Re: [Xen-devel] [PATCH v10 for-xen-4.5 2/2] dpci: Replace tasklet with an softirq

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 12.11.14 at 03:23, <konrad.wilk@xxxxxxxxxx> wrote:
> +static void pt_pirq_softirq_reset(struct hvm_pirq_dpci *pirq_dpci)
> +{
> +    struct domain *d = pirq_dpci->dom;
> +
> +    ASSERT(spin_is_locked(&d->event_lock));
> +
> +    switch ( cmpxchg(&pirq_dpci->state, 1 << STATE_SCHED, 0) )
> +    {
> +    case (1 << STATE_SCHED):
> +        /*
> +         * We are going to try to de-schedule the softirq before it goes in
> +         * STATE_RUN. Whoever clears STATE_SCHED MUST refcount the 'dom'.
> +         */
> +        put_domain(d);
> +        /* fallthrough. */

Considering Sander's report, the only suspicious place I find is this
one: When the STATE_SCHED flag is set, pirq_dpci is on some
CPU's list. What guarantees it to get removed from that list before
getting inserted on another one?

Jan


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