To: Jeff Garzik <jgarzik@pobox.com>
Cc: akpm@osdl.org, linux-kernel@vger.kernel.org, openib-general@openib.org
Subject: Re: [PATCH][16/26] IB/mthca: mem-free doorbell record writing
References: <2005331520.WW3zbnVIUjZ4q0Ov@topspin.com>
	<4227A606.50703@pobox.com>
From: Roland Dreier <roland@topspin.com>
Date: Thu, 03 Mar 2005 16:33:15 -0800
In-Reply-To: <4227A606.50703@pobox.com> (Jeff Garzik's message of "Thu, 03
 Mar 2005 19:04:22 -0500")
Message-ID: <52vf88ntbo.fsf@topspin.com>
User-Agent: Gnus/5.1006 (Gnus v5.10.6) XEmacs/21.4 (Jumbo Shrimp, linux)
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 800
Lines: 19

    Jeff> Are you concerned about ordering, or write-combining?

ordering... write combining would be fine.

    Jeff> I am unaware of a situation where writes are re-ordered into
    Jeff> a reversed, descending order for no apparent reason.

Hmm... I've seen ppc64 do some pretty freaky reordering but on the
other hand that's a 64-bit arch so we don't care in this case.  I
guess I'd rather keep the barrier there so we don't have the
possibility of a rare hardware crash when the HCA just happens to read
the doorbell record in a corrupt state.

 - R.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/