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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 69587C48BCD for ; Wed, 9 Jun 2021 16:03:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5160D6136D for ; Wed, 9 Jun 2021 16:03:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233389AbhFIQFF convert rfc822-to-8bit (ORCPT ); Wed, 9 Jun 2021 12:05:05 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.86.151]:42565 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232394AbhFIQFC (ORCPT ); Wed, 9 Jun 2021 12:05:02 -0400 Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mtapsc-5-2Yu2ruzTMluBmPssrWHMwQ-1; Wed, 09 Jun 2021 17:03:04 +0100 X-MC-Unique: 2Yu2ruzTMluBmPssrWHMwQ-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.18; Wed, 9 Jun 2021 17:03:04 +0100 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.018; Wed, 9 Jun 2021 17:03:04 +0100 From: David Laight To: 'Stanimir Varbanov' , "linux-media@vger.kernel.org" , "linux-arm-msm@vger.kernel.org" , "linux-kernel@vger.kernel.org" CC: Vikash Garodia , Mansur Alisha Shaik Subject: RE: [PATCH v2 2/5] venus: Make sys_error flag an atomic bitops Thread-Topic: [PATCH v2 2/5] venus: Make sys_error flag an atomic bitops Thread-Index: AQHXXFtgDEtagiA3DU+NdMc9pzKAAasL2IqA Date: Wed, 9 Jun 2021 16:03:03 +0000 Message-ID: References: <20210608114156.87018-1-stanimir.varbanov@linaro.org> <20210608114156.87018-3-stanimir.varbanov@linaro.org> In-Reply-To: <20210608114156.87018-3-stanimir.varbanov@linaro.org> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Stanimir Varbanov > Sent: 08 June 2021 12:42 > > Make the sys_error flag an atomic bitops in order to avoid > locking in sys_error readers. I don't think that makes any difference at all. It is only atomic w.r.t other bitops in the same bitmap. Even if it contained the fullest memory barrier you can imagine the result of test_bit() is immediately stale. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)