CARP panic

Thomas E. Spanjaard tgen at
Mon Mar 3 07:22:49 PST 2008

Matthew Dillon wrote:
    Well, I see a problem immediately.  The lockmgr macros in ip_carp.c
    are specifying non-blocking locks but all the calls to them assume
    I'm not sure what the best solution is here.  The lockmgr is not supposed
    to be called from an interrupt, which is why I think it was coded
    LK_NOWAIT in the carp port, but the carp code doesn't check for an
    EBUSY return value.  That's a real problem.
    We can't use spin locks, there are blockable paths called with the
    CARP_LOCK held.   It looks like our only real choice is to allow
    lockmgr locks from interrupts... which by the way precludes being able
    to use a FAST interrupt for network interrupts (which we don't at the
    moment anyway, but...).
I'd prefer CARP to grow EBUSY handling rather than changing our locking 
        Thomas E. Spanjaard
        tgen at
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