On Tue, Sep 10, 2024 at 02:11:46PM +0100, Matthew Auld wrote:
> There is a real deadlock as well as sleeping in atomic() bug in here, if
> the bo put happens to be the last ref, since bo destruction wants to
> grab the same spinlock and sleeping locks. Fix that by dropping the ref
> using xe_bo_put_deferred(), and moving the final commit outside of the
> lock. Dropping the lock around the put is tricky since the bo can go
> out of scope and delete itself from the list, making it difficult to
> navigate to the next list entry.
>
> Fixes: 0845233388f8 ("drm/xe: Implement fdinfo memory stats printing")
> Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/2727
> Signed-off-by: Matthew Auld <matthew.auld@xxxxxxxxx>
Reviewed-by: Matthew Brost <matthew.brost@xxxxxxxxx>
> Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@xxxxxxxxx>
> Cc: Tejas Upadhyay <tejas.upadhyay@xxxxxxxxx>
> Cc: "Thomas Hellström" <thomas.hellstrom@xxxxxxxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx> # v6.8+
> ---
> drivers/gpu/drm/xe/xe_drm_client.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_drm_client.c b/drivers/gpu/drm/xe/xe_drm_client.c
> index e64f4b645e2e..badfa045ead8 100644
> --- a/drivers/gpu/drm/xe/xe_drm_client.c
> +++ b/drivers/gpu/drm/xe/xe_drm_client.c
> @@ -196,6 +196,7 @@ static void show_meminfo(struct drm_printer *p, struct drm_file *file)
> struct xe_drm_client *client;
> struct drm_gem_object *obj;
> struct xe_bo *bo;
> + LLIST_HEAD(deferred);
> unsigned int id;
> u32 mem_type;
>
> @@ -215,11 +216,14 @@ static void show_meminfo(struct drm_printer *p, struct drm_file *file)
> list_for_each_entry(bo, &client->bos_list, client_link) {
> if (!kref_get_unless_zero(&bo->ttm.base.refcount))
> continue;
> +
> bo_meminfo(bo, stats);
> - xe_bo_put(bo);
> + xe_bo_put_deferred(bo, &deferred);
> }
> spin_unlock(&client->bos_lock);
>
> + xe_bo_put_commit(&deferred);
> +
> for (mem_type = XE_PL_SYSTEM; mem_type < TTM_NUM_MEM_TYPES; ++mem_type) {
> if (!xe_mem_type_to_name[mem_type])
> continue;
> --
> 2.46.0
>
