change to automatic reaping of zombie processes started by 'subprocess'

svn: r15520

collects/scribblings/reference/subprocess.scrbl

@@ -73,11 +73,7 @@ The @scheme[subprocess] procedure returns four values:
 
 @bold{Important:} All ports returned from @scheme[subprocess] must be
 explicitly closed with @scheme[close-input-port] or
-@scheme[close-output-port]. Similarly, waiting on the subprocess value
-(using @scheme[subprocess-wait] or @scheme[sync]) ensures that the
-operating system can release the subprocess; for example,
-exiting without waiting on a subprocess under Unix risks leaving the
-subprocess as a zombie.
+@scheme[close-output-port].
 
 The returned ports are @tech{file-stream ports} (see
 @secref["file-ports"]), and they are placed into the management of

src/mzscheme/src/port.c

@@ -6814,6 +6814,8 @@ static int MyPipe(int *ph, int near_index) {
 # define GC_write_barrier(x) /* empty */
 #endif
 
+static int need_to_check_children;
+
 #ifdef MZ_XFORM
 START_XFORM_SKIP;
 #endif
@@ -6832,6 +6834,7 @@ void scheme_block_child_signals(int block)
 
 static void child_done(int ingored)
 {
+  need_to_check_children = 1;
   scheme_signal_received();
 
 # ifdef SIGSET_NEEDS_REINSTALL
@@ -6896,6 +6899,14 @@ static void check_child_done()
   }
 }
 
+void scheme_check_child_done(void)
+{
+  if (need_to_check_children) {
+    need_to_check_children = 0;
+    check_child_done();
+  }
+}
+
 #endif
 
 /*========================================================================*/

src/mzscheme/src/schpriv.h

@@ -414,6 +414,7 @@ void scheme_start_itimer_thread(long usec);
 
 #ifdef UNIX_PROCESSES
 void scheme_block_child_signals(int block);
+void scheme_check_child_done(void);
 #endif
 
 Scheme_Object **scheme_alloc_runstack(long len);

src/mzscheme/src/thread.c

@@ -4088,6 +4088,11 @@ void scheme_thread_block(float sleep_time)
   /* Check scheduled_kills early and often. */
   check_scheduled_kills();
 
+#ifdef UNIX_PROCESSES
+  /* Reap zombie processes: */
+  scheme_check_child_done();
+#endif
+
   shrink_cust_box_array();
 
   if (scheme_active_but_sleeping)