stress-ng mwc8() getting reset when mwc1() is called

[Colin Ian King]

== SRU [Bionic][Disco][Eoan] ==

The 8 bit pseudo-random number generator mwc8() is being zero'd whenever a 1 bit value from mwc1() is generated. This causes mwc8() to generate a stream of 1 to 31 zeros until all the bits are shifted out of a 32 bit entropy state and the next 8 bit value is generated.

== Fix ==

Upstream fix (in Focal):

commit 99e65ccceedc12e68e34dc1ceb51ae0d5f3787ff
Author: Colin Ian King <email address hidden>
Date: Fri Nov 29 10:55:42 2019 +0000

    core-mwc: fix mwc8() being reset when using mwc1()

== Test ==

This cannot be easily regression tested, one has to attach a debugger to observe mwc1() clobbering the mwc8() internal state.

== Regression Potential ==

Since this fixes the random number generation when mwc1() is called, it changes the random behaviour of various stressors that use mwc1() and mwc8() together. This affects the following stressors: mmapfixed, sock and swap. The changes now make the stressors behave more randomly and hence this may affect the way a system is being stressed.

[Timo Aaltonen (tjaalton)]

Hello Colin, or anyone else affected,

Accepted stress-ng into eoan-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/stress-ng/0.10.07-1ubuntu3 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 and change the tag from verification-needed-eoan to verification-done-eoan. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-eoan. 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.

[Timo Aaltonen (tjaalton)]

Hello Colin, or anyone else affected,

Accepted stress-ng into disco-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/stress-ng/0.09.57-0ubuntu5 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 and change the tag from verification-needed-disco to verification-done-disco. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-disco. 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.

[Timo Aaltonen (tjaalton)]

Hello Colin, or anyone else affected,

Accepted stress-ng into bionic-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/stress-ng/0.09.25-1ubuntu6 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 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.

[Colin Ian King (colin-king)]

Verified for bionic, disco, eoan. Issue fixed.

[Chris Halse Rogers (raof)]

The verification of the Stable Release Update for stress-ng has completed successfully and the package is now being released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.

[Launchpad Janitor (janitor)]

This bug was fixed in the package stress-ng - 0.09.57-0ubuntu5

---------------
stress-ng (0.09.57-0ubuntu5) disco; urgency=medium

  * Fix --timer-slack from consuming the following arg (LP: #1853832)
    Currently the timer slack option eats the next argument, causing
    missing argument parsing behaviour on the command line.
  * Fix mwc8() being reset when using mwc1() (LP: #1855851)
    Fic Psuedo-random 8 bit numbers from mwc8() accidentally
    being zero'd when mwc1() is called.

 -- Colin King <email address hidden> Tue, 10 Dec 2019 09:32:11 +0000

[Launchpad Janitor (janitor)]

This bug was fixed in the package stress-ng - 0.10.07-1ubuntu3

---------------
stress-ng (0.10.07-1ubuntu3) eoan; urgency=medium

  * Fix --timer-slack from consuming the following arg (LP: #1853832)
    Currently the timer slack option eats the next argument, causing
    missing argument parsing behaviour on the command line.
  * Fix mwc8() being reset when using mwc1() (LP: #1855851)
    Fic Psuedo-random 8 bit numbers from mwc8() accidentally
    being zero'd when mwc1() is called.

 -- Colin King <email address hidden> Tue, 10 Dec 2019 09:32:11 +0000

[Brian Murray (brian-murray)]

Hello Colin, or anyone else affected,

Accepted stress-ng into bionic-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/stress-ng/0.09.25-1ubuntu8 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 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.

[Colin Ian King (colin-king)]

Bionic: random values look correct. Marking this is fixed.

[Ubuntu SRU Bot (ubuntu-sru-bot)]

All autopkgtests for the newly accepted stress-ng (0.09.25-1ubuntu8) for bionic have finished running.
The following regressions have been reported in tests triggered by the package:

stress-ng/0.09.25-1ubuntu8 (armhf)

Please visit the excuses page listed below and investigate the failures, proceeding afterwards as per the StableReleaseUpdates policy regarding autopkgtest regressions [1].

https://people.canonical.com/~ubuntu-archive/proposed-migration/bionic/update_excuses.html#stress-ng

[1] https://wiki.ubuntu.com/StableReleaseUpdates#Autopkgtest_Regressions

Thank you!

[Launchpad Janitor (janitor)]

This bug was fixed in the package stress-ng - 0.09.25-1ubuntu8

---------------
stress-ng (0.09.25-1ubuntu8) bionic; urgency=medium

  * Ensure --aggressive mode terminates early (LP: #1858858)
    Add a waitpid NOHANG wait on each child process and if we get ESRCH
    on all the child pids we can terminate the loop early.
  * Fix --timer-slack arg handling (LP: #1853832)
  * Fix mwc8() being reset when using mwc1() (LP: #1855851)
    Fix Psuedo-random 8 bit numbers from mwc8() accidentally
    being zero'd when mwc1() is called.

 -- Colin King <email address hidden> Tue, 10 Dec 2019 09:32:11 +0000