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: 16065fcdd19d ("drm/virtio: do NOT reuse resource ids") Signed-off-by: John Bates jbates@chromium.org --- drivers/gpu/drm/virtio/virtgpu_object.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c index 017a9e0fc3bb..890121a45625 100644 --- a/drivers/gpu/drm/virtio/virtgpu_object.c +++ b/drivers/gpu/drm/virtio/virtgpu_object.c @@ -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);
On Fri, Feb 21, 2020 at 3:14 AM John Bates jbates@chromium.org wrote:
Reviewed-by: Chia-I Wu olvaffe@gmail.com
resid 1 is (was) discriminated :D
dri-devel@lists.freedesktop.org
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John Bates