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

[Steve Langasek]

Hello Martin, or anyone else affected,

Accepted glibc into bionic-proposed. The package will build now and be
available at https://launchpad.net/ubuntu/+source/glibc/2.27-3ubuntu1.3
in a few hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.  Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested, what testing has been
performed on the package and change the tag from verification-needed-
bionic to verification-done-bionic. If it does not fix the bug for you,
please add a comment stating that, and change the tag to verification-
failed-bionic. In either case, without details of your testing we will
not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

** Changed in: glibc (Ubuntu Bionic)
       Status: Confirmed => Fix Committed

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

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https://bugs.launchpad.net/bugs/1858203

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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