[PATCH] [BZ #19329] Fix race during concurrent dlopen and pthread_create

[Ilya Palachev]

On 29.12.2015 21:06, Szabolcs Nagy wrote:
> thanks
>
> i have a different fix for this, but even that's not complete.
>
> there are several globals (related to tls) accessed in dlopen and
> pthread_create without synchronization, those should be fixed
> even if they haven't caused observable problems yet.
Very interesting, so we're waiting for your implementation.

>
> this approach changes behaviour:
>
> previously when a new dso was loaded all of its dependencies got
> the same generation number: GL(dl_tls_generation)+1
>
> with the patch each loaded dso increments the generation counter.
> (so at least the overflow detection needs to be different)
Sorry, now I see the mistake that has been done.

>
> i don't know if this is a problem, but my approach is conservative
> and tries to fix the issue in _dl_allocate_tls_init by only
> considering tls for which the generation counter is already updated.
>
> (slotinfo etc also has to use atomics to make the changes visible
> to other threads)
>
> i can only post my fix after my holiday (sometime on the first week
> of jan), but there still seem to be some fundamental issues with the
> design (i think these races can be fixed, but the async-signal safe
> allocation of tls will require significant changes here and without
> that tls access from signal handlers is broken)
>