2011-03-28  Tor Perkins
  
  * fhandler_termios.cc (fhandler_termios::bg_check): Do not return EIO
  when a process group has no leader as this is allowed and does not imply
  an orphaned process group.  Add a test for orphaned process groups.

Index: cygwin/fhandler_termios.cc
===================================================================
RCS file: /cvs/src/src/winsup/cygwin/fhandler_termios.cc,v
retrieving revision 1.78
diff -u -p -r1.78 fhandler_termios.cc
--- cygwin/fhandler_termios.cc	23 Oct 2010 18:07:08 -0000	1.78
+++ cygwin/fhandler_termios.cc	2 Apr 2011 23:20:49 -0000
@@ -111,6 +111,26 @@ fhandler_pty_master::tcgetpgrp ()
   return tc->pgid;
 }
 
+int
+tty_min::is_orphaned_process_group (int pgid)
+{
+  /* An orphaned process group is a process group in which the parent
+     of every member is either itself a member of the group or is not
+     a member of the group's session. */
+  winpids pids ((DWORD) PID_MAP_RW);
+  for (unsigned i = 0; i < pids.npids; i++)
+    {
+      _pinfo *p = pids[i];
+      if (!p->exists () || p->pgid != pgid)
+        continue;
+      pinfo ppid (p->ppid);
+      if (ppid->pgid != pgid &&
+          ppid->sid == myself->sid)
+        return 0;
+    }
+  return 1;
+}
+
 void
 tty_min::kill_pgrp (int sig)
 {
@@ -157,36 +177,41 @@ fhandler_termios::bg_check (int sig)
       return bg_eof;
     }
 
-  /* If the process group is no more or if process is ignoring or blocks 'sig',
-     return with error */
-  int pgid_gone = !pid_exists (myself->pgid);
+  /* Determine if process ignores or blocks 'sig' */
   int sigs_ignored =
     ((void *) global_sigs[sig].sa_handler == (void *) SIG_IGN) ||
     (_main_tls->sigmask & SIGTOMASK (sig));
 
-  if (pgid_gone)
-    goto setEIO;
-  else if (!sigs_ignored)
-    /* nothing */;
-  else if (sig == SIGTTOU)
-    return bg_ok;		/* Just allow the output */
-  else
-    goto setEIO;	/* This is an output error */
-
-  /* Don't raise a SIGTT* signal if we have already been interrupted
-     by another signal. */
-  if (WaitForSingleObject (signal_arrived, 0) != WAIT_OBJECT_0)
-    {
-      siginfo_t si = {0};
-      si.si_signo = sig;
-      si.si_code = SI_KERNEL;
-      kill_pgrp (myself->pgid, si);
-    }
-  return bg_signalled;
-
-setEIO:
-  set_errno (EIO);
-  return bg_error;
+  /* If the process is ignoring SIGTT*, then background IO is OK.  If
+     the process is not ignoring SIGTT*, then the sig is to be sent to
+     all processes in the process group (unless the process group of the
+     process is orphaned, in which case we return EIO). */
+  if ( sigs_ignored )
+    { 
+      return bg_ok;   /* Just allow the IO */
+    } 
+  else 
+    { 
+      if ( tc->is_orphaned_process_group (myself->pgid) )
+        {
+          termios_printf ("process group is orphaned");
+          set_errno (EIO);   /* This is an IO error */
+          return bg_error;
+        }
+      else
+        {
+          /* Don't raise a SIGTT* signal if we have already been
+             interrupted by another signal. */
+          if (WaitForSingleObject (signal_arrived, 0) != WAIT_OBJECT_0)
+            {
+              siginfo_t si = {0};
+              si.si_signo = sig;
+              si.si_code = SI_KERNEL;
+              kill_pgrp (myself->pgid, si);
+            }
+          return bg_signalled;
+        } 
+    } 
 }
 
 #define set_input_done(x) input_done = input_done || (x)
Index: cygwin/tty.h
===================================================================
RCS file: /cvs/src/src/winsup/cygwin/tty.h,v
retrieving revision 1.26
diff -u -p -r1.26 tty.h
--- cygwin/tty.h	19 Apr 2010 19:52:43 -0000	1.26
+++ cygwin/tty.h	2 Apr 2011 23:20:49 -0000
@@ -76,6 +76,7 @@ public:
   int getsid () {return sid;}
   void setsid (pid_t tsid) {sid = tsid;}
   void kill_pgrp (int sig);
+  int is_orphaned_process_group (int pgid);
   HWND gethwnd () {return hwnd;}
   void sethwnd (HWND wnd) {hwnd = wnd;}
 };