From owner-svn-src-head@freebsd.org Thu Jul 28 06:30:30 2016 Return-Path: Delivered-To: svn-src-head@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 546C8BA65AD; Thu, 28 Jul 2016 06:30:30 +0000 (UTC) (envelope-from sephe@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 1A1D21786; Thu, 28 Jul 2016 06:30:30 +0000 (UTC) (envelope-from sephe@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id u6S6UTZs008006; Thu, 28 Jul 2016 06:30:29 GMT (envelope-from sephe@FreeBSD.org) Received: (from sephe@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id u6S6UTnR008005; Thu, 28 Jul 2016 06:30:29 GMT (envelope-from sephe@FreeBSD.org) Message-Id: <201607280630.u6S6UTnR008005@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: sephe set sender to sephe@FreeBSD.org using -f From: Sepherosa Ziehau Date: Thu, 28 Jul 2016 06:30:29 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r303421 - head/sys/dev/hyperv/vmbus X-SVN-Group: head MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 28 Jul 2016 06:30:30 -0000 Author: sephe Date: Thu Jul 28 06:30:29 2016 New Revision: 303421 URL: https://svnweb.freebsd.org/changeset/base/303421 Log: hyperv/vmbus: Avoid unnecessary mb() MFC after: 1 week Sponsored by: Microsoft Differential Revision: https://reviews.freebsd.org/D7333 Modified: head/sys/dev/hyperv/vmbus/vmbus_br.c Modified: head/sys/dev/hyperv/vmbus/vmbus_br.c ============================================================================== --- head/sys/dev/hyperv/vmbus/vmbus_br.c Thu Jul 28 05:59:56 2016 (r303420) +++ head/sys/dev/hyperv/vmbus/vmbus_br.c Thu Jul 28 06:30:29 2016 (r303421) @@ -209,9 +209,7 @@ vmbus_txbr_need_signal(const struct vmbu if (tbr->txbr_imask) return (FALSE); - /* XXX only compiler fence is needed */ - /* Read memory barrier */ - rmb(); + __compiler_membar(); /* * This is the only case we need to signal when the @@ -308,15 +306,10 @@ vmbus_txbr_write(struct vmbus_txbr *tbr, sizeof(save_windex)); /* - * XXX only compiler fence is needed. - * Full memory barrier before upding the write index. - */ - mb(); - - /* * Update the write index _after_ the channel packet * is copied. */ + __compiler_membar(); tbr->txbr_windex = windex; mtx_unlock_spin(&tbr->txbr_lock); @@ -396,16 +389,9 @@ vmbus_rxbr_read(struct vmbus_rxbr *rbr, rindex = VMBUS_BR_IDXINC(rindex, sizeof(uint64_t), br_dsize); /* - * XXX only compiler fence is needed. - * Make sure all reads are done before we update the read index since - * the writer may start writing to the read area once the read index - * is updated. - */ - wmb(); - - /* * Update the read index _after_ the channel packet is fetched. */ + __compiler_membar(); rbr->rxbr_rindex = rindex; mtx_unlock_spin(&rbr->rxbr_lock);