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

• To: [email protected]
• Subject: Re: [openib-general] Re: [PATCH 53 of 53] ipath - add memory barrier when waiting for writes
• From: Roland Dreier <[email protected]>
• Date: Mon, 15 May 2006 16:28:12 -0700
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• In-reply-to: <[email protected]> ([email protected]'s message of "Mon, 15 May 2006 16:25:00 -0700 (PDT)")
• References: <[email protected]> <[email protected]> <[email protected]> <[email protected]> <[email protected]> <[email protected]>
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    ralphc> We had a power failure here so I'm not able to reproduce
    ralphc> the assembly code at the moment.  What I remember from
    ralphc> looking at the code is that the code for
    ralphc> ipath_read_kreg32() was present in i2c_wait_for_writes()
    ralphc> when compiled -Os so it didn't look like a compiler bug.
    ralphc> I probably could put the mb() at the end of i2c_gpio_set()
    ralphc> if that makes you more comfortable.  The mb() is
    ralphc> definitely needed though.

Is it the mb()?  Or is just a barrier() enough?  In other words do you
really need the mfence, or do you just need to stop the compiler from
reordering things?

 - R.
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