i#2075 flaky pthread_exit test: relax vmm_heap_exit check.

Adds flag dynamo_thread_init_during_process_exit to indicate if the process
exits during any threads init.
Relax vmm_heap_exit check if dynamo_thread_init_during_process_exit is true.

Review-URL: https://codereview.appspot.com/319770043

core/dynamo.c

@@ -2065,6 +2065,9 @@ remove_thread(IF_WINDOWS_(HANDLE hthread) thread_id_t tid)
 /* this bool is protected by reset_pending_lock */
 DECLARE_FREQPROT_VAR(static bool reset_at_nth_thread_triggered, false);
 
+#ifdef DEBUG
+bool dynamo_thread_init_during_process_exit = false;
+#endif
 /* thread-specific initialization
  * if dstack_in is NULL, then a dstack is allocated; else dstack_in is used
  * as the thread's dstack
@@ -2112,6 +2115,8 @@ dynamo_thread_init(byte *dstack_in, priv_mcontext_t *mc
     /* under current implementation of process exit, can happen only under
      * debug build, or app_start app_exit interface */
     while (dynamo_exited) {
+        /* FIXME i#2075: free the dstack. */
+        DODEBUG({dynamo_thread_init_during_process_exit = true; });
         /* logging should be safe, though might not actually result in log
          * message */
         DODEBUG_ONCE(LOG(GLOBAL, LOG_THREADS, 1,

core/globals.h

@@ -444,6 +444,8 @@ extern bool dynamo_exited;       /* has dynamo exited? */
 extern bool dynamo_exited_and_cleaned; /* has dynamo component cleanup started? */
 #ifdef DEBUG
 extern bool dynamo_exited_log_and_stats; /* are stats and logfile shut down? */
+/* process exit in middle of any thread init? */
+extern bool dynamo_thread_init_during_process_exit;
 #endif
 extern bool dynamo_resetting;    /* in middle of global reset? */
 extern bool dynamo_all_threads_synched; /* are all other threads suspended safely? */

core/heap.c

@@ -1400,6 +1400,10 @@ vmm_heap_exit()
                detach
             */
             ASSERT(IF_WINDOWS(doing_detach || )  /* not deterministic when detaching */
+                   /* FIXME i#2075: if a thread is being initialized during the
+                    * process exit, the thread will not free its dstack.
+                    */
+                   IF_DEBUG(dynamo_thread_init_during_process_exit || )
                    heapmgt->vmheap.num_free_blocks == heapmgt->vmheap.num_blocks
                    - unfreed_blocks ||
                    /* >=, not ==, b/c if we hit the vmm limit the cur dstack