Re: [PATCH] x86: Remove readq()/writeq() on 32-bit
From: Jeff Garzik
Date: Wed May 13 2009 - 16:44:07 EST
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
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