Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!utgpu!utcsri!uthub!ecf!larry
From: larry@ecf.UUCP
Newsgroups: comp.bugs.4bsd
Subject: Re: Programs can thwart cpu time limit
Message-ID: <164@ecf.toronto.edu>
Date: Tue, 26-May-87 09:09:17 EDT
Article-I.D.: ecf.164
Posted: Tue May 26 09:09:17 1987
Date-Received: Wed, 27-May-87 01:14:49 EDT
References: <6208@shemp.UCLA.EDU>
Reply-To: larry@ecf.toronto.edu (Larry Philps)
Distribution: world
Organization: Engineering Computing Facility, University of Toronto
Lines: 57
Keywords: cputime RLIMIT_CPU SIGXCPU
Summary: Add a sigkill

In article <6208@shemp.UCLA.EDU> heather@CS.UCLA.EDU (Heather Burris) writes:
>
>I believe that the following behavior is a bug:
>
>	I write a program that specifies a hard and a soft cpu time
>	limit using the setrlimit() system call.  I also use
>	signal() to catch SIGXCPU signals (cpu time exceeded).
>	...
>	Instead what happens is that the the signal handler gets 
>	called once every 5 seconds from the time I hit the soft 
>	limit to the time I hit the hard limit (see line 144 of 
>	kern_clock.c for 5 second figure-- why isn't this documented).  
>	At that point, the signal handler is constantly called.

Yup, I think that is a bug also.  We do enforce resource limits on our
student who are the world's most adept at writing programs with infinite
loops.  The following trivial fix will cause the program to die when it
exceeds the hard limit.

*** /tmp/,RCSt1024359	Tue May 26 09:02:48 1987
--- kern_clock.c	Wed Nov  5 11:35:10 1986
***************
*** 4,10 ****
   * specifies the terms and conditions for redistribution.
   *
   *	@(#)kern_clock.c	7.1 (Berkeley) 6/5/86
!  * $Header: kern_clock.c,v 1.2 86/10/21 14:55:15 larry Exp $
   */
  
  #include "../machine/reg.h"
--- 4,10 ----
   * specifies the terms and conditions for redistribution.
   *
   *	@(#)kern_clock.c	7.1 (Berkeley) 6/5/86
!  * $Header: kern_clock.c,v 1.3 86/11/05 11:35:05 larry Exp $
   */
  
  #include "../machine/reg.h"
***************
*** 146,151 ****
--- 146,154 ----
  			if (u.u_rlimit[RLIMIT_CPU].rlim_cur <
  			    u.u_rlimit[RLIMIT_CPU].rlim_max)
  				u.u_rlimit[RLIMIT_CPU].rlim_cur += 5;
+ 			else
+ 				/* kill the proc if hard cpu limit exceeded */
+ 				psignal(u.u_procp, SIGKILL);
  		}
  		if (timerisset(&u.u_timer[ITIMER_PROF].it_value) &&
  		    itimerdecr(&u.u_timer[ITIMER_PROF], tick) == 0)

Larry Philps	Engineering Computing Facility	University of Toronto
NEW PATH:   larry@ecf.toronto.edu
USENET:     {linus, ihnp4, allegra, decvax, floyd}!utcsri!ecf!larry
CSNET:      larry@Toronto
ARPA:       larry%Toronto@CSNet-Relay
BITNET:     larry@ecf.utoronto.BITNET