[ofa-general] Re: [PATCH 01 of 12] Core of mmu notifiers

[Andrea Arcangeli]

On Tue, Apr 22, 2008 at 05:37:38PM +0200, Eric Dumazet wrote:
> I am saying your intent was probably to test
>
> else if ((unsigned long)*(spinlock_t **)a ==
> 	    (unsigned long)*(spinlock_t **)b)
> 		return 0;

Indeed...

> Hum, it's not a micro-optimization, but a bug fix. :)

The good thing is that even if this bug would lead to a system crash,
it would be still zero risk for everybody that isn't using KVM/GRU
actively with mmu notifiers. The important thing is that this patch
has zero risk to introduce regressions into the kernel, both when
enabled and disabled, it's like a new driver. I'll shortly resend 1/12
and likely 12/12 for theoretical correctness. For now you can go ahead
testing with this patch as it'll work fine despite of the bug (if it
wasn't the case I would have noticed already ;).