Re: [PATCH 4/4] usb: libusual: locking cleanup

Daniel Walker
2007-12-23T16:47:50Z

On Sat, 2007-12-22 at 23:37 -0800, Pete Zaitcev wrote:
> On Sat, 22 Dec 2007 09:01:50 -0800, Daniel Walker <dwalker@mvista.com> wrote:
>
> > Then in usu_probe_thread() your basically stopping it at the start of
> > the function with a down(), and the up() is just ancillary .. So you
> > could easily move the up() further down in the function and still have
> > the same level of exclusion..
>
> The unfortunate complication here is request_module. I didn't want to
> keep a semaphore locked across it, in case child waits for something.
> I wonder if there may be some deadlock that we cannot foresee.
> But I guess it won't hurt to try.

I noticed you also have a spinlock held in usu_probe_thread(), the
usu_lock.. That spinlock would preclude anything inside request_module()
from sleeping..

One thing that has bothered me is that I don't see a reason why this
couldn't become a complete, yet you have a comment which says that it
can't be a complete.. I honestly didn't understand the comment.. I would
imagine that you tried a complete , and it didn't work?

> I tested the patch and it seems to work ok.

Great, thanks ..

Daniel