Re: Re: Hotplug events during sleep transition

[Dmitry Torokhov <dtor_core@ameritech.net>]

On Wednesday 28 December 2005 21:10, Alan Stern wrote:
> On Tue, 27 Dec 2005, Dmitry Torokhov wrote:
> 
> > > Would it be possible to simply mark the device as 'removed' and ignore it
> > > until we resumed, and then clean it up (hotplug events and everything)?
> > >
> > 
> > Unfortunately swsusp resumes devices in the middle of suspend process
> > with everything frozen and drivers don't know if they may clean up or
> > have to postpone doing so.
> 
> Drivers should strive to avoid cleaning up after removed devices during 
> their resume methods in any case.  Such cleanups shouldn't happen until 
> userspace has been unfrozen.
> 
> >  To do it uniformly you'd need to introduce
> > threads and offload cleanups. I doubt it is good idea to require each
> > subsystem to define cleanup thread or [ab]used keventd?
> 
> Why do you need a new cleanup thread?  What's wrong with the existing 
> strategy for handling removed devices -- i.e., the procedure that would 
> have been followed if there was no suspend/resume transition?
> 

Sometimes there is no such procedure. For example if you yank PS/2 mouse
there is no way for the system to detect it's missing. Only when you try
to resume and mouse does not respond you realize it's gone. I bet there
are other devices like that. 

-- 
Dmitry