[Bug sanitizer/59302] tsan: Unexpected mmap in InternalAllocator!

["kcc at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59302

--- Comment #3 from Kostya Serebryany <kcc at gcc dot gnu.org> ---
(In reply to Joost VandeVondele from comment #2)
> (In reply to Kostya Serebryany from comment #1)
> > This isn't expected to happen and so we did not write a better warning
> > message.
> > We may be able to fix it, but the underlying problem is in your tests: 
> > it has a race that tsan is trying to report and which is suppressed
> > (probably because a similar races was reported before).
> > 
> > How many race reports do you see before tsan crashes? 
> > Did you suppress any of those?
> 
> yes, I have a suppression in place to workaround PR59194. As it is an atomic
> update in a hot loop, it will be triggered millions of times.

Suppressing a race that happens so many times is no good. 
Even if we fix the crash above (which I'd prefer not to; instead we should emit
a more descriptive message and die; we'll do that) tsan will remain very slow. 
The right solution is of course to fix the code to not have that race.
The next good solution is to annotate the function with
__attribute__((no_sanitize_thread)) -- but I don't know if fortran has anything
like this. 
The next somewhat good solution is to blacklist the function
(https://code.google.com/p/thread-sanitizer/wiki/Flags?ts=1385538776&updated=Flags#Blacklist_Format)
but that is not supported by GCC and will have to be implemented first.