Re: [Xen-devel] [PATCH] x86: xen: size struct xen_spinlock to always fit in arch_spinlock_t

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

On Jan 23, 2012, at 11:32 AM, David Vrabel wrote:

> From: David Vrabel <david.vrabel@xxxxxxxxxx>
> 
> If NR_CPUS < 256 then arch_spinlock_t is only 16 bits wide but struct
> xen_spinlock is 32 bits.  When a spin lock is contended and
> xl->spinners is modified the two bytes immediately after the spin lock
> would be corrupted.
> 
> This is a regression caused by 84eb950db13ca40a0572ce9957e14723500943d6
> (x86, ticketlock: Clean up types and accessors) which reduced the size
> of arch_spinlock_t.

Oh, *ouch*.  Very sorry about that one.

        J

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