[Bug 1858203] Re: Patch for glibc Bug 23538 - "Hang in pthread_cond_broadcast" not available on Ubuntu LTS

[Martin Unzner]

Tested glibc/2.27-3ubuntu1.3 for a week on a regular Ubuntu workstation,
no problems detected.

Patch itself is already tried and tested, will fix the issue that we
encountered, but is hard to reproduce and was therefore not explicitly
retested (mere user regression testing).

>From my side you can go ahead and release the update.

** Tags removed: verification-needed-bionic
** Tags added: verification-done-bionic

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Title:
  Patch for glibc Bug 23538 - "Hang in pthread_cond_broadcast" not
  available on Ubuntu LTS

Status in glibc package in Ubuntu:
  Fix Released
Status in glibc source package in Bionic:
  Fix Committed

Bug description:
  [Impact]
   * Glibc can hang when using pthread condition variables

  [Test Case]
  * Not provided, thus observe the upstream patch being applied while building the package:

  commit 2b47bb9cba048e778a7d832f284feccb14a40483
  Author: Martin Kuchta <martin.kuchta at netapp.com>
  Date:   Mon Aug 27 18:54:46 2018 +0200

      pthread_cond_broadcast: Fix waiters-after-spinning case [BZ
  #23538]

      (cherry picked from commit
  99ea93ca31795469d2a1f1570f17a5c39c2eb7e2)

  [Regression Potential]
  * Can cause incorrect sinchronization across threads leading various stability and correctness problems, but the fix is small and is part of the upstream branch for some time. Also extensive regression testing was performed to detect regressions.

  [Original Bug Text]
  There is a patch for versions of glibc prior to 2.29 which fixes a hang that can occur when using pthread condition variables. [1]

  I was unable to locate the patch [2] in the glibc-source tree.
  However, I can confirm that the defect also occurs on Ubuntu 18.04
  with glibc 2.27-3.

  Would it be possible to backport the patch to the glibc version
  shipped with the current LTS of Ubuntu?

  Thanks!

  Martin

  [1] https://sourceware.org/bugzilla/show_bug.cgi?id=23538
  [2] https://sourceware.org/ml/libc-alpha/2018-08/msg00513.html

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