Commit 83f7bc6f authored by Jason Gunthorpe's avatar Jason Gunthorpe
Browse files

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: default avatarKevin Tian <kevin.tian@intel.com>
Tested-by: default avatarNicolin Chen <nicolinc@nvidia.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@nvidia.com>
parent e88d4ec1

drivers/iommu/iommufd/iommufd_private.h

+1 −0
Original line number Diff line number Diff line
@@ -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. */

drivers/iommu/iommufd/main.c

+10 −1
Original line number Diff line number Diff line
@@ -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);



	/*