Should we be using CONFIG_PREEMPT_BKL in the Fedora kernel?

[Pete Zaitcev]

On Wed, 21 Mar 2007 12:27:17 -0700 (PDT), Roland McGrath <roland at redhat.com> wrote:

> FWIW, I have taken to CONFIG_PREEMPT=y in my hacking kernels because it
> exposed on my clunky test machines bugs that were otherwise reproduced only
> on big honking machines with lots of parallelism. [...]

It helps with that, but I just don't trust it to work at all times.
It's a really kludgy code from MontaVista, developed with embedded
devices in mind. It's a certified miracle that it boots on SMP at all.

That said, I love to hoist it onto others. It really helps to flush
mb() from drivers. Before, it always was a hassle to persuade driver
writers that they must not do it; not worth the trouble. Now you just
turn the preempt on and voila, the box crashes. Heck, I had preempt
find a bug in ub once (guess what... used mb() there too -- nobody
is perfect).

But running it on a production box is pure madness, IMHO.

-- Pete