[PATCH v4 2/2] vkd3d: Don't allow concurrent writes to descriptors.

[Derek Lesho]

On 9/19/19 11:12 AM, Conor McCarthy wrote:
> On Fri, Sep 20, 2019 at 1:32 AM Derek Lesho <dlesho at codeweavers.com 
> <mailto:dlesho at codeweavers.com>> wrote:
>
>     Also, in your patch, I noticed that you intentionally unlock before
>     performing the copy or overwrite.  This puzzles me, if one thread
>     waits
>     on the global mutex for access to a descriptor's view to dereference,
>     and we unlock the mutex for them when the view is NULL, they may
>     crash
>     when trying to decrement the reference of the NULL view.
>
>
> Yes, it's missing a null check after locking the mutex. If it's null 
> after locking then the function can return because it means another 
> thread has destroyed the descriptor. I think the only remaining 
> problem is the old one of a single mutex being used for all 
> descriptors. Maybe performance can be improved.
Even if one thread destroys a descriptor, and then we let both 
concurrently write their data, we will leak the Vulkan handle of written 
by the thread which writes it to the descriptor first and gets overwritten.
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