Date: Sat, 14 Feb 2015 20:57:41 +0000 From: "kmacy (Kip Macy)" <phabric-noreply@FreeBSD.org> To: freebsd-arm@freebsd.org Subject: [Differential] [Updated] D1833: Add memory barriers to buf_ring Message-ID: <9488b40e69c7ed9a70a252770a91f7c9@localhost.localdomain> In-Reply-To: <differential-rev-PHID-DREV-ntnotl4wj5wcj2eoukly-req@FreeBSD.org> References: <differential-rev-PHID-DREV-ntnotl4wj5wcj2eoukly-req@FreeBSD.org>
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kmacy added a comment. I'm mostly echoing Ian Lepore's comments here: - The wmb() is equivalent to an atomic_store_acq_32 - which is not part of the API. It would seem we'd rather have a atomic_load_acq_32 where the value is actually later to be read. - I don't know what the rmb() is protecting against. - This penalizes architectures that don't need it so at the very least a local macro needs to be defined that is a no-op on all other architectures. Are you actually seeing problems that is fixed by this change? REVISION DETAIL https://reviews.freebsd.org/D1833 To: zbb, imp, rpaulo, kmacy Cc: andrew, ian, adrian, freebsd-arm
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