Re: [Xen-devel] [PATCH 2/2] grant_table: convert grant table rwlock to percpu rwlock

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 18.11.15 at 12:23, <malcolm.crossley@xxxxxxxxxx> wrote:
> On 18/11/15 10:54, Jan Beulich wrote:
>> That's not how I understood it, the rwlock isn't per-pCPU (at least not
>> in what this patch does - it remains a per-domain one). The per-pCPU
>> object is a pointer to an rwlock, which gets made point to whatever
>> domain's rwlock the pCPU wants to own.
> 
> This description is correct but it's important to note that the rwlock
> is only used by the writers and could be effectively replaced with a 
> spinlock.

While such replacement may indeed be possible (whether desirable
is another question), I'm pretty sure I saw readers taking the read
lock on the slow path.

Jan


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