Re: [PATCH] x86: Remove readq()/writeq() on 32-bit

[Jeff Garzik <jeff@garzik.org>]

Hitoshi Mitake wrote:
> I think it's good time to decide making all architectures
> which have readq/writeq provide HAVE_READQ/HAVE_WRITEQ or not.
> 
> Adding HAVE_READQ/HAVE_WRITEQ to Kconfig of architectures needs
> agreement of all maintainers of these.
> 
> But, David Miller, maintainer of SPARC architecture, acked Roland's patch
> because of the possibility of bugs non-atomicity of readq/writeq of
> x86-32 will cause.
> 
> And, Jeff Garzik said that he saw zero justification for API removal.
> 
> Which way should we choose?
> Remove readq/writeq from x86-32?
> Or add HAVE... to all architectures with readq/writeq?

To repeat what has already been stated, each case was re-evaluated: 
http://marc.info/?l=linux-kernel&m=124103527326835&w=2

Roland's patch was acked, apparently, _in spite of_ the commonly 
accepted readq() definition already being in use!

Thusfar, I see two things:

(1) years of history has shown that non-atomic readq/writeq on 32-bit 
platforms has been sufficient, based on testing and experience.  In 
fact, in niu's case, a common readq/writeq would have PREVENTED a bug.

(2) unspecified fears continue to linger about non-atomicity

We should not base decisions on fear, particularly when the weight of 
evidence and experience points in the other direction.

	Jeff