From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751958AbcEUEJo (ORCPT ); Sat, 21 May 2016 00:09:44 -0400 Received: from mail-by2on0137.outbound.protection.outlook.com ([207.46.100.137]:21920 "EHLO na01-by2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750699AbcEUEJn (ORCPT ); Sat, 21 May 2016 00:09:43 -0400 Authentication-Results: stgolabs.net; dkim=none (message not signed) header.d=none;stgolabs.net; dmarc=none action=none header.from=hpe.com; Message-ID: <573FDF7A.6090607@hpe.com> Date: Sat, 21 May 2016 00:09:30 -0400 From: Waiman Long User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.12) Gecko/20130109 Thunderbird/10.0.12 MIME-Version: 1.0 To: Davidlohr Bueso CC: Jason Low , Peter Zijlstra , Ingo Molnar , , "Paul E. McKenney" , Terry Rudd , Scott J Norton , Jason Low Subject: Re: [PATCH] locking/mutex: Set and clear owner using WRITE_ONCE() References: <1463696630.2587.95.camel@j-VirtualBox> <573F734C.7050708@hpe.com> <20160521010044.GC28231@linux-uzut.site> In-Reply-To: <20160521010044.GC28231@linux-uzut.site> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [72.71.243.228] X-ClientProxiedBy: BY2PR05CA042.namprd05.prod.outlook.com (10.141.250.32) To DF4PR84MB0313.NAMPRD84.PROD.OUTLOOK.COM (10.162.193.27) X-MS-Office365-Filtering-Correlation-Id: d3b2268e-ce47-4f33-e411-08d3812dbb20 X-Microsoft-Exchange-Diagnostics: 1;DF4PR84MB0313;2:Pt1aWH8ewvvJ7DOyCKCGBNt+CqEpp0OleqFF7EmRuUZnetAwe58zOKn/+1B0aQh0BporOIvGLcgPcydFjHp2kHcmAxOCdlJ+GEcRdY4b6LOXcX/dthkxzitvsUHF4yYORfzFpfSlQ9dNdMaFJpAQ711PY2Xbs07bFcDlfKAKZ6Y1JxD5bZxn38UlKW6qJSeT;3:Em7zNylL4Qn0HoZbrLE0O0cDbWv1+fcXF+R26GeEPFzDkktEXXoZv2y8FuSPDZ37o5ynO4ynaqQiov2rsG7iKBmdR668lAEoGKW8t0pN6f2nyzhpOPzFzYXaNzaFb1Ks X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:;SRVR:DF4PR84MB0313; X-Microsoft-Exchange-Diagnostics: 1;DF4PR84MB0313;25: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 X-LD-Processed: 105b2061-b669-4b31-92ac-24d304d195dc,ExtAddr X-Microsoft-Exchange-Diagnostics: 1;DF4PR84MB0313;20:HovfwePFvx2t91iEk7lX2tgKLa0OHxvQITZZDRzGrOJukVEsRi8D/i28xiD5rXtL+xIs8WXOB3hDim6gBasAn2PCzDAnGoB4VJJxfYn94NsypTafNnDOHEUazCmSb2OQ/UKLoMYclwlrvvR4WC2pHYn615RoBixMz2HqORVrNnl5cMpR9ISek0cXHo2ADCHMTXxkA08BN7MWbUm+HyrCJ51xJgYqp3cRaUsVZGWIh5hHyHyfdteBISZZ83HTuHtvHWRhvrGEzYDgbx3koeavsJbHePXQHBRmv+GgQPr7MX4NxJr43g62Lv3XlOaN83Zak6qItZABfptvBVN0PD4NlQ==;4:gpc5LzYVIIrv5nnhcZ2B++RgIRbygbv3eg2hFJXoHTA0nV7OyrE+pt1EOwPYWA6J55TNd8RYG3MxpXV8czvaNA/LjE6/cnQ7V+mqbZxHXOHmJ6Msvp8D4hhOFKLuWUnQoD7/GHSBTIzH7rC5JpAzDwhRzJNklTNlxy2paFKJnNw6jTNHUwe069b5FVcOoK9wgV59iPTifSCIJuD1J+VFFD2x60o/5Bo2TV7xauSxBq14uGRpb8ADZ84FUrCL4QWBSYoQjFYFFPhW9VTCDxzwb+qBHd0uk7Pqv/tz2WbWfagQIQdOLNwWiMTMYAHSZJKPmvtWnR3pUeQDqQL0C6pa2EIQY7rfPoWy2NySgz+xGVFgntso+FLgywVHDvoCL8XP X-Microsoft-Antispam-PRVS: X-Exchange-Antispam-Report-Test: UriScan:; X-Exchange-Antispam-Report-CFA-Test: BCL:0;PCL:0;RULEID:(601004)(2401047)(5005006)(8121501046)(3002001)(10201501046);SRVR:DF4PR84MB0313;BCL:0;PCL:0;RULEID:;SRVR:DF4PR84MB0313; X-Forefront-PRVS: 09497C15EB X-Forefront-Antispam-Report: SFV:NSPM;SFS:(10019020)(4630300001)(6009001)(6049001)(24454002)(377454003)(36756003)(4001350100001)(117156001)(2906002)(77096005)(4326007)(42186005)(23756003)(5008740100001)(64126003)(50466002)(230700001)(83506001)(33656002)(586003)(50986999)(6116002)(3846002)(110136002)(65816999)(189998001)(81166006)(76176999)(86362001)(8676002)(54356999)(5004730100002)(47776003)(65806001)(66066001)(65956001)(2950100001)(92566002)(8666003)(7059030);DIR:OUT;SFP:1102;SCL:1;SRVR:DF4PR84MB0313;H:[192.168.142.135];FPR:;SPF:None;MLV:sfv;LANG:en; X-Microsoft-Exchange-Diagnostics: =?iso-8859-1?Q?1;DF4PR84MB0313;23:o+Yap7iVNDy/J7MuP93rQCpNe2vxdSZsnZZnK0F?= =?iso-8859-1?Q?tnIpd3eezQWBqQOh/58oZsX1JEc0u96GO/oUkPOcCk8ZmQg2rHXXLsfLx7?= =?iso-8859-1?Q?D8yjk0i6NdGLtImzMeXWaTPXwIgvZUtep6/W4mJ8oRmEHIz490Uk049UeE?= =?iso-8859-1?Q?bFvABfV4Hduv/jMfv3V5+ZLo5ys5XmQE4JZbHwsJy8jcGyVGHcDxkMfaVR?= =?iso-8859-1?Q?2HfI23j/29bWwriKNCfPHzgKVaUvLB17eYRqP3NO3pE2eNY/3n8shsiGtx?= =?iso-8859-1?Q?g0i+/luT2IfqF1164/6OQjY8fvEqwvPedB9pH7//aipo0x17xzQqO1uDW/?= =?iso-8859-1?Q?a9xRDWoGzO76NcSWBWJjtctLFxOwLZPpKXY1/NFn7Yy6SMvLX6DgqihJj/?= =?iso-8859-1?Q?EnIPwNF+ZRdAyVtOcekYvcsnInkxCNqaZjP9D+IqFCk4BeYNuIvp4Rw+WW?= =?iso-8859-1?Q?b6EeL5IauqaUfEvOSFcB54lhAdMRH2Pd6iUAo/5AMCgiLI8xD/adMo6Dj7?= =?iso-8859-1?Q?rviGqEqrpkHfa+T0ak17174BCmjLoP5+c69F4v6QgaX7q4PsdB2fGt2PmG?= =?iso-8859-1?Q?JNTkHexyFREDGS7ORXHAQxPe614sVZrRBJPji3s0OehIb1hKuk74jl1tGt?= =?iso-8859-1?Q?YLwhhQTA6x9cFBQQYnpKxtS/qADbTqmW0bTL8jli/J1UnQlRDaCRCsVlon?= =?iso-8859-1?Q?1cSxs3PpjGyBseXHjR1me6WyZxSLzWbWsJFdHr+IBaiWvG6Z+bwq56tv8l?= =?iso-8859-1?Q?97NaJUuYf7W/izbHmxaxyx1tArjXAHy6nIGELb7uDNg3Htoin2mu4ibxFl?= =?iso-8859-1?Q?irUewUr5O1qENz5ToNJnHdIbq+ps0f9G/7vEQOF5kA4uPJXxblPET2cddO?= =?iso-8859-1?Q?BPQk9eL2Sx+RykC4P97cvwRnpVuS6eCrXuN9NA1nilPBbgdQjAdaCYyCSj?= =?iso-8859-1?Q?VhSNYoA9bpjBOFSYO0dtrjB9lVTNuUziqyCwc0CCt7OZlxrU0HjO8TpmSY?= =?iso-8859-1?Q?EjTnBBQC8/BpPusqKyA1/ugohSMd/2AJTKhpz4T97nKldJu3BwqR3yPxS8?= =?iso-8859-1?Q?Dqa/qAFW0Ur4dsdpRBo8w6VjLtHO3IMPs3ZdWPuEj4=3D?= X-Microsoft-Exchange-Diagnostics: 1;DF4PR84MB0313;5:+z5bhJxHeUHC/9Hy4YIvUJ3z08wj5K9SGPxBYe48Aux4R0HHkfVMynEEdeKWnnr+cGVddQlPY6lMSeXFz0xIKhNBUoIVcI1pOZulnmey/uqOXla0jjyWBFUaJfIkmpHQXiUWIICdbn3hZ72v00VNRw==;24:7TeAZX1LiMgWTSOr4bkRHXgiVh71k2qpH2S1+1GHmBOjc+l/pSmxgQRhjipzs2bhB2x2AxPeLQDCVxqXFYShI6LNHjfAprBZmSa7RSNKO6o=;7:XJBubpRKPRwZ63XLEItcbsFcJED/luHpQ7kmAfI3Ul/hlax+MOjOpIyCgOxGXt7Oe4p20Vawo8neWO1LZVdTXIQ0vIKK0XTb2dnkN6X4f0Nv87cfvFEIfMF2qAHuZVzX+Yorr17gKhFM89caPvKzCuH/jC2Dx+PhKDgaIYr9VegmP6MwuMRfQz6P4yBTH/yZ SpamDiagnosticOutput: 1:23 SpamDiagnosticMetadata: NSPM X-OriginatorOrg: hpe.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 May 2016 04:09:38.6439 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-Transport-CrossTenantHeadersStamped: DF4PR84MB0313 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/20/2016 09:00 PM, Davidlohr Bueso wrote: > On Fri, 20 May 2016, Waiman Long wrote: > >> I think mutex-debug.h also needs similar changes for completeness. > > Maybe, but given that with debug the wait_lock is unavoidable, doesn't > this send the wrong message? > > Thanks, > Davidlohr You are right. Optimistic spinning is disabled when DEBUG_MUTEXES is true. So WRITE_ONCE() is not really needed. However, I think we should have at least a comment in mutex-debug.h as to why the owner field is handled differently from mutex.h. Cheers, Longman