From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 36CABC2D0DB for ; Wed, 29 Jan 2020 18:25:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1D63E20702 for ; Wed, 29 Jan 2020 18:25:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726799AbgA2SZx (ORCPT ); Wed, 29 Jan 2020 13:25:53 -0500 Received: from mx2.suse.de ([195.135.220.15]:45858 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726560AbgA2SZx (ORCPT ); Wed, 29 Jan 2020 13:25:53 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 01C25AECB; Wed, 29 Jan 2020 18:25:52 +0000 (UTC) From: Davidlohr Bueso To: oneukum@suse.com Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, dave@stgolabs.net, Davidlohr Bueso Subject: [PATCH 7/8] usb, cdc-acm: optimize barrier usage for Rmw atomic bitops Date: Wed, 29 Jan 2020 10:15:45 -0800 Message-Id: <20200129181545.25302-1-dave@stgolabs.net> X-Mailer: git-send-email 2.16.4 Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org We can avoid the unnecessary barrier on non LL/SC architectures, such as x86. Instead, use the smp_mb__after_atomic() call. Signed-off-by: Davidlohr Bueso --- drivers/usb/class/cdc-acm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index 62f4fb9b362f..0bc4b558f387 100644 --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -842,7 +842,7 @@ static void acm_tty_unthrottle(struct tty_struct *tty) clear_bit(ACM_THROTTLED, &acm->flags); /* Matches the smp_mb__after_atomic() in acm_read_bulk_callback(). */ - smp_mb(); + smp_mb__after_atomic(); acm_submit_read_urbs(acm, GFP_KERNEL); } -- 2.16.4