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Date: Mon, 26 Jan 1998 10:41:27 -0800 (PST)
From: Matt Dillon <dillon@best.net>
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To: FreeBSD-gnats-submit@FreeBSD.ORG
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Subject: bin/5572: major time step blows cron up
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>Number:         5572
>Category:       bin
>Synopsis:       A major time step blows cron up, runs thousands of processes
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:
>Keywords:
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Jan 26 10:50:00 PST 1998
>Last-Modified:
>Originator:     Matt Dillon
>Organization:
Best Internet Communications
>Release:        FreeBSD 2.2.5-STABLE i386
>Environment:

	Loaded shell machines with lots of accounts and lots of cron
	jobs.

>Description:

	If a major time step occurs, for example a backwards time step,
	cron will attempt to run every single job in between.  This
	can result in cron starting thousands of jobs for the last N
	hours or N days, depending on how large a time step occured.

>How-To-Repeat:

	Create some cron jobs and set the time backwards by a few hours.

>Fix:

	The fix is included below.  We check for nonsensical time steps
	and deal with them by resynchronizing cron's internal time
	tracking.
	
*** LINK/cron.c	Wed Sep 17 15:10:45 1997
--- cron.c	Mon Jan 26 10:36:26 1998
***************
*** 229,234 ****
--- 229,248 ----
  cron_sleep() {
  	register int	seconds_to_wait;
  
+ 	/*
+ 	 * Look for time step and don't run all the friggin cron jobs in
+ 	 * between if a major backwards step occurs.  Otherwise, a major 
+ 	 * time step (e.g. if the time gets messed up on the machine) may 
+ 	 * cause thousands of cron jobs to be run, especially if you have a lot
+ 	 * of users.
+ 	 */
+ 
+ 	seconds_to_wait = (int) (TargetTime - time((time_t*)0));
+ 
+ 	if (seconds_to_wait < -600 || seconds_to_wait > 600) {
+ 	    cron_sync();
+ 	}
+ 
  	do {
  		seconds_to_wait = (int) (TargetTime - time((time_t*)0));
  		Debug(DSCH, ("[%d] TargetTime=%ld, sec-to-wait=%d\n",


>Audit-Trail:
>Unformatted: