[Bug 1563784] Re: S390: glibc should not be configured with lock elision.

[Dimitri John Ledkov]

lock elision is enabled by default on s390x, ppc64el, amd64 on Ubuntu.

Note that s390x port of Ubuntu _only_ targets zEC12 and up, thus we can
rely on TX (Hardware Transactional Execution / Transacational Memory) to
be available.

This is inline with other distributions too, e.g. fedora and opensuse
both build with lock elision enabled by default.

http://s390.koji.fedoraproject.org/kojifiles/packages/glibc/2.23.90/2.fc25/data/logs/s390x/build.log

https://build.opensuse.org/package/live_build_log/openSUSE:Factory:zSystems/glibc/standard/s390x

glibc upload has been validated through a full archive rebuild (see
announcement on https://lists.ubuntu.com/archives/ubuntu-devel-
announce/2016-April/001178.html ) and autopkgtest suites for integration
testing.

Disabling lock elision at this point of release cycle could only be
realistic driven by publicly known hardware issues of shipped zEC12 or
later z Systems. Are there any publicly disclosed hardware issues with
TX that release team needs to be aware of?

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https://bugs.launchpad.net/bugs/1563784

Title:
  S390: glibc should not be configured with lock elision.

Status in glibc package in Ubuntu:
  Incomplete

Bug description:
  == Comment: #0 - Stefan Liebler <STLI at de.ibm.com> - 2016-03-30 03:11:44 ==
  Hi,

  The current glibc for s390 is configured with --enable-lock-elision.
  This could lead to an overall performance regression compared to locks without transactions.
  Please disable lock-elsion for s390.

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