From owner-freebsd-hackers  Tue Apr 20  3:12:52 1999
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Date: Tue, 20 Apr 1999 12:09:17 +0200
From: Graham Wheeler <gram@cdsec.com>
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Subject: Re: Using select() to implement a delay
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Marc van Kempen wrote:
> 
> Graham Wheeler wrote:
>
> > Hi all
> >
> > I have an interesting problem. I have a routine to implement delays:
> >
> > void Sleep(int secs, int usecs = 0)
> > {
> >     struct timeval tv;
> >     tv.tv_sec = secs;
> >     tv.tv_usec = usecs;
> >     (void)select(0, 0, 0, 0, &tv);
> > }
> >
> > I am using this both because it gives better resolution than sleep(),
> > and also because it doesn't require the use of SIGALRM, which I am
> > using elsewhere.
> >
> > On my development machine, Sleep(60) does exactly what is expected. On
> > my clients machine, Sleep(60) returns immediately. Both are running
> > FreeBSD 2.2.7. I don't have access to the clients machine, which is
> > in another city, and has no development environment, so I can't run gdb,
> > although it may not give away anything in any case.
> >
> > Does anyone have any ideas why the one works and the other doesn't?
> >
> 
> Did you try catching the return value from select, it might be getting a
> signal.
> 

I've changed the code to:

  void Sleep(int secs, int usecs = 0)
  {
      struct timeval tv;
      tv.tv_sec = secs;
      tv.tv_usec = usecs;
      if (select(0, 0, 0, 0, &tv)<0)
          syslog(LOG_INFO, "Sleep(): select: %m");
  }

and have asked the client to run the program. I'll post the results
when I get them back. On the one hand, a signal seems like the only
explanation; on the other, there are no calls to alarm() or other
SIGALRM related routines in the code, and this is also happening with
100% consistency.

-- 
Dr Graham Wheeler                          E-mail: gram@cdsec.com
Citadel Data Security                      Phone:  +27(21)423-6065/6/7
Firewalls/Virtual Private Networks         Fax:    +27(21)24-3656
Internet/Intranet Network Specialists      
Data Security Products                     WWW:    http://www.cdsec.com/


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