[RFC PATCH 1/5] tty: push the BKL down into the handlers a bit

Alan Cox
2009-11-18T14:42:09Z

Start trying to untangle the remaining BKL mess

Signed-off-by: Alan "I must be out of my tree" Cox <alan@linux.intel.com>
---

drivers/char/pty.c | 2 -
drivers/char/tty_io.c | 140 ++++++++++++++++++++++++++--------------------
drivers/char/tty_ldisc.c | 13 ++++
include/linux/tty.h | 2 -
4 files changed, 94 insertions(+), 63 deletions(-)

diff --git a/drivers/char/pty.c b/drivers/char/pty.c
index d516e9c..169cdcc 100644
--- a/drivers/char/pty.c
+++ b/drivers/char/pty.c
@@ -659,7 +659,7 @@ static int __ptmx_open(struct inode *inode, struct file *filp)
if (!retval)
return 0;
out1:
- tty_release_dev(filp);
+ tty_release(inode, filp);
return retval;
out:
devpts_kill_index(inode, index);
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 59499ee..05e94a2 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -142,7 +142,6 @@ ssize_t redirected_tty_write(struct file *, const char __user *,
size_t, loff_t *);
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 *);
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,
@@ -1017,14 +1016,16 @@ out:

void tty_write_message(struct tty_struct *tty, char *msg)
{
- lock_kernel();
if (tty) {
mutex_lock(&tty->atomic_write_lock);
- if (tty->ops->write && !test_bit(TTY_CLOSING, &tty->flags))
+ lock_kernel();
+ if (tty->ops->write && !test_bit(TTY_CLOSING, &tty->flags)) {
+ unlock_kernel();
tty->ops->write(tty, msg, strlen(msg));
+ } else
+ unlock_kernel();
tty_write_unlock(tty);
}
- unlock_kernel();
return;
}

@@ -1202,14 +1203,21 @@ static int tty_driver_install_tty(struct tty_driver *driver,
struct tty_struct *tty)
{
int idx = tty->index;
+ int ret;

- if (driver->ops->install)
- return driver->ops->install(driver, tty);
+ if (driver->ops->install) {
+ lock_kernel();
+ ret = driver->ops->install(driver, tty);
+ unlock_kernel();
+ return ret;
+ }

if (tty_init_termios(tty) == 0) {
+ lock_kernel();
tty_driver_kref_get(driver);
tty->count++;
driver->ttys[idx] = tty;
+ unlock_kernel();
return 0;
}
return -ENOMEM;
@@ -1302,10 +1310,14 @@ struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx,
struct tty_struct *tty;
int retval;

+ lock_kernel();
/* Check if pty master is being opened multiple times */
if (driver->subtype == PTY_TYPE_MASTER &&
- (driver->flags & TTY_DRIVER_DEVPTS_MEM) && !first_ok)
+ (driver->flags & TTY_DRIVER_DEVPTS_MEM) && !first_ok) {
+ unlock_kernel();
return ERR_PTR(-EIO);
+ }
+ unlock_kernel();

/*
* First time open is complex, especially for PTY devices.
@@ -1335,8 +1347,9 @@ struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx,
* If we fail here just call release_tty to clean up. No need
* to decrement the use counts, as release_tty doesn't care.
*/
-
+ lock_kernel();
retval = tty_ldisc_setup(tty, tty->link);
+ unlock_kernel();
if (retval)
goto release_mem_out;
return tty;
@@ -1350,7 +1363,9 @@ release_mem_out:
if (printk_ratelimit())
printk(KERN_INFO "tty_init_dev: ldisc open failed, "
"clearing slot %d\n", idx);
+ lock_kernel();
release_tty(tty, idx);
+ unlock_kernel();
return ERR_PTR(retval);
}

@@ -1464,7 +1479,17 @@ static void release_tty(struct tty_struct *tty, int idx)
tty_kref_put(tty);
}

-/*
+/**
+ * tty_release - vfs callback for close
+ * @inode: inode of tty
+ * @filp: file pointer for handle to tty
+ *
+ * Called the last time each file handle is closed that references
+ * this tty. There may however be several such references.
+ *
+ * Locking:
+ * Takes bkl. See tty_release_dev
+ *
* Even releasing the tty structures is a tricky business.. We have
* to be very careful that the structures are all released at the
* same time, as interrupts might otherwise get the wrong pointers.
@@ -1472,20 +1497,20 @@ static void release_tty(struct tty_struct *tty, int idx)
* WSH 09/09/97: rewritten to avoid some nasty race conditions that could
* lead to double frees or releasing memory still in use.
*/
-void tty_release_dev(struct file *filp)
+
+int tty_release(struct inode *inode, struct file *filp)
{
struct tty_struct *tty, *o_tty;
int pty_master, tty_closing, o_tty_closing, do_sleep;
int devpts;
int idx;
char buf[64];
- struct inode *inode;

- inode = filp->f_path.dentry->d_inode;
tty = (struct tty_struct *)filp->private_data;
if (tty_paranoia_check(tty, inode, "tty_release_dev"))
- return;
+ return 0;

+ lock_kernel();
check_tty_count(tty, "tty_release_dev");

tty_fasync(-1, filp, 0);
@@ -1500,19 +1525,22 @@ void tty_release_dev(struct file *filp)
if (idx < 0 || idx >= tty->driver->num) {
printk(KERN_DEBUG "tty_release_dev: bad idx when trying to "
"free (%s)\n", tty->name);
- return;
+ unlock_kernel();
+ return 0;
}
if (!devpts) {
if (tty != tty->driver->ttys[idx]) {
+ unlock_kernel();
printk(KERN_DEBUG "tty_release_dev: driver.table[%d] not tty "
"for (%s)\n", idx, tty->name);
- return;
+ return 0;
}
if (tty->termios != tty->driver->termios[idx]) {
+ unlock_kernel();
printk(KERN_DEBUG "tty_release_dev: driver.termios[%d] not termios "
"for (%s)\n",
idx, tty->name);
- return;
+ return 0;
}
}
#endif
@@ -1526,26 +1554,29 @@ void tty_release_dev(struct file *filp)
if (tty->driver->other &&
!(tty->driver->flags & TTY_DRIVER_DEVPTS_MEM)) {
if (o_tty != tty->driver->other->ttys[idx]) {
+ unlock_kernel();
printk(KERN_DEBUG "tty_release_dev: other->table[%d] "
"not o_tty for (%s)\n",
idx, tty->name);
- return;
+ return 0 ;
}
if (o_tty->termios != tty->driver->other->termios[idx]) {
+ unlock_kernel();
printk(KERN_DEBUG "tty_release_dev: other->termios[%d] "
"not o_termios for (%s)\n",
idx, tty->name);
- return;
+ return 0;
}
if (o_tty->link != tty) {
printk(KERN_DEBUG "tty_release_dev: bad pty pointers\n");
- return;
+ return 0;
}
}
#endif
if (tty->ops->close)
tty->ops->close(tty, filp);

+ unlock_kernel();
/*
* Sanity check: if tty->count is going to zero, there shouldn't be
* any waiters on tty->read_wait or tty->write_wait. We test the
@@ -1568,6 +1599,7 @@ void tty_release_dev(struct file *filp)
opens on /dev/tty */

mutex_lock(&tty_mutex);
+ lock_kernel();
tty_closing = tty->count <= 1;
o_tty_closing = o_tty &&
(o_tty->count <= (pty_master ? 1 : 0));
@@ -1598,6 +1630,7 @@ void tty_release_dev(struct file *filp)

printk(KERN_WARNING "tty_release_dev: %s: read/write wait queue "
"active!\n", tty_name(tty, buf));
+ unlock_kernel();
mutex_unlock(&tty_mutex);
schedule();
}
@@ -1661,8 +1694,10 @@ void tty_release_dev(struct file *filp)
mutex_unlock(&tty_mutex);

/* check whether both sides are closing ... */
- if (!tty_closing || (o_tty && !o_tty_closing))
- return;
+ if (!tty_closing || (o_tty && !o_tty_closing)) {
+ unlock_kernel();
+ return 0;
+ }

#ifdef TTY_DEBUG_HANGUP
printk(KERN_DEBUG "freeing tty structure...");
@@ -1680,10 +1715,12 @@ void tty_release_dev(struct file *filp)
/* Make this pty number available for reallocation */
if (devpts)
devpts_kill_index(inode, idx);
+ unlock_kernel();
+ return 0;
}

/**
- * __tty_open - open a tty device
+ * tty_open - open a tty device
* @inode: inode of device file
* @filp: file pointer to tty
*
@@ -1703,7 +1740,7 @@ void tty_release_dev(struct file *filp)
* ->siglock protects ->signal/->sighand
*/

-static int __tty_open(struct inode *inode, struct file *filp)
+static int tty_open(struct inode *inode, struct file *filp)
{
struct tty_struct *tty = NULL;
int noctty, retval;
@@ -1720,10 +1757,12 @@ retry_open:
retval = 0;

mutex_lock(&tty_mutex);
+ lock_kernel();

if (device == MKDEV(TTYAUX_MAJOR, 0)) {
tty = get_current_tty();
if (!tty) {
+ unlock_kernel();
mutex_unlock(&tty_mutex);
return -ENXIO;
}
@@ -1755,12 +1794,14 @@ retry_open:
goto got_driver;
}
}
+ unlock_kernel();
mutex_unlock(&tty_mutex);
return -ENODEV;
}

driver = get_tty_driver(device, &index);
if (!driver) {
+ unlock_kernel();
mutex_unlock(&tty_mutex);
return -ENODEV;
}
@@ -1770,6 +1811,7 @@ got_driver:
tty = tty_driver_lookup_tty(driver, inode, index);

if (IS_ERR(tty)) {
+ unlock_kernel();
mutex_unlock(&tty_mutex);
return PTR_ERR(tty);
}
@@ -1784,8 +1826,10 @@ got_driver:

mutex_unlock(&tty_mutex);
tty_driver_kref_put(driver);
- if (IS_ERR(tty))
+ if (IS_ERR(tty)) {
+ unlock_kernel();
return PTR_ERR(tty);
+ }

filp->private_data = tty;
file_move(filp, &tty->tty_files);
@@ -1813,11 +1857,15 @@ got_driver:
printk(KERN_DEBUG "error %d in opening %s...", retval,
tty->name);
#endif
- tty_release_dev(filp);
- if (retval != -ERESTARTSYS)
+ tty_release(inode, filp);
+ if (retval != -ERESTARTSYS) {
+ unlock_kernel();
return retval;
- if (signal_pending(current))
+ }
+ if (signal_pending(current)) {
+ unlock_kernel();
return retval;
+ }
schedule();
/*
* Need to reset f_op in case a hangup happened.
@@ -1826,8 +1874,11 @@ got_driver:
filp->f_op = &tty_fops;
goto retry_open;
}
+ unlock_kernel();
+

mutex_lock(&tty_mutex);
+ lock_kernel();
spin_lock_irq(&current->sighand->siglock);
if (!noctty &&
current->signal->leader &&
@@ -1835,44 +1886,13 @@ got_driver:
tty->session == NULL)
__proc_set_tty(current, tty);
spin_unlock_irq(&current->sighand->siglock);
+ unlock_kernel();
mutex_unlock(&tty_mutex);
return 0;
}

-/* BKL pushdown: scary code avoidance wrapper */
-static int tty_open(struct inode *inode, struct file *filp)
-{
- int ret;
-
- lock_kernel();
- ret = __tty_open(inode, filp);
- unlock_kernel();
- return ret;
-}

-
-
-/**
- * tty_release - vfs callback for close
- * @inode: inode of tty
- * @filp: file pointer for handle to tty
- *
- * Called the last time each file handle is closed that references
- * this tty. There may however be several such references.
- *
- * Locking:
- * Takes bkl. See tty_release_dev
- */
-
-static int tty_release(struct inode *inode, struct file *filp)
-{
- lock_kernel();
- tty_release_dev(filp);
- unlock_kernel();
- return 0;
-}
-
/**
* tty_poll - check tty status
* @filp: file being polled
@@ -2317,9 +2337,7 @@ static int tiocsetd(struct tty_struct *tty, int __user *p)
if (get_user(ldisc, p))
return -EFAULT;

- lock_kernel();
ret = tty_set_ldisc(tty, ldisc);
- unlock_kernel();

return ret;
}
diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c
index feb5507..d914e77 100644
--- a/drivers/char/tty_ldisc.c
+++ b/drivers/char/tty_ldisc.c
@@ -34,6 +34,8 @@
#include <linux/vt_kern.h>
#include <linux/selection.h>

+#include <linux/smp_lock.h> /* For the moment */
+
#include <linux/kmod.h>
#include <linux/nsproxy.h>

@@ -545,6 +547,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
if (IS_ERR(new_ldisc))
return PTR_ERR(new_ldisc);

+ lock_kernel();
/*
* We need to look at the tty locking here for pty/tty pairs
* when both sides try to change in parallel.
@@ -558,6 +561,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
*/

if (tty->ldisc->ops->num == ldisc) {
+ unlock_kernel();
tty_ldisc_put(new_ldisc);
return 0;
}
@@ -569,6 +573,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)

tty_wait_until_sent(tty, 0);

+ unlock_kernel();
mutex_lock(&tty->ldisc_mutex);

/*
@@ -582,6 +587,9 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0);
mutex_lock(&tty->ldisc_mutex);
}
+
+ lock_kernel();
+
set_bit(TTY_LDISC_CHANGING, &tty->flags);

/*
@@ -592,6 +600,8 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
tty->receive_room = 0;

o_ldisc = tty->ldisc;
+
+ unlock_kernel();
/*
* Make sure we don't change while someone holds a
* reference to the line discipline. The TTY_LDISC bit
@@ -617,12 +627,14 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
flush_scheduled_work();

mutex_lock(&tty->ldisc_mutex);
+ lock_kernel();
if (test_bit(TTY_HUPPED, &tty->flags)) {
/* We were raced by the hangup method. It will have stomped
the ldisc data and closed the ldisc down */
clear_bit(TTY_LDISC_CHANGING, &tty->flags);
mutex_unlock(&tty->ldisc_mutex);
tty_ldisc_put(new_ldisc);
+ unlock_kernel();
return -EIO;
}

@@ -664,6 +676,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
if (o_work)
schedule_delayed_work(&o_tty->buf.work, 1);
mutex_unlock(&tty->ldisc_mutex);
+ unlock_kernel();
return retval;
}

diff --git a/include/linux/tty.h b/include/linux/tty.h
index e6da667..405a903 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -449,7 +449,7 @@ extern void initialize_tty_struct(struct tty_struct *tty,
struct tty_driver *driver, int idx);
extern struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx,
int first_ok);
-extern void tty_release_dev(struct file *filp);
+extern int tty_release(struct inode *inode, struct file *filp);
extern int tty_init_termios(struct tty_struct *tty);

extern struct tty_struct *tty_pair_get_tty(struct tty_struct *tty);