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

[Maxim Kuvyrkov <maxim.kuvyrkov@linaro.org>]

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PING ^ 2.  The patch is sitting without comments for 4+ months.

--
Maxim Kuvyrkov
www.linaro.org



> On Dec 10, 2015, at 4:47 PM, Maxim Kuvyrkov <maxim.kuvyrkov@linaro.org> wrote:
> 
>> On Nov 11, 2015, at 7:56 PM, Maxim Kuvyrkov <maxim.kuvyrkov@linaro.org> wrote:
>> 
>> Hi,
>> 
>> 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.
>> 
> 
> Ping.
> 
> --
> Maxim Kuvyrkov
> www.linaro.org

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From d4330fb411366ae39865c303c92e35cec73543c9 Mon Sep 17 00:00:00 2001
From: Maxim Kuvyrkov <maxim.kuvyrkov@linaro.org>
Date: Fri, 30 Oct 2015 14:05:40 +0100
Subject: [PATCH] Use setrlimit for testing libstdc++ in cross toolchains

	* acinclude.m4 (GLIBCXX_CONFIGURE_TESTSUITE): Check for presence of
	setrlimit on both native and cross targets.
	* configure: Regenerate.

Change-Id: I72745beedc7d8976e0c142806348450785face82
---
 libstdc++-v3/acinclude.m4 | 6 +++---
 libstdc++-v3/configure    | 4 ++--
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index abf2e93..aed5be8 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -632,10 +632,10 @@ dnl  baseline_dir
 dnl  baseline_subdir_switch
 dnl
 AC_DEFUN([GLIBCXX_CONFIGURE_TESTSUITE], [
-  if $GLIBCXX_IS_NATIVE ; then
-    # Do checks for resource limit functions.
-    GLIBCXX_CHECK_SETRLIMIT
+  # Do checks for resource limit functions.
+  GLIBCXX_CHECK_SETRLIMIT
 
+  if $GLIBCXX_IS_NATIVE ; then
     # Look for setenv, so that extended locale tests can be performed.
     GLIBCXX_CHECK_STDLIB_DECL_AND_LINKAGE_3(setenv)
   fi
diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index 1eb6db4..614e703 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -78612,8 +78612,7 @@ $as_echo "$ac_cv_x86_rdrand" >&6; }
 
 # This depends on GLIBCXX_ENABLE_SYMVERS and GLIBCXX_IS_NATIVE.
 
-  if $GLIBCXX_IS_NATIVE ; then
-    # Do checks for resource limit functions.
+  # Do checks for resource limit functions.
 
   setrlimit_have_headers=yes
   for ac_header in unistd.h sys/time.h sys/resource.h
@@ -78842,6 +78841,7 @@ $as_echo "#define _GLIBCXX_RES_LIMITS 1" >>confdefs.h
 $as_echo "$ac_res_limits" >&6; }
 
 
+  if $GLIBCXX_IS_NATIVE ; then
     # Look for setenv, so that extended locale tests can be performed.
 
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for setenv declaration" >&5
-- 
1.9.1