From: Gary Wright <gwtmp01@...>
Date: 2007-03-06T01:32:39+09:00
Subject: Re: replacing the use of gettimeofday in the scheduler


On Mar 5, 2007, at 9:03 AM, Tomas Pospisek wrote:
> With the current "broken" semantics, that would work just right,  
> since with
> the current implementation sleep() time would increase/decrease in  
> parallel
> with the "sysadmin" changing the system time with "date -s" or  
> similar.

Any serious sysadmin will use a NTP based configuration to manage the  
time
on their system.  Time adjustments will slow or speed up the clock  
but won't
cause it to skip ahead or back.

Your proposal seems like a lot of effort to go through and it  
certainly won't
prevent a sysadmin from just issuing "kill -9 pid".  My point is that  
you'll
never be able to write a program that successfully operates in the  
presence of
a malicious or ignorant superuser.

As a compromise, maybe a scheme could be devised to *detect* when the  
clock
has been readjusted and to cause an exception.  I'm not sure if that  
would
be helpful or useful, but it is probably easier than trying to craft a
portable user-space scheduler that is independent of the system clock
(especially without vendor support via POSIX or other industry  
standard).

Gary Wright