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Thu, 28 Jan 2021 12:13:12 +0000 Subject: Re: [PATCH 3/6] MIPS: Octeon: qspinlock: Flush write buffer To: Peter Zijlstra Cc: Paul Burton , linux-mips@vger.kernel.org, Thomas Bogendoerfer , Will Deacon , Boqun Feng , Ingo Molnar , linux-kernel@vger.kernel.org References: <20210127203627.47510-1-alexander.sverdlin@nokia.com> <20210127203627.47510-4-alexander.sverdlin@nokia.com> From: Alexander Sverdlin Message-ID: Date: Thu, 28 Jan 2021 13:13:03 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [131.228.32.169] X-ClientProxiedBy: AM0PR10CA0018.EURPRD10.PROD.OUTLOOK.COM (2603:10a6:208:17c::28) To AM0PR07MB4531.eurprd07.prod.outlook.com (2603:10a6:208:6e::15) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from ulegcpsvhp1.emea.nsn-net.net (131.228.32.169) by AM0PR10CA0018.EURPRD10.PROD.OUTLOOK.COM (2603:10a6:208:17c::28) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3805.16 via Frontend Transport; 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On 28/01/2021 12:35, Peter Zijlstra wrote: >> My point was that original MIPS spinlocks had this write-buffer-flush and >> it got lost on the conversion to qspinlocks. The referenced commit just >> allows to see the last MIPS-specific implementation before deletion. > Hardware that needs a store-buffer flush after release is highly suspect > and needs big and explicit comments. Not vague hints. I have a feeling that you are not going to suggest the comments for the code and one has to guess what is it you have in mind? Do you think the proper approach would be to undelete MIPS spinlocks and make these broken qspinlocks a configurable option for MIPS? I don't even mind if they will be default option for those not interested in performance or latency. -- Best regards, Alexander Sverdlin.