Author: pho
Date: Mon Jun 18 07:34:38 2012
New Revision: 237219
URL: http://svn.freebsd.org/changeset/base/237219
Log:
In tty_makedev() the following construction:
dev = make_dev_cred();
dev->si_drv1 = tp;
leaves a small window where the newly created device may be opened
and si_drv1 is NULL.
As this is a vary rare situation, using a lock to close the window
seems overkill. Instead just wait for the assignment of si_drv1.
Suggested by: kib
MFC after: 1 week
Modified:
head/sys/kern/tty.c
Modified: head/sys/kern/tty.c
==============================================================================
--- head/sys/kern/tty.c Mon Jun 18 05:02:21 2012 (r237218)
+++ head/sys/kern/tty.c Mon Jun 18 07:34:38 2012 (r237219)
@@ -219,9 +219,15 @@ ttydev_leave(struct tty *tp)
static int
ttydev_open(struct cdev *dev, int oflags, int devtype, struct thread *td)
{
- struct tty *tp = dev->si_drv1;
+ struct tty *tp;
int error = 0;
+ while ((tp = dev->si_drv1) == NULL) {
+ error = tsleep(&dev->si_drv1, PCATCH, "ttdrv1", 1);
+ if (error != EWOULDBLOCK)
+ return (error);
+ }
+
tty_lock(tp);
if (tty_gone(tp)) {
/* Device is already gone. */
@@ -738,9 +744,14 @@ static struct cdevsw ttydev_cdevsw = {
static int
ttyil_open(struct cdev *dev, int oflags, int devtype, struct thread *td)
{
- struct tty *tp = dev->si_drv1;
+ struct tty *tp;
int error = 0;
+ while ((tp = dev->si_drv1) == NULL) {
+ error = tsleep(&dev->si_drv1, PCATCH, "ttdrv1", 1);
+ if (error != EWOULDBLOCK)
+ return (error);
+ }
tty_lock(tp);
if (tty_gone(tp))
error = ENODEV;
@@ -1203,6 +1214,7 @@ tty_makedev(struct tty *tp, struct ucred
dev = make_dev_cred(&ttydev_cdevsw, 0, cred,
uid, gid, mode, "%s%s", prefix, name);
dev->si_drv1 = tp;
+ wakeup(&dev->si_drv1);
tp->t_dev = dev;
/* Slave call-in devices. */
@@ -1211,12 +1223,14 @@ tty_makedev(struct tty *tp, struct ucred
uid, gid, mode, "%s%s.init", prefix, name);
dev_depends(tp->t_dev, dev);
dev->si_drv1 = tp;
+ wakeup(&dev->si_drv1);
dev->si_drv2 = &tp->t_termios_init_in;
dev = make_dev_cred(&ttyil_cdevsw, TTYUNIT_LOCK, cred,
uid, gid, mode, "%s%s.lock", prefix, name);
dev_depends(tp->t_dev, dev);
dev->si_drv1 = tp;
+ wakeup(&dev->si_drv1);
dev->si_drv2 = &tp->t_termios_lock_in;
}
@@ -1226,6 +1240,7 @@ tty_makedev(struct tty *tp, struct ucred
UID_UUCP, GID_DIALER, 0660, "cua%s", name);
dev_depends(tp->t_dev, dev);
dev->si_drv1 = tp;
+ wakeup(&dev->si_drv1);
/* Slave call-out devices. */
if (tp->t_flags & TF_INITLOCK) {
@@ -1234,6 +1249,7 @@ tty_makedev(struct tty *tp, struct ucred
UID_UUCP, GID_DIALER, 0660, "cua%s.init", name);
dev_depends(tp->t_dev, dev);
dev->si_drv1 = tp;
+ wakeup(&dev->si_drv1);
dev->si_drv2 = &tp->t_termios_init_out;
dev = make_dev_cred(&ttyil_cdevsw,
@@ -1241,6 +1257,7 @@ tty_makedev(struct tty *tp, struct ucred
UID_UUCP, GID_DIALER, 0660, "cua%s.lock", name);
dev_depends(tp->t_dev, dev);
dev->si_drv1 = tp;
+ wakeup(&dev->si_drv1);
dev->si_drv2 = &tp->t_termios_lock_out;
}
}
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