Re: RT patch acceptance

Andrea Arcangeli
2005-06-01T15:09:25Z

On Wed, Jun 01, 2005 at 04:45:57PM +0200, Esben Nielsen wrote:
> the implementation of the former spinlock, now a mutex, is using a
> raw_spin_lock, which disables interrupts.

It's not _raw_spin_lock that disables irq. It's spin_lock_irq that does
that and it has been redefinined into an operation that doesn't disable
irq.

The patent text goes like this "providing a software emulator to disable
and enable interrupts from the general purpose operating system;

marking interrupts as "soft disabled" and not "soft enabled" in response
to requests from the general purpose operating system to disable
interrupts; ".

I'm not a lawyer and I hope to be wrong, but I sure wouldn't bet the
farm on it. You should ask a lawyer to make sure that non-GPL code is
not infringing IMHO. This assuming that this could be a problem. It was
a problem for RTAI users, people is used to the fact userland doesn't
need to be GPL. Note that LGPL and BSD code will infringe too (i.e. no
glibc etc..).