On Thu, Feb 12, 2015 at 12:07:24PM -0500, Rich Felker wrote: > On Thu, Feb 12, 2015 at 08:56:26AM -0800, H.J. Lu wrote: > > On Thu, Feb 12, 2015 at 8:11 AM, Jakub Jelinek <ja...@redhat.com> wrote: > > > On Thu, Feb 12, 2015 at 11:09:59AM -0500, Rich Felker wrote: > > >> On Thu, Feb 12, 2015 at 04:18:57PM +0100, Ulrich Weigand wrote: > > >> > Hello, > > >> > > > >> > we're running into a problem related to use of initial-exec access to > > >> > TLS variables in dynamically-loaded libraries. Now, in general, this > > >> > is actually not supported. However, there seems to an "inofficial" > > >> > extension that allows selected system libraries to use small amounts > > >> > of static TLS space to allow critical variables to be defined to use > > >> > the initial-exec model even in dynamically-loaded libraries. > > >> > > >> This usage is supposed to be deprecated. Why isn't libgomp using > > >> TLSDESC/gnu2 model? > > > > > > Because it is significantly slower. > > > > And TLSDESC/gnu2 model isn't implemented for x32. > > There are no tests for TLSDESC/gnu2 model in glibc. > > I have no ideas if it works in glibc master on x86-32 or > > x86-64 today. > > Then fixing this should be a priority, IMO. Broken libraries using IE > model "for performance" are a problem that's not going to go away > until TLSDESC gets properly adopted.
I posted support for TLSDESC on powerpc back in 2009 (search for powerpc _tls_get_addr call optimization). The patch wasn't reviewed, and I didn't push it because my benchmark tests didn't show a much of a gain. Quite possibly I wasn't using the right benchmark. -- Alan Modra Australia Development Lab, IBM
