Re: [linuxsh-dev] Question on SH/kernel discrepancies

[Jesper S. <js...@re...>]

>>>>> "NIIBE" == NIIBE Yutaka <gn...@m1...> writes:

NIIBE> Jeremy Siegel wrote:
>> We've been considering SH support in future distributions, and I've
>> noticed a couple differences between the SourceForge CVS and
>> kernel.org in non-SH-specific areas.  In particular:
>> 
>> - In mm/memory.c:do_swap_page(), a pair of page/cache flush calls
>> were
>> 
>> moved out of an "if (!page)" block down toward the function end, so
>> they are executed in more cases and at a different time.  This
>> change was apparently put into the SH CVS source at version 1.7
>> nearly 6 months ago, but isn't in kernel.org v2.4.1.  I'm not that
>> familiar with the memory-management internals for linux (or SH); is
>> this something that SH requires, or is it a "leftover" artifact of
>> earlier cache/MMU testing?  If it's needed, is there some reason
>> why
>> 
>> it has been rejected by the main linux tree?

NIIBE> I believe it's needed for SH-4.  SH-4 has virtually indexed and
NIIBE> physically tagged cache system with write back.  For such
NIIBE> architecture the changes are required.

Such changes should be wrapped in #ifdef/#endif to make it clear why
it differs from the main sources. Otherwise it'll just be considered a
merge bug at some time and get ditched.

Same goes for the SolutionEngine hack.

IMHO, of course.

Jesper