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    SubjectRe: [PATCH v2] rwsem: Support optimistic spinning
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    On Wed, 2014-04-30 at 14:06 -0700, Davidlohr Bueso wrote:

    > > > > >
    > > > > > if (count == RWSEM_WAITING_BIAS)
    > > > > > old = cmpxchg(&sem->count, count, count + RWSEM_ACTIVE_BIAS);
    > > > > > else
    > > > > > old = cmpxchg(&sem->count, count, count + RWSEM_ACTIVE_WRITE_BIAS);
    > > > >
    > > > > I think I simply mis-typed it; shouldn't both cases be
    > > > > RWSEM_ACTIVE_WRITE_BIAS ?
    > > >
    > > > Yeah, we should just write it as
    > > > old = cmpxchg(&sem->count, count, RWSEM_ACTIVE_WRITE_BIAS);
    > >
    > > Oops, I mean
    > > old = cmpxchg(&sem->count, count, count + RWSEM_ACTIVE_WRITE_BIAS);
    > >
    > > for count == 0, we need sem->count to be RWSEM_ACTIVE_WRITE_BIAS,
    > > for count == RWSEM_WAITING_BIAS, we need sem->count to be RWSEM_WAITING_BIAS + RWSEM_ACTIVE_WRITE_BIAS
    >
    > Yep, I had just noticed this. Peter's original suggestion was correct,
    > just needed to change RWSEM_ACTIVE_BIAS for RWSEM_ACTIVE_WRITE_BIAS.
    >

    Yes, I think we are all on the same page now.

    Tim



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