Commit 04f378b1 authored by Alan Cox's avatar Alan Cox Committed by Linus Torvalds

tty: BKL pushdown

- Push the BKL down into the line disciplines
- Switch the tty layer to unlocked_ioctl
- Introduce a new ctrl_lock spin lock for the control bits
- Eliminate much of the lock_kernel use in n_tty
- Prepare to (but don't yet) call the drivers with the lock dropped
  on the paths that historically held the lock

BKL now primarily protects open/close/ldisc change in the tty layer

[jirislaby@gmail.com: a couple of fixes]
Signed-off-by: default avatarAlan Cox <alan@redhat.com>
Signed-off-by: default avatarJiri Slaby <jirislaby@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e5238442
...@@ -578,26 +578,36 @@ static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file, ...@@ -578,26 +578,36 @@ static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
return -EFAULT; return -EFAULT;
} }
lock_kernel();
for (;;) { for (;;) {
if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
unlock_kernel();
return -EIO; return -EIO;
}
n_hdlc = tty2n_hdlc (tty); n_hdlc = tty2n_hdlc (tty);
if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC || if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
tty != n_hdlc->tty) tty != n_hdlc->tty) {
unlock_kernel();
return 0; return 0;
}
rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list); rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
if (rbuf) if (rbuf)
break; break;
/* no data */ /* no data */
if (file->f_flags & O_NONBLOCK) if (file->f_flags & O_NONBLOCK) {
unlock_kernel();
return -EAGAIN; return -EAGAIN;
}
interruptible_sleep_on (&tty->read_wait); interruptible_sleep_on (&tty->read_wait);
if (signal_pending(current)) if (signal_pending(current)) {
unlock_kernel();
return -EINTR; return -EINTR;
}
} }
if (rbuf->count > nr) if (rbuf->count > nr)
...@@ -618,7 +628,7 @@ static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file, ...@@ -618,7 +628,7 @@ static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
kfree(rbuf); kfree(rbuf);
else else
n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,rbuf); n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,rbuf);
unlock_kernel();
return ret; return ret;
} /* end of n_hdlc_tty_read() */ } /* end of n_hdlc_tty_read() */
...@@ -661,6 +671,8 @@ static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file, ...@@ -661,6 +671,8 @@ static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
count = maxframe; count = maxframe;
} }
lock_kernel();
add_wait_queue(&tty->write_wait, &wait); add_wait_queue(&tty->write_wait, &wait);
set_current_state(TASK_INTERRUPTIBLE); set_current_state(TASK_INTERRUPTIBLE);
...@@ -695,7 +707,7 @@ static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file, ...@@ -695,7 +707,7 @@ static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf); n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf);
n_hdlc_send_frames(n_hdlc,tty); n_hdlc_send_frames(n_hdlc,tty);
} }
unlock_kernel();
return error; return error;
} /* end of n_hdlc_tty_write() */ } /* end of n_hdlc_tty_write() */
......
...@@ -1075,12 +1075,15 @@ static ssize_t r3964_read(struct tty_struct *tty, struct file *file, ...@@ -1075,12 +1075,15 @@ static ssize_t r3964_read(struct tty_struct *tty, struct file *file,
TRACE_L("read()"); TRACE_L("read()");
lock_kernel();
pClient = findClient(pInfo, task_pid(current)); pClient = findClient(pInfo, task_pid(current));
if (pClient) { if (pClient) {
pMsg = remove_msg(pInfo, pClient); pMsg = remove_msg(pInfo, pClient);
if (pMsg == NULL) { if (pMsg == NULL) {
/* no messages available. */ /* no messages available. */
if (file->f_flags & O_NONBLOCK) { if (file->f_flags & O_NONBLOCK) {
unlock_kernel();
return -EAGAIN; return -EAGAIN;
} }
/* block until there is a message: */ /* block until there is a message: */
...@@ -1090,8 +1093,10 @@ static ssize_t r3964_read(struct tty_struct *tty, struct file *file, ...@@ -1090,8 +1093,10 @@ static ssize_t r3964_read(struct tty_struct *tty, struct file *file,
/* If we still haven't got a message, we must have been signalled */ /* If we still haven't got a message, we must have been signalled */
if (!pMsg) if (!pMsg) {
unlock_kernel();
return -EINTR; return -EINTR;
}
/* deliver msg to client process: */ /* deliver msg to client process: */
theMsg.msg_id = pMsg->msg_id; theMsg.msg_id = pMsg->msg_id;
...@@ -1102,12 +1107,15 @@ static ssize_t r3964_read(struct tty_struct *tty, struct file *file, ...@@ -1102,12 +1107,15 @@ static ssize_t r3964_read(struct tty_struct *tty, struct file *file,
kfree(pMsg); kfree(pMsg);
TRACE_M("r3964_read - msg kfree %p", pMsg); TRACE_M("r3964_read - msg kfree %p", pMsg);
if (copy_to_user(buf, &theMsg, count)) if (copy_to_user(buf, &theMsg, count)) {
unlock_kernel();
return -EFAULT; return -EFAULT;
}
TRACE_PS("read - return %d", count); TRACE_PS("read - return %d", count);
return count; return count;
} }
unlock_kernel();
return -EPERM; return -EPERM;
} }
...@@ -1156,6 +1164,8 @@ static ssize_t r3964_write(struct tty_struct *tty, struct file *file, ...@@ -1156,6 +1164,8 @@ static ssize_t r3964_write(struct tty_struct *tty, struct file *file,
pHeader->locks = 0; pHeader->locks = 0;
pHeader->owner = NULL; pHeader->owner = NULL;
lock_kernel();
pClient = findClient(pInfo, task_pid(current)); pClient = findClient(pInfo, task_pid(current));
if (pClient) { if (pClient) {
pHeader->owner = pClient; pHeader->owner = pClient;
...@@ -1173,6 +1183,8 @@ static ssize_t r3964_write(struct tty_struct *tty, struct file *file, ...@@ -1173,6 +1183,8 @@ static ssize_t r3964_write(struct tty_struct *tty, struct file *file,
add_tx_queue(pInfo, pHeader); add_tx_queue(pInfo, pHeader);
trigger_transmit(pInfo); trigger_transmit(pInfo);
unlock_kernel();
return 0; return 0;
} }
......
...@@ -183,22 +183,24 @@ static void reset_buffer_flags(struct tty_struct *tty) ...@@ -183,22 +183,24 @@ static void reset_buffer_flags(struct tty_struct *tty)
* at hangup) or when the N_TTY line discipline internally has to * at hangup) or when the N_TTY line discipline internally has to
* clean the pending queue (for example some signals). * clean the pending queue (for example some signals).
* *
* FIXME: tty->ctrl_status is not spinlocked and relies on * Locking: ctrl_lock
* lock_kernel() still.
*/ */
static void n_tty_flush_buffer(struct tty_struct *tty) static void n_tty_flush_buffer(struct tty_struct *tty)
{ {
unsigned long flags;
/* clear everything and unthrottle the driver */ /* clear everything and unthrottle the driver */
reset_buffer_flags(tty); reset_buffer_flags(tty);
if (!tty->link) if (!tty->link)
return; return;
spin_lock_irqsave(&tty->ctrl_lock, flags);
if (tty->link->packet) { if (tty->link->packet) {
tty->ctrl_status |= TIOCPKT_FLUSHREAD; tty->ctrl_status |= TIOCPKT_FLUSHREAD;
wake_up_interruptible(&tty->link->read_wait); wake_up_interruptible(&tty->link->read_wait);
} }
spin_unlock_irqrestore(&tty->ctrl_lock, flags);
} }
/** /**
...@@ -264,7 +266,7 @@ static inline int is_continuation(unsigned char c, struct tty_struct *tty) ...@@ -264,7 +266,7 @@ static inline int is_continuation(unsigned char c, struct tty_struct *tty)
* relevant in the world today. If you ever need them, add them here. * relevant in the world today. If you ever need them, add them here.
* *
* Called from both the receive and transmit sides and can be called * Called from both the receive and transmit sides and can be called
* re-entrantly. Relies on lock_kernel() still. * re-entrantly. Relies on lock_kernel() for tty->column state.
*/ */
static int opost(unsigned char c, struct tty_struct *tty) static int opost(unsigned char c, struct tty_struct *tty)
...@@ -275,6 +277,7 @@ static int opost(unsigned char c, struct tty_struct *tty) ...@@ -275,6 +277,7 @@ static int opost(unsigned char c, struct tty_struct *tty)
if (!space) if (!space)
return -1; return -1;
lock_kernel();
if (O_OPOST(tty)) { if (O_OPOST(tty)) {
switch (c) { switch (c) {
case '\n': case '\n':
...@@ -323,6 +326,7 @@ static int opost(unsigned char c, struct tty_struct *tty) ...@@ -323,6 +326,7 @@ static int opost(unsigned char c, struct tty_struct *tty)
} }
} }
tty->driver->put_char(tty, c); tty->driver->put_char(tty, c);
unlock_kernel();
return 0; return 0;
} }
...@@ -337,7 +341,8 @@ static int opost(unsigned char c, struct tty_struct *tty) ...@@ -337,7 +341,8 @@ static int opost(unsigned char c, struct tty_struct *tty)
* the simple cases normally found and helps to generate blocks of * the simple cases normally found and helps to generate blocks of
* symbols for the console driver and thus improve performance. * symbols for the console driver and thus improve performance.
* *
* Called from write_chan under the tty layer write lock. * Called from write_chan under the tty layer write lock. Relies
* on lock_kernel for the tty->column state.
*/ */
static ssize_t opost_block(struct tty_struct *tty, static ssize_t opost_block(struct tty_struct *tty,
...@@ -353,6 +358,7 @@ static ssize_t opost_block(struct tty_struct *tty, ...@@ -353,6 +358,7 @@ static ssize_t opost_block(struct tty_struct *tty,
if (nr > space) if (nr > space)
nr = space; nr = space;
lock_kernel();
for (i = 0, cp = buf; i < nr; i++, cp++) { for (i = 0, cp = buf; i < nr; i++, cp++) {
switch (*cp) { switch (*cp) {
case '\n': case '\n':
...@@ -387,6 +393,7 @@ break_out: ...@@ -387,6 +393,7 @@ break_out:
if (tty->driver->flush_chars) if (tty->driver->flush_chars)
tty->driver->flush_chars(tty); tty->driver->flush_chars(tty);
i = tty->driver->write(tty, buf, i); i = tty->driver->write(tty, buf, i);
unlock_kernel();
return i; return i;
} }
...@@ -1194,6 +1201,11 @@ extern ssize_t redirected_tty_write(struct file *, const char __user *, ...@@ -1194,6 +1201,11 @@ extern ssize_t redirected_tty_write(struct file *, const char __user *,
* Perform job control management checks on this file/tty descriptor * Perform job control management checks on this file/tty descriptor
* and if appropriate send any needed signals and return a negative * and if appropriate send any needed signals and return a negative
* error code if action should be taken. * error code if action should be taken.
*
* FIXME:
* Locking: None - redirected write test is safe, testing
* current->signal should possibly lock current->sighand
* pgrp locking ?
*/ */
static int job_control(struct tty_struct *tty, struct file *file) static int job_control(struct tty_struct *tty, struct file *file)
...@@ -1246,6 +1258,7 @@ static ssize_t read_chan(struct tty_struct *tty, struct file *file, ...@@ -1246,6 +1258,7 @@ static ssize_t read_chan(struct tty_struct *tty, struct file *file,
ssize_t size; ssize_t size;
long timeout; long timeout;
unsigned long flags; unsigned long flags;
int packet;
do_it_again: do_it_again:
...@@ -1289,16 +1302,19 @@ do_it_again: ...@@ -1289,16 +1302,19 @@ do_it_again:
if (mutex_lock_interruptible(&tty->atomic_read_lock)) if (mutex_lock_interruptible(&tty->atomic_read_lock))
return -ERESTARTSYS; return -ERESTARTSYS;
} }
packet = tty->packet;
add_wait_queue(&tty->read_wait, &wait); add_wait_queue(&tty->read_wait, &wait);
while (nr) { while (nr) {
/* First test for status change. */ /* First test for status change. */
if (tty->packet && tty->link->ctrl_status) { if (packet && tty->link->ctrl_status) {
unsigned char cs; unsigned char cs;
if (b != buf) if (b != buf)
break; break;
spin_lock_irqsave(&tty->link->ctrl_lock, flags);
cs = tty->link->ctrl_status; cs = tty->link->ctrl_status;
tty->link->ctrl_status = 0; tty->link->ctrl_status = 0;
spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
if (tty_put_user(tty, cs, b++)) { if (tty_put_user(tty, cs, b++)) {
retval = -EFAULT; retval = -EFAULT;
b--; b--;
...@@ -1333,6 +1349,7 @@ do_it_again: ...@@ -1333,6 +1349,7 @@ do_it_again:
retval = -ERESTARTSYS; retval = -ERESTARTSYS;
break; break;
} }
/* FIXME: does n_tty_set_room need locking ? */
n_tty_set_room(tty); n_tty_set_room(tty);
timeout = schedule_timeout(timeout); timeout = schedule_timeout(timeout);
continue; continue;
...@@ -1340,7 +1357,7 @@ do_it_again: ...@@ -1340,7 +1357,7 @@ do_it_again:
__set_current_state(TASK_RUNNING); __set_current_state(TASK_RUNNING);
/* Deal with packet mode. */ /* Deal with packet mode. */
if (tty->packet && b == buf) { if (packet && b == buf) {
if (tty_put_user(tty, TIOCPKT_DATA, b++)) { if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
retval = -EFAULT; retval = -EFAULT;
b--; b--;
...@@ -1388,6 +1405,8 @@ do_it_again: ...@@ -1388,6 +1405,8 @@ do_it_again:
break; break;
} else { } else {
int uncopied; int uncopied;
/* The copy function takes the read lock and handles
locking internally for this case */
uncopied = copy_from_read_buf(tty, &b, &nr); uncopied = copy_from_read_buf(tty, &b, &nr);
uncopied += copy_from_read_buf(tty, &b, &nr); uncopied += copy_from_read_buf(tty, &b, &nr);
if (uncopied) { if (uncopied) {
...@@ -1429,7 +1448,6 @@ do_it_again: ...@@ -1429,7 +1448,6 @@ do_it_again:
goto do_it_again; goto do_it_again;
n_tty_set_room(tty); n_tty_set_room(tty);
return retval; return retval;
} }
......
...@@ -181,6 +181,7 @@ static int pty_set_lock(struct tty_struct *tty, int __user * arg) ...@@ -181,6 +181,7 @@ static int pty_set_lock(struct tty_struct *tty, int __user * arg)
static void pty_flush_buffer(struct tty_struct *tty) static void pty_flush_buffer(struct tty_struct *tty)
{ {
struct tty_struct *to = tty->link; struct tty_struct *to = tty->link;
unsigned long flags;
if (!to) if (!to)
return; return;
...@@ -189,8 +190,10 @@ static void pty_flush_buffer(struct tty_struct *tty) ...@@ -189,8 +190,10 @@ static void pty_flush_buffer(struct tty_struct *tty)
to->ldisc.flush_buffer(to); to->ldisc.flush_buffer(to);
if (to->packet) { if (to->packet) {
spin_lock_irqsave(&tty->ctrl_lock, flags);
tty->ctrl_status |= TIOCPKT_FLUSHWRITE; tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
wake_up_interruptible(&to->read_wait); wake_up_interruptible(&to->read_wait);
spin_unlock_irqrestore(&tty->ctrl_lock, flags);
} }
} }
......
...@@ -152,8 +152,7 @@ ssize_t redirected_tty_write(struct file *, const char __user *, ...@@ -152,8 +152,7 @@ ssize_t redirected_tty_write(struct file *, const char __user *,
static unsigned int tty_poll(struct file *, poll_table *); static unsigned int tty_poll(struct file *, poll_table *);
static int tty_open(struct inode *, struct file *); static int tty_open(struct inode *, struct file *);
static int tty_release(struct inode *, struct file *); static int tty_release(struct inode *, struct file *);
int tty_ioctl(struct inode *inode, struct file *file, long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
unsigned int cmd, unsigned long arg);
#ifdef CONFIG_COMPAT #ifdef CONFIG_COMPAT
static long tty_compat_ioctl(struct file *file, unsigned int cmd, static long tty_compat_ioctl(struct file *file, unsigned int cmd,
unsigned long arg); unsigned long arg);
...@@ -1205,7 +1204,7 @@ EXPORT_SYMBOL_GPL(tty_find_polling_driver); ...@@ -1205,7 +1204,7 @@ EXPORT_SYMBOL_GPL(tty_find_polling_driver);
* not in the foreground, send a SIGTTOU. If the signal is blocked or * not in the foreground, send a SIGTTOU. If the signal is blocked or
* ignored, go ahead and perform the operation. (POSIX 7.2) * ignored, go ahead and perform the operation. (POSIX 7.2)
* *
* Locking: none * Locking: none - FIXME: review this
*/ */
int tty_check_change(struct tty_struct *tty) int tty_check_change(struct tty_struct *tty)
...@@ -1247,8 +1246,8 @@ static unsigned int hung_up_tty_poll(struct file *filp, poll_table *wait) ...@@ -1247,8 +1246,8 @@ static unsigned int hung_up_tty_poll(struct file *filp, poll_table *wait)
return POLLIN | POLLOUT | POLLERR | POLLHUP | POLLRDNORM | POLLWRNORM; return POLLIN | POLLOUT | POLLERR | POLLHUP | POLLRDNORM | POLLWRNORM;
} }
static int hung_up_tty_ioctl(struct inode *inode, struct file *file, static long hung_up_tty_ioctl(struct file *file, unsigned int cmd,
unsigned int cmd, unsigned long arg) unsigned long arg)
{ {
return cmd == TIOCSPGRP ? -ENOTTY : -EIO; return cmd == TIOCSPGRP ? -ENOTTY : -EIO;
} }
...@@ -1264,7 +1263,7 @@ static const struct file_operations tty_fops = { ...@@ -1264,7 +1263,7 @@ static const struct file_operations tty_fops = {
.read = tty_read, .read = tty_read,
.write = tty_write, .write = tty_write,
.poll = tty_poll, .poll = tty_poll,
.ioctl = tty_ioctl, .unlocked_ioctl = tty_ioctl,
.compat_ioctl = tty_compat_ioctl, .compat_ioctl = tty_compat_ioctl,
.open = tty_open, .open = tty_open,
.release = tty_release, .release = tty_release,
...@@ -1277,7 +1276,7 @@ static const struct file_operations ptmx_fops = { ...@@ -1277,7 +1276,7 @@ static const struct file_operations ptmx_fops = {
.read = tty_read, .read = tty_read,
.write = tty_write, .write = tty_write,
.poll = tty_poll, .poll = tty_poll,
.ioctl = tty_ioctl, .unlocked_ioctl = tty_ioctl,
.compat_ioctl = tty_compat_ioctl, .compat_ioctl = tty_compat_ioctl,
.open = ptmx_open, .open = ptmx_open,
.release = tty_release, .release = tty_release,
...@@ -1290,7 +1289,7 @@ static const struct file_operations console_fops = { ...@@ -1290,7 +1289,7 @@ static const struct file_operations console_fops = {
.read = tty_read, .read = tty_read,
.write = redirected_tty_write, .write = redirected_tty_write,
.poll = tty_poll, .poll = tty_poll,
.ioctl = tty_ioctl, .unlocked_ioctl = tty_ioctl,
.compat_ioctl = tty_compat_ioctl, .compat_ioctl = tty_compat_ioctl,
.open = tty_open, .open = tty_open,
.release = tty_release, .release = tty_release,
...@@ -1302,7 +1301,7 @@ static const struct file_operations hung_up_tty_fops = { ...@@ -1302,7 +1301,7 @@ static const struct file_operations hung_up_tty_fops = {
.read = hung_up_tty_read, .read = hung_up_tty_read,
.write = hung_up_tty_write, .write = hung_up_tty_write,
.poll = hung_up_tty_poll, .poll = hung_up_tty_poll,
.ioctl = hung_up_tty_ioctl, .unlocked_ioctl = hung_up_tty_ioctl,
.compat_ioctl = hung_up_tty_compat_ioctl, .compat_ioctl = hung_up_tty_compat_ioctl,
.release = tty_release, .release = tty_release,
}; };
...@@ -1626,16 +1625,17 @@ void disassociate_ctty(int on_exit) ...@@ -1626,16 +1625,17 @@ void disassociate_ctty(int on_exit)
struct tty_struct *tty; struct tty_struct *tty;
struct pid *tty_pgrp = NULL; struct pid *tty_pgrp = NULL;
lock_kernel();
mutex_lock(&tty_mutex); mutex_lock(&tty_mutex);
tty = get_current_tty(); tty = get_current_tty();
if (tty) { if (tty) {
tty_pgrp = get_pid(tty->pgrp); tty_pgrp = get_pid(tty->pgrp);
mutex_unlock(&tty_mutex); mutex_unlock(&tty_mutex);
lock_kernel();
/* XXX: here we race, there is nothing protecting tty */ /* XXX: here we race, there is nothing protecting tty */
if (on_exit && tty->driver->type != TTY_DRIVER_TYPE_PTY) if (on_exit && tty->driver->type != TTY_DRIVER_TYPE_PTY)
tty_vhangup(tty); tty_vhangup(tty);
unlock_kernel();
} else if (on_exit) { } else if (on_exit) {
struct pid *old_pgrp; struct pid *old_pgrp;
spin_lock_irq(&current->sighand->siglock); spin_lock_irq(&current->sighand->siglock);
...@@ -1648,7 +1648,6 @@ void disassociate_ctty(int on_exit) ...@@ -1648,7 +1648,6 @@ void disassociate_ctty(int on_exit)
put_pid(old_pgrp); put_pid(old_pgrp);
} }
mutex_unlock(&tty_mutex); mutex_unlock(&tty_mutex);
unlock_kernel();
return; return;
} }
if (tty_pgrp) { if (tty_pgrp) {
...@@ -1683,7 +1682,6 @@ void disassociate_ctty(int on_exit) ...@@ -1683,7 +1682,6 @@ void disassociate_ctty(int on_exit)
read_lock(&tasklist_lock); read_lock(&tasklist_lock);
session_clear_tty(task_session(current)); session_clear_tty(task_session(current));
read_unlock(&tasklist_lock); read_unlock(&tasklist_lock);
unlock_kernel();
} }
/** /**
...@@ -1693,8 +1691,10 @@ void disassociate_ctty(int on_exit) ...@@ -1693,8 +1691,10 @@ void disassociate_ctty(int on_exit)
void no_tty(void) void no_tty(void)
{ {
struct task_struct *tsk = current; struct task_struct *tsk = current;
lock_kernel();
if (tsk->signal->leader) if (tsk->signal->leader)
disassociate_ctty(0); disassociate_ctty(0);
unlock_kernel();
proc_clear_tty(tsk); proc_clear_tty(tsk);
} }
...@@ -1714,19 +1714,24 @@ void no_tty(void) ...@@ -1714,19 +1714,24 @@ void no_tty(void)
* but not always. * but not always.
* *
* Locking: * Locking:
* Broken. Relies on BKL which is unsafe here. * Uses the tty control lock internally
*/ */
void stop_tty(struct tty_struct *tty) void stop_tty(struct tty_struct *tty)
{ {
if (tty->stopped) unsigned long flags;
spin_lock_irqsave(&tty->ctrl_lock, flags);
if (tty->stopped) {
spin_unlock_irqrestore(&tty->ctrl_lock, flags);
return; return;
}
tty->stopped = 1; tty->stopped = 1;
if (tty->link && tty->link->packet) { if (tty->link && tty->link->packet) {