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Bug 211956 - top goes into hard loop on xterm exit
top goes into hard loop on xterm exit
Product: Red Hat Enterprise Linux 4
Classification: Red Hat
Component: procps (Show other bugs)
i686 Linux
medium Severity medium
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Assigned To: Karel Zak
Brian Brock
: 211957 (view as bug list)
Depends On:
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Reported: 2006-10-24 00:16 EDT by Major
Modified: 2007-11-16 20:14 EST (History)
0 users

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Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Last Closed: 2006-10-24 06:26:22 EDT
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RHEL 7.3 requirements from Atomic Host:
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Description Major 2006-10-24 00:16:51 EDT
Description of problem:
top run as root goes into hard loop if the xterm it is running under exits

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1. Start an xterm
2. su to root
3. run top
4. kill the xterm
Actual results:
top process goes into hard loop consuming 100% of available cpu

Expected results:
top process terminates

Additional info:
Comment 1 Karel Zak 2006-10-24 06:17:17 EDT
*** Bug 211957 has been marked as a duplicate of this bug. ***
Comment 2 Karel Zak 2006-10-24 06:26:22 EDT
Your xterm runs with non-root permissions and it can't send SIGHUP to the su
which runs with root permissions. This problem cannot be fixed. Sorry.

BTW, I you want to run the top with root permissions in a xterm, you can start
it by: su -c "xterm -e top".
Comment 3 Albert Cahalan 2006-12-25 14:08:15 EST
This is actually a kernel bug.

The xterm itself DOES NOT send the SIGHUP. The SIGHUP is sent by the kernel
itself, automatically as the xterm dies.

On a real BSD system, where this whole idea originates AFAIK, the signal will
always get sent. Linux used to do this too, but broke when some other changes
went it. I believe it was the SE Linux merge that caused this, but note that the
bug shows up even when SE Linux is not compiled into the kernel. In other words,
I think the SE Linux changes broke non-SE systems.

I've been unable to find the bug from an examination of the kernel source. As
far as I can tell, the signal is sent in a way that will bypass permission
checking. Somehow though, this isn't working.

Please reopen this bug and assign it to the kernel.

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