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,
return -EFAULT;
}
lock_kernel();
for (;;) {
if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
unlock_kernel();
return -EIO;
}
n_hdlc = tty2n_hdlc (tty);
if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
tty != n_hdlc->tty)
tty != n_hdlc->tty) {
unlock_kernel();
return 0;
}
rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
if (rbuf)
break;
/* no data */
if (file->f_flags & O_NONBLOCK)
if (file->f_flags & O_NONBLOCK) {
unlock_kernel();
return -EAGAIN;
}
interruptible_sleep_on (&tty->read_wait);
if (signal_pending(current))
if (signal_pending(current)) {
unlock_kernel();
return -EINTR;
}
}
if (rbuf->count > nr)
......@@ -618,7 +628,7 @@ static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
kfree(rbuf);
else
n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,rbuf);
unlock_kernel();
return ret;
} /* end of n_hdlc_tty_read() */
......@@ -661,6 +671,8 @@ static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
count = maxframe;
}
lock_kernel();
add_wait_queue(&tty->write_wait, &wait);
set_current_state(TASK_INTERRUPTIBLE);
......@@ -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_send_frames(n_hdlc,tty);
}
unlock_kernel();
return error;
} /* end of n_hdlc_tty_write() */
......
......@@ -1075,12 +1075,15 @@ static ssize_t r3964_read(struct tty_struct *tty, struct file *file,
TRACE_L("read()");
lock_kernel();
pClient = findClient(pInfo, task_pid(current));
if (pClient) {
pMsg = remove_msg(pInfo, pClient);
if (pMsg == NULL) {
/* no messages available. */
if (file->f_flags & O_NONBLOCK) {
unlock_kernel();
return -EAGAIN;
}
/* block until there is a message: */
......@@ -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 (!pMsg)
if (!pMsg) {
unlock_kernel();
return -EINTR;
}
/* deliver msg to client process: */
theMsg.msg_id = pMsg->msg_id;
......@@ -1102,12 +1107,15 @@ static ssize_t r3964_read(struct tty_struct *tty, struct file *file,
kfree(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;
}
TRACE_PS("read - return %d", count);
return count;
}
unlock_kernel();
return -EPERM;
}
......@@ -1156,6 +1164,8 @@ static ssize_t r3964_write(struct tty_struct *tty, struct file *file,
pHeader->locks = 0;
pHeader->owner = NULL;
lock_kernel();
pClient = findClient(pInfo, task_pid(current));
if (pClient) {
pHeader->owner = pClient;
......@@ -1173,6 +1183,8 @@ static ssize_t r3964_write(struct tty_struct *tty, struct file *file,
add_tx_queue(pInfo, pHeader);
trigger_transmit(pInfo);
unlock_kernel();
return 0;
}
......
......@@ -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
* clean the pending queue (for example some signals).
*
* FIXME: tty->ctrl_status is not spinlocked and relies on
* lock_kernel() still.
* Locking: ctrl_lock
*/
static void n_tty_flush_buffer(struct tty_struct *tty)
{
unsigned long flags;
/* clear everything and unthrottle the driver */
reset_buffer_flags(tty);
if (!tty->link)
return;
spin_lock_irqsave(&tty->ctrl_lock, flags);
if (tty->link->packet) {
tty->ctrl_status |= TIOCPKT_FLUSHREAD;
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)
* 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
* 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)
......@@ -275,6 +277,7 @@ static int opost(unsigned char c, struct tty_struct *tty)
if (!space)
return -1;
lock_kernel();
if (O_OPOST(tty)) {
switch (c) {
case '\n':
......@@ -323,6 +326,7 @@ static int opost(unsigned char c, struct tty_struct *tty)
}
}
tty->driver->put_char(tty, c);
unlock_kernel();
return 0;
}
......@@ -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
* 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,
......@@ -353,6 +358,7 @@ static ssize_t opost_block(struct tty_struct *tty,
if (nr > space)
nr = space;
lock_kernel();
for (i = 0, cp = buf; i < nr; i++, cp++) {
switch (*cp) {
case '\n':
......@@ -387,6 +393,7 @@ break_out:
if (tty->driver->flush_chars)
tty->driver->flush_chars(tty);
i = tty->driver->write(tty, buf, i);
unlock_kernel();
return i;
}
......@@ -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
* and if appropriate send any needed signals and return a negative
* 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)
......@@ -1246,6 +1258,7 @@ static ssize_t read_chan(struct tty_struct *tty, struct file *file,
ssize_t size;
long timeout;
unsigned long flags;
int packet;
do_it_again:
......@@ -1289,16 +1302,19 @@ do_it_again:
if (mutex_lock_interruptible(&tty->atomic_read_lock))
return -ERESTARTSYS;
}
packet = tty->packet;
add_wait_queue(&tty->read_wait, &wait);
while (nr) {
/* First test for status change. */
if (tty->packet && tty->link->ctrl_status) {
if (packet && tty->link->ctrl_status) {
unsigned char cs;
if (b != buf)
break;
spin_lock_irqsave(&tty->link->ctrl_lock, flags);
cs = tty->link->ctrl_status;
tty->link->ctrl_status = 0;
spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
if (tty_put_user(tty, cs, b++)) {
retval = -EFAULT;
b--;
......@@ -1333,6 +1349,7 @@ do_it_again:
retval = -ERESTARTSYS;
break;
}
/* FIXME: does n_tty_set_room need locking ? */
n_tty_set_room(tty);
timeout = schedule_timeout(timeout);
continue;
......@@ -1340,7 +1357,7 @@ do_it_again:
__set_current_state(TASK_RUNNING);
/* Deal with packet mode. */
if (tty->packet && b == buf) {
if (packet && b == buf) {
if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
retval = -EFAULT;
b--;
......@@ -1388,6 +1405,8 @@ do_it_again:
break;
} else {
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);
if (uncopied) {
......@@ -1429,7 +1448,6 @@ do_it_again:
goto do_it_again;
n_tty_set_room(tty);
return retval;
}
......
......@@ -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)
{
struct tty_struct *to = tty->link;
unsigned long flags;
if (!to)
return;
......@@ -189,8 +190,10 @@ static void pty_flush_buffer(struct tty_struct *tty)
to->ldisc.flush_buffer(to);
if (to->packet) {
spin_lock_irqsave(&tty->ctrl_lock, flags);
tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
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 *,
static unsigned int tty_poll(struct file *, poll_table *);
static int tty_open(struct inode *, struct file *);
static int tty_release(struct inode *, struct file *);
int tty_ioctl(struct inode *inode, struct file *file,
unsigned int cmd, unsigned long arg);
long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
#ifdef CONFIG_COMPAT
static long tty_compat_ioctl(struct file *file, unsigned int cmd,
unsigned long arg);
......@@ -1205,7 +1204,7 @@ EXPORT_SYMBOL_GPL(tty_find_polling_driver);
* not in the foreground, send a SIGTTOU. If the signal is blocked or
* 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)
......@@ -1247,8 +1246,8 @@ static unsigned int hung_up_tty_poll(struct file *filp, poll_table *wait)
return POLLIN | POLLOUT | POLLERR | POLLHUP | POLLRDNORM | POLLWRNORM;
}
static int hung_up_tty_ioctl(struct inode *inode, struct file *file,
unsigned int cmd, unsigned long arg)
static long hung_up_tty_ioctl(struct file *file, unsigned int cmd,
unsigned long arg)
{
return cmd == TIOCSPGRP ? -ENOTTY : -EIO;
}
......@@ -1264,7 +1263,7 @@ static const struct file_operations tty_fops = {
.read = tty_read,
.write = tty_write,
.poll = tty_poll,
.ioctl = tty_ioctl,
.unlocked_ioctl = tty_ioctl,
.compat_ioctl = tty_compat_ioctl,
.open = tty_open,
.release = tty_release,
......@@ -1277,7 +1276,7 @@ static const struct file_operations ptmx_fops = {
.read = tty_read,
.write = tty_write,
.poll = tty_poll,
.ioctl = tty_ioctl,
.unlocked_ioctl = tty_ioctl,
.compat_ioctl = tty_compat_ioctl,
.open = ptmx_open,
.release = tty_release,
......@@ -1290,7 +1289,7 @@ static const struct file_operations console_fops = {
.read = tty_read,
.write = redirected_tty_write,
.poll = tty_poll,
.ioctl = tty_ioctl,
.unlocked_ioctl = tty_ioctl,
.compat_ioctl = tty_compat_ioctl,
.open = tty_open,
.release = tty_release,
......@@ -1302,7 +1301,7 @@ static const struct file_operations hung_up_tty_fops = {
.read = hung_up_tty_read,
.write = hung_up_tty_write,
.poll = hung_up_tty_poll,
.ioctl = hung_up_tty_ioctl,
.unlocked_ioctl = hung_up_tty_ioctl,
.compat_ioctl = hung_up_tty_compat_ioctl,
.release = tty_release,
};
......@@ -1626,16 +1625,17 @@ void disassociate_ctty(int on_exit)
struct tty_struct *tty;
struct pid *tty_pgrp = NULL;
lock_kernel();
mutex_lock(&tty_mutex);
tty = get_current_tty();
if (tty) {
tty_pgrp = get_pid(tty->pgrp);
mutex_unlock(&tty_mutex);
lock_kernel();
/* XXX: here we race, there is nothing protecting tty */
if (on_exit && tty->driver->type != TTY_DRIVER_TYPE_PTY)
tty_vhangup(tty);
unlock_kernel();
} else if (on_exit) {
struct pid *old_pgrp;
spin_lock_irq(&current->sighand->siglock);
......@@ -1648,7 +1648,6 @@ void disassociate_ctty(int on_exit)
put_pid(old_pgrp);
}
mutex_unlock(&tty_mutex);
unlock_kernel();
return;
}
if (tty_pgrp) {
......@@ -1683,7 +1682,6 @@ void disassociate_ctty(int on_exit)
read_lock(&tasklist_lock);
session_clear_tty(task_session(current));
read_unlock(&tasklist_lock);
unlock_kernel();
}
/**
......@@ -1693,8 +1691,10 @@ void disassociate_ctty(int on_exit)
void no_tty(void)
{
struct task_struct *tsk = current;
lock_kernel();
if (tsk->signal->leader)
disassociate_ctty(0);
unlock_kernel();
proc_clear_tty(tsk);
}
......@@ -1714,19 +1714,24 @@ void no_tty(void)
* but not always.
*
* Locking:
* Broken. Relies on BKL which is unsafe here.
* Uses the tty control lock internally
*/
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;
}
tty->stopped = 1;
if (tty->link && tty->link->packet) {
tty->ctrl_status &= ~TIOCPKT_START;
tty->ctrl_status |= TIOCPKT_STOP;
wake_up_interruptible(&tty->link->read_wait);
}
spin_unlock_irqrestore(&tty->ctrl_lock, flags);
if (tty->driver->stop)
(tty->driver->stop)(tty);
}
......@@ -1743,19 +1748,24 @@ EXPORT_SYMBOL(stop_tty);
* driver start method is invoked and the line discipline woken.
*
* Locking:
* Broken. Relies on BKL which is unsafe here.
* ctrl_lock
*/
void start_tty(struct tty_struct *tty)
{
if (!tty->stopped || tty->flow_stopped)
unsigned long flags;
spin_lock_irqsave(&tty->ctrl_lock, flags);
if (!tty->stopped || tty->flow_stopped) {
spin_unlock_irqrestore(&tty->ctrl_lock, flags);
return;
}
tty->stopped = 0;
if (tty->link && tty->link->packet) {
tty->ctrl_status &= ~TIOCPKT_STOP;
tty->ctrl_status |= TIOCPKT_START;
wake_up_interruptible(&tty->link->read_wait);
}
spin_unlock_irqrestore(&tty->ctrl_lock, flags);
if (tty->driver->start)
(tty->driver->start)(tty);
/* If we have a running line discipline it may need kicking */
......@@ -1799,13 +1809,11 @@ 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);
lock_kernel();
if (ld->read)
i = (ld->read)(tty, file, buf, count);
else
i = -EIO;
tty_ldisc_deref(ld);
unlock_kernel();
if (i > 0)
inode->i_atime = current_fs_time(inode->i_sb);
return i;
......@@ -1893,9 +1901,7 @@ static inline ssize_t do_tty_write(
ret = -EFAULT;
if (copy_from_user(tty->write_buf, buf, size))
break;
lock_kernel();
ret = write(tty, file, tty->write_buf, size);
unlock_kernel();
if (ret <= 0)
break;
written += ret;
......@@ -3070,10 +3076,13 @@ static int fionbio(struct file *file, int __user *p)
if (get_user(nonblock, p))
return -EFAULT;
/* file->f_flags is still BKL protected in the fs layer - vomit */
lock_kernel();
if (nonblock)
file->f_flags |= O_NONBLOCK;
else
file->f_flags &= ~O_NONBLOCK;
unlock_kernel();
return 0;
}
......@@ -3162,7 +3171,7 @@ static int tiocgpgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t
* Set the process group of the tty to the session passed. Only
* permitted where the tty session is our session.
*
* Locking: None
* Locking: RCU
*/
static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
......@@ -3237,10 +3246,16 @@ static int tiocgsid(struct tty_struct *tty, struct tty_struct *real_tty, pid_t _
static int tiocsetd(struct tty_struct *tty, int __user *p)
{
int ldisc;
int ret;
if (get_user(ldisc, p))
return -EFAULT;
return tty_set_ldisc(tty, ldisc);
lock_kernel();
ret = tty_set_ldisc(tty, ldisc);
unlock_kernel();
return ret;
}
/**
......@@ -3258,16 +3273,21 @@ static int tiocsetd(struct tty_struct *tty, int __user *p)
static int send_break(struct tty_struct *tty, unsigned int duration)
{
int retval = -EINTR;
lock_kernel();
if (tty_write_lock(tty, 0) < 0)
return -EINTR;
goto out;
tty->driver->break_ctl(tty, -1);
if (!signal_pending(current))
msleep_interruptible(duration);
tty->driver->break_ctl(tty, 0);
tty_write_unlock(tty);
if (signal_pending(current))
return -EINTR;
return 0;
if (!signal_pending(current))
retval = 0;
out:
unlock_kernel();
return retval;
}
/**
......@@ -3287,7 +3307,9 @@ static int tty_tiocmget(struct tty_struct *tty, struct file *file, int __user *p
int retval = -EINVAL;
if (tty->driver->tiocmget) {
lock_kernel();
retval = tty->driver->tiocmget(tty, file);
unlock_kernel();
if (retval >= 0)
retval = put_user(retval, p);
......@@ -3337,7 +3359,9 @@ static int tty_tiocmset(struct tty_struct *tty, struct file *file, unsigned int
set &= TIOCM_DTR|TIOCM_RTS|TIOCM_OUT1|TIOCM_OUT2|TIOCM_LOOP;
clear &= TIOCM_DTR|TIOCM_RTS|TIOCM_OUT1|TIOCM_OUT2|TIOCM_LOOP;
lock_kernel();
retval = tty->driver->tiocmset(tty, file, set, clear);
unlock_kernel();
}
return retval;
}
......@@ -3345,20 +3369,18 @@ static int tty_tiocmset(struct tty_struct *tty, struct file *file, unsigned int
/*
* Split this up, as gcc can choke on it otherwise..
*/
int tty_ioctl(struct inode *inode, struct file *file,
unsigned int cmd, unsigned long arg)
long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
struct tty_struct *tty, *real_tty;
void __user *p = (void __user *)arg;
int retval;
struct tty_ldisc *ld;
struct inode *inode = file->f_dentry->d_inode;
tty = (struct tty_struct *)file->private_data;
if (tty_paranoia_check(tty, inode, "tty_ioctl"))
return -EINVAL;
/* CHECKME: is this safe as one end closes ? */
real_tty = tty;
if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
tty->driver->subtype == PTY_TYPE_MASTER)
......@@ -3367,13 +3389,19 @@ int tty_ioctl(struct inode *inode, struct file *file,
/*
* Break handling by driver
*/
retval = -EINVAL;
if (!tty->driver->break_ctl) {
switch (cmd) {
case TIOCSBRK:
case TIOCCBRK:
if (tty->driver->ioctl)
return tty->driver->ioctl(tty, file, cmd, arg);
return -EINVAL;
if (tty->driver->ioctl) {
lock_kernel();
retval = tty->driver->ioctl(tty, file, cmd, arg);
unlock_kernel();
}
return retval;
/* These two ioctl's always return success; even if */
/* the driver doesn't support them. */
......@@ -3381,7 +3409,9 @@ int tty_ioctl(struct inode *inode, struct file *file,
case TCSBRKP:
if (!tty->driver->ioctl)
return 0;
lock_kernel();
retval = tty->driver->ioctl(tty, file, cmd, arg);
unlock_kernel();
if (retval == -ENOIOCTLCMD)
retval = 0;
return retval;
......@@ -3401,7 +3431,9 @@ int tty_ioctl(struct inode *inode, struct file *file,
if (retval)
return retval;
if (cmd != TIOCCBRK) {
lock_kernel();
tty_wait_until_sent(tty, 0);
unlock_kernel();
if (signal_pending(current))
return -EINTR;
}
......@@ -3451,11 +3483,15 @@ int tty_ioctl(struct inode *inode, struct file *file,
* Break handling
*/
case TIOCSBRK: /* Turn break on, unconditionally */
lock_kernel();
tty->driver->break_ctl(tty, -1);
unlock_kernel();
return 0;
case TIOCCBRK: /* Turn break off, unconditionally */
lock_kernel();
tty->driver->break_ctl(tty, 0);
unlock_kernel();
return 0;
case TCSBRK: /* SVID version: non-zero arg --> no break */
/* non-zero arg means wait for all output data
......@@ -3485,14 +3521,18 @@ int tty_ioctl(struct inode *inode, struct file *file,
break;
}
if (tty->driver->ioctl) {
lock_kernel();
retval = (tty->driver->ioctl)(tty, file, cmd, arg);
unlock_kernel();
if (retval != -ENOIOCTLCMD)
return retval;
}
ld = tty_ldisc_ref_wait(tty);
retval = -EINVAL;
if (ld->ioctl) {
lock_kernel();
retval = ld->ioctl(tty, file, cmd, arg);
unlock_kernel();
if (retval == -ENOIOCTLCMD)
retval = -EINVAL;
}
......@@ -3770,6 +3810,7 @@ static void initialize_tty_struct(struct tty_struct *tty)
mutex_init(&tty->atomic_read_lock);