On Wed, 2 Mar 2022 at 10:22, Thomas Hellström thomas.hellstrom@linux.intel.com wrote:
vms are not getting properly closed. Rather than fixing that, Remove the vm open count and instead rely on the vm refcount.
The vm open count existed solely to break the strong references the vmas had on the vms. Now instead make those references weak and ensure vmas are destroyed when the vm is destroyed.
Unfortunately if the vm destructor and the object destructor both wants to destroy a vma, that may lead to a race in that the vm destructor just unbinds the vma and leaves the actual vma destruction to the object destructor. However in order for the object destructor to ensure the vma is unbound it needs to grab the vm mutex. In order to keep the vm mutex alive until the object destructor is done with it, somewhat hackishly grab a vm_resv refcount that is released late in the vma destruction process, when the vm mutex is no longer needed.
v2: Address review-comments from Niranjana
- Clarify that the struct i915_address_space::skip_pte_rewrite is a hack and should ideally be replaced in an upcoming patch.
- Remove an unneeded continue in clear_vm_list and update comment.
Co-developed-by: Niranjana Vishwanathapura niranjana.vishwanathapura@intel.com Signed-off-by: Niranjana Vishwanathapura niranjana.vishwanathapura@intel.com Signed-off-by: Thomas Hellström thomas.hellstrom@linux.intel.com
Reviewed-by: Matthew Auld matthew.auld@intel.com