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Subject: Re: [OMPI devel] autoconf warnings: openib BTL
From: Vasily Filipov (vasily_at_[hidden])
Date: 2014-03-04 01:59:35

Yes, it is possible, but there is some different if I will do it this way -
   With the current implementation (today into a trunk) if AC_RUN_IFELSE
fails => old code of RDMACM will rise,
   And by way you suggest, if we postpone the decision to a run time and
the check fails =>
   we have to abort RDMACM at all, because it was compiled for working
with AF_IB.
   So my question to you, if we take into account all this stuff above -
    What's the right way to implement it ? What do you think ?

Thank you,

On 03-Mar-14 17:31, Jeff Squyres (jsquyres) wrote:
> Can't you test for that at run-time?
> I.e., can't you do the configure-time test to see if AF_IB exists, and if it does, do a run-time check to see if it's useful/supported in the kernel? Or is there a reason not to do this (e.g., it would impose a performance penalty at run time because the check would need to be in the performance-critical code path)?
> On Mar 2, 2014, at 11:02 PM, Vasily Filipov <vasily_at_[hidden]> wrote:
>> some additional explanation - it could be a situation when AF_IB is defined in user space but kernel doesn't support it.
>> On 03-Mar-14 08:53, Vasily Filipov wrote:
>>> Hi Jeff,
>>> I've committed the fixes (r30905). It is a problem to detect kernel defines (such as AF_IB ), so we have to use AC_RUN_IFELSE macro.
>>> Thanks,
>>> Vasily.
>>> On 27-Feb-14 17:09, Jeff Squyres (jsquyres) wrote:
>>>> I'm seeing this warning this morning:
>>>> -----
>>>> warning: AC_RUN_IFELSE called without default to allow cross c\
>>>> ompiling
>>>> ../../lib/autoconf/general.m4:2748: AC_RUN_IFELSE is expanded from...
>>>> ../../lib/m4sugar/m4sh.m4:639: AS_IF is expanded from...
>>>> ompi/mca/btl/openib/configure.m4:37: MCA_ompi_btl_openib_CONFIG is expanded from.\
>>>> ..
>>>> config/ompi_mca.m4:571: MCA_CONFIGURE_M4_CONFIG_COMPONENT is expanded from...
>>>> config/ompi_mca.m4:352: MCA_CONFIGURE_FRAMEWORK is expanded from...
>>>> config/ompi_mca.m4:252: MCA_CONFIGURE_PROJECT is expanded from...
>>>> config/ompi_mca.m4:39: OMPI_MCA is expanded from...
>>>> the top level
>>>> -----
>>>> Is it necessary to AC_RUN_IFELSE here? Is AC_CHECK_DECLS not sufficient for some reason?
>>>> It strikes me that this test you currently have in configure.m4 really should be a run-time test, and that all you need in configure.m4 should be an AC_CHECK_DECLS to see if AF_IB exists.
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