From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id EFF7F3858D39 for ; Wed, 2 Mar 2022 05:56:09 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org EFF7F3858D39 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-647-XfO7rvllO6GrknlNlZFoWQ-1; Wed, 02 Mar 2022 00:56:02 -0500 X-MC-Unique: XfO7rvllO6GrknlNlZFoWQ-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 25FC1180A08F; Wed, 2 Mar 2022 05:56:00 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.192.88]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A59D15DB93; Wed, 2 Mar 2022 05:55:58 +0000 (UTC) From: Florian Weimer To: Satish Vasudeva Cc: Xi Ruoyao , Stefan Ring , Xi Ruoyao via Gcc-help Subject: Re: Libatomic 16B References: <6349834d9ea31f579b04ba9215b6449ce13f008e.camel@mengyan1223.wang> <1bb8ab09556727917d07ec31683996bb7e493fa6.camel@mengyan1223.wang> <20220224201334.GQ614@gate.crashing.org> <37e3b73aba3fd6dd6c109d0a06680af3577c4b41.camel@mengyan1223.wang> <874k4nvye3.fsf@oldenburg.str.redhat.com> <313b0e6eca1846dd5e994fd4c9f5d77d000247a0.camel@mengyan1223.wang> <9623880f9cd3d097bb76440413eae16b94204cae.camel@mengyan1223.wang> Date: Wed, 02 Mar 2022 06:55:56 +0100 In-Reply-To: (Satish Vasudeva's message of "Tue, 1 Mar 2022 16:16:29 -0800") Message-ID: <87zgm8kidv.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-6.3 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, KAM_SHORT, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H5, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gcc-help@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-help mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 02 Mar 2022 05:56:12 -0000 * Satish Vasudeva: > Looking back at the description in > https://gcc.gnu.org/legacy-ml/gcc-patches/2017-01/msg02344.html It > sounds like CAS based implementation is a problem for volatile atomic > loads. Can any one please elaborate what is the issue with volatile > atomic loads. I am trying to do risk analysis in our code. The page could be mapped read-only (say if it's in memory shared across processes). Reading such values using CAS will fault, so CAS is not a full replacement. Thanks, Florian