• Joern Engel's avatar
    target: encapsulate smp_mb__after_atomic() · 33940d09
    Joern Engel authored
    The target code has a rather generous helping of smp_mb__after_atomic()
    throughout the code base.  Most atomic operations were followed by one
    and none were preceded by smp_mb__before_atomic(), nor accompanied by a
    comment explaining the need for a barrier.
    Instead of trying to prove for every case whether or not it is needed,
    this patch introduces atomic_inc_mb() and atomic_dec_mb(), which
    explicitly include the memory barriers before and after the atomic
    operation.  For now they are defined in a target header, although they
    could be of general use.
    Most of the existing atomic/mb combinations were replaced by the new
    helpers.  In a few cases the atomic was sandwiched in
    spin_lock/spin_unlock and I simply removed the barrier.
    I suspect that in most cases the correct conversion would have been to
    drop the barrier.  I also suspect that a few cases exist where a) the
    barrier was necessary and b) a second barrier before the atomic would
    have been necessary and got added by this patch.
    Signed-off-by: default avatarJoern Engel <joern@logfs.org>
    Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
target_core_base.h 26.5 KB