Re: [PATCH v13 01/10] drm/shmem-helper: Switch to reservation lock

[Dmitry Osipenko]

On 3/14/23 05:26, Dmitry Osipenko wrote:
> @@ -633,7 +605,10 @@ int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct
>  		return ret;
>  	}
>  
> +	dma_resv_lock(shmem->base.resv, NULL);
>  	ret = drm_gem_shmem_get_pages(shmem);
> +	dma_resv_unlock(shmem->base.resv);

Intel CI reported locking problem [1] here. It actually was also
reported for v12, but I missed that report because of the other noisy
reports.

[1]
https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_114671v2/shard-snb5/igt@prime_vgem@sync@xxxxxxxxx

The test does the following:

1. creates vgem
2. export it do dmabuf
3. mmaps dmabuf

There is an obvious deadlock there. The DRM code assumes that mmap() is
unlocked, while for dma-buf it's locked. I'll see how to fix it for v14.

-- 
Best regards,
Dmitry