[Bug 1071209] [NEW] memtest86 test #7 false positives (random number sequence error)

[Launchpad Bug Tracker]

You have been subscribed to a public bug by Chris J Arges (christopherarges):

Trying to check the memory at newly bought notebook I found a bug in the
memtest86+ version 4.20 in ubuntu 12.10, in ubuntu 12.04 it is ok. The
bug is reported at least in Fedora and Opensuse. It is assumed that the
bug is caused by the gcc-4.7.

It is easily  reproducible - select the test #7 in memtest or just wait
till it - starting from the 129Mb it will report a lot of errors. I have
checked it on three different systems , two of them I use on a daily
basis and would note if RAM is really bad.

https://bugzilla.redhat.com/show_bug.cgi?id=805813

http://lists.opensuse.org/opensuse-bugs/2012-09/msg04386.html

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SRU Justification

[Impact]
Users of memtest86+ will get false positives of memory failures. This will cause users to suspect hardware and require unnecessary testing/headaches.

[Test Case]
Boot Ubuntu in Quantal/Raring. At GRUB select memtest86+. Wait until the 7th test. It will fail at the 7th test.

[Regression Potential]
The fix is just adding another register to clobber in the inline assembly routine. Because  this affects newer GCC versions, older releases aren't affected. Thus, if there are compiler changes we should re-test.

** Affects: memtest86+
     Importance: Unknown
         Status: Unknown

** Affects: ubuntu-release-notes
     Importance: Undecided
         Status: New

** Affects: memtest86+ (Ubuntu)
     Importance: Medium
     Assignee: Chris J Arges (christopherarges)
         Status: Fix Committed

** Affects: memtest86+ (Ubuntu Quantal)
     Importance: Medium
     Assignee: Chris J Arges (christopherarges)
         Status: In Progress

** Affects: memtest86+ (Ubuntu Raring)
     Importance: Medium
     Assignee: Chris J Arges (christopherarges)
         Status: Fix Committed

** Affects: memtest86+ (openSUSE)
     Importance: Medium
         Status: Fix Released


** Tags: memtest86 quantal random-number-sequence
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memtest86 test #7 false positives (random number sequence error)
https://bugs.launchpad.net/bugs/1071209
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