[openib-general] Re: [PATCH 53 of 53] ipath - add memory barrier when waiting for writes

[Roland Dreier]

    ralphc> I don't have a lot to add to this other than I looked at
    ralphc> the assembly code output for -Os and -O3 and both looked
    ralphc> OK.  I put the mb() in to be sure the writes were complete
    ralphc> and I found this to work by experimentation.  Without it,
    ralphc> the driver fails to read the EEPROM correctly.

Hmm, that doesn't give me a warm fuzzy feeling.  Basically on x86-64
you're adding an unneeded mfence instruction to work around
miscompilation?

Is i2c_wait_for_writes miscompiled without the mb() with -Os?  What
does the bad assembly look like?

 - R.