[lttng-dev] liburcu sparc support, build failure on buildd

[Patrick Baggett]

On Fri, Feb 22, 2013 at 8:15 AM, Mathieu Desnoyers <
mathieu.desnoyers at efficios.com> wrote:

> Hi,
>
> I notice the following build failure here
>
> https://buildd.debian.org/status/package.php?p=liburcu
>
> Tail of log for liburcu on sparc:
>
> urcu/static/wfqueue.h:84:2: warning: implicit declaration of function
> 'CMM_STORE_SHARED' [-Wimplicit-function-declaration]
> urcu/static/wfqueue.h: In function '___cds_wfq_node_sync_next':
> urcu/static/wfqueue.h:99:2: warning: implicit declaration of function
> 'CMM_LOAD_SHARED' [-Wimplicit-function-declaration]
> urcu/static/wfqueue.h:99:15: warning: assignment makes pointer from
> integer without a cast [enabled by default]
> urcu/static/wfqueue.h:104:4: warning: implicit declaration of function
> 'caa_cpu_relax' [-Wimplicit-function-declaration]
> urcu/static/wfqueue.h: In function '___cds_wfq_dequeue_blocking':
> urcu/static/wfqueue.h:126:55: warning: comparison between pointer and
> integer [enabled by default]
> make[3]: *** [wfqueue.lo] Error 1
> make[3]: Leaving directory
> `/build/buildd-liburcu_0.7.6-1-sparc-GySyug/liburcu-0.7.6'
> make[2]: *** [all-recursive] Error 1
> make[2]: Leaving directory
> `/build/buildd-liburcu_0.7.6-1-sparc-GySyug/liburcu-0.7.6'
> make[1]: *** [all] Error 2
> make[1]: Leaving directory
> `/build/buildd-liburcu_0.7.6-1-sparc-GySyug/liburcu-0.7.6'
> dh_auto_build: make -j1 returned exit code 2
> make: *** [build-arch] Error 2
>
> One main question I have: what sparc architectures are supported by
> Debian's "sparc" architecture ? Userspace RCU only supports Sparcv9 and
> onward, because it requires some atomic instructions.
>
>
Debian definitely only supports[1] SPARCv9 compatible CPUs (sun4u, sun4v).
I've heard that Linux on 32-bit SPARC (i.e. sparc <= v8) is shoddy now, but
I certainly haven't tried it.

[1] http://www.debian.org/ports/sparc/

As documented in the urcu README file, building a package that includes
> sparcv9 isntructions for 32-bit sparc can be done with:
>
> CFLAGS="-m32 -Wa,-Av9a -g -O2" ./configure
>

"v9a" includes VIS instruction set, which is an extension of SPARCv9. I
think only some early Fujitsu SPARC CPUs (pre 2000) are missing it -- the
original UltraSPARC from Sun does include it. Probably safe to turn on, but
technically extends requirements to use the program.


>
> But if Debian sparc needs to support pre-v9 sparcs, then I guess it
> would not be appropriate to use v9 instructions for urcu sparc build.
>
> Thoughts ?
>
> Thanks,
>
> Mathieu
>
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
>
>
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