Re: Add a hack to deinstall pthread_atexit handlers at dso unload time

[Joerg Sonnenberger <joerg%bec.de@localhost>]

On Wed, Feb 08, 2017 at 05:08:49PM +0100, Martin Husemann wrote:
> I would like to adopt a hack like FreeBSD did here:
> 
> https://lists.freebsd.org/pipermail/svn-src-head/2010-August/019849.html
> 
> This allows dynamically loaded shared libraries to install
> pthread_atexit handlers. Currently there is no way for the lib to
> deinstall the handler in time, and later fork()s would crash the app.
> 
> The same behaviour (auto deinstall the handlers) has been implemented
> in Linux and Solaris as well.
> 
> I don't like the solution, but now solving it differently sounds painfull
> as well.
> 
> What do others think?

The FreeBSD way is not acceptable at all. It violates core assumptions
for all the ways TLS can be used. The claims are not correct either,
since pthread_[gs]etspecific can be used correctly from shared
libraries. The only implementation choice that is somewhat reasonable is
to just mark the DSO as busy.

Joerg