• Christoph Lameter's avatar
    [IA64] Fix race in the accessed/dirty bit handlers · d8117ce5
    Christoph Lameter authored
    A pte may be zapped by the swapper, exiting process, unmapping or page
    migration while the accessed or dirty bit handers are about to run. In that
    case the accessed bit or dirty is set on an zeroed pte which leads the VM to
    conclude that this is a swap pte. This may lead to
    
    - Messages from the vm like
    
    swap_free: Bad swap file entry 4000000000000000
    
    - Processes being aborted
    
    swap_dup: Bad swap file entry 4000000000000000
    VM: killing process ....
    
    Page migration is particular suitable for the creation of this race since
    it needs to remove and restore page table entries.
    
    The fix here is to check for the present bit and simply not update
    the pte if the page is not present anymore. If the page is not present
    then the fault handler should run next which will take care of the problem
    by bringing the page back and then mark the page dirty or move it onto the
    active list.
    Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
    Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
    d8117ce5
ivt.S 51.2 KB