[Bug 1891403] Re: glibc tst-getrandom test needs more entropy causing test failures

[Julian Andres Klode]

We have now enabled installing rng-tools for autopkgtest (and removing
haveged), by rebasing on latest git master, so this is fixed from our
side. If this turns out to not produce enough entropy, I guess the hosts
need more entropy.

** Changed in: auto-package-testing
       Status: New => Fix Released

** Changed in: auto-package-testing
       Status: Fix Released => Fix Committed

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https://bugs.launchpad.net/bugs/1891403

Title:
  glibc tst-getrandom test needs more entropy causing test failures

Status in Auto Package Testing:
  Fix Committed
Status in launchpad-buildd:
  New
Status in glibc package in Ubuntu:
  New

Bug description:
  [Impact]

   * Builds and autpkgtests frequently fail due to failing tst-getrandom
  probably due to insufficient source of entropy on Launchpad. This
  causes extra work by requiring retriggering failing builds and
  autopkgtests.

  [Test Case]

  * Observe tst-getrandom tests being marked XFAIL in build logs.

  [Regression Potential]

  * The fix does not change run-time behaviour of glibc, just ignores a
  test. This lets potential breakages in getrandom()'s implementation or
  in kernel's random source being undetected, but the test results can
  still be observed in the logs if needed and the random implementation
  is also most likely exercised in other tests, too.

  [Other Info]

  The issue can be reproduced locally in a built glibc package tree
  without haveged or any other good entropy source installed:

  rbalint at gaia:~/projects/deb/build-area/glibc-2.31$ for i in $(seq 1000); do ./build-tree/amd64-libc/stdlib/tst-getrandom; done
  Timed out: killed the child process
  Termination time: 2020-08-12T21:05:28.234517252
  Last write to standard output: 2020-08-12T21:05:04.069616637
  Timed out: killed the child process
  Termination time: 2020-08-12T21:05:48.337084141
  Last write to standard output: 2020-08-12T21:05:28.069616637
  Timed out: killed the child process
  Termination time: 2020-08-12T21:06:08.439695563
  Last write to standard output: 2020-08-12T21:05:48.069616637
  Timed out: killed the child process
  Termination time: 2020-08-12T21:06:28.542962616
  Last write to standard output: 2020-08-12T21:06:08.069616637
  Timed out: killed the child process
  ...

  With haveged installed the tests pass quickly and without error:

  rbalint at gaia:~/projects/deb/build-area/glibc-2.31$ for i in $(seq 1000); do ./build-tree/amd64-libc/stdlib/tst-getrandom; done
  rbalint at gaia:~/projects/deb/build-area/glibc-2.31$

  An other way of fixing the issue would be installing better entropy
  sources in the build and autopkgtest infrastructure.

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