[PATCH stable-2.15 2/2] Use threaded runtime when linking Haskell unit tests

['Brian Foley' via ganeti-devel]

...but only for GHC>7.6.x due to a bug in the base library.

Using the threaded runtime allows us to run the unit tests in parallel.
Set the default runtime options to use as many CPUs as available.

While here, remove the unused HEXTRA_INT Make variable.

Signed-off-by: Brian Foley <bpfo...@google.com>
---
 Makefile.am | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/Makefile.am b/Makefile.am
index b0bf0aa..bc8d2bc 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -851,10 +851,20 @@ HTEST_FLAGS = $(HFLAGS) -fhpc -itest/hs \
 
 # extra flags that can be overriden on the command line (e.g. -Wwarn, etc.)
 HEXTRA =
-# internal extra flags (used for test/hs/htest mainly)
-HEXTRA_INT =
 # combination of HEXTRA and HEXTRA_CONFIGURE
 HEXTRA_COMBINED = $(HEXTRA) $(HEXTRA_CONFIGURE)
+
+# extra flags used for test/hs/htest
+# Only use the threaded runtime and run tests in parallel for GHC > 7.6. A bug
+# in base that wasn't fixed until 4.7.0.0 in GHC 7.8 causes random file lock
+# errors in the JQueue tests with the threaded runtime.
+# See https://ghc.haskell.org/trac/ghc/ticket/7646
+if GHC_LE_76
+HEXTRA_TEST =
+else
+HEXTRA_TEST = -threaded -with-rtsopts=-N
+endif
+
 # exclude options for coverage reports
 HPCEXCL = --exclude Main \
        --exclude Ganeti.Constants \
@@ -1394,7 +1404,7 @@ test/hs/%.o: $(HASKELL_PACKAGE_VERSIONS_FILE)
        @echo '[GHC|test]: $@ <- test/hs/$^'
        @set -o pipefail ; \
        $(GHC) -c $(HFLAGS) -itest/hs $(HFLAGS_DYNAMIC) \
-               $(HEXTRA_COMBINED) $(@:%.o=%.hs) | \
+               $(HEXTRA_COMBINED) $(HEXTRA_TEST) $(@:%.o=%.hs) | \
                sed '/^Loading package /d'
 
 %.o: $(HASKELL_PACKAGE_VERSIONS_FILE)
@@ -1426,7 +1436,7 @@ endif
        @echo '[GHC|test]: $@ <- $^'
        @set -o pipefail ; \
        $(GHC) -c $(HTEST_FLAGS) \
-               $(HEXTRA_COMBINED) $(@:%.$(HTEST_SUFFIX)_o=%.hs) | \
+               $(HEXTRA_COMBINED) $(HEXTRA_TEST) $(@:%.$(HTEST_SUFFIX)_o=%.hs) 
| \
                sed '/^Loading package /d'
 
 %.hi: %.o ;
@@ -1456,7 +1466,7 @@ $(HS_TEST_PROGS): %: %.$(HTEST_SUFFIX)_o \
        fi
        @echo '[GHC-link|test]: $@'
        $(GHC) $(HTEST_FLAGS) \
-               $(HEXTRA_COMBINED) --make $(@:%=%.hs)
+               $(HEXTRA_COMBINED) $(HEXTRA_TEST) --make $(@:%=%.hs)
        @rm -f $(notdir $@).tix
        @touch "$@"
 
-- 
2.8.0.rc3.226.g39d4020