** Description changed:
- == SRU [Disco][Eoan] ==
+ == 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 protected]>
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.
** Also affects: stress-ng (Ubuntu Disco)
Importance: Undecided
Status: New
** Also affects: stress-ng (Ubuntu Eoan)
Importance: Undecided
Status: New
** Also affects: stress-ng (Ubuntu Bionic)
Importance: Undecided
Status: New
** Also affects: stress-ng (Ubuntu Focal)
Importance: Undecided
Status: New
** Changed in: stress-ng (Ubuntu Focal)
Status: New => Fix Committed
** Changed in: stress-ng (Ubuntu Bionic)
Status: New => In Progress
** Changed in: stress-ng (Ubuntu Disco)
Status: New => In Progress
** Changed in: stress-ng (Ubuntu Eoan)
Status: New => In Progress
** Changed in: stress-ng (Ubuntu Focal)
Assignee: (unassigned) => Colin Ian King (colin-king)
** Changed in: stress-ng (Ubuntu Focal)
Importance: Undecided => Medium
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https://bugs.launchpad.net/bugs/1855851
Title:
stress-ng mwc8() getting reset when mwc1() is called
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