Re: devfs: BKL *not* taken while opening devices

Arjan van de Ven
2002-04-30T16:54:27Z

On Tue, Apr 30, 2002 at 09:42:32AM -0700, Dave Hansen wrote:
> Russell King wrote:
> > On Mon, Apr 29, 2002 at 06:21:34PM +0100, Arjan van de Ven wrote:
> >
> >>I'm not convinced of that. It's not nearly a critical path and it's
> >>better to get even the "dumb" drivers safe than to risk having big
> >>security holes in there for years to come.
> >
> > Would it be worth dropping a BUG_ON(!kernel_locked()) in tty_open() to
> > catch this type of error? The tty code heavily relies on the BKL.
> >
> > This way, such locking problems would get caught early, since everyone
> > uses the tty code during boot, right?
>
> I like the idea. But, while we're at it, does anyone have a good enough
> grasp of locking the the TTY layer that we can start peeling some of the
> BKL out of there? Somebody was doing tests over a serial console here
> and the lockmeter data showed horrible BKL contention and hold times.

I really really doubt that fixing contention will make serial ports go
faster... it'll just move to another lock since I suspect we're
just waiting for hardware