Hello, I'm working on a project at school to develop a multimedia system (a la Windows Media Center) based on FreeBSD. I was looking at some code in sys/kern/kern_descrip.c to figure out how the fcntl() with F_DUPFD and dup() differ.
I discovered that kern_fcntl() contains some redundant code. Right
before calling do_dup(), it locks the process and checks that the
minimal file descriptor is lower than the limit for the process. The
do_dup() call does exactly the same check almost at the beginning. This
causes the fcntl() call to call PROC_LOCK() once too much.
The patch below prevents this by performing this check by do_dup(). It
will prevent fcntl() from PROC_LOCK()'ing twice. It also fixes the
return value of fcntl(). The manual page states that it should return
EMFILE when it exceeds its limit, though the actual code sets EINVAL.
%%%
--- kern_descrip.c Thu Nov 9 13:23:40 2006
+++ kern_descrip.c Thu Nov 9 13:32:28 2006
@@ -355,7 +355,6 @@
struct proc *p;
char *pop;
struct vnode *vp;
- u_int newmin;
int error, flg, tmp;
int giant_locked;
@@ -393,16 +392,7 @@
case F_DUPFD:
/* mtx_assert(&Giant, MA_NOTOWNED); */
FILEDESC_UNLOCK(fdp);
- newmin = arg;
- PROC_LOCK(p);
- if (newmin >= lim_cur(p, RLIMIT_NOFILE) ||
- newmin >= maxfilesperproc) {
- PROC_UNLOCK(p);
- error = EINVAL;
- break;
- }
- PROC_UNLOCK(p);
- error = do_dup(td, DUP_VARIABLE, fd, newmin, td->td_retval);
+ error = do_dup(td, DUP_VARIABLE, fd, arg, td->td_retval);
break;
case F_GETFD:
%%%
--
Ed Schouten <[EMAIL PROTECTED]>
WWW: http://g-rave.nl/
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