Comment 2 for bug 1026690

This looked much like something that was discussed on stable for 3.2 and looking there we have the following commit (which for Precise is directly after the commit that introduced the problem and both being not released, yet). Natty has neither patch.

commit 6e60d7d7667a47b1b8760a45d95547799f4df2c5
Author: Andrea Arcangeli <email address hidden>
Date: Wed Jun 20 12:52:57 2012 -0700
    thp: avoid atomic64_read in pmd_read_atomic for 32bit PAE
    BugLink: http://bugs.launchpad.net/bugs/1022747
    commit e4eed03fd06578571c01d4f1478c874bb432c815 upstream.

commit 8c35b3d703285b89e5508cf74c786177ffabf216
Author: Andrea Arcangeli <email address hidden>
Date: Tue May 29 15:06:49 2012 -0700
    mm: pmd_read_atomic: fix 32bit PAE pmd walk vs pmd_populate SMP race conditi
    BugLink: http://bugs.launchpad.net/bugs/1022747
    commit 26c191788f18129af0eb32a358cdaea0c7479626 upstream.