make the testsuite work with THREADS=2

Also, I get a number of framework failures when running with THREADS=2:

OVERALL SUMMARY for test run started at Wed Aug  1 15:15:16 BST 2007
    1829 total tests, which gave rise to
    7144 test cases, of which
      74 caused framework failures
    5607 were skipped

    1405 expected passes
      55 expected failures
       0 unexpected passes
       3 unexpected failures

Unexpected failures:
   cabal01(normal)
   mod144(normal)
   mod167(normal)

e.g.

=====> getEnvironment01(normal)
cd ../../../libraries/unix/tests && '/64playpen/simonmar/testing/compiler/stage2/ghc-inplace' -no-recomp -dcore-lint -dcmm-lint -Dx86_64_unknown_linux  -o getEnvironment01 getEnvironment01.hs  -package unix  >getEnvironment01.comp.stderr 2>&1
Compile failed (status 6656) errors were:
*** framework failure for getEnvironment01(normal) :
Traceback (most recent call last):
  File "/home/simonmar/darcs-all/work/ghc-testing/testsuite/driver/testlib.py", line 428, in do_test
    result = apply(func, [name,way] + args)
  File "/home/simonmar/darcs-all/work/ghc-testing/testsuite/driver/testlib.py", line 586, in compile_and_run
    return compile_and_run__( name, way, extra_hc_opts, '' , '')
  File "/home/simonmar/darcs-all/work/ghc-testing/testsuite/driver/testlib.py", line 573, in compile_and_run__
    result = simple_build( name, way, extra_hc_opts, 0, top_mod, 1 )
  File "/home/simonmar/darcs-all/work/ghc-testing/testsuite/driver/testlib.py", line 635, in simple_build
    if_verbose(1,open(actual_stderr).read())
IOError: [Errno 2] No such file or directory: '../../../libraries/unix/tests/getEnvironment01.comp.stderr'

This could be a bug in Python, perhaps related to signals and spawning processes.

I have fixed the ordering constraints and the framework failures noted above. However, with 'THREADS=2' I'm still occasionally getting a different kind of framework failure, So I'll leave the bug open and validate is still defaulting to unthreaded. We're very close now, though.

Here's one of those framework failures, on x86_64/Linux:

=====> signals002(normal)
cd ../../../libraries/unix/tests && '/64playpen/simonmar/testing/compiler/stage2/ghc-inplace' -no-recomp -dcore-lint -dcmm-lint -Dx86_64_unknown_linux  -o signals002 signals002.hs  -package unix  >signals002.comp.stderr 2>&1
cd ../../../libraries/unix/tests && ./signals002    </dev/null >signals002.run.stdout 2>signals002*** framework failure for conc027(normal) :
Traceback (most recent call last):
  File "/home/simonmar/darcs-all/work/ghc-testing/testsuite/driver/testlib.py", line 445, in do_te
st
    result = apply(func, [name,way] + args)
  File "/home/simonmar/darcs-all/work/ghc-testing/testsuite/driver/testlib.py", line 603, in compi
le_and_run
    return compile_and_run__( name, way, extra_hc_opts, '' , '')
  File "/home/simonmar/darcs-all/work/ghc-testing/testsuite/driver/testlib.py", line 590, in compi
le_and_run__
    result = simple_build( name, way, extra_hc_opts, 0, top_mod, 1 )
  File "/home/simonmar/darcs-all/work/ghc-testing/testsuite/driver/testlib.py", line 647, in simpl
e_build
    result = runCmd(cmd)
  File "/home/simonmar/darcs-all/work/ghc-testing/testsuite/driver/testlib.py", line 1115, in runC
md
    r = rawSystem([config.timeout_prog, str(config.timeout), cmd])
  File "/home/simonmar/darcs-all/work/ghc-testing/testsuite/driver/testlib.py", line 1092, in rawS
ystem
    return subprocess.call(cmd_and_args)
  File "/usr/lib64/python2.4/subprocess.py", line 412, in call
    return Popen(*args, **kwargs).wait()
  File "/usr/lib64/python2.4/subprocess.py", line 1007, in wait
    pid, sts = os.waitpid(self.pid, 0)
OSError: [Errno 10] No child processes

Python ticket for the issue reported by Simon above

Having had a quick look at the above bug report and the code, I think that this has been fixed. In my python 2.4.4 I have

def _cleanup():
    for inst in _active[:]:
        inst.poll()

(poll calls _active.remove(self)) while in my 2.5.2 I have

def _cleanup():
    for inst in _active[:]:
        if inst.poll(_deadstate=sys.maxint) >= 0:
            try:
                _active.remove(inst)
            except ValueError:
                # This can happen if two threads create a new Popen instance.
                # It's harmless that it was already removed, so ignore.
                pass

and I think that caught exception is the one that we are seeing.

Even if it is not fixed, I think that we could work around it by wrapping the Popen class in our own class, and taking a lock before calling the Popen constructor.

Now fixed, if you have python >= 2.5.2. I've fixed a few problems with specific tests, but there might be more as it's non-deterministic.