On Thu, Aug 13, 2009 at 12:49:45PM +0300, Avi Kivity wrote:
> On 08/13/2009 12:48 PM, Gleb Natapov wrote:
> >On Thu, Aug 13, 2009 at 06:13:30AM -0300, Marcelo Tosatti wrote:
> >>>+++ b/virt/kvm/ioapic.c
> >>>@@ -182,6 +182,7 @@ int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level)
> >>> union kvm_ioapic_redirect_entry entry;
> >>> int ret = 1;
> >>>
> >>>+ mutex_lock(&ioapic->lock);
> >>> if (irq>= 0&& irq< IOAPIC_NUM_PINS) {
> >>> entry = ioapic->redirtbl[irq];
> >>> level ^= entry.fields.polarity;
> >>But this is an RCU critical section now, right?
> >>
> >Correct! Forget about that. It was spinlock, but Avi prefers mutexes.
>
> Well, I prefer correct code to mutexes.
>
> >>If so, you can't sleep, must use a spinlock.
> >Either that or I can collect callbacks in critical section and call them
> >afterwords.
>
> There's also srcu.
>
What are the disadvantages? There should be some, otherwise why not use
it all the time.
--
Gleb.
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