RFC ThreadSanitizer testsuite

[Yury Gribov]

Jakub Jelinek wrote:
 > The problem is that at least by default we
 > don't want very expensive tests in the testsuite, whether it is runtime
 > expensive or eats too much memory.

I see. We can only merge small tests then. From what I see in 
compiler-rt/lib/tsan/lit_tests, most of the tests are rather short: fork 
one or two threads, do something fast and simple (e.g. do unsynchronized 
access), join and exit.

-Y