Loosen test deadlines to reduce spurious failures in Swift CI

Add build flag that defaults to true when building
with Swift support enabled (like when in Swift CI)
that relaxes the passing criteria for timing-sensitive
dispatch tests.  We continue to see occasional spurious
failures of dispatch tests in the Swift CI caused by
test machine load; this is an attempt to reduce the frequency
of load-induced failures without removing the test cases
entirely.

Author: dgrove-oss

tests/Makefile.am

@@ -74,6 +74,11 @@ TESTS=							\
 	dispatch_select				\
 	$(ADDITIONAL_TESTS)
 
+# For testing in swift.org CI system; make deadlines lenient by default
+# to reduce probability of test failures due to machine load.
+if HAVE_SWIFT
+CI_CFLAGS=-DLENIENT_DEADLINES=1
+endif
 
 dispatch_c99_CFLAGS=$(DISPATCH_TESTS_CFLAGS) $(CBLOCKS_FLAGS) -std=c99
 dispatch_plusplus_SOURCES=dispatch_plusplus.cpp
@@ -82,7 +87,7 @@ dispatch_priority2_CPPFLAGS=$(AM_CPPFLAGS) -DUSE_SET_TARGET_QUEUE=1
 
 AM_CPPFLAGS=-I$(top_builddir) -I$(top_srcdir)
 
-DISPATCH_TESTS_CFLAGS=-Wall -Wno-deprecated-declarations $(MARCH_FLAGS)
+DISPATCH_TESTS_CFLAGS=-Wall -Wno-deprecated-declarations $(MARCH_FLAGS) $(CI_CFLAGS)
 AM_CFLAGS=$(DISPATCH_TESTS_CFLAGS) $(CBLOCKS_FLAGS) $(BSD_OVERLAY_CFLAGS)
 AM_OBJCFLAGS=$(DISPATCH_TESTS_CFLAGS) $(CBLOCKS_FLAGS)
 AM_CXXFLAGS=$(DISPATCH_TESTS_CFLAGS) $(CXXBLOCKS_FLAGS) $(BSD_OVERLAY_CFLAGS)

tests/dispatch_drift.c

@@ -32,7 +32,11 @@
 #include <bsdtests.h>
 #include "dispatch_test.h"
 
+#if LENIENT_DEADLINES
+#define ACCEPTABLE_DRIFT 0.1
+#else
 #define ACCEPTABLE_DRIFT 0.001
+#endif
 
 int
 main(int argc __attribute__((unused)), char* argv[] __attribute__((unused)))

tests/dispatch_starfish.c

@@ -37,7 +37,9 @@
 #define COUNT	1000ul
 #define LAPS	10ul
 
-#if TARGET_OS_EMBEDDED
+#if LENIENT_DEADLINES
+#define ACCEPTABLE_LATENCY 10000
+#elif TARGET_OS_EMBEDDED
 #define ACCEPTABLE_LATENCY 3000
 #else
 #define ACCEPTABLE_LATENCY 1000