[Karmic] SRU: fnctl: f_modown should call write_lock_irqsave/restore

[Andy Whitcroft]

On Fri, Jan 29, 2010 at 10:43:23AM +0100, Stefan Bader wrote:
> SRU Justification:
> 
> Impact: While we have no real bug reported (at least not one we can simply
> connect to it) I really would like to have this backported to Karmic.
> 
> Fix: This has gone into 2.6.32.y (and 2.6.27.y) and moving from a *_irq to
> a *_irqsave variant can only make things better. Plus we might get patches
> that expose the problem, too. And then forget to pull this as well.
> 
> Thoughts? I would create a bug report for it, should we decide it should
> go in.

Seems that there is a known case where we can call it with IRQs disabled,
and with the _irq variant all sorts of hard to diagnose hangs would
be possible.  I'd support putting that in given its a call which can be
tickled from userspace.

-apw