jim@artecon.UUCP (Jim Wang) (01/17/86)
Is there any reason why the select(2) system call on 4.2bsd
systems can't be used for a quick and dirty (QND) sub-second
sleep? Granted that it is not portable to non-Berkeley, but in
cases where that is not a consideration, it has a few advantages:
1) Does not require setting up a timer (You don't have to
remember all those nested structures).
2) You don't have to worry about taking over the SIGALRM
signal. You also needn't set up a dummy routine that
does nothing except provide a place to point to.
3) Most importantly, you don't have to worry about critical
races where the timer expires before the signal catcher
is set up. These are a distinct possibility for
sub-second intervals.
Not knowing how select() works internally, I can't determine if
a tremendous amount of overhead is required. I have used it in
a number of applications (see below for example) without apparent
detrimental effects, but I've wondered if perhaps I'm missing
something.
Jim Wang
Artecon, Inc.
(jim@seismo, seismo!kobold!artecon!jim)
-----------------------------------------------------
#include <stdio.h>
#include <sys/time.h>
static
void
nap(seconds, microseconds)
int seconds, microseconds;
{
struct timeval timeout;
timeout.tv_sec = seconds;
timeout.tv_usec = microseconds;
(void) select(1, 0, 0, 0, &timeout);
}
/* That's all there is to it. */wls@astrovax.UUCP (William L. Sebok) (01/20/86)
In article <109@artecon.UUCP> jim@artecon.UUCP (Jim Wang) writes: >Is there any reason why the select(2) system call on 4.2bsd >systems can't be used for a quick and dirty (QND) sub-second >sleep? Granted that it is not portable to non-Berkeley, but in >cases where that is not a consideration, it has a few advantages: It's what is used for sub-second sleeps here. -- Bill Sebok Princeton University, Astrophysics {allegra,akgua,cbosgd,decvax,ihnp4,noao,philabs,princeton,vax135}!astrovax!wls