freebsd-dev/sys/kern/tty_tty.c
Ed Schouten 5db88944ac Remove unneeded Giant locking of /dev/tty.
The Giant lock is acquired in two places in tty_tty.c. In both places,
it is unneeded.

There is no reason to specify D_NEEDGIANT on this device node. The
device node has only been designed to return ENXIO when opened. It
doesn't make any sense to lock/unlock Giant, just to return this error.
D_TTY is also unneeded. The unimplemented functions don't need to be
patched by devfs.

We don't need to lock Giant when we want to lookup the proper TTY vnode.
s_ttyvp is already protected by proctree_lock (see devfs_vnops.c).

Approved by:	philip (mentor)
2008-06-03 12:38:00 +00:00

94 lines
2.8 KiB
C

/*-
* Copyright (c) 2003 Poul-Henning Kamp. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/conf.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/sx.h>
#include <sys/vnode.h>
#include <fs/devfs/devfs.h>
#include <fs/devfs/devfs_int.h>
static d_open_t cttyopen;
static struct cdevsw ctty_cdevsw = {
.d_version = D_VERSION,
.d_open = cttyopen,
.d_name = "ctty",
};
static struct cdev *ctty;
static int
cttyopen(struct cdev *dev, int flag, int mode, struct thread *td)
{
return (ENXIO);
}
static void
ctty_clone(void *arg, struct ucred *cred, char *name, int namelen,
struct cdev **dev)
{
if (*dev != NULL)
return;
if (strcmp(name, "tty"))
return;
sx_sunlock(&clone_drain_lock);
sx_slock(&proctree_lock);
sx_slock(&clone_drain_lock);
dev_lock();
if (!(curthread->td_proc->p_flag & P_CONTROLT))
*dev = ctty;
else if (curthread->td_proc->p_session->s_ttyvp == NULL)
*dev = ctty;
else if (curthread->td_proc->p_session->s_ttyvp->v_type == VBAD ||
curthread->td_proc->p_session->s_ttyvp->v_rdev == NULL) {
/* e.g. s_ttyvp was revoked */
*dev = ctty;
} else
*dev = curthread->td_proc->p_session->s_ttyvp->v_rdev;
dev_refl(*dev);
dev_unlock();
sx_sunlock(&proctree_lock);
}
static void
ctty_drvinit(void *unused)
{
EVENTHANDLER_REGISTER(dev_clone, ctty_clone, 0, 1000);
ctty = make_dev(&ctty_cdevsw, 0, 0, 0, 0666, "ctty");
}
SYSINIT(cttydev,SI_SUB_DRIVERS,SI_ORDER_MIDDLE,ctty_drvinit,NULL);