[Xen-devel] Re: [PATCH 10/13] xen/pvticket: allow interrupts to be enabled while blocking

[Peter Zijlstra <peterz@xxxxxxxxxxxxx>]

On Thu, 2011-09-01 at 17:55 -0700, Jeremy Fitzhardinge wrote:
> +       /* Make sure an interrupt handler can't upset things in a
> +          partially setup state. */
>         local_irq_save(flags);
>  
> +       /*
> +        * We don't really care if we're overwriting some other
> +        * (lock,want) pair, as that would mean that we're currently
> +        * in an interrupt context, and the outer context had
> +        * interrupts enabled.  That has already kicked the VCPU out
> +        * of xen_poll_irq(), so it will just return spuriously and
> +        * retry with newly setup (lock,want).
> +        *
> +        * The ordering protocol on this is that the "lock" pointer
> +        * may only be set non-NULL if the "want" ticket is correct.
> +        * If we're updating "want", we must first clear "lock".
> +        */
> +       w->lock = NULL; 

I mean, I don't much care about Xen code, but that's two different
comment styles.

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