Date: Fri, 29 Jun 2012 12:08:27 +0000 (UTC) From: Peter Holm <pho@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-9@freebsd.org Subject: svn commit: r237775 - stable/9/sys/kern Message-ID: <201206291208.q5TC8Rac044638@svn.freebsd.org>
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Author: pho Date: Fri Jun 29 12:08:26 2012 New Revision: 237775 URL: http://svn.freebsd.org/changeset/base/237775 Log: MFC: r237219 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. Modified: stable/9/sys/kern/tty.c Directory Properties: stable/9/sys/ (props changed) Modified: stable/9/sys/kern/tty.c ============================================================================== --- stable/9/sys/kern/tty.c Fri Jun 29 12:05:19 2012 (r237774) +++ stable/9/sys/kern/tty.c Fri Jun 29 12:08:26 2012 (r237775) @@ -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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