From 046d6c563b1c6226bbf0f84e5b2413ad8ab921a1 Mon Sep 17 00:00:00 2001 From: Robin Holt Date: Tue, 15 Dec 2009 16:47:59 -0800 Subject: [PATCH] x86: uv: XPC receive message reuse triggers invalid BUG_ON() 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 Cc: Jack Steiner Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/misc/sgi-xp/xpc_uv.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/drivers/misc/sgi-xp/xpc_uv.c b/drivers/misc/sgi-xp/xpc_uv.c index 241ea5f01aaa..d2f4e9121f93 100644 --- a/drivers/misc/sgi-xp/xpc_uv.c +++ b/drivers/misc/sgi-xp/xpc_uv.c @@ -1428,7 +1428,6 @@ xpc_handle_notify_mq_msg_uv(struct xpc_partition *part, 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); @@ -1652,8 +1651,6 @@ xpc_received_payload_uv(struct xpc_channel *ch, void *payload) 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 = { -- 2.20.1