USB2+umass: root mount fails

[M. Warner Losh]

In message: <741FAA3B-B91A-4A23-B47F-21141A8D0B5D at mac.com>
            Marcel Moolenaar <xcllnt at mac.com> writes:
: 
: On Feb 16, 2009, at 3:13 PM, M. Warner Losh wrote:
: 
: > In message: <ACB7DFF1-6C8E-4936-9BD9-BB2FD375F3BB at mac.com>
: >            Marcel Moolenaar <xcllnt at mac.com> writes:
: > : Before I dig into the code, what's the current status of
: > : root mounts on USB mass storage devices?
: >
: > First, there's a kludge-o-round that is similar to your "sleep 10"
: > that you've added.  It loops waiting for more devices to show up if
: > the desired root file system hasn't appeared yet.
: >
: > There's no way for hot-plug busses to tell the kernel "I've tried my
: > best to enumerate everything on my bus, and I'm done"
: 
: Of course there is. Any and all USB hubs have a certain
: number of ports. You can trivially iterate over all of
: them and declare completion when you've tried them all.

The hot-plug busses know.  The mountroot code doesn't have a way to
wait for the hot-plug busses.

: Recursion is also not a big deal. When you find a HUB
: underneath a port, you iterate over all the ports of
: that downstream hub before you declare completion of
: the USB discovery process.
: 
: When the USB discovery process is done, you release
: the root mount lock...
: 
: So what's the problem?

You're looking on the wrong side of the problem.

Warner