kern/76144: poll doesn't set POLLHUP when FIFO is closed

[Drazen Kacar]

>Number:         76144
>Category:       kern
>Synopsis:       poll doesn't set POLLHUP when FIFO is closed
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Jan 12 14:40:23 GMT 2005
>Closed-Date:
>Last-Modified:
>Originator:     Drazen Kacar
>Release:        FreeBSD 5.3-RELEASE-p2 i386
>Organization:
Cardak ni na nebu, ni na zemlji
>Environment:
Observed with FreeBSD 5.2.1 and 5.3 kernels on i386.

>Description:
	When the other end of a FIFO closes file descriptor, poll(2)
	doesn't return with POLLHUP set in revents. Instead it keeps
	waiting.

>How-To-Repeat:
	The attached program demonstrates the problem. Compile the program
	and run it. It another terminal (in the same directory) type:

	  echo foo >fifo

	The program should output:

	poll() returned 1
	revents = 17
	read() returned 4

	and exit. (It does this on Linux and Solaris). Instead, on
	FreeBSD, the output is:

	poll() returned 1
	revents = 1
	read() returned 4

	and the program doesn't exit.

>Fix:
	Unknown.

--- fifo_poll.c begins here ---
#include <stdio.h>
#include <stdlib.h>
#include <poll.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <sys/uio.h>
#include <fcntl.h>

int main()
{
    int ret;
    struct pollfd p[1];
    char buf[256];

    if (mkfifo("fifo", 0600))
    {
	perror("mkfifo");
	exit(1);
    }

    p[0].fd = open("fifo", O_RDONLY | O_NONBLOCK);
    if (p[0].fd < 0)
    {
	perror("open");
	exit(1);
    }
    /* fcntl(p[0].fd, F_SETFL, 0); /* No change with this line. */

    p[0].events = POLLIN;

    do {
	ret = poll(p, 1, -1);

	printf("poll() returned %d\n", ret);
	printf("revents = %d\n", (int)(p[0].revents));

	if (p[0].revents & POLLIN)
	{
	    ret = read(p[0].fd, buf, sizeof buf);
	    printf("read() returned %d\n", ret);
	}
    } while (!(p[0].revents & (POLLERR | POLLHUP | POLLNVAL)));

    return 0;
}
--- fifo_poll.c ends here ---



>Release-Note:
>Audit-Trail:
>Unformatted: