• Robin Getz's avatar
    Blackfin: make deferred hardware errors more exact · b9a3899d
    Robin Getz authored
    Hardware errors on the Blackfin architecture are queued by nature of the
    hardware design.  Things that could generate a hardware level queue up at
    the system interface and might not process until much later, at which
    point the system would send a notification back to the core.
    
    As such, it is possible for user space code to do something that would
    trigger a hardware error, but have it delay long enough for the process
    context to switch.  So when the hardware error does signal, we mistakenly
    evaluate it as a different process or as kernel context and panic (erp!).
    This makes it pretty difficult to find the offending context.  But wait,
    there is good news somewhere.
    
    By forcing a SSYNC in the interrupt entry, we force all pending queues at
    the system level to be processed and all hardware errors to be signaled.
    Then we check the current interrupt state to see if the hardware error is
    now signaled.  If so, we re-queue the current interrupt and return thus
    allowing the higher priority hardware error interrupt to process properly.
    Since we haven't done any other context processing yet, the right context
    will be selected and killed.  There is still the possibility that the
    exact offending instruction will be unknown, but at least we'll have a
    much better idea of where to look.
    
    The downside of course is that this causes system-wide syncs at every
    interrupt point which results in significant performance degradation.
    Since this situation should not occur in any properly configured system
    (as hardware errors are triggered by things like bad pointers), make it a
    debug configuration option and disable it by default.
    Signed-off-by: default avatarRobin Getz <robin.getz@analog.com>
    Signed-off-by: default avatarMike Frysinger <vapier@gentoo.org>
    b9a3899d
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