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Re: [PATCH] Change __ASSUME_ACCEPT4 on powerpc to 2.6.37


On Tue, 4 Jun 2013, Adam Conrad wrote:

> In Debian, we currently build with a minimum kernel version of 2.6.32
> for backward compat with squeeze, lucid, and RHEL6.  __ASSUME_ACCEPT4
> is enabled for kernel versions >= 2.6.28 on x86, sparc, powerpc, and
> s390, however this wasn't actually exported on powerpc until 2.6.37ish
> in commit 86250b9d12caa1a3dee12a7cf638b7dd70eaadb6:

This bug should be filed in Bugzilla as it looks like something that would 
have been a user-visible bug in a release.  (Whereas cases where an 
__ASSUME_* macro isn't defined but could be are simply missing 
optimizations, so don't need bugs filed when fixing them.)

Really we could do with a proper review of all the Linux kernel versions 
used in kernel-features.h files, both in libc and ports, to assess whether 
each macro is defined for the correct set of versions for all 
architectures (to find both cases like this where the macro is defined for 
too early a version, and also cases where a port should now define the 
macro for some versions, but doesn't define it at all, and the main 
kernel-features.h defines it only for a limited set of libc 
architectures) - I very much doubt this is the only such bug.

That would be quite a substantial project ... maybe there should be a wiki 
list of __ASSUME_* macros where people can check them off after verifying 
that a single macro is defined for the correct versions, taking into 
account all released kernels up to 3.9 (modulo ambiguity about whether to 
use version N or N+1 when support was added in N-rcM) for all 
architectures.  It would be nice if such a list recorded cases where an 
architecture didn't have the relevant feature as of 3.9 but might get it 
in future, so we know what to watch out for regarding updating 
kernel-features.h for new kernel releases in future.

-- 
Joseph S. Myers
joseph@codesourcery.com


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