ia64 r256624: Syncing disks... Giving up on 2 buffers

Issuing reboot:

Waiting (max 60 seconds) for system process `bufdaemon' to stop...done
Syncing disks, buffers remaining... 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 
1: buf:0xa00000009e10e200, vnode:0, flags:0, blkno:0, lblkno:0, buflock:lock type bufwait: EXCL by thread 0xe000000012741680 (pid 1047, tcsh, tid 100085)
2: buf:0xa00000009e0fd5e0, vnode:0, flags:0, blkno:0, lblkno:0, buflock:lock type bufwait: EXCL by thread 0xe0000000124e3b00 (pid 1037, tcsh, tid 100089)
Giving up on 2 buffers

I haven't seen these messages before.
What do they mean?

This is on r256624M, where the only modification is:

# svn diff /usr/src/
Index: /usr/src/sys/kern/uipc_syscalls.c
===================================================================
--- /usr/src/sys/kern/uipc_syscalls.c   (revision 256624)
+++ /usr/src/sys/kern/uipc_syscalls.c   (working copy)
_at__at_ -2070,7 +2070,7 _at__at_
        }
        KASSERT(error != 0 || (m->wire_count > 0 &&
            vm_page_is_valid(m, off & PAGE_MASK, xfsize)),
-           ("wrong page state m %p", m));
+           ("wrong page state m %p off %#jx xfsize %d", m, off, xfsize));
        VM_OBJECT_WUNLOCK(obj);
        return (error);
 }
# 


Thanks

Anton