Bug 336289 – sys-process/procps: top keeps running when from su and terminal is closed

• Status: RESOLVED FIXED
• Product: Gentoo Linux

[Description Ambroz Bizjak 2010-09-06 22:01:00 UTC]

When top is running in a terminal emulator (Konsole, xterm) from within "su", and the terminal is closed, it keeps running and hogs the CPU.

Reproducible: Always

Steps to Reproduce:
1. Open a terminal emulator (as a user) in a desktop session. I've tested Konsole and xterm from within KDE 4.5.1.
2. su
3. top
4. while top is running, close the terminal window

Actual Results:  
top keeps running, and eats all CPU.
pstree shows:
init─┬
     ...
     ├─su───bash───top


Expected Results:  
top should exit when terminal is closed.

[Comment 1 Jeroen Roovers (RETIRED) 2010-09-07 16:51:39 UTC]

I can't reproduce that with x11-terms/rxvt-unicode under x11-wm/musca. I also doubt it's a problem with sys-process/procps. Please post your `emerge --info'. A gdb backtrace of the top process in question would also be nice.

[Comment 2 Ambroz Bizjak 2010-09-07 17:49:42 UTC]

Created attachment 246374 [details]
backtraces

I also cannot reproduce it x11-terms/rxvt-unicode. I am sure you will be able to with Konsole and xterm, because others have too.
I am attaching three backtraces

[Comment 3 Ambroz Bizjak 2010-09-07 17:50:23 UTC]

Created attachment 246376 [details]
paludis --info sys-process/procps

[Comment 4 Michał Górny 2010-09-21 17:26:42 UTC]

I am able to reproduce that with x11-terms/terminal and xterm. Not sure, however, how could we fix this...

I guess the terminal simply is unable to send SIGHUP to 'su' as it is setuid. This is a very general issue, and it seems not really related to a particular terminal. On the other hand, I can't reproduce it on a login shell...

[Comment 5 Ambroz Bizjak 2010-09-21 23:28:11 UTC]

(In reply to comment #4)
> I guess the terminal simply is unable to send SIGHUP to 'su' as it is setuid.
This is not true; the bug can be reproduced even if xterm is running as root (I believe the terminal does not need to send SIGHUP to the program; it is sent by the kernel when the controlling end of the pseudo-terminal is closed).
IMO, this is an issue with top and not any terminal, since top is the process caught in an infinite loop. Even if it's waiting for something, busy waiting is the wrong thing to do.

[Comment 6 Michał Górny 2010-09-22 07:55:11 UTC]

I've retried this with gdb-attached top and it doesn't receive SIGHUP at all. Neither does su or bash running it.

[Comment 7 Michał Górny 2010-09-22 08:06:11 UTC]

Created attachment 248336 [details, diff]
Patch to fix the issue

Ah, got it. Someone smart wanted to optimize the code too much.

[Comment 8 Michał Górny 2010-09-22 18:15:41 UTC]

I've reported the issue upstream. Hope sourceforge does deliver messages better than it archives them.

[Comment 9 Jekyll Wu 2012-04-14 03:00:32 UTC]

Seems fixed using sys-process/procps-3.3.2_p2-r1