tsan tests randomly failing

[Paolo Carlini]

Hi,

a couple of tsan tests:
    c-c++-common/tsan/simple_race.c
    g++.dg/tsan/default_options.C

relatively often fail for me at various optimization levels (eg, in my 
last run the former at -O2: no WARNING: ThreadSanitizer... thus the test 
failed).

Is this a known issue? The machine I'm talking about is otherwise very 
stable (i980x, glibc2.18, nothing special)

Thanks,
Paolo.