• Anton Blanchard's avatar
    powerpc/time: Handle wrapping of decrementer · 37fb9a02
    Anton Blanchard authored
    When re-enabling interrupts we have code to handle edge sensitive
    decrementers by resetting the decrementer to 1 whenever it is negative.
    If interrupts were disabled long enough that the decrementer wrapped to
    positive we do nothing. This means interrupts can be delayed for a long
    time until it finally goes negative again.
    
    While we hope interrupts are never be disabled long enough for the
    decrementer to go positive, we have a very good test team that can
    drive any kernel into the ground. The softlockup data we get back
    from these fails could be seconds in the future, completely missing
    the cause of the lockup.
    
    We already keep track of the timebase of the next event so use that
    to work out if we should trigger a decrementer exception.
    Signed-off-by: default avatarAnton Blanchard <anton@samba.org>
    Cc: stable@kernel.org
    Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
    37fb9a02
time.c 30.3 KB