Date: Thu, 7 Aug 1997 17:25:16 +0900 From: tetsuya@secom-sis.co.jp To: FreeBSD-gnats-submit@FreeBSD.ORG Subject: kern/4243: file locking doesn't work for pipe Message-ID: <199708070825.RAA10674@juria.secom-sis.co.jp> Resent-Message-ID: <199708070830.BAA27289@hub.freebsd.org>
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>Number: 4243
>Category: kern
>Synopsis: file locking doesn't work for pipe
>Confidential: no
>Severity: non-critical
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Thu Aug 7 01:30:01 PDT 1997
>Last-Modified:
>Originator: Tetsuya Furukawa
>Organization:
Secom Information System Co.,Ltd.
>Release: FreeBSD 2.2-STABLE i386
>Environment:
FreeBSD 2.2-STABLE i386 on July 11, 1997
>Description:
In flock() in /sys/kern/kern_descrip.c, the following statement:
f (fp->f_type != DTYPE_VNODE)
return (EOPNOTSUPP);
rejects the file descriptor if fp->f_type == DTYPE_PIPE.
F_SETLK and F_GETLK of fcntl() have also the similar statements.
"Program rewriting map" (RewriteMap mapname prg:filename) of
the URL rewriting module (mod_rewrite) of the Apache HTTP server
uses file locking for pipe, so FreeBSD users cannot use the fine
feature of "program rewriting map".
>How-To-Repeat:
The following program prints "flock: Operation not supported".
--------
#include <sys/file.h>
#include <stdio.h>
#include <unistd.h>
int
main()
{
int fds[2];
char c;
pipe(fds);
if (flock(fds[1], LOCK_EX) == -1)
perror("flock");
write(fds[1], "a", 1);
read(fds[0], &c, 1);
return 0;
}
--------
>Fix:
Maybe, modify the three lines like
if (fp->f_type != DTYPE_VNODE)
into
if (fp->f_type != DTYPE_VNODE && fp->f_type != DTYPE_PIPE)
I have not tried it, and I'm not convinced that it is safe and right
for I don't know detail of the kernel.
>Audit-Trail:
>Unformatted:
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