metacity is not reaped, failure is not detected

[quozl]

Sugar starts the Metacity window manager in src/jarabe/main.py

If Metacity fails, the process remains in Z (defunct) state, it is not reaped by jarabe calling wait(2), and several display behaviours occur;

• alt+tab and shift+alt+tab don't work,
• frame works, but selecting alternate views doesn't work.

The learner must restart the computer using power button.

Perhaps Sugar should restart Metacity if it fails.

[quozl]

Reproducer:

1. on a native or virtual installation of Sugar (not sugar-build), start Terminal and become root;

   guest ~$ sudo su
   root:~# █
   

2. check metacity process started by Sugar is present on system;

   root:~# ps ax|grep metacity
     953 ?        Sl     0:00 metacity --no-force-fullscreen
   root:~# █
   

3. kill the process and check status;

   root:~# kill 953
   root:~# ps ax|grep metacity
     953 ?        Z      0:00 [metacity] <defunct>
    2385 pts/0    S+     0:00 grep --color=auto metacity
   root:~# █
   

4. try to use window management or switching features; they will fail,
5. observe that a repeated kill is accepted without error;

   root:~# kill 953
   root:~# █
   

6. return to the non-root parent shell and restart metacity manually;

   root:~# exit
   guest ~$ metacity --no-force-fullscreen &
   

7. observe window management or switching features are restored.

[quozl]

Competing pull requests;

• ​https://github.com/sugarlabs/sugar/pull/682
• ​https://github.com/sugarlabs/sugar/pull/733

[manashraja]

​https://github.com/sugarlabs/sugar/pull/682

[quozl]

​https://github.com/sugarlabs/sugar/pull/733 was merged.