[PATCH] drm/ttm: Reorder sys manager cleanup step

[Christian König]

Am 16.10.23 um 14:15 schrieb Karolina Stolarek:
> With the current cleanup flow, we could trigger a NULL pointer
> dereference if there is a delayed destruction of a BO with a
> system resource that gets executed on drain_workqueue() call,
> as we attempt to free a resource using an already released
> resource manager.
>
> Remove the device from the device list and drain its workqueue
> before releasing the system domain manager in ttm_device_fini().
>
> Signed-off-by: Karolina Stolarek <karolina.stolarek at intel.com>

Reviewed and pushed to drm-misc-fixes.

Thanks,
Christian

> ---
> This is actually a reiteration of a patch sent in [1], but the
> solution and commit message changed significantly, so I decided
> not to send it as v2.
> [1] - 20231013143423.1503088-1-karolina.stolarek at intel.com
>
>   drivers/gpu/drm/ttm/ttm_device.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_device.c b/drivers/gpu/drm/ttm/ttm_device.c
> index 7726a72befc5..d48b39132b32 100644
> --- a/drivers/gpu/drm/ttm/ttm_device.c
> +++ b/drivers/gpu/drm/ttm/ttm_device.c
> @@ -232,10 +232,6 @@ void ttm_device_fini(struct ttm_device *bdev)
>   	struct ttm_resource_manager *man;
>   	unsigned i;
>   
> -	man = ttm_manager_type(bdev, TTM_PL_SYSTEM);
> -	ttm_resource_manager_set_used(man, false);
> -	ttm_set_driver_manager(bdev, TTM_PL_SYSTEM, NULL);
> -
>   	mutex_lock(&ttm_global_mutex);
>   	list_del(&bdev->device_list);
>   	mutex_unlock(&ttm_global_mutex);
> @@ -243,6 +239,10 @@ void ttm_device_fini(struct ttm_device *bdev)
>   	drain_workqueue(bdev->wq);
>   	destroy_workqueue(bdev->wq);
>   
> +	man = ttm_manager_type(bdev, TTM_PL_SYSTEM);
> +	ttm_resource_manager_set_used(man, false);
> +	ttm_set_driver_manager(bdev, TTM_PL_SYSTEM, NULL);
> +
>   	spin_lock(&bdev->lru_lock);
>   	for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i)
>   		if (list_empty(&man->lru[0]))