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Thu, 20 May 2021 13:12:19 +0000 From: Shinichiro Kawasaki To: Mike Christie CC: "martin.petersen@oracle.com" , "linux-scsi@vger.kernel.org" , "target-devel@vger.kernel.org" Subject: Re: [PATCH] scsi: target: iblock: Fix smp_processor_id BUG messages Thread-Topic: [PATCH] scsi: target: iblock: Fix smp_processor_id BUG messages Thread-Index: AQHXTP4VDBrWNlKukkGBaFtJUdZkhKrsWYgA Date: Thu, 20 May 2021 13:12:19 +0000 Message-ID: <20210520131218.yxmiwriwbyq4v5q7@shindev.dhcp.fujisawa.hgst.com> References: <20210519222640.5153-1-michael.christie@oracle.com> In-Reply-To: <20210519222640.5153-1-michael.christie@oracle.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: oracle.com; dkim=none (message not signed) header.d=none;oracle.com; dmarc=none action=none header.from=wdc.com; x-originating-ip: [129.253.182.60] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: aa2daf0e-12b5-4a60-08b3-08d91b90e5ce x-ms-traffictypediagnostic: BYAPR04MB4101: x-microsoft-antispam-prvs: wdcipoutbound: EOP-TRUE x-ms-oob-tlc-oobclassifiers: OLM:9508; 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charset="us-ascii" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: wdc.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: SJ0PR04MB7184.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: aa2daf0e-12b5-4a60-08b3-08d91b90e5ce X-MS-Exchange-CrossTenant-originalarrivaltime: 20 May 2021 13:12:19.2748 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: b61c8803-16f3-4c35-9b17-6f65f441df86 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: IKTBL6g0ROqqrBxtjkWyLzr4mRaSchHx8CTMeRCeqnxasjsrrk4FX/Im2+RGLG11owJBuja6J8Hsm8vAY9eUhm1rVxsRAnm9y4u5kGZbo/E= X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR04MB4101 Precedence: bulk List-ID: X-Mailing-List: target-devel@vger.kernel.org On May 19, 2021 / 17:26, Mike Christie wrote: > This has us use raw_smp_processor_id in iblock's plug_device callout. > smp_processor_id is not needed here, because we are running from a per CP= U > work item that is also queued to run on a worker thread that is normally > bound to a specific CPU. If the worker thread did end up switching CPUs > then it's handled the same way we handle when the work got moved to a > different CPU's worker thread, where we will just end up sending IO from > the new CPU. >=20 > Fixes: 415ccd9811da ("scsi: target: iblock: Add backend plug/unplug > callouts") > Signed-off-by: Mike Christie Thanks Mike. To confirm this patch, I tried to trigger the BUG message usin= g block backstore on kernel configured with DEBUG_PREEMPT, but I was not able= to trigger it. Having said that, I think this change prevents the potential BU= G message with the same reasoning as the other fix in target_core_transport [= 1]. As far as I read through the code, the code should work even when CPU switc= hes. [1] https://marc.info/?l=3Dlinux-scsi&m=3D162106219905019 --=20 Best Regards, Shin'ichiro Kawasaki=