• David S. Miller's avatar
    sparc64: Fix cpu strand yielding. · 270c10e0
    David S. Miller authored
    For atomic backoff, we just loop over an exponentially backed off
    counter.  This is extremely ineffective as it doesn't actually yield
    the cpu strand so that other competing strands can use the cpu core.
    
    In cpus previous to SPARC-T4 we have to do this in a slightly hackish
    way, by doing an operation with no side effects that also happens to
    mark the strand as unavailable.
    
    The mechanism we choose for this is three reads of the %ccr
    (condition-code) register into %g0 (the zero register).
    
    SPARC-T4 has an explicit "pause" instruction, and we'll make use of
    that in a subsequent commit.
    
    Yield strands also in cpu_relax().  We really should have done this a
    very long time ago.
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    270c10e0
processor_64.h 6.94 KB