From owner-freebsd-hackers  Wed Apr  7 15:55:42 1999
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Date: Wed, 7 Apr 1999 16:51:30 -0600 (MDT)
From: Chad David <davidc@colnta.acns.ab.ca>
To: freebsd-hackers@freebsd.org
Subject: Closing file descriptors with cc -pthread
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I have been porting a threaded server from Solaris to
FreeBSD, and I noticed that on FreeBSD the server uses
100% of the processor even when it is "idle".  top shows
it climb to the top of the list and eventually take
up 99.8% on a fairly idle system.

truss shows that the process is calling select() and
gettimeofday() over and over...

I tracked the problem to an init_daemon() call
(much like daemon(), only a little more complete), and
within that I found it was a loop that closed all open
descriptors and dup2()'d 0,1,2 -> /dev/null that was causing
the problem.

In a seperate test I was able to duplicate the problem, but
I am not sure what I am seeing or why.  Is this a bug, or
am I missing something?  Also, why are descriptors 3 and 4
open when the program starts?


--CODE--
/* testfd.c */
#include <unistd.h>
#include <stdio.h>
#include <errno.h>

extern int errno;

int main() {
int fd;
int nfile=256;
int i;


        for (i = nfile; i >= 0; i--) {
                printf("[%d]",i);
                if (i == 3 || i == 4) {
                        printf(" ??\n");
			close(i);
                        continue;
                }
                if (i == STDOUT_FILENO) {
                        printf(" stdout\n");
                        continue;
                }       
                if (close(i) != 0)
                        printf(" error [%d]\n",errno);
                else    printf(" ok\n");
        }

        sleep(100);
}

If this code is compiled with 
	cc -o testfd testfd.c 
it will run as expected.  If it is compiled with 
	cc -pthread -o testfd testfd.c
then it seems to loop out of control.

If I do not close 3 and 4 the code will run normally both
with -pthread and without.  Again, what are they for?

Not closing all open descriptors, and dup2()'ing 0,1, and 2 like
daemon() does solves my problem, but I do not understand why.

Any information would be appreciated.

Thanks.

Chad David
ACNS Inc.



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