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  • David S. Miller's avatar
    [SPARC64]: Avoid membar instructions in delay slots. · b445e26c
    David S. Miller authored
    
    
    In particular, avoid membar instructions in the delay
    slot of a jmpl instruction.
    
    UltraSPARC-I, II, IIi, and IIe have a bug, documented in
    the UltraSPARC-IIi User's Manual, Appendix K, Erratum 51
    
    The long and short of it is that if the IMU unit misses
    on a branch or jmpl, and there is a store buffer synchronizing
    membar in the delay slot, the chip can stop fetching instructions.
    
    If interrupts are enabled or some other trap is enabled, the
    chip will unwedge itself, but performance will suffer.
    
    We already had a workaround for this bug in a few spots, but
    it's better to have the entire tree sanitized for this rule.
    
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    b445e26c