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Wed, 2 Oct 2024 09:55:15 -0700 Date: Wed, 2 Oct 2024 09:55:14 -0700 From: Nicolin Chen To: Jason Gunthorpe CC: Pranjal Shrivastava , Joerg Roedel , Will Deacon , Robin Murphy , "Mostafa Saleh" , , Daniel Mentz Subject: Re: [PATCH v3 1/2] iommu/arm-smmu-v3: Print better events records Message-ID: References: <20240928005143.2378938-1-praan@google.com> <20240928005143.2378938-2-praan@google.com> <20241002135728.GD1369530@ziepe.ca> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20241002135728.GD1369530@ziepe.ca> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MN1PEPF0000F0E0:EE_|MW4PR12MB6849:EE_ X-MS-Office365-Filtering-Correlation-Id: 4c8c8da5-b5ed-4938-6e1a-08dce3030a39 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|82310400026|36860700013|1800799024; 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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 02 Oct 2024 16:55:37.3679 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 4c8c8da5-b5ed-4938-6e1a-08dce3030a39 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.160];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: MN1PEPF0000F0E0.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW4PR12MB6849 On Wed, Oct 02, 2024 at 10:57:28AM -0300, Jason Gunthorpe wrote: > On Mon, Sep 30, 2024 at 12:15:10PM -0700, Nicolin Chen wrote: > > > +static void arm_smmu_get_evt_info(struct arm_smmu_device *smmu, u64 *evt, > > > + struct arm_smmu_event *event) > > > +{ > > > + mutex_lock(&smmu->streams_mutex); > > > + event->master = arm_smmu_find_master(smmu, event->sid); > > > + mutex_unlock(&smmu->streams_mutex); > > > + > > > + if (event->master) > > > + event->master_name = dev_name(event->master->dev); > > > + else > > > + event->master_name = "(unassigned sid)"; > > > > Likely safer for dev_name to be in the mutex too. > > The result of arm_smmu_find_master() should not leave the lock, and Yea, "master_name = dev_name()" must be locked. Yet.. > dev_name()'s result can't leave the lock either, at least not with out > some refcounting on the struct device. I found dev_name returns "const char *" so the string source is likely in the data section? If so, could the result of a locked "master_name = dev_name()" get away from the lock? Thanks Nicolin