1. 25 Nov, 2010 1 commit
    • 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
      future.
      
      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>
      e8129c64
  2. 24 Nov, 2010 39 commits