On Wed, Feb 19, 2020 at 4:20 PM John Bates <jbates@xxxxxxxxxx> wrote:
>
>
>
> On Wed, Feb 19, 2020 at 12:40 PM John Bates <jbates@xxxxxxxxxxxx> wrote:
>>
>> 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.
>>
>> Signed-off-by: John Bates <jbates@xxxxxxxxxxxx>
>> ---
>>
>> 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..b11c1fce1770 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;
nit: ATOMIC_INIT(0)?
>> + int handle = atomic_inc_return(&seqno);
>> *resid = handle + 1;
>> } else {
>> int handle = ida_alloc(&vgdev->resource_ida, GFP_KERNEL);
>> --
>> 2.25.0.265.gbab2e86ba0-goog
>>
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