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From: naftoli@aecom.UUCP (Robert N. Berlinger)
Newsgroups: net.unix,net.bugs.usg
Subject: Bug in System V relating to accounting
Message-ID: <2481@aecom.UUCP>
Date: Wed, 7-May-86 12:06:46 EDT
Article-I.D.: aecom.2481
Posted: Wed May  7 12:06:46 1986
Date-Received: Thu, 8-May-86 05:57:27 EDT
Distribution: net
Organization: Albert Einstein Coll. of Med., NY
Lines: 34
Xref: linus net.unix:7138 net.bugs.usg:448

I have recently found a bug relating to System V accounting.
Consider the following scenario:

1.  User 'a' logs out at 10pm.  A new getty is spawned for the 
    tty and hangs around waiting for next lucky soul to come 
    along.  

2.  User 'b' comes in at 9am the next morning and logs in to the 
    same tty.  He logs out five minutes later.  

3.  User 'b' comes to me the next morning.  He's noticed that he 
    has some non-prime cpu charges, even though he never logged in 
    at night.  

I did a little research and found the problem.  The "start time" 
of his shell was 10pm, the night before, and therefore got 
charged for the cpu of his shell as if he was on all night (as 
far as p/np goes).  This is because 'exec' does not reset the 
start time to the current time, and user b's shell is the same 
process as the getty that was started the night before.  

This is somewhat of a philosophical problem.  Should the start 
time be the creation time of the process (i.e., pid), or should 
it be the time of the most recent 'exec'?  

In any case, it's a bug in System V accounting, and the same 
problem might exist in 4.2BSD.  

Suggested fixes (other than major mods to getty to make it fork, 
I can't even think of the ramifications of that one...) would be 
welcome.  
-- 
Robert Berlinger
...{philabs,cucard,pegasus,ihnp4,rocky2}!aecom!naftoli