Re: [Xen-devel] [PATCHv12 1/5] gnttab: per-active entry locking

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 12.06.15 at 15:33, <david.vrabel@xxxxxxxxxx> wrote:
> Introduce a per-active entry spin lock to protect active entry state
> The grant table lock must be locked before acquiring (locking) an
> active entry.
> 
> This is a step in reducing contention on the grant table lock, but
> will only do so once the grant table lock is turned into a read-write
> lock.
> 
> Based on a patch originally by Matt Wilson <msw@xxxxxxxxxx>.
> 
> Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
> ---
> v12:
> - Check for same refs in __gnttab_swap_grant_ref() to avoid deadlock.

I'm glad you spotted this, because the check having been there
until v8 I didn't notice it got lost later on.

Jan


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