Re: [PATCH] Fix detection of setrlimit in libstdc++ testsuite

[Mike Stump <mikestump at comcast dot net>]

On Mar 2, 2016, at 2:08 AM, Maxim Kuvyrkov <maxim.kuvyrkov@linaro.org> wrote:
> PING ^ 2.  The patch is sitting without comments for 4+ months.

So the libstdc++ people are usually pretty active and responsive, I usually let them review these sorts of patches as domain experts.  I only kick in if they are unreasonably absent.  Reviewing the case, I don’t see any hint that the libstdc++ list was ever sent an email.  You will want to include it in any patches and pings.

I did look at the patch, and it does seem reasonable.  Given that the libstdc+ folks never saw it, I’lll defer to them.  You can ping patches once a week, if you would like.

Below is the original email and patch:


This patch fixes an obscure cross-testing problem that crashed (OOMed) our boards at Linaro.  Several tests in libstdc++ (e.g., [1]) limit themselves to some reasonable amount of RAM and then try to allocate 32 gigs.  Unfortunately, the configure test that checks presence of setrlimit is rather strange: if target is native, then try compile file with call to setrlimit -- if compilation succeeds, then use setrlimit, otherwise, ignore setrlimit.  The strange part is that the compilation check is done only for native targets, as if cross-toolchains can't generate working executables.  [This is rather odd, and I might be missing some underlaying caveat.]

Therefore, when testing a cross toolchain, the test [1] still tries to allocate 32GB of RAM with no setrlimit restrictions.  On most targets that people use for cross-testing this is not an issue because either
- the target is 32-bit, so there is no 32GB user-space to speak of, or
- the target board has small amount of RAM and no swap, so allocation immediately fails, or
- the target board has plenty of RAM, so allocating 32GB is not an issue.

However, if one is testing on a 64-bit board with 16GB or RAM and 16GB of swap, then one gets into an obscure near-OOM swapping condition.  This is exactly the case with cross-testing aarch64-linux-gnu toolchains on APM Mustang.

The attached patch removes "native" restriction from configure test for setrlimit.  This enables setrlimit restrictions on the testsuite, and the test [1] expectedly fails to allocate 32GB due to setrlimit restriction.

I have tested it on x86_64-linux-gnu and i686-linux-gnu native toolchains, and aarch64-linux-gnu and arm-linux-gnueabi[hf] cross-toolchains with no regressions [*].

OK to commit?

I didn't go as far as enabling setenv/locale tests when cross-testing libstdc++ because I remember of issues with generating locales in cross-built glibc. In any case, locale tests are unlikely to OOM the test board the way that absence of setrlimit does.

[1] 27_io/ios_base/storage/2.cc

[*] Cross-testing using user-mode QEMU made 27_io/fpos/14775.cc execution test to FAIL.  This test uses setrlimit set max file size, and is misbehaving only under QEMU.  I believe this a QEMU issue with not handling setrlimit correctly.

--
Maxim Kuvyrkov
www.linaro.org

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