Allow deleted processes to be reaped by SIGCHLD handler on MS-Windows.

 src/w32proc.c (new_child): Free up to 2 slots of dead processes at a
 time.  Improve diagnostics in DebPrint.
 (reader_thread): If cp->char_avail is NULL, set the FILE_AT_EOF
 flag, so that sys_select could have a chance of noticing that this
 process is dead, and call a SIGCHLD handler for it.  Improve
 diagnostics in DebPrint.
 (reap_subprocess): Reset the FILE_AT_EOF flag set by
 reader_thread.
 (sys_select): Watch a process whose procinfo.hProcess is non-NULL
 even if its char_avail is NULL.  Allows to reap subprocesses that
 were forcibly deleted by delete-process.  (Bug#13546)

2 files changed, 48 insertions, 6 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 47a55535870..f4bee9f0905 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,17 @@
 2013-02-15  Eli Zaretskii  <eliz@gnu.org>
 
+        * w32proc.c (new_child): Free up to 2 slots of dead processes at a
+        time.  Improve diagnostics in DebPrint.
+        (reader_thread): If cp->char_avail is NULL, set the FILE_AT_EOF
+        flag, so that sys_select could have a chance of noticing that this
+        process is dead, and call a SIGCHLD handler for it.  Improve
+        diagnostics in DebPrint.
+        (reap_subprocess): Reset the FILE_AT_EOF flag set by
+        reader_thread.
+        (sys_select): Watch a process whose procinfo.hProcess is non-NULL
+        even if its char_avail is NULL.  Allows to reap subprocesses that
+        were forcibly deleted by delete-process.  (Bug#13546)
+
         * w32.c (sys_socket, sys_bind, sys_connect, sys_gethostname)
         (sys_gethostbyname, sys_getservbyname, sys_getpeername)
         (sys_shutdown, sys_setsockopt, sys_listen, sys_getsockname)
diff --git a/src/w32proc.c b/src/w32proc.c
index 1e72d41e16b..e9860a66468 100644
--- a/src/w32proc.c
+++ b/src/w32proc.c
@@ -799,6 +799,9 @@ new_child (void)
       goto Initialize;
   if (child_proc_count == MAX_CHILDREN)
     {
+      int i = 0;
+      child_process *dead_cp;
+
       DebPrint (("new_child: No vacant slots, looking for dead processes\n"));
       for (cp = child_procs + (child_proc_count-1); cp >= child_procs; cp--)
         if (!CHILD_ACTIVE (cp) && cp->procinfo.hProcess)
@@ -814,13 +817,23 @@ new_child (void)
             if (status != STILL_ACTIVE
                 || WaitForSingleObject (cp->procinfo.hProcess, 0) == WAIT_OBJECT_0)
               {
-                DebPrint (("new_child: Freeing slot of dead process %d\n",
-                           cp->procinfo.dwProcessId));
+                DebPrint (("new_child: Freeing slot of dead process %d, fd %d\n",
+                           cp->procinfo.dwProcessId, cp->fd));
                 CloseHandle (cp->procinfo.hProcess);
                 cp->procinfo.hProcess = NULL;
                 CloseHandle (cp->procinfo.hThread);
                 cp->procinfo.hThread = NULL;
-                goto Initialize;
+                /* Free up to 2 dead slots at a time, so that if we
+                   have a lot of them, they will eventually all be
+                   freed when the tornado ends.  */
+                if (i == 0)
+                  dead_cp = cp;
+                else
+                  {
+                    cp = dead_cp;
+                    goto Initialize;
+                  }
+                i++;
               }
           }
     }
@@ -975,12 +988,24 @@ reader_thread (void *arg)
       else
         rc = _sys_read_ahead (cp->fd);
 
+      if (!CHILD_ACTIVE (cp) && cp->procinfo.hProcess && cp->fd >= 0)
+        {
+          /* Somebody already called delete_child on this child, since
+             only delete_child zeroes out cp->char_avail.  This means
+             no one will read from cp->fd and will not set the
+             FILE_AT_EOF flag, therefore preventing sys_select from
+             noticing that the process died.  Set the flag here
+             instead.  */
+          fd_info[cp->fd].flags |= FILE_AT_EOF;
+        }
+
       /* The name char_avail is a misnomer - it really just means the
          read-ahead has completed, whether successfully or not. */
       if (!SetEvent (cp->char_avail))
         {
-          DebPrint (("reader_thread.SetEvent failed with %lu for fd %ld\n",
-                     GetLastError (), cp->fd));
+          DebPrint (("reader_thread.SetEvent(0x%x) failed with %lu for fd %ld (PID %d)\n",
+                     (DWORD_PTR)cp->char_avail, GetLastError (),
+                     cp->fd, cp->pid));
           return 1;
         }
 
@@ -1141,6 +1166,11 @@ reap_subprocess (child_process *cp)
      register_child has not been called. */
   if (cp->fd == -1)
     delete_child (cp);
+  else
+    {
+      /* Reset the flag set by reader_thread.  */
+      fd_info[cp->fd].flags &= ~FILE_AT_EOF;
+    }
 }
 
 /* Wait for any of our existing child processes to die
@@ -1925,7 +1955,7 @@ count_children:
     /* Some child_procs might be sockets; ignore them.  Also some
        children may have died already, but we haven't finished reading
        the process output; ignore them too.  */
-    if (CHILD_ACTIVE (cp) && cp->procinfo.hProcess
+    if ((CHILD_ACTIVE (cp) || cp->procinfo.hProcess)
         && (cp->fd < 0
             || (fd_info[cp->fd].flags & FILE_SEND_SIGCHLD) == 0
             || (fd_info[cp->fd].flags & FILE_AT_EOF) != 0)