Messages in this thread Patch in this message | | | Date | Tue, 07 Dec 2010 16:45:11 -0800 | From | Greg KH <> | Subject | [125/127] x86: uv: XPC receive message reuse triggers invalid BUG_ON() |
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2.6.32-stable review patch. If anyone has any objections, please let us know.
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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 = {
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