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. To: Ingo Molnar To: tglx@linutronix.de Signed-off-by: Robin Holt Cc: Jack Steiner Cc: linux-kernel@vger.kernel.org --- drivers/misc/sgi-xp/xpc_uv.c | 3 --- 1 file changed, 3 deletions(-) Index: linux-x86/drivers/misc/sgi-xp/xpc_uv.c =================================================================== --- linux-x86.orig/drivers/misc/sgi-xp/xpc_uv.c 2009-11-18 22:16:45.000000000 -0600 +++ linux-x86/drivers/misc/sgi-xp/xpc_uv.c 2009-11-18 22:16:45.000000000 -0600 @@ -1428,7 +1428,6 @@ 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); @@ -1652,8 +1651,6 @@ 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 = { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/