Received: by 2002:a05:6a10:206:0:0:0:0 with SMTP id 6csp5185731pxj; Wed, 9 Jun 2021 11:07:48 -0700 (PDT) X-Google-Smtp-Source: ABdhPJyOyoAA+YLSjEaaVQRK+6vzEbsHWno5GBYvUvDD31iWZ6oOo/oOh9yDoQW1NbG3RmlbZXmU X-Received: by 2002:a17:906:6d45:: with SMTP id a5mr1029110ejt.399.1623262068511; Wed, 09 Jun 2021 11:07:48 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1623262068; cv=none; d=google.com; s=arc-20160816; b=pvuPETDUyRe8xxeOUr5ixMzN01UutZ1u6uDE2GISxtk+7iKx1Iic35QyJRsO4o6GTX 3Wz7Ld8JR8K1mvKMiJ0/YSJcUljnOH/cOlSA5ibnxc4dORXZqy+XohqwhMJyzVnZ0iMR CW7obYq95pXNynCkr0c5w+QYKV1fwkEvFwLn81Tf3Hal0Js6/Crw7PdbPw2X6CrBMNpY bcCG/OXUQDHUnMVQsAOwJ3bOqbG858AfDQyf4ftWYY59YGXxct9K9js4mUorRS745Iek rK9695SwtUVNofwFZQD7ctTXUzgqFkGARo/3AUjfkKnu9CCa8SLcOTBVScIs96cj4orq 4uWg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:content-language :mime-version:accept-language:in-reply-to:references:message-id:date :thread-index:thread-topic:subject:cc:to:from; bh=gJg+rdWjB4mwrN+c1qur62/y36v0aTzk6nONiEsPFng=; b=JWZ9uA7L7tJc+b4KfxX1jaJ+D6NadnxnA/mJno4TTNw1CA4AIY+Pj80Vjp3SbH5USB 9nKoS4+pQ/v8/3fkKudZJRBhl7jrI0TJUzmvdL+NttsYRsMrp/DjeHXej5wyTYxCUrXH IgkwdbYuQObkRYfHfSEUHk6xds9rJdCWH86CThaKTqNEXXf7U03sy8TfnH4q6leGIZ31 SdUnWbzwzu9esUMBM4cWZqGpC9fa3KCrxIVpYzylsIzhnCCXjxs5BJk3qXqk9R+DVv/6 VxZhktFWDi9/CqRWRIP5W+OOFmXZOx4zCclcxsMjzZxdvXCrF3iKOk3f/fTbdZb1/58j 1/5w== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=aculab.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id w6si278444edc.592.2021.06.09.11.07.04; Wed, 09 Jun 2021 11:07:48 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=aculab.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231704AbhFIQFE convert rfc822-to-8bit (ORCPT + 99 others); Wed, 9 Jun 2021 12:05:04 -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)