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iommufd: Make destroy_rwsem use a lock class per object type 

The selftest invokes things like replace under the object lock of its
idev which protects the idev in a similar way to a real user.
Unfortunately this triggers lockdep. A lock class per type will solve the
problem.

Link: https://lore.kernel.org/r/15-v8-6659224517ea+532-iommufd_alloc_jgg@nvidia.com
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
This commit is contained in:
Jason Gunthorpe 2023-07-17 15:12:11 -03:00
parent e88d4ec154
commit 83f7bc6fdf
2 changed files with 11 additions and 1 deletions
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1
drivers/iommu/iommufd/iommufd_private.h
View File

@ -119,6 +119,7 @@ enum iommufd_object_type {
#ifdef CONFIG_IOMMUFD_TEST
IOMMUFD_OBJ_SELFTEST,
#endif
IOMMUFD_OBJ_MAX,
};
/* Base struct for all objects with a userspace ID handle. */

11
drivers/iommu/iommufd/main.c
View File

@ -33,6 +33,7 @@ struct iommufd_object *_iommufd_object_alloc(struct iommufd_ctx *ictx,
size_t size,
enum iommufd_object_type type)
{
static struct lock_class_key obj_keys[IOMMUFD_OBJ_MAX];
struct iommufd_object *obj;
int rc;
@ -40,7 +41,15 @@ struct iommufd_object *_iommufd_object_alloc(struct iommufd_ctx *ictx,
if (!obj)
return ERR_PTR(-ENOMEM);
obj->type = type;
init_rwsem(&obj->destroy_rwsem);
/*
* In most cases the destroy_rwsem is obtained with try so it doesn't
* interact with lockdep, however on destroy we have to sleep. This
* means if we have to destroy an object while holding a get on another
* object it triggers lockdep. Using one locking class per object type
* is a simple and reasonable way to avoid this.
*/
__init_rwsem(&obj->destroy_rwsem, "iommufd_object::destroy_rwsem",
&obj_keys[type]);
refcount_set(&obj->users, 1);
/*