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Re: [PATCH] rwlock: remove unneeded subtraction


  • To: Roger Pau Monne <roger.pau@xxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Tue, 15 Feb 2022 11:37:45 +0100
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  • Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
  • Delivery-date: Tue, 15 Feb 2022 10:37:53 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 15.02.2022 10:39, Roger Pau Monne wrote:
> There's no need to subtract _QR_BIAS from the lock value for storing
> in the local cnts variable in the read lock slow path: the users of
> the value in cnts only care about the writer-related bits and use a
> mask to get the value.
> 
> Note that further setting of cnts in rspin_until_writer_unlock already
> do not subtract _QR_BIAS.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>




 


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