Messages in this thread | | | Subject | Re: RT patch acceptance | From | Thomas Gleixner <> | Date | Wed, 01 Jun 2005 22:56:07 +0200 |
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On Wed, 2005-06-01 at 21:22 +0200, Andrea Arcangeli wrote: > On Wed, Jun 01, 2005 at 07:53:11PM +0200, Thomas Gleixner wrote: > > Thank god thats not the case. We did a patent research on this last year > > and the result was that you can replace the cli/sti by a software flag > > in the OS itself without violating the patent. > > Did you publish something about it (so that people won't have to do it > over and over again)?
I have no permission from the customer who actually payed the survey to publish the results yet. But I continue asking for it.
> > The combination of replacing it in the host OS and running said host OS > > as an idle task of the underlying RTOS would violate the patent. > > > > So if PREEMPT-RT would use a soft cli/sti emulation, no problem should > > arise. > > So I wonder why it doesn't do that and it leaves local_irq_disable > uncovered making it a "metal hard" instead of "ruby hard" like rtai.
I have a slightly outdated patch with that around on top of RT, but it introduces yet another level of ugliness. You must carefully identify the places where you really need the hard_local_irq_dis/enable(). It's not hard though.
I used it in the early days of PREEMPT_RT to identify the IRQ off sections and some other deadlocking scenarios. I kept this always as an option for adding on top of Ingos implementation to close the gap to "ruby".
tglx
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