Yes, if /usr were mounted over NFS, we'd experience this hang too.
There are secondary implications of the NFS unmount not being seen by the NFS server, since the NFS server still has an mount entry for the client, which is no longer contactable. It tries to make a delegation callback, which invariably times out, causing other problems.
This may well fit into the category of 'high' priority, but life is good, as we have a fix ;-) .
Yes, if /usr were mounted over NFS, we'd experience this hang too.
There are secondary implications of the NFS unmount not being seen by the NFS server, since the NFS server still has an mount entry for the client, which is no longer contactable. It tries to make a delegation callback, which invariably times out, causing other problems.
This may well fit into the category of 'high' priority, but life is good, as we have a fix ;-) .