From owner-freebsd-current@freebsd.org Sat Aug 1 19:46:40 2015 Return-Path: Delivered-To: freebsd-current@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id DA29C9B1150; Sat, 1 Aug 2015 19:46:39 +0000 (UTC) (envelope-from alan.l.cox@gmail.com) Received: from mail-yk0-x236.google.com (mail-yk0-x236.google.com [IPv6:2607:f8b0:4002:c07::236]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 98A0E93B; Sat, 1 Aug 2015 19:46:39 +0000 (UTC) (envelope-from alan.l.cox@gmail.com) Received: by ykdu72 with SMTP id u72so83372848ykd.2; Sat, 01 Aug 2015 12:46:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:reply-to:in-reply-to:references:date:message-id :subject:from:to:cc:content-type; bh=rIclPY9OqIUjlda48cKWv0rwRM0CB1BIN1mCOTV5I4I=; b=GCXZuBXYcvAJmuDRbCG8arTkf1uEwnkLUSIkPOJXPFUCELx/nZvLSA/rC9NNaz4UcO KfEHEferwYmCG6HJ2n/A/rBN5rR0TA4ftwQL5ocQtTDnlyet8YQXYuBOxb4LUaJ6nmNk e2YkKlcf5Lyl6jpFkOvNXnVBTYyQulBiCyDZ1oUPQ3pH4VieMy+mnGIJzQaSl3MVzyoQ wDvIbg9tE6ZZwfX/4EZ7N4233JUEWPGMtYA1pKkbcViq8ZO+Z/bIqIwmlKV9RoEH6iqA 0SEZBcB5IMuRPOF7SGH7qfv0bDOd6IYqVWKpn4ojJgEkaXA1yXCBmJE5cZnwpn+xBsU8 NjXQ== MIME-Version: 1.0 X-Received: by 10.170.75.194 with SMTP id r185mr10502618ykr.121.1438458398749; Sat, 01 Aug 2015 12:46:38 -0700 (PDT) Received: by 10.37.66.206 with HTTP; Sat, 1 Aug 2015 12:46:38 -0700 (PDT) Reply-To: alc@freebsd.org In-Reply-To: References: Date: Sat, 1 Aug 2015 14:46:38 -0500 Message-ID: Subject: Re: Buf ring cleanups From: Alan Cox To: Zbigniew Bodek Cc: K Macy , imp@freebsd.org, freebsd-current , "freebsd-arm@freebsd.org" Content-Type: text/plain; charset=UTF-8 X-Content-Filtered-By: Mailman/MimeDel 2.1.20 X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 01 Aug 2015 19:46:40 -0000 On Thu, Jul 30, 2015 at 6:34 AM, Zbigniew Bodek wrote: > Hello, > > I'm writing to ensure what to do with that patch: > https://reviews.freebsd.org/D1945 > > It was created as a result of discussion related to this review: > https://reviews.freebsd.org/D1833 > The patch (D1945) is still waiting to be committed. We really need fix > for ARM in buf_ring so if someone is sure that the patch is OK then > please commit. > > Thanks in advance and best regards > bde@, kib@, and I have been slogging through kern/, net/, and sys/ reviewing the use of memory ordering primitives and correcting problems. We should get to buf_ring.h soon. However, we also need to pause and update the atomic(9) man page. It defines the semantics of acquire and release in a way that is inconsistent with the architectures that natively support the release consistency model, e.g., arm64 and ia64, as well as the C11 and C++11 standards. Lines 330 through 339 of the patch in D1945 is one example of where the incorrect definition in the current man page has an effect. Alan