Path: utzoo!yunexus!geac!syntron!jtsv16!uunet!mcvax!ukc!acorn!john
From: john@acorn.UUCP (John Bowler)
Newsgroups: comp.windows.x
Subject: Re: SUN select error
Summary: select() is sometimes passed a negative timeout
Message-ID: <522@acorn.UUCP>
Date: 21 Oct 88 15:15:57 GMT
Article-I.D.: acorn.522
References: <16520@shemp.CS.UCLA.EDU>
Organization: Acorn Computers Limited, Cambridge, UK
Lines: 44

In article <16520@shemp.CS.UCLA.EDU>, tek@CS.UCLA.EDU writes:
> Every now and then the server stops responding for a while and gives
> me a whole bunch (like a screen full) of these error messages:
> 
> 	WaitForSomething(): select: errno=22
> 
> Usually, this happens just after (within a second) of moving the
> mouse. Eventually, the server recovers and all is fine. After a while
> though this gets annoying.

The problem also occurs in BSD43 based servers typically when the ``logo''
screen saver is switched on and the timeout is relatively short - colour
servers are particularly prone.  It is caused by ``timeout'' remaining
negative in the following piece of code in WaitFor() (from WaitFor.c)

/*-------- WaitFor.c -- Waitfor() --------*/
if (timeout < 0) /* may be forced by AutoResetServer() */
{
    if (clientsDoomed)
    {
	*nnew = *nready = 0;
	break;
    }
    if (timeout < intervalCount)
    {
/*-- SaveScreens can take a very long time!! --*/
	SaveScreens(SCREEN_SAVER_ON, ScreenSaverActive);
	if (intervalCount)
	    intervalCount -= ScreenSaverInterval;
	else
	    intervalCount = 
			-(ScreenSaverInterval + ScreenSaverTime);
    }
    timeout -= intervalCount;
/*-- timeout may still be <0 fix by adding the following line:- --*/
    if (timeout < 0)					/* BUG FIX */
    {							/* BUG FIX */
	intervalCount = timeout-ScreenSaverInterval;	/* BUG FIX */
	timeout = 0;					/* BUG FIX */
    }							/* BUG FIX */
}
/*------------------------------------------*/

John Bowler (jbowler@acorn.co.uk)