Accessing pthread_key_create thread-specific data

Accessing pthread_key_create thread-specific data

[Florian Weimer]

We have some functionality in libthread_db in glibc that provides access
to pthread_key_create thread-specific data (aka pthread_setspecific and
pthread_getspecific).  I would like to write a GDB test for this
functionality, but I can't find how GDB exposes this data in the UI.  Is
this just dead code?

The symbols we provide are td_ta_tsd_iter and td_thr_tsd.

Thanks,
Florian

Re: Accessing pthread_key_create thread-specific data

[Tom Tromey]

>>>>> "Florian" == Florian Weimer via Gdb <gdb@sourceware.org> writes:

Florian> We have some functionality in libthread_db in glibc that provides access
Florian> to pthread_key_create thread-specific data (aka pthread_setspecific and
Florian> pthread_getspecific).  I would like to write a GDB test for this
Florian> functionality, but I can't find how GDB exposes this data in the UI.  Is
Florian> this just dead code?

As far as I know, these aren't used and I think have never been used.

I'm not sure how I would go about exposing this to users.  The most
natural way might be to intercept calls to pthread_*specific.  Maybe a
couple of new convenience functions would be good though, and less
magical.

I guess this would primarily be useful for core file debugging?
Assuming inferior calls to pthread_*specific already work -- I haven't
tried.

thanks,
Tom

Re: Accessing pthread_key_create thread-specific data

[Florian Weimer]

* Tom Tromey:

>>>>>> "Florian" == Florian Weimer via Gdb <gdb@sourceware.org> writes:
>
> Florian> We have some functionality in libthread_db in glibc that provides access
> Florian> to pthread_key_create thread-specific data (aka pthread_setspecific and
> Florian> pthread_getspecific).  I would like to write a GDB test for this
> Florian> functionality, but I can't find how GDB exposes this data in the UI.  Is
> Florian> this just dead code?
>
> As far as I know, these aren't used and I think have never been used.

Thanks for conforming.

> I'm not sure how I would go about exposing this to users.  The most
> natural way might be to intercept calls to pthread_*specific.  Maybe a
> couple of new convenience functions would be good though, and less
> magical.
>
> I guess this would primarily be useful for core file debugging?

That's a good point.  The data structures are not completely trivial to
decode even if you have debuginfo symbols.

I do not plan to work on that.  I just had to make some changes on the
glibc side, but I guess I just won't be able to test them.

Thanks,
Florian

Re: Accessing pthread_key_create thread-specific data

[Andrew Dinn]

On 12/03/2021 16:00, Florian Weimer via Gdb wrote:
> * Tom Tromey:
>> As far as I know, these aren't used and I think have never been used.
> 
> Thanks for conforming.
I have never heard Tom accused of that before ;-)

regards,


Andrew Dinn
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