Fiasco.OC Kernel Semaphores r38->r40

Adam Lackorzynski adam at
Wed Nov 14 20:15:30 CET 2012


On Mon Nov 12, 2012 at 14:03:23 -0800, Daniel Waddington wrote:
> I noticed that kernel semaphores seem to have vanished from
> Fiasco.OC r40 (when they were definitely there in r38).
> They seem to have been replaced with an ipc/sw irq solution - is
> this true?  Can someone explain the design rationale behind this?
> If we want to back-port them into r40 is there anything we need to
> be aware of?

Indeed we removed that. We think this is actually redundant as the same
can be done via IRQs and atomic ops. Additionally there were cornercase
in MP which made it all more complicated then wanted. I think you should
also switch a IRQ-based mechanism.

Adam                 adam at

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