv));
if (ret != xpSuccess)
XPC_DEACTIVATE_PARTITION(&xpc_partitions[ch->partid], ret);
-
- msg->hdr.msg_slot_number += ch->remote_nentries;
}

static struct xpc_arch_operations xpc_arch_ops_uv = {



\
 
 \ /
  Last update: 2010-12-08 01:53    [from the cache]
©2003-2011 Jasper Spaans