Re: [linux-usb-devel] Re: bug 2400

[David Brownell <david-b@pacbell.net>]

James Bottomley wrote:
>  that's intra subsystem synchronisation, not inter subsystem

I'd say that device_driver.remove() calls from the bus management
code to a given device driver are inter-subsystem...


> Look, the rules are very simple:
> 
> - Every subsystem gives out refcounted objects.
> 
> - Every subsystem takes in a disconnection event for another object. 
> ..
> 
> If you follow these rules, there's no *inter* subsystem ordering or
> synchronisation requirement.

Well, either handling the disconnection event from the lower level
subsystem (bus) is such a requirement, or it's not necessary!  I've
got to assume the former, since the Linux kernel doesn't garbage
collect its memory.

Refcounting systems need loop-breaking protocols ("disconnect");
this is needed for that sort of reason, if no other.

- Dave