Re: [COUNTERPATCH] mm: avoid overflowing preempt_count() in mmu_take_all_locks()

[Avi Kivity]

On 04/01/2010 01:31 PM, Peter Zijlstra wrote:
> I'm sure you dropped Ingo and Thomas by accident.
>
> On Thu, 2010-04-01 at 12:40 +0300, Avi Kivity wrote:
>    
> > mmu_take_all_locks() takes a spinlock for each vma, which means we increase
> > the preempt count by the number of vmas in an address space.  Since the user
> > controls the number of vmas, they can cause preempt_count to overflow.
> >
> > Fix by making mmu_take_all_locks() only disable preemption once by making
> > the spinlocks preempt-neutral.
> >      
> Right, so while this will get rid of the warning it doesn't make the
> code any nicer, its still a massive !preempt latency spot.
>    

True.  But this is a band-aid we can apply now while the correct fix is 
being worked out.

--
error compiling committee.c: too many arguments to function

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