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

[Lars Ola Liavåg]

I git this bug too. Tried to figure out problems with an old computer
gone instable and found memtest86+ claiming that all three RAM sticks
were faulty. Then tried some good (I thought) sticks from another
computer with the same result. Then tried all sticks from both computers
in the second computer. Then went to my problem-free main system and
found that all of my brand new memory in that computer was also supposed
to be bad.

Having all the RAM memory in the house in every computer I own all of a
sudden gone rotten on test #7 didn't seem right at all, and I've been
searching for days before I found this thread. Slipped in a 12.04 and
ran memtest86+ from there and voila: no problems anymore - at least not
with the sticks I know to be all right.

Now, I can go back to the actual work of fixing the computer that
actually has problems. But I hope this bug is fixed by the release of
13.04 because to me, this has been a real time-waster.

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https://bugs.launchpad.net/bugs/1071209

Title:
  memtest86+ test #7 false positives (random number sequence error)

Status in Memtest86+:
  Unknown
Status in Release Notes for Ubuntu:
  New
Status in “memtest86+” package in Ubuntu:
  Fix Released
Status in “memtest86+” source package in Quantal:
  In Progress
Status in “memtest86+” source package in Raring:
  Fix Released
Status in “memtest86+” package in openSUSE:
  Fix Released

Bug description:
  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

  --

  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.

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