Index: src/threads.c
==================================================================
--- src/threads.c
+++ src/threads.c
@@ -65,10 +65,14 @@
   p = sqlite3Malloc(sizeof(*p));
   if( p==0 ) return SQLITE_NOMEM;
   memset(p, 0, sizeof(*p));
   p->xTask = xTask;
   p->pIn = pIn;
+  /* If the SQLITE_TESTCTRL_FAULT_INSTALL callback is registered to a 
+  ** function that returns SQLITE_ERROR when passed the argument 200, that
+  ** forces worker threads to run sequentially and deterministically 
+  ** for testing purposes. */
   if( sqlite3FaultSim(200) ){
     rc = 1;
   }else{    
     rc = pthread_create(&p->tid, 0, xTask, pIn);
   }
@@ -149,11 +153,16 @@
   assert( ppThread!=0 );
   assert( xTask!=0 );
   *ppThread = 0;
   p = sqlite3Malloc(sizeof(*p));
   if( p==0 ) return SQLITE_NOMEM;
-  if( sqlite3GlobalConfig.bCoreMutex==0 ){
+  /* If the SQLITE_TESTCTRL_FAULT_INSTALL callback is registered to a 
+  ** function that returns SQLITE_ERROR when passed the argument 200, that
+  ** forces worker threads to run sequentially and deterministically 
+  ** (via the sqlite3FaultSim() term of the conditional) for testing
+  ** purposes. */
+  if( sqlite3GlobalConfig.bCoreMutex==0 || sqlite3FaultSim(200) ){
     memset(p, 0, sizeof(*p));
   }else{
     p->xTask = xTask;
     p->pIn = pIn;
     p->tid = (void*)_beginthreadex(0, 0, sqlite3ThreadProc, p, 0, &p->id);