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SubjectRe: [V3][PATCH 2/6] x86, nmi: create new NMI handler routines
On Fri, Aug 26, 2011 at 11:44:12AM +0200, Peter Zijlstra wrote:
> On Thu, 2011-08-25 at 12:45 -0400, Don Zickus wrote:
> > +static int __setup_nmi(unsigned int type, struct nmiaction *action)
> > +{
> > + struct nmi_desc *desc = nmi_to_desc(type);
> > + struct nmiaction **a = &(desc->head);
> > + unsigned long flags;
> > +
> > + spin_lock_irqsave(&desc->lock, flags);
> > +
> > + /*
> > + * some handlers need to be executed first otherwise a fake
> > + * event confuses some handlers (kdump uses this flag)
> > + */
> > + if (!(action->flags & NMI_FLAG_FIRST))
> > + while ((*a) != NULL)
> > + a = &((*a)->next);
> > +
> > + action->next = *a;
> > + rcu_assign_pointer(*a, action);
> > +
> > + spin_unlock_irqrestore(&desc->lock, flags);
> > + return 0;
> > +}
> > +
> > +static struct nmiaction *__free_nmi(unsigned int type, const char *name)
> > +{
> > + struct nmi_desc *desc = nmi_to_desc(type);
> > + struct nmiaction *n, **np = &(desc->head);
> > + unsigned long flags;
> > +
> > + spin_lock_irqsave(&desc->lock, flags);
> > +
> > + while ((*np) != NULL) {
> > + n = *np;
> > +
> > + /*
> > + * the name passed in to describe the nmi handler
> > + * is used as the lookup key
> > + */
> > + if (!strcmp(n->name, name)) {
> > + WARN(in_nmi(),
> > + "Trying to free NMI (%s) from NMI context!\n", n->name);
> > + rcu_assign_pointer(*np, n->next);
> > + break;
> > + }
> > + np = &(n->next);
> > + }
> > +
> > + spin_unlock_irqrestore(&desc->lock, flags);
> > + synchronize_rcu();
> > + return (*np);
> > +}
>
> Probably not worth fixing, but if someone was silly enough to register
> with an already existing name we're up shit creek, right? :-)

Hmm, I thought I put a check in there during registration to prevent that.
Guess not. But yeah, I thought about doing that just to have one less
thing bite me later.

Cheers,
Don


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