Revised version – the previous had a lock inversion, which could lead to 
a deadlock, found by -fsanitize=thread. See transfer.c for the changes.

OK?

Tobias

On 11.03.21 10:42, Tobias Burnus wrote:
> Hi all,
>
> as found by Martin (thanks!) there is a race for newunit_free.
> While that call is within the unitlock for the calls in io/unit.c,
> the call in transfer.c did not use locks.
>
> Additionally,
>       unit = get_gfc_unit (dtp->common.unit, do_create);
>       set_internal_unit (dtp, unit, kind);
> gets first the unit (with proper locking when using the unit number
> dtp->common.unit) but then in set_internal_unit it re-sets the
> unit number to the same number without locking. That causes
> race warnings and if the assignment is not atomic it is a true race.
>
> OK for mainline? What about GCC 10?
>
> As Martin notes in the email thread and in the PR there are more
> race warnings (and likely true race issues).
>
> Tobias
>