Re: Your clang TSA patches

[Stefan Hajnoczi <stefanha@gmail.com>]

On Tue, 9 May 2023 at 03:01, Marc-André Lureau
<marcandre.lureau@gmail.com> wrote:
>
> Hi Stefan
>
> On Mon, May 8, 2023 at 6:54 PM Stefan Hajnoczi <stefanha@gmail.com> wrote:
>>
>> Hi Marc-André,
>> clang's Thread Safety Analysis is being used more in the QEMU block
>> layer and a few limitations have been hit:
>> 1. Mutexes that are struct fields are not supported (only global mutexes work).
>> 2. Analysis does not extend across function pointers. See
>> GRAPH_RDLOCK_PTR for a workaround that is currently used.
>>
>> (There was a third limitation that I don't remember. Maybe Kevin remembers.)
>>
>> I heard you had clang or LLVM patches in that past that improve TSA.
>> Did your patches address these things? Any idea how hard it is to fix
>> these limitations?
>
>
>
> I don't remember much about that work, I didn't spend that much time on it, and it was 5y ago already!
>
> My WIP branch is still available: https://github.com/elmarco/clang/commits/qemu-ta
>
> it seems I was trying to modify clang to support TSA annotations on typedef and function pointers, and warn on unmatching. I have no idea if this is still relevant. I remember dropping the effort at that time because of lack of interest or help in both projects.

Thanks! The changes seem small enough that it may be possible to get
them merged without a major time commitment.

It seems the function pointer analysis limitation still exists after
these 5 years :).

Stefan