svn commit: r197643 - in head/sys: kern sys

Attilio Rao attilio at freebsd.org
Wed Sep 30 13:49:00 UTC 2009


2009/9/30 Ivan Voras <ivoras at freebsd.org>:
> 2009/9/30 Attilio Rao <attilio at freebsd.org>:
>> Author: attilio
>> Date: Wed Sep 30 13:26:31 2009
>> New Revision: 197643
>> URL: http://svn.freebsd.org/changeset/base/197643
>>
>> Log:
>>  When releasing a read/shared lock we need to use a write memory barrier
>>  in order to avoid, on architectures which doesn't have strong ordered
>>  writes, CPU instructions reordering.
>
> Will this influence performance on those architecture that do?
>

No.
In those architectures, memory barriers are crafted in the lighter
possible way (aka often are the same operation as a 'simple' atomic,
like the ia32 case).

Attilio


-- 
Peace can only be achieved by understanding - A. Einstein


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