diff options
| author |   Peter Hurley <peter@hurleysoftware.com> | 2016-01-10 22:41:01 -0800 |
|---|---|---|
| committer |   Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-01-27 15:01:44 -0800 |
| commit | e55afd11a48354c810caf6b6ad4c103016a88230 (patch) | |
| tree | eb073c28c1e21785fcbe92740ce1290da7fcb85c /drivers/tty/tty_io.c | |
| parent | tty: Fix comments for tty_ldisc_release() (diff) | |
| download | linux-dev-e55afd11a48354c810caf6b6ad4c103016a88230.tar.xz linux-dev-e55afd11a48354c810caf6b6ad4c103016a88230.zip | |
tty: Prepare for destroying line discipline on hangup
tty file_operations (read/write/ioctl) wait for the ldisc reference
indefinitely (until ldisc lifetime events, such as hangup or TIOCSETD,
finish). Since hangup now destroys the ldisc and does not instance
another copy, file_operations must now be prepared to receive a NULL
ldisc reference from tty_ldisc_ref_wait():
CPU 0 CPU 1
----- -----
(*f_op->read)() => tty_read()
__tty_hangup()
...
f_op = &hung_up_tty_fops;
...
tty_ldisc_hangup()
tty_ldisc_lock()
tty_ldisc_kill()
tty->ldisc = NULL
tty_ldisc_unlock()
ld = tty_ldisc_ref_wait()
/* ld == NULL */
Instead, the action taken now is to return the same value as if the
tty had been hungup a moment earlier:
CPU 0 CPU 1
----- -----
__tty_hangup()
...
f_op = &hung_up_tty_fops;
(*f_op->read)() => hung_up_tty_read()
return 0;
...
tty_ldisc_hangup()
tty_ldisc_lock()
tty_ldisc_kill()
tty->ldisc = NULL
tty_ldisc_unlock()
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/tty_io.c')
| -rw-r--r-- | drivers/tty/tty_io.c | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 71a9409c8d7e..eb26754b2e5d 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1068,6 +1068,8 @@ static ssize_t tty_read(struct file *file, char __user *buf, size_t count, /* We want to wait for the line discipline to sort out in this situation */ ld = tty_ldisc_ref_wait(tty); + if (!ld) + return hung_up_tty_read(file, buf, count, ppos); if (ld->ops->read) i = ld->ops->read(tty, file, buf, count); else @@ -1242,6 +1244,8 @@ static ssize_t tty_write(struct file *file, const char __user *buf, if (tty->ops->write_room == NULL) tty_err(tty, "missing write_room method\n"); ld = tty_ldisc_ref_wait(tty); + if (!ld) + return hung_up_tty_write(file, buf, count, ppos); if (!ld->ops->write) ret = -EIO; else @@ -2201,6 +2205,8 @@ static unsigned int tty_poll(struct file *filp, poll_table *wait) return 0; ld = tty_ldisc_ref_wait(tty); + if (!ld) + return hung_up_tty_poll(filp, wait); if (ld->ops->poll) ret = ld->ops->poll(tty, filp, wait); tty_ldisc_deref(ld); @@ -2290,6 +2296,8 @@ static int tiocsti(struct tty_struct *tty, char __user *p) return -EFAULT; tty_audit_tiocsti(tty, ch); ld = tty_ldisc_ref_wait(tty); + if (!ld) + return -EIO; ld->ops->receive_buf(tty, &ch, &mbz, 1); tty_ldisc_deref(ld); return 0; @@ -2682,6 +2690,8 @@ static int tiocgetd(struct tty_struct *tty, int __user *p) int ret; ld = tty_ldisc_ref_wait(tty); + if (!ld) + return -EIO; ret = put_user(ld->ops->num, p); tty_ldisc_deref(ld); return ret; @@ -2979,6 +2989,8 @@ long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg) return retval; } ld = tty_ldisc_ref_wait(tty); + if (!ld) + return hung_up_tty_ioctl(file, cmd, arg); retval = -EINVAL; if (ld->ops->ioctl) { retval = ld->ops->ioctl(tty, file, cmd, arg); @@ -3007,6 +3019,8 @@ static long tty_compat_ioctl(struct file *file, unsigned int cmd, } ld = tty_ldisc_ref_wait(tty); + if (!ld) + return hung_up_tty_compat_ioctl(file, cmd, arg); if (ld->ops->compat_ioctl) retval = ld->ops->compat_ioctl(tty, file, cmd, arg); else |