• Heiko Carstens's avatar
    [S390] nmi: fix clock comparator revalidation · e8129c64
    Heiko Carstens authored
    On each machine check all registers are revalidated. The save area for
    the clock comparator however only contains the upper most seven bytes
    of the former contents, if valid.
    Therefore the machine check handler uses a store clock instruction to
    get the current time and writes that to the clock comparator register
    which in turn will generate an immediate timer interrupt.
    However within the lowcore the expected time of the next timer
    interrupt is stored. If the interrupt happens before that time the
    handler won't be called. In turn the clock comparator won't be
    reprogrammed and therefore the interrupt condition stays pending which
    causes an interrupt loop until the expected time is reached.
    On NOHZ machines this can result in unresponsive machines since the
    time of the next expected interrupted can be a couple of days in the
    To fix this just revalidate the clock comparator register with the
    expected value.
    In addition the special handling for udelay must be changed as well.
    Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
    Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
nmi.c 9.75 KB