[oe] [meta-java] Sporadic segfaults when compiling jamvm-native and classpath-native

[Kaaria, Erkka]

> From: openembedded-devel-bounces at lists.openembedded.org
> [mailto:openembedded-devel-bounces at lists.openembedded.org] On
> Behalf Of Otavio Salvador
> Sent: Friday, November 6, 2015 4:40 PM
> To: OpenEmbedded Devel List <openembedded-
> devel at lists.openembedded.org>
> Subject: Re: [oe] [meta-java] Sporadic segfaults when compiling jamvm-
> native and classpath-native
> 
> On Fri, Nov 6, 2015 at 9:44 AM, Kaaria, Erkka <erkka.kaaria at intel.com>
> wrote:
> > There seems to be something wrong with cacao-initial-native JIT compiler
> that causes sporadic segfaults when compiling jamvm-native or classpath-
> native. This is fairly rare, I estimate around 1% of the builds fail due to
> segfault. I use 64 bit Ubuntu 15.04 with GCC 4.9.2 as build machine.
> 
> Did you check if cacao-staging tree does not include a fix for it?
> 

Hi,

I briefly glanced at the cacao-staging commit history, but I didn't find any patches that would fix this segfault specifically. There are several patches that fix issues and race conditions in the jit compiler, for example https://bitbucket.org/cacaovm/cacao-staging/commits/7e6eef2b4c94 and https://bitbucket.org/cacaovm/cacao-staging/commits/56697326cf27. One of these patches may very well fix the segfault, but the problem is that the cacao version that is used in the bootstrapping process is positively ancient (0.98, released in 2007). The linked patches for example are patching files that are either substantially different from the ones in 0.98 or don't even exist in 0.98. Backporting any patches to would not be easy. 

While the workaround would leave the underlying cause unfixed, it only requires changing one line. Since the cacao-initial-native is only used briefly during the build process, I think small workaround is better than large scale changes to the old codebase. I also didn't notice any difference in classpath-native or jamvm-native build times, so the performance impact is negligible.  

On a related note, I ran the clean\recompile script over the weekend and saw no segfaults, so I think the workaround works. 

Best Regards,
Erkka Kääriä
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