On Thu, 2023-01-12 at 16:17 +0000, Paul Durrant wrote:
> >
> > @@ -309,7 +317,14 @@ static void kvm_xen_update_runstate_guest(struct kvm_vcpu *v, bool atomic)
> > * gpc1 lock to make lockdep shut up about it.
> > */
> > lock_set_subclass(&gpc1->lock.dep_map, 1, _THIS_IP_);
> > - read_lock(&gpc2->lock);
> > + if (atomic) {
> > + if (!read_trylock(&gpc2->lock)) {
>
> You could avoid the nesting in this case with:
>
> if (atomic && !read_trylock(&gpc2->lock))
>
> > + read_unlock_irqrestore(&gpc1->lock, flags);
> > + return;
> > + }
> > + } else {
> > + read_lock(&gpc2->lock);
> > + }
Hm? Wouldn't it take the lock twice then? It'd still take the 'else' branch.
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