locking/lockdep/selftests: Fix mixed read-write ABBA tests

Commit:

  e91498589746 ("locking/lockdep/selftests: Add mixed read-write ABBA tests")

adds an explicit FAILURE to the locking selftest but overlooked the
fact that this kills lockdep. Fudge the test to avoid this.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: hpa@zytor.com
Link: http://lkml.kernel.org/r/20170828124245.xlo2yshxq2btgmuf@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>

lib/locking-selftest.c

@@ -2031,6 +2031,12 @@ void locking_selftest(void)
 	print_testname("mixed read-lock/lock-write ABBA");
 	pr_cont("             |");
 	dotest(rlock_ABBA1, FAILURE, LOCKTYPE_RWLOCK);
+	/*
+	 * Lockdep does indeed fail here, but there's nothing we can do about
+	 * that now.  Don't kill lockdep for it.
+	 */
+	unexpected_testcase_failures--;
+
 	pr_cont("             |");
 	dotest(rwsem_ABBA1, FAILURE, LOCKTYPE_RWSEM);