On Wed, Dec 05, 2012 at 01:40:24PM +0000, Marc Zyngier wrote: > Admittedly, the whole sequence should be rewritten to be clearer. What > it does is "If we're running a guest and there is no active interrupt, > then kick the guest". On the whole this entire thing should be written clearer; from the explanations you've given it seems that the only reason this code works is because you're relying on several behaviours all coming together to achieve the right result - which makes for fragile code. You're partly relying on atomic types to ensure that the increment and decrement happen exclusively. You're then relying on a combination of IRQ protection and cmpxchg() to ensure that the non-atomic read of the atomic type won't be a problem. This doesn't inspire confidence, and I have big concerns over whether this code will still be understandable in a number of years time. And I still wonder how safe this is even with your explanations. IRQ disabling only works for the local CPU core so I still have questions over this wrt a SMP host OS. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
