Do not rely on invalid pthread API use in thread test

Calling mutex_lock from one thread and then mutex_unlock from another is
not permitted.  Replace the awkward mutex usage with a mutex and
condition variable.

llvm.org/pr18061                                                            

llvm-svn: 205900

lldb/test/functionalities/thread/TestNumThreads.py

@@ -19,7 +19,6 @@ class NumberOfThreadsTestCase(TestBase):
         self.buildDsym()
         self.number_of_threads_test()
 
-    @expectedFailureFreeBSD("llvm.org/pr18061") # test relies on undefined behaviour
     @dwarf_test
     def test_with_dwarf(self):
         """Test number of threads."""

lldb/test/functionalities/thread/main.c

@@ -1,24 +1,24 @@
 #include <pthread.h>
 
-pthread_mutex_t mutex1 = PTHREAD_MUTEX_INITIALIZER;
-pthread_mutex_t mutex2 = PTHREAD_MUTEX_INITIALIZER;
-pthread_mutex_t mutex3 = PTHREAD_MUTEX_INITIALIZER;
+pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
+pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
 
 void *
 thread3 (void *input)
 {
-    pthread_mutex_unlock(&mutex2); // Set break point at this line.
-    pthread_mutex_unlock(&mutex1);
+    pthread_mutex_lock(&mutex);
+    pthread_cond_signal(&cond); // Set break point at this line. 
+    pthread_mutex_unlock(&mutex);
     return NULL;
 }
 
 void *
 thread2 (void *input)
 {
-    pthread_mutex_unlock(&mutex3);
-    pthread_mutex_lock(&mutex2);
-    pthread_mutex_unlock(&mutex2);
-
+    pthread_mutex_lock(&mutex);
+    pthread_cond_signal(&cond);
+    pthread_cond_wait(&cond, &mutex);
+    pthread_mutex_unlock(&mutex);
     return NULL;
 }
 
@@ -28,9 +28,6 @@ thread1 (void *input)
     pthread_t thread_2;
     pthread_create (&thread_2, NULL, thread2, NULL);
 
-    pthread_mutex_lock(&mutex1);
-    pthread_mutex_unlock(&mutex1);
-
     pthread_join(thread_2, NULL);
 
     return NULL;
@@ -38,21 +35,23 @@ thread1 (void *input)
 
 int main ()
 {
-  pthread_t thread_1;
-  pthread_t thread_3;
+    pthread_t thread_1;
+    pthread_t thread_3;
 
-  pthread_mutex_lock (&mutex1);
-  pthread_mutex_lock (&mutex2);
-  pthread_mutex_lock (&mutex3);
+    pthread_mutex_lock (&mutex);
 
-  pthread_create (&thread_1, NULL, thread1, NULL);
+    pthread_create (&thread_1, NULL, thread1, NULL);
 
-  pthread_mutex_lock(&mutex3);
-  pthread_create (&thread_3, NULL, thread3, NULL);
+    pthread_cond_wait (&cond, &mutex);
 
-  pthread_join (thread_1, NULL);
-  pthread_join (thread_3, NULL);
+    pthread_create (&thread_3, NULL, thread3, NULL);
 
-  return 0;
+    pthread_cond_wait (&cond, &mutex);
 
+    pthread_mutex_unlock (&mutex);
+
+    pthread_join (thread_1, NULL);
+    pthread_join (thread_3, NULL);
+
+    return 0;
 }