[openib-general] [PATCH][5/18] InfiniBand/mthca: add needed rmb() in event queue poll

[Roland Dreier]

    Michael> Since we are using the eqe here, it seems that
    Michael> read_barrier_depends shall be sufficient (as well as in
    Michael> the cq case)?

    Michael> However, I see that read_barrier_depends is a nop on ppc,
    Michael> and the comment indicates that problems were seen on ppc
    Michael> 970.  What gives? do I misunderstand what a dependency
    Michael> is?

There is no dependency between the EQE ownership field and the rest of
the EQE, so read_barrier_depends() is not sufficient.  I think you are
misunderstanding what a dependency is.  The comments in
asm-i386/system.h or http://lse.sourceforge.net/locking/wmbdd.html may
help clear things up.

 - R.