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Fri, 24 Apr 2026 12:12:41 -0700 Date: Fri, 24 Apr 2026 12:12:40 -0700 From: Nicolin Chen To: Jason Gunthorpe CC: Baolu Lu , Will Deacon , "Robin Murphy" , Joerg Roedel , Bjorn Helgaas , "Rafael J . Wysocki" , Len Brown , Pranjal Shrivastava , Mostafa Saleh , Kevin Tian , , , , , , , Shuai Xue Subject: Re: [PATCH v3 05/11] iommu: Change group->devices to RCU-protected list Message-ID: References: <12a224061de4fff9e0725909fd0ba4e14996ff08.1776381841.git.nicolinc@nvidia.com> <779dad61-d7e7-4ae0-83a9-8c5920222219@linux.intel.com> <20260424131148.GB3444440@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260424131148.GB3444440@nvidia.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH1PEPF0000A34C:EE_|DS7PR12MB6165:EE_ X-MS-Office365-Filtering-Correlation-Id: 1da50109-f34c-44aa-b748-08dea2357bdb X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700016|1800799024|82310400026|7416014|376014|22082099003|56012099003|18002099003; X-Microsoft-Antispam-Message-Info: kxJyYShzdGF4VYgjHFkQsRKYJUGmzu1gofksDD/C3iUdpFqD4yb76FThviHARCGL/lCT3ltr9cKreXP4ybBp/Y6IbIVq86RGJbz/2GEf4E3uR/0cAZT7K4jm53QbE9bBR1IKO+m3/ugSAyNdt6xkqJPG6ed/cEznwDqxAhOurAj/2NmrzcW9OfPG2ip5T/sUNLtq6zN3elYYRi/H+Q1wfAqqBAJOAHbIpIBH8CUmuYM4MOkwqa4PAzteBau23LE2VIf4ZWU9qC9D+1QxkKRMEfSZWPVDBxZSIXVOobilMAMzXGZfTqlJliQ9uxAiFfmtKeeg2q0ByQRWAzulmRKXecB/+ZubTQ12cUnLCMztwzIE4qokl7nCOOdTklexUG4eGzIyOFd0cLciZn1oMf3Mn+HHpjmXjXWJ6eR29D5roQk0qwlu3e+vAc+hWCBvpfFXukA2orSuEHu3qRmpuHQTO6hea7Exy+hGkfOdwSOEpVvqy1L/PxnmcuxiJ7LecQWueIOiScyGJ+KAzUG/MSEemJWYmmwE/V1q30HnY7LfwdKjLM4z/+2iKidjAq9qT6lEkBGvK795f47xbsNDJZ2yYMq4QmBRLU0I3IHMFG2EhupeeffJ1TpELsL8XhXczNHKP5G7lyHljlPQH6pgOf6ZszAQ9xSGzl89yJKlXCTrUtIvKQItqccMFV110Hn58ol1eXbvBPSfY0C6VmM5vFSzJWiXM332V0xf5Ummf6ud8OpjezkoVS3L3fsuoqblTT/LGMlJ2sC09F2UjQFpl2RC/w== X-Forefront-Antispam-Report: CIP:216.228.117.161;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge2.nvidia.com;CAT:NONE;SFS:(13230040)(36860700016)(1800799024)(82310400026)(7416014)(376014)(22082099003)(56012099003)(18002099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: Jap90dX63RHXFOeUTL5OUT2bUtkxwWtQJ7geaciMsn404klYyeg2UPLteHlUdB2NAr0moqBp/UDt19XzfbpsebtZnGaFXFXXjBNKQAtD/eEdDeMOMojlvLf1YCYyNRuRH9W6BiACBcuDuhUSxD3Zh0uZabi1eTnzG03MUY9cIe2FMybBTHC+SNWXtuLtwdUc6yfGiUX6/ZrY59OBQ6qfJnbTNziy8m4sbykhNL8TV/jGKQz0RX4KwlsTz6woMZk/By3yMDOxDEgGqEHrjflw65hmPGPIll2/WfZNRwZL8OanJXf9OGiEC+j3JjFDwf4/aBptDMtAM0of9kh2UlUntpk4dgglx+OagghIHTPO/RY70H1YK3d6OoeugvvzBBkxsXrSGC6m4eLsIFirD1fbyzYR/0EN85NCVxyQPMcfQsbG1I9yndgWBtUvbG0dML7i X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 24 Apr 2026 19:12:52.6560 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 1da50109-f34c-44aa-b748-08dea2357bdb X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CH1PEPF0000A34C.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS7PR12MB6165 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260424_121301_008438_AECB8164 X-CRM114-Status: GOOD ( 16.35 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Apr 24, 2026 at 10:11:48AM -0300, Jason Gunthorpe wrote: > On Thu, Apr 23, 2026 at 08:08:59PM -0700, Nicolin Chen wrote: > > On Fri, Apr 24, 2026 at 10:53:49AM +0800, Baolu Lu wrote: > > > On 4/17/26 07:28, Nicolin Chen wrote: > > > mutex_unlock(&group->mutex); > > > /* > > > * FIXME: Mis-locked because the ops->probe_finalize() call-back > > > * of some IOMMU drivers calls arm_iommu_attach_device() which > > > * in-turn might call back into IOMMU core code, where it tries > > > * to take group->mutex, resulting in a deadlock. > > > */ > > > for_each_group_device(group, gdev) > > > iommu_group_do_probe_finalize(gdev->dev); > > > } > > > > > > return 0; > > > } > > > > > > Will the change above trigger a lockdep splat due to this "mis-locked" > > > case?" > > > > Oh, I missed this one. That's a good finding! > > > > Perhaps we can just change it to list_for_each_entry_rcu holding > > rcu_read_lock() and drop the FIXME. > > You can't hold rcu across that function IIRC Oh right. I didn't think too carefully... I tend to keep it as-is. So, maybe just list_for_each_entry? Nicolin