Commit fbb30168 authored Feb 20, 2020 by John Bates Committed by Gerd Hoffmann Feb 24, 2020

drm/virtio: fix resource id creation race



The previous code was not thread safe and caused
undefined behavior from spurious duplicate resource IDs.
In this patch, an atomic_t is used instead. We no longer
see any duplicate IDs in tests with this change.

Fixes: 16065fcd ("drm/virtio: do NOT reuse resource ids")
Signed-off-by: John Bates <jbates@chromium.org>
Reviewed-by: Chia-I Wu <olvaffe@gmail.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20200220225319.45621-1-jbates@chromium.org


Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

parent dde2bb2d

drivers/gpu/drm/virtio/virtgpu_object.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -42,8 +42,8 @@ static int virtio_gpu_resource_id_get(struct virtio_gpu_device *vgdev,
		* "f91a9dd35715 Fix unlinking resources from hash
		* table." (Feb 2019) fixes the bug.
		*/
		static int handle;
		handle++;
		static atomic_t seqno = ATOMIC_INIT(0);
		int handle = atomic_inc_return(&seqno);
		*resid = handle + 1;
		} else {
		int handle = ida_alloc(&vgdev->resource_ida, GFP_KERNEL);

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