[Emacs-diffs] /srv/bzr/emacs/emacs-24 r111268: Allow deleted processes to be reaped by SIGCHLD handler on MS-Windows.

[Eli Zaretskii]

------------------------------------------------------------
revno: 111268
fixes bug: http://debbugs.gnu.org/13546
committer: Eli Zaretskii <address@hidden>
branch nick: emacs-24
timestamp: Fri 2013-02-15 11:41:31 +0200
message:
  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)
modified:
  src/ChangeLog
  src/w32proc.c

=== modified file 'src/ChangeLog'
--- a/src/ChangeLog     2013-02-15 09:01:13 +0000
+++ b/src/ChangeLog     2013-02-15 09:41:31 +0000
@@ -1,5 +1,17 @@
 2013-02-15  Eli Zaretskii  <address@hidden>
 
+       * 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)

=== modified file 'src/w32proc.c'
--- a/src/w32proc.c     2013-02-13 17:04:30 +0000
+++ b/src/w32proc.c     2013-02-15 09:41:31 +0000
@@ -799,6 +799,9 @@
       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 @@
            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 @@
       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 @@
      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 @@
     /* 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)