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Thu, 16 Apr 2026 16:29:08 -0700 From: Nicolin Chen To: Will Deacon , Robin Murphy , "Joerg Roedel" , Bjorn Helgaas , "Jason Gunthorpe" CC: "Rafael J . Wysocki" , Len Brown , Pranjal Shrivastava , Mostafa Saleh , Lu Baolu , Kevin Tian , , , , , , , Shuai Xue Subject: [PATCH v3 06/11] iommu: Defer __iommu_group_free_device() to be outside group->mutex Date: Thu, 16 Apr 2026 16:28:35 -0700 Message-ID: <3f5d229267d1f4d918641bc5b896f54b5c4b7782.1776381841.git.nicolinc@nvidia.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO1PEPF00012E83:EE_|CY5PR12MB6406:EE_ X-MS-Office365-Filtering-Correlation-Id: 91f09374-ca9b-463a-aebf-08de9c1002f0 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|82310400026|36860700016|376014|7416014|22082099003|56012099003|18002099003; X-Microsoft-Antispam-Message-Info: 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 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)(1800799024)(82310400026)(36860700016)(376014)(7416014)(22082099003)(56012099003)(18002099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: os7agqf34mPecweExe+OIEBp8GwocEy/KZez7ZlGh3WTUuX4t1/X+ihltYyaBfcMwnrDv6DsA3jr0fyZo2iGWymV79AqFQRbXzf29ig+IgS5+O3ydSUEnJWf3SplM3+ll6oKsoJVolTQnyAjtmvqZs1YOksE2qvVkiWaYg32CQTS7792E9LYcNVP71elmsPUWp6nB8cdaDxtAAcnL7BEacXRWXXQABU9+8DkdF1ZeUACpFXfTpSeM2yQFmk+MLkCh/VHkeCypAqMU81wfwwKo1INvn6tD0FfPQFMl5MVtfsPBDFOIAosHXTJsw89SAxZfiZ9+LvUXEWm8Wgo6YDDNZv1uLoLX70DAcNOnu7mrU/h4a0bMHbRwTYlZmFsXogHq7RdJ+r7BzNDS3TfKphb9FA76PBZdbM7OUacIdJ7pguDcfA1+haPfBMAGgaKESY4 X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Apr 2026 23:29:31.5004 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 91f09374-ca9b-463a-aebf-08de9c1002f0 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: CO1PEPF00012E83.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY5PR12MB6406 __iommu_group_remove_device() holds group->mutex across the entire call to __iommu_group_free_device() that performs sysfs removals, tracing, and the final kfree_rcu(). But in fact, most of these operations don't really need the group->mutex. The group_device structure will support a work_struct to quarantine broken devices asynchronously. The work function must hold group->mutex to safely update group state. cancel_work_sync() must be called, to cancel that work before freeing the device. But doing so under group->mutex would deadlock if the worker is already running and waiting to acquire the same lock. Separate the assertion from __iommu_group_free_device() to another helper __iommu_group_empty_assert_owner_cnt(). Defer the __iommu_group_free_device() until the mutex is released. This is a preparatory refactor with no functional change. Signed-off-by: Nicolin Chen --- drivers/iommu/iommu.c | 35 +++++++++++++++++++++++------------ 1 file changed, 23 insertions(+), 12 deletions(-) diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index d1be62a07904a..810e7b94a1ae2 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -627,6 +627,19 @@ static struct iommu_domain *pasid_array_entry_to_domain(void *entry) DEFINE_MUTEX(iommu_probe_device_lock); +static void __iommu_group_empty_assert_owner_cnt(struct iommu_group *group) +{ + lockdep_assert_held(&group->mutex); + /* + * If the group has become empty then ownership must have been + * released, and the current domain must be set back to NULL or + * the default domain. + */ + if (list_empty(&group->devices)) + WARN_ON(group->owner_cnt || + group->domain != group->default_domain); +} + static int __iommu_probe_device(struct device *dev, struct list_head *group_list) { struct iommu_group *group; @@ -700,10 +713,12 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list err_remove_gdev: list_del_rcu(&gdev->list); - __iommu_group_free_device(group, gdev); + __iommu_group_empty_assert_owner_cnt(group); err_put_group: iommu_deinit_device(dev); mutex_unlock(&group->mutex); + if (!IS_ERR(gdev)) + __iommu_group_free_device(group, gdev); iommu_group_put(group); return ret; @@ -732,20 +747,13 @@ static void __iommu_group_free_device(struct iommu_group *group, { struct device *dev = grp_dev->dev; + lockdep_assert_not_held(&group->mutex); + sysfs_remove_link(group->devices_kobj, grp_dev->name); sysfs_remove_link(&dev->kobj, "iommu_group"); trace_remove_device_from_group(group->id, dev); - /* - * If the group has become empty then ownership must have been - * released, and the current domain must be set back to NULL or - * the default domain. - */ - if (list_empty(&group->devices)) - WARN_ON(group->owner_cnt || - group->domain != group->default_domain); - kfree(grp_dev->name); kfree_rcu(grp_dev, rcu); } @@ -754,7 +762,7 @@ static void __iommu_group_free_device(struct iommu_group *group, static void __iommu_group_remove_device(struct device *dev) { struct iommu_group *group = dev->iommu_group; - struct group_device *device; + struct group_device *device, *to_free = NULL; mutex_lock(&group->mutex); for_each_group_device(group, device) { @@ -762,15 +770,18 @@ static void __iommu_group_remove_device(struct device *dev) continue; list_del_rcu(&device->list); - __iommu_group_free_device(group, device); + __iommu_group_empty_assert_owner_cnt(group); if (dev_has_iommu(dev)) iommu_deinit_device(dev); else dev->iommu_group = NULL; + to_free = device; break; } mutex_unlock(&group->mutex); + if (to_free) + __iommu_group_free_device(group, to_free); /* * Pairs with the get in iommu_init_device() or * iommu_group_add_device() -- 2.43.0