Re: [RFC PATCH 05/35] Add sync bitops

Christoph Lameter
2006-05-09T22:57:40Z

On Tue, 9 May 2006, Chris Wright wrote:

> Add "always lock'd" implementations of set_bit, clear_bit and
> change_bit and the corresponding test_and_ functions. Also add
> "always lock'd" implementation of cmpxchg. These give guaranteed
> strong synchronisation and are required for non-SMP kernels running on
> an SMP hypervisor.

Could you explain why this is done and what is exactly meant with "always
looked"? Wh the performance impact?