RFR(S) 8239449: [TESTBUG] test/hotspot/jtreg/runtime/TLS/TestTLS.java: skip test if glibc too old for AdjustStackSizeForTLS

[Reingruber, Richard]

Hi Jiangli,

thanks for providing feedback.

    > David's suggestion of using dlsym seems to be more reliable. Regarding the stability of
    > __pthread_get_minstack in future glibc versions, Florian has added comment to
    > __pthread_get_minstack about external users to ensure it's not removed until TCB is
    > separately allocated.  Please see: http://51.15.138.76/patch/18989/ and
    > https://gcc.gnu.org/bugzilla//show_bug.cgi?id=91628#c2.

So if I understand you and David correctly, then the test should be skipped if the lookup of
__pthread_get_minstack fails.

Then the test would be skipped on future glibc versions where __pthread_get_minstack was removed
because TLS and TCB are not placed on a threads stack anymore.

Actually I would prefer not to skip the test then. I'd like to verify if large data structures can
be placed in TLS without stack size adjustment or if there is some kind of regression. That's the
point of regression tests after all.

In other words: I wouldn't change test coverage of future glibc versions. I just want to exclude
glibc versions were the tested feature cannot work.

Thanks, Richard.

-----Original Message-----
From: Jiangli Zhou <jianglizhou at google.com> 
Sent: Mittwoch, 19. Februar 2020 19:24
To: Reingruber, Richard <richard.reingruber at sap.com>
Cc: hotspot-dev at openjdk.java.net; hotspot-runtime-dev at openjdk.java.net
Subject: Re: RFR(S) 8239449: [TESTBUG] test/hotspot/jtreg/runtime/TLS/TestTLS.java: skip test if glibc too old for AdjustStackSizeForTLS

Hi Richard,

David's suggestion of using dlsym seems to be more reliable. Regarding
the stability of __pthread_get_minstack in future glibc versions,
Florian has added comment to __pthread_get_minstack about external
users to ensure it's not removed until TCB is separately allocated.
Please see: http://51.15.138.76/patch/18989/ and
https://gcc.gnu.org/bugzilla//show_bug.cgi?id=91628#c2.

Best regards,
Jiangli




On Wed, Feb 19, 2020 at 2:44 AM Reingruber, Richard
<richard.reingruber at sap.com> wrote:
>
> Hi,
>
> please review this small test fix
>
> Webrev: http://cr.openjdk.java.net/~rrich/webrevs/8239449/webrev.0/
> Bug:    https://bugs.openjdk.java.net/browse/JDK-8239449
>
> On linux systems with older glibc versions (e.g. 2.11) the option -XX:+AdjustStackSizeForTLS has no effect, because the private function __pthread_get_minstack is not provided, and the test fails. With the fix the test is skipped instead.
>
> Thanks, Richard.