Index: otherlibs/systhreads/st_stubs.c
===================================================================
--- otherlibs/systhreads/st_stubs.c	(revision 15967)
+++ otherlibs/systhreads/st_stubs.c	(working copy)
@@ -95,10 +95,10 @@
 /* The master lock protecting the OCaml runtime system */
 static st_masterlock caml_master_lock;

-/* Whether the ``tick'' thread is already running */
+/* Whether the "tick" thread is already running */
 static int caml_tick_thread_running = 0;

-/* The thread identifier of the ``tick'' thread */
+/* The thread identifier of the "tick" thread */
 static st_thread_id caml_tick_thread_id;

 /* The key used for storing the thread descriptor in the specific data
@@ -444,7 +444,12 @@

 CAMLprim value caml_thread_cleanup(value unit)   /* ML */
 {
-  if (caml_tick_thread_running) st_thread_kill(caml_tick_thread_id);
+  if (caml_tick_thread_running){
+    caml_tick_thread_stop = 1;
+    st_thread_join(caml_tick_thread_id);
+    caml_tick_thread_stop = 0;
+    caml_tick_thread_running = 0;
+  }
   return Val_unit;
 }

Index: otherlibs/systhreads/st_win32.h
===================================================================
--- otherlibs/systhreads/st_win32.h	(revision 15967)
+++ otherlibs/systhreads/st_win32.h	(working copy)
@@ -84,11 +84,10 @@
   ExitThread(0);
 }

-static void st_thread_kill(st_thread_id thr)
+static void st_thread_join(st_thread_id thr)
 {
-  TRACE1("st_thread_kill", thr);
-  TerminateThread(thr, 0);
-  CloseHandle(thr);
+  TRACE1("st_thread_join", h);
+  WaitForSingleObject(thr, INFINITE);
 }

 /* Scheduling hints */
@@ -383,18 +382,21 @@
   raise_sys_error(str);
 }

+/* Variable used to stop the "tick" thread */
+static volatile int caml_tick_thread_stop = 0;
+
 /* The tick thread: posts a SIGPREEMPTION signal periodically */

 static DWORD WINAPI caml_thread_tick(void * arg)
 {
-  while(1) {
+  while(! caml_tick_thread_stop) {
     Sleep(Thread_timeout);
     /* The preemption signal should never cause a callback, so don't
      go through caml_handle_signal(), just record signal delivery via
      caml_record_signal(). */
     caml_record_signal(SIGPREEMPTION);
   }
-  return 0;                     /* prevents compiler warning */
+  return 0;
 }

 /* "At fork" processing -- none under Win32 */
Index: otherlibs/systhreads/st_posix.h
===================================================================
--- otherlibs/systhreads/st_posix.h	(revision 15967)
+++ otherlibs/systhreads/st_posix.h	(working copy)
@@ -78,14 +78,10 @@
   pthread_exit(NULL);
 }

-static void st_thread_kill(st_thread_id thr)
+static void st_thread_join(st_thread_id thr)
 {
-#if !defined(__ANDROID__)
-  /* pthread_cancel is unsafe, as it does not allow the thread an opportunity
-     to free shared resources such as mutexes. Thus, it is not implemented
-     in Android's libc. */
-  pthread_cancel(thr);
-#endif
+  pthread_join(thr, NULL);
+  /* best effort: ignore errors */
 }

 /* Scheduling hints */
@@ -317,6 +313,9 @@
   raise_sys_error(str);
 }

+/* Variable used to stop the "tick" thread */
+static volatile int caml_tick_thread_stop = 0;
+
 /* The tick thread: posts a SIGPREEMPTION signal periodically */

 static void * caml_thread_tick(void * arg)
@@ -327,11 +326,7 @@
   /* Block all signals so that we don't try to execute an OCaml signal handler*/
   sigfillset(&mask);
   pthread_sigmask(SIG_BLOCK, &mask, NULL);
-#if !defined(__ANDROID__)
-  /* Allow async cancellation */
-  pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, NULL);
-#endif
-  while(1) {
+  while(! caml_tick_thread_stop) {
     /* select() seems to be the most efficient way to suspend the
        thread for sub-second intervals */
     timeout.tv_sec = 0;
@@ -342,7 +337,7 @@
      caml_record_signal(). */
     caml_record_signal(SIGPREEMPTION);
   }
-  return NULL;                  /* prevents compiler warning */
+  return NULL;
 }

 /* "At fork" processing */