Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1305449 > unrolled thread

[PATCH v2 00/10] Rework tty_reopen()

Back to article view | Back to linux.kernel

This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by below is the oldest one visible, not the original post.

Contents

  [PATCH v2 00/10] Rework tty_reopen() Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:20 +0100
    [PATCH v2 01/10] tty: Wait interruptibly for tty lock on reopen Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:20 +0100
    [PATCH v2 06/10] tty: Re-declare tty_driver_remove_tty() file scope Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:20 +0100
    [PATCH v2 03/10] tty: Fix ldisc leak in failed tty_init_dev() Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:20 +0100
    [PATCH v2 05/10] tty: Fix tty_init_termios() declaration Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:20 +0100
    [PATCH v2 04/10] tty: Remove !tty check from free_tty_struct() Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:20 +0100
    [PATCH v2 07/10] pty: Remove pty_unix98_shutdown() Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:20 +0100
    [PATCH v2 08/10] tty: Remove __lockfunc annotation from tty lock functions Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:20 +0100
    [PATCH v2 02/10] tty: Retry failed reopen if tty teardown in-progress Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:20 +0100
    [PATCH v2 09/10] tty: Consolidate noctty checks in tty_open() Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:20 +0100
    [PATCH v2 10/10] tty: Refactor tty_open() Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:20 +0100

#1305449 — [PATCH v2 00/10] Rework tty_reopen()

Hi Greg,

I re-ordered the patches in this series because the first two patches
fix regressions in 4.4-rc. (I did not originally write the patches
to fix regressions; that's just how it turned out).

Obviously, it's too late for those to make 4.4 but at least this way
they're ready for 4.4.1 stable.

Also, Herton Krzesinski brought to my attention a long-resident problem
with releasing the devpts index when the last file reference is /dev/tty.
Since that impacted the tty driver remove() method changes, I just
removed those patches from this series.

original message follows:

This patch series implements two important improvements to tty open()
behavior: interruptible open() and automatic retry when tty teardown
has already commenced.

Interruptible open() allows signals to cancel the open wait if stalled
waiting for tty teardown to complete.

Automatic retry of tty open() when racing a tty teardown now makes tty
open() fully POSIX compliant. For some time, the Linux kernel has
returned EIO from open() under certain circumstances. This happens when
tty_open() observes a valid tty from driver lookup but the tty is
being released (in final close) and teardown is about to commence.

The observable userspace change is that userspace will no longer need
to retry open() on EIO error.

This series also continues the ongoing effort to cleanup and reduce the
kernel tty interface.

Regards,

Peter Hurley (10):
  tty: Wait interruptibly for tty lock on reopen
  tty: Retry failed reopen if tty teardown in-progress
  tty: Fix ldisc leak in failed tty_init_dev()
  tty: Remove !tty check from free_tty_struct()
  tty: Fix tty_init_termios() declaration
  tty: Re-declare tty_driver_remove_tty() file scope
  pty: Remove pty_unix98_shutdown()
  tty: Remove __lockfunc annotation from tty lock functions
  tty: Consolidate noctty checks in tty_open()
  tty: Refactor tty_open()

 drivers/tty/pty.c            |  27 +------
 drivers/tty/tty_io.c         | 174 ++++++++++++++++++++++---------------------
 drivers/tty/tty_ldisc.c      |  21 +++---
 drivers/tty/tty_mutex.c      |  16 +++-
 drivers/usb/serial/console.c |   6 +-
 include/linux/tty.h          |  16 ++--
 6 files changed, 121 insertions(+), 139 deletions(-)

-- 
2.7.0

[toc] | [next] | [standalone]

#1305450 — [PATCH v2 01/10] tty: Wait interruptibly for tty lock on reopen

Allow a signal to interrupt the wait for a tty reopen; eg., if
the tty has starting final close and is waiting for the device to
drain.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
 drivers/tty/tty_io.c    | 8 +++++++-
 drivers/tty/tty_mutex.c | 8 ++++++++
 include/linux/tty.h     | 1 +
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index eda8715..1bf67a2 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2071,7 +2071,12 @@ retry_open:
 
 		if (tty) {
 			mutex_unlock(&tty_mutex);
-			tty_lock(tty);
+			retval = tty_lock_interruptible(tty);
+			if (retval) {
+				if (retval == -EINTR)
+					retval = -ERESTARTSYS;
+				goto err_unref;
+			}
 			/* safe to drop the kref from tty_driver_lookup_tty() */
 			tty_kref_put(tty);
 			retval = tty_reopen(tty);
@@ -2158,6 +2163,7 @@ retry_open:
 	return 0;
 err_unlock:
 	mutex_unlock(&tty_mutex);
+err_unref:
 	/* after locks to avoid deadlock */
 	if (!IS_ERR_OR_NULL(driver))
 		tty_driver_kref_put(driver);
diff --git a/drivers/tty/tty_mutex.c b/drivers/tty/tty_mutex.c
index 77703a3..d2f3c4c 100644
--- a/drivers/tty/tty_mutex.c
+++ b/drivers/tty/tty_mutex.c
@@ -19,6 +19,14 @@ void __lockfunc tty_lock(struct tty_struct *tty)
 }
 EXPORT_SYMBOL(tty_lock);
 
+int tty_lock_interruptible(struct tty_struct *tty)
+{
+	if (WARN(tty->magic != TTY_MAGIC, "L Bad %p\n", tty))
+		return -EIO;
+	tty_kref_get(tty);
+	return mutex_lock_interruptible(&tty->legacy_mutex);
+}
+
 void __lockfunc tty_unlock(struct tty_struct *tty)
 {
 	if (WARN(tty->magic != TTY_MAGIC, "U Bad %p\n", tty))
diff --git a/include/linux/tty.h b/include/linux/tty.h
index b17f759..acc53ad 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -646,6 +646,7 @@ extern long vt_compat_ioctl(struct tty_struct *tty,
 /* tty_mutex.c */
 /* functions for preparation of BKL removal */
 extern void __lockfunc tty_lock(struct tty_struct *tty);
+extern int  tty_lock_interruptible(struct tty_struct *tty);
 extern void __lockfunc tty_unlock(struct tty_struct *tty);
 extern void __lockfunc tty_lock_slave(struct tty_struct *tty);
 extern void __lockfunc tty_unlock_slave(struct tty_struct *tty);
-- 
2.7.0

[toc] | [prev] | [next] | [standalone]

#1305451 — [PATCH v2 06/10] tty: Re-declare tty_driver_remove_tty() file scope

tty_driver_remove_tty() is only local-scope; declare as static.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
 drivers/tty/tty_io.c | 2 +-
 include/linux/tty.h  | 2 --
 2 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 0894293..1f8d06f 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1442,7 +1442,7 @@ static int tty_driver_install_tty(struct tty_driver *driver,
  *
  *	Locking: tty_mutex for now
  */
-void tty_driver_remove_tty(struct tty_driver *driver, struct tty_struct *tty)
+static void tty_driver_remove_tty(struct tty_driver *driver, struct tty_struct *tty)
 {
 	if (driver->ops->remove)
 		driver->ops->remove(driver, tty);
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 1b58ead..7e1034f 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -446,8 +446,6 @@ extern void tty_unthrottle(struct tty_struct *tty);
 extern int tty_throttle_safe(struct tty_struct *tty);
 extern int tty_unthrottle_safe(struct tty_struct *tty);
 extern int tty_do_resize(struct tty_struct *tty, struct winsize *ws);
-extern void tty_driver_remove_tty(struct tty_driver *driver,
-				  struct tty_struct *tty);
 extern int is_current_pgrp_orphaned(void);
 extern int is_ignored(int sig);
 extern int tty_signal(int sig, struct tty_struct *tty);
-- 
2.7.0

[toc] | [prev] | [next] | [standalone]

#1305452 — [PATCH v2 03/10] tty: Fix ldisc leak in failed tty_init_dev()

release_tty() leaks the ldisc instance when called directly (rather
than when releasing the file descriptor from tty_release()).

Since tty_ldisc_release() clears tty->ldisc, releasing the ldisc
instance at tty teardown if tty->ldisc is non-null is not in danger
of double-releasing the ldisc.

Remove deinitialize_tty_struct() now that free_tty_struct() always
performs the tty_ldisc_deinit().

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
 drivers/tty/pty.c       |  5 ++---
 drivers/tty/tty_io.c    | 20 +++-----------------
 drivers/tty/tty_ldisc.c |  5 +++--
 include/linux/tty.h     |  1 -
 4 files changed, 8 insertions(+), 23 deletions(-)

diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index b311004..8cbe802 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -408,7 +408,7 @@ static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
 		   the easy way .. */
 		retval = tty_init_termios(tty);
 		if (retval)
-			goto err_deinit_tty;
+			goto err_free_tty;
 
 		retval = tty_init_termios(o_tty);
 		if (retval)
@@ -447,8 +447,7 @@ static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
 err_free_termios:
 	if (legacy)
 		tty_free_termios(tty);
-err_deinit_tty:
-	deinitialize_tty_struct(o_tty);
+err_free_tty:
 	free_tty_struct(o_tty);
 err_put_module:
 	module_put(driver->other->owner);
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 93fe10d..e487076 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -173,6 +173,7 @@ void free_tty_struct(struct tty_struct *tty)
 {
 	if (!tty)
 		return;
+	tty_ldisc_deinit(tty);
 	put_device(tty->dev);
 	kfree(tty->write_buf);
 	tty->magic = 0xDEADDEAD;
@@ -1535,7 +1536,7 @@ struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx)
 	tty_lock(tty);
 	retval = tty_driver_install_tty(driver, tty);
 	if (retval < 0)
-		goto err_deinit_tty;
+		goto err_free_tty;
 
 	if (!tty->port)
 		tty->port = driver->ports[idx];
@@ -1557,9 +1558,8 @@ struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx)
 	/* Return the tty locked so that it cannot vanish under the caller */
 	return tty;
 
-err_deinit_tty:
+err_free_tty:
 	tty_unlock(tty);
-	deinitialize_tty_struct(tty);
 	free_tty_struct(tty);
 err_module_put:
 	module_put(driver->owner);
@@ -3179,20 +3179,6 @@ struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx)
 }
 
 /**
- *	deinitialize_tty_struct
- *	@tty: tty to deinitialize
- *
- *	This subroutine deinitializes a tty structure that has been newly
- *	allocated but tty_release cannot be called on that yet.
- *
- *	Locking: none - tty in question must not be exposed at this point
- */
-void deinitialize_tty_struct(struct tty_struct *tty)
-{
-	tty_ldisc_deinit(tty);
-}
-
-/**
  *	tty_put_char	-	write one character to a tty
  *	@tty: tty
  *	@ch: character
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index b404c20..92d2898 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -814,7 +814,7 @@ void tty_ldisc_init(struct tty_struct *tty)
 }
 
 /**
- *	tty_ldisc_init		-	ldisc cleanup for new tty
+ *	tty_ldisc_deinit	-	ldisc cleanup for new tty
  *	@tty: tty that was allocated recently
  *
  *	The tty structure must not becompletely set up (tty_ldisc_setup) when
@@ -822,7 +822,8 @@ void tty_ldisc_init(struct tty_struct *tty)
  */
 void tty_ldisc_deinit(struct tty_struct *tty)
 {
-	tty_ldisc_put(tty->ldisc);
+	if (tty->ldisc)
+		tty_ldisc_put(tty->ldisc);
 	tty->ldisc = NULL;
 }
 
diff --git a/include/linux/tty.h b/include/linux/tty.h
index acc53ad..9ce3dbc 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -510,7 +510,6 @@ extern int tty_alloc_file(struct file *file);
 extern void tty_add_file(struct tty_struct *tty, struct file *file);
 extern void tty_free_file(struct file *file);
 extern void free_tty_struct(struct tty_struct *tty);
-extern void deinitialize_tty_struct(struct tty_struct *tty);
 extern struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx);
 extern int tty_release(struct inode *inode, struct file *filp);
 extern int tty_init_termios(struct tty_struct *tty);
-- 
2.7.0

[toc] | [prev] | [next] | [standalone]

#1305453 — [PATCH v2 05/10] tty: Fix tty_init_termios() declaration

tty_init_termios() never returns an error; re-declare as void. Remove
unnecessary error handling from callers. Remove extern declarations
of tty_free_termios() and free_tty_struct() and re-declare in file
scope.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
 drivers/tty/pty.c            | 15 +++------------
 drivers/tty/tty_io.c         | 13 ++++---------
 drivers/usb/serial/console.c |  6 +-----
 include/linux/tty.h          |  4 +---
 4 files changed, 9 insertions(+), 29 deletions(-)

diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index 8cbe802..7e885a2 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -406,13 +406,8 @@ static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
 	if (legacy) {
 		/* We always use new tty termios data so we can do this
 		   the easy way .. */
-		retval = tty_init_termios(tty);
-		if (retval)
-			goto err_free_tty;
-
-		retval = tty_init_termios(o_tty);
-		if (retval)
-			goto err_free_termios;
+		tty_init_termios(tty);
+		tty_init_termios(o_tty);
 
 		driver->other->ttys[idx] = o_tty;
 		driver->ttys[idx] = tty;
@@ -444,11 +439,7 @@ static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
 	tty->count++;
 	o_tty->count++;
 	return 0;
-err_free_termios:
-	if (legacy)
-		tty_free_termios(tty);
-err_free_tty:
-	free_tty_struct(o_tty);
+
 err_put_module:
 	module_put(driver->other->owner);
 err:
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 17a3ffb..0894293 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -169,7 +169,7 @@ static void release_tty(struct tty_struct *tty, int idx);
  *	Locking: none. Must be called after tty is definitely unused
  */
 
-void free_tty_struct(struct tty_struct *tty)
+static void free_tty_struct(struct tty_struct *tty)
 {
 	tty_ldisc_deinit(tty);
 	put_device(tty->dev);
@@ -1381,7 +1381,7 @@ static struct tty_struct *tty_driver_lookup_tty(struct tty_driver *driver,
  *	the tty_mutex currently so we can be relaxed about ordering.
  */
 
-int tty_init_termios(struct tty_struct *tty)
+void tty_init_termios(struct tty_struct *tty)
 {
 	struct ktermios *tp;
 	int idx = tty->index;
@@ -1400,16 +1400,12 @@ int tty_init_termios(struct tty_struct *tty)
 	/* Compatibility until drivers always set this */
 	tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios);
 	tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios);
-	return 0;
 }
 EXPORT_SYMBOL_GPL(tty_init_termios);
 
 int tty_standard_install(struct tty_driver *driver, struct tty_struct *tty)
 {
-	int ret = tty_init_termios(tty);
-	if (ret)
-		return ret;
-
+	tty_init_termios(tty);
 	tty_driver_kref_get(driver);
 	tty->count++;
 	driver->ttys[tty->index] = tty;
@@ -1572,7 +1568,7 @@ err_release_tty:
 	return ERR_PTR(retval);
 }
 
-void tty_free_termios(struct tty_struct *tty)
+static void tty_free_termios(struct tty_struct *tty)
 {
 	struct ktermios *tp;
 	int idx = tty->index;
@@ -1591,7 +1587,6 @@ void tty_free_termios(struct tty_struct *tty)
 	}
 	*tp = tty->termios;
 }
-EXPORT_SYMBOL(tty_free_termios);
 
 /**
  *	tty_flush_works		-	flush all works of a tty/pty pair
diff --git a/drivers/usb/serial/console.c b/drivers/usb/serial/console.c
index 3806e70..a66b01b 100644
--- a/drivers/usb/serial/console.c
+++ b/drivers/usb/serial/console.c
@@ -147,10 +147,7 @@ static int usb_console_setup(struct console *co, char *options)
 			kref_get(&tty->driver->kref);
 			__module_get(tty->driver->owner);
 			tty->ops = &usb_console_fake_tty_ops;
-			if (tty_init_termios(tty)) {
-				retval = -ENOMEM;
-				goto put_tty;
-			}
+			tty_init_termios(tty);
 			tty_port_tty_set(&port->port, tty);
 		}
 
@@ -185,7 +182,6 @@ static int usb_console_setup(struct console *co, char *options)
 
  fail:
 	tty_port_tty_set(&port->port, NULL);
- put_tty:
 	tty_kref_put(tty);
  reset_open_count:
 	port->port.count = 0;
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 9ce3dbc..1b58ead 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -448,7 +448,6 @@ extern int tty_unthrottle_safe(struct tty_struct *tty);
 extern int tty_do_resize(struct tty_struct *tty, struct winsize *ws);
 extern void tty_driver_remove_tty(struct tty_driver *driver,
 				  struct tty_struct *tty);
-extern void tty_free_termios(struct tty_struct *tty);
 extern int is_current_pgrp_orphaned(void);
 extern int is_ignored(int sig);
 extern int tty_signal(int sig, struct tty_struct *tty);
@@ -509,10 +508,9 @@ extern struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx);
 extern int tty_alloc_file(struct file *file);
 extern void tty_add_file(struct tty_struct *tty, struct file *file);
 extern void tty_free_file(struct file *file);
-extern void free_tty_struct(struct tty_struct *tty);
 extern struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx);
 extern int tty_release(struct inode *inode, struct file *filp);
-extern int tty_init_termios(struct tty_struct *tty);
+extern void tty_init_termios(struct tty_struct *tty);
 extern int tty_standard_install(struct tty_driver *driver,
 		struct tty_struct *tty);
 
-- 
2.7.0

[toc] | [prev] | [next] | [standalone]

#1305454 — [PATCH v2 04/10] tty: Remove !tty check from free_tty_struct()

free_tty_struct() is never called with NULL tty; the two call sites
would already have faulted on earlier access.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
 drivers/tty/tty_io.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index e487076..17a3ffb 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -171,8 +171,6 @@ static void release_tty(struct tty_struct *tty, int idx);
 
 void free_tty_struct(struct tty_struct *tty)
 {
-	if (!tty)
-		return;
 	tty_ldisc_deinit(tty);
 	put_device(tty->dev);
 	kfree(tty->write_buf);
-- 
2.7.0

[toc] | [prev] | [next] | [standalone]

#1305455 — [PATCH v2 07/10] pty: Remove pty_unix98_shutdown()

The tty core invokes the optional driver shutdown() just before
the optional driver remove() (shutdown() has access to the termios
and remove() does not). Because pty drivers must prevent the default
remove() action, the Unix98 pty drivers define a dummy remove() function.

Instead, release the slave index in the remove() method and delete the
optional shutdown() method.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
 drivers/tty/pty.c | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index 7e885a2..be5020d 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -656,20 +656,13 @@ static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 	return tty;
 }
 
-/* We have no need to install and remove our tty objects as devpts does all
-   the work for us */
-
 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 {
 	return pty_common_install(driver, tty, false);
 }
 
-static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
-{
-}
-
 /* this is called once with whichever end is closed last */
-static void pty_unix98_shutdown(struct tty_struct *tty)
+static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 {
 	devpts_kill_index(tty->driver_data, tty->index);
 }
@@ -687,7 +680,6 @@ static const struct tty_operations ptm_unix98_ops = {
 	.unthrottle = pty_unthrottle,
 	.ioctl = pty_unix98_ioctl,
 	.resize = pty_resize,
-	.shutdown = pty_unix98_shutdown,
 	.cleanup = pty_cleanup
 };
 
@@ -705,7 +697,6 @@ static const struct tty_operations pty_unix98_ops = {
 	.set_termios = pty_set_termios,
 	.start = pty_start,
 	.stop = pty_stop,
-	.shutdown = pty_unix98_shutdown,
 	.cleanup = pty_cleanup,
 };
 
-- 
2.7.0

[toc] | [prev] | [next] | [standalone]

#1305456 — [PATCH v2 08/10] tty: Remove __lockfunc annotation from tty lock functions

The tty lock/unlock code does not belong in the special lockfunc section
which is treated specially by stack backtraces.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
 drivers/tty/tty_ldisc.c | 16 +++++++---------
 drivers/tty/tty_mutex.c |  8 ++++----
 include/linux/tty.h     |  8 ++++----
 3 files changed, 15 insertions(+), 17 deletions(-)

diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index 92d2898..4cb5e572 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -315,13 +315,13 @@ void tty_ldisc_deref(struct tty_ldisc *ld)
 EXPORT_SYMBOL_GPL(tty_ldisc_deref);
 
 
-static inline int __lockfunc
+static inline int
 __tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout)
 {
 	return ldsem_down_write(&tty->ldisc_sem, timeout);
 }
 
-static inline int __lockfunc
+static inline int
 __tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout)
 {
 	return ldsem_down_write_nested(&tty->ldisc_sem,
@@ -333,8 +333,7 @@ static inline void __tty_ldisc_unlock(struct tty_struct *tty)
 	ldsem_up_write(&tty->ldisc_sem);
 }
 
-static int __lockfunc
-tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout)
+static int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout)
 {
 	int ret;
 
@@ -351,7 +350,7 @@ static void tty_ldisc_unlock(struct tty_struct *tty)
 	__tty_ldisc_unlock(tty);
 }
 
-static int __lockfunc
+static int
 tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2,
 			    unsigned long timeout)
 {
@@ -387,14 +386,13 @@ tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2,
 	return 0;
 }
 
-static void __lockfunc
-tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2)
+static void tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2)
 {
 	tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT);
 }
 
-static void __lockfunc tty_ldisc_unlock_pair(struct tty_struct *tty,
-					     struct tty_struct *tty2)
+static void tty_ldisc_unlock_pair(struct tty_struct *tty,
+				  struct tty_struct *tty2)
 {
 	__tty_ldisc_unlock(tty);
 	if (tty2)
diff --git a/drivers/tty/tty_mutex.c b/drivers/tty/tty_mutex.c
index d2f3c4c..75351e4 100644
--- a/drivers/tty/tty_mutex.c
+++ b/drivers/tty/tty_mutex.c
@@ -10,7 +10,7 @@
  * Getting the big tty mutex.
  */
 
-void __lockfunc tty_lock(struct tty_struct *tty)
+void tty_lock(struct tty_struct *tty)
 {
 	if (WARN(tty->magic != TTY_MAGIC, "L Bad %p\n", tty))
 		return;
@@ -27,7 +27,7 @@ int tty_lock_interruptible(struct tty_struct *tty)
 	return mutex_lock_interruptible(&tty->legacy_mutex);
 }
 
-void __lockfunc tty_unlock(struct tty_struct *tty)
+void tty_unlock(struct tty_struct *tty)
 {
 	if (WARN(tty->magic != TTY_MAGIC, "U Bad %p\n", tty))
 		return;
@@ -36,13 +36,13 @@ void __lockfunc tty_unlock(struct tty_struct *tty)
 }
 EXPORT_SYMBOL(tty_unlock);
 
-void __lockfunc tty_lock_slave(struct tty_struct *tty)
+void tty_lock_slave(struct tty_struct *tty)
 {
 	if (tty && tty != tty->link)
 		tty_lock(tty);
 }
 
-void __lockfunc tty_unlock_slave(struct tty_struct *tty)
+void tty_unlock_slave(struct tty_struct *tty)
 {
 	if (tty && tty != tty->link)
 		tty_unlock(tty);
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 7e1034f..1b31736 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -640,11 +640,11 @@ extern long vt_compat_ioctl(struct tty_struct *tty,
 
 /* tty_mutex.c */
 /* functions for preparation of BKL removal */
-extern void __lockfunc tty_lock(struct tty_struct *tty);
+extern void tty_lock(struct tty_struct *tty);
 extern int  tty_lock_interruptible(struct tty_struct *tty);
-extern void __lockfunc tty_unlock(struct tty_struct *tty);
-extern void __lockfunc tty_lock_slave(struct tty_struct *tty);
-extern void __lockfunc tty_unlock_slave(struct tty_struct *tty);
+extern void tty_unlock(struct tty_struct *tty);
+extern void tty_lock_slave(struct tty_struct *tty);
+extern void tty_unlock_slave(struct tty_struct *tty);
 extern void tty_set_lock_subclass(struct tty_struct *tty);
 
 #ifdef CONFIG_PROC_FS
-- 
2.7.0

[toc] | [prev] | [next] | [standalone]

#1305457 — [PATCH v2 02/10] tty: Retry failed reopen if tty teardown in-progress

A small window exists where a tty reopen will observe the tty
just prior to imminent teardown (tty->count == 0); in this case, open()
returns EIO to userspace.

Instead, retry the open after checking for signals and yielding;
this interruptible retry loop allows teardown to commence and initialize
a new tty on retry. Never retry the BSD master pty reopen; there is no
guarantee the pty pair teardown is imminent since the slave file
descriptors may remain open indefinitely.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
 drivers/tty/tty_io.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 1bf67a2..93fe10d 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1468,13 +1468,13 @@ static int tty_reopen(struct tty_struct *tty)
 {
 	struct tty_driver *driver = tty->driver;
 
-	if (!tty->count)
-		return -EIO;
-
 	if (driver->type == TTY_DRIVER_TYPE_PTY &&
 	    driver->subtype == PTY_TYPE_MASTER)
 		return -EIO;
 
+	if (!tty->count)
+		return -EAGAIN;
+
 	if (test_bit(TTY_EXCLUSIVE, &tty->flags) && !capable(CAP_SYS_ADMIN))
 		return -EBUSY;
 
@@ -2094,7 +2094,11 @@ retry_open:
 
 	if (IS_ERR(tty)) {
 		retval = PTR_ERR(tty);
-		goto err_file;
+		if (retval != -EAGAIN || signal_pending(current))
+			goto err_file;
+		tty_free_file(filp);
+		schedule();
+		goto retry_open;
 	}
 
 	tty_add_file(tty, filp);
-- 
2.7.0

[toc] | [prev] | [next] | [standalone]

#1305458 — [PATCH v2 09/10] tty: Consolidate noctty checks in tty_open()

Evaluate the conditions which prevent this tty being the controlling
terminal in one place, just before setting the controlling terminal.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
 drivers/tty/tty_io.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 1f8d06f..d223e54 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1966,7 +1966,7 @@ static struct tty_struct *tty_open_current_tty(dev_t device, struct file *filp)
  *	Locking: tty_mutex protects get_tty_driver
  */
 static struct tty_driver *tty_lookup_driver(dev_t device, struct file *filp,
-		int *noctty, int *index)
+		int *index)
 {
 	struct tty_driver *driver;
 
@@ -1976,7 +1976,6 @@ static struct tty_driver *tty_lookup_driver(dev_t device, struct file *filp,
 		extern struct tty_driver *console_driver;
 		driver = tty_driver_kref_get(console_driver);
 		*index = fg_console;
-		*noctty = 1;
 		break;
 	}
 #endif
@@ -1987,7 +1986,6 @@ static struct tty_driver *tty_lookup_driver(dev_t device, struct file *filp,
 			if (driver) {
 				/* Don't let /dev/console block */
 				filp->f_flags |= O_NONBLOCK;
-				*noctty = 1;
 				break;
 			}
 		}
@@ -2042,14 +2040,13 @@ retry_open:
 	if (retval)
 		return -ENOMEM;
 
-	noctty = filp->f_flags & O_NOCTTY;
 	index  = -1;
 	retval = 0;
 
 	tty = tty_open_current_tty(device, filp);
 	if (!tty) {
 		mutex_lock(&tty_mutex);
-		driver = tty_lookup_driver(device, filp, &noctty, &index);
+		driver = tty_lookup_driver(device, filp, &index);
 		if (IS_ERR(driver)) {
 			retval = PTR_ERR(driver);
 			goto err_unlock;
@@ -2097,10 +2094,6 @@ retry_open:
 	tty_add_file(tty, filp);
 
 	check_tty_count(tty, __func__);
-	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
-	    tty->driver->subtype == PTY_TYPE_MASTER)
-		noctty = 1;
-
 	tty_debug_hangup(tty, "opening (count=%d)\n", tty->count);
 
 	if (tty->ops->open)
@@ -2133,6 +2126,12 @@ retry_open:
 
 	read_lock(&tasklist_lock);
 	spin_lock_irq(&current->sighand->siglock);
+	noctty = (filp->f_flags & O_NOCTTY) ||
+			device == MKDEV(TTY_MAJOR, 0) ||
+			device == MKDEV(TTYAUX_MAJOR, 1) ||
+			(tty->driver->type == TTY_DRIVER_TYPE_PTY &&
+			 tty->driver->subtype == PTY_TYPE_MASTER);
+
 	if (!noctty &&
 	    current->signal->leader &&
 	    !current->signal->tty &&
-- 
2.7.0

[toc] | [prev] | [next] | [standalone]

#1305459 — [PATCH v2 10/10] tty: Refactor tty_open()

Extract the driver lookup and reopen-or-initialize logic into helper
function tty_open_by_driver(). No functional change.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
 drivers/tty/tty_io.c | 120 ++++++++++++++++++++++++++++-----------------------
 1 file changed, 67 insertions(+), 53 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index d223e54..cef913c 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2001,6 +2001,69 @@ static struct tty_driver *tty_lookup_driver(dev_t device, struct file *filp,
 }
 
 /**
+ *	tty_open_by_driver	-	open a tty device
+ *	@device: dev_t of device to open
+ *	@inode: inode of device file
+ *	@filp: file pointer to tty
+ *
+ *	Performs the driver lookup, checks for a reopen, or otherwise
+ *	performs the first-time tty initialization.
+ *
+ *	Returns the locked initialized or re-opened &tty_struct
+ *
+ *	Claims the global tty_mutex to serialize:
+ *	  - concurrent first-time tty initialization
+ *	  - concurrent tty driver removal w/ lookup
+ *	  - concurrent tty removal from driver table
+ */
+static struct tty_struct *tty_open_by_driver(dev_t device, struct inode *inode,
+					     struct file *filp)
+{
+	struct tty_struct *tty;
+	struct tty_driver *driver = NULL;
+	int index = -1;
+	int retval;
+
+	mutex_lock(&tty_mutex);
+	driver = tty_lookup_driver(device, filp, &index);
+	if (IS_ERR(driver)) {
+		mutex_unlock(&tty_mutex);
+		return ERR_CAST(driver);
+	}
+
+	/* check whether we're reopening an existing tty */
+	tty = tty_driver_lookup_tty(driver, inode, index);
+	if (IS_ERR(tty)) {
+		mutex_unlock(&tty_mutex);
+		goto out;
+	}
+
+	if (tty) {
+		mutex_unlock(&tty_mutex);
+		retval = tty_lock_interruptible(tty);
+		if (retval) {
+			if (retval == -EINTR)
+				retval = -ERESTARTSYS;
+			tty = ERR_PTR(retval);
+			goto out;
+		}
+		/* safe to drop the kref from tty_driver_lookup_tty() */
+		tty_kref_put(tty);
+		retval = tty_reopen(tty);
+		if (retval < 0) {
+			tty_unlock(tty);
+			tty = ERR_PTR(retval);
+		}
+	} else { /* Returns with the tty_lock held for now */
+		tty = tty_init_dev(driver, index);
+		mutex_unlock(&tty_mutex);
+	}
+out:
+	tty_driver_kref_put(driver);
+	return tty;
+}
+
+/**
  *	tty_open		-	open a tty device
  *	@inode: inode of device file
  *	@filp: file pointer to tty
@@ -2028,8 +2091,6 @@ static int tty_open(struct inode *inode, struct file *filp)
 {
 	struct tty_struct *tty;
 	int noctty, retval;
-	struct tty_driver *driver = NULL;
-	int index;
 	dev_t device = inode->i_rdev;
 	unsigned saved_flags = filp->f_flags;
 
@@ -2040,53 +2101,15 @@ retry_open:
 	if (retval)
 		return -ENOMEM;
 
-	index  = -1;
-	retval = 0;
-
 	tty = tty_open_current_tty(device, filp);
-	if (!tty) {
-		mutex_lock(&tty_mutex);
-		driver = tty_lookup_driver(device, filp, &index);
-		if (IS_ERR(driver)) {
-			retval = PTR_ERR(driver);
-			goto err_unlock;
-		}
-
-		/* check whether we're reopening an existing tty */
-		tty = tty_driver_lookup_tty(driver, inode, index);
-		if (IS_ERR(tty)) {
-			retval = PTR_ERR(tty);
-			goto err_unlock;
-		}
-
-		if (tty) {
-			mutex_unlock(&tty_mutex);
-			retval = tty_lock_interruptible(tty);
-			if (retval) {
-				if (retval == -EINTR)
-					retval = -ERESTARTSYS;
-				goto err_unref;
-			}
-			/* safe to drop the kref from tty_driver_lookup_tty() */
-			tty_kref_put(tty);
-			retval = tty_reopen(tty);
-			if (retval < 0) {
-				tty_unlock(tty);
-				tty = ERR_PTR(retval);
-			}
-		} else { /* Returns with the tty_lock held for now */
-			tty = tty_init_dev(driver, index);
-			mutex_unlock(&tty_mutex);
-		}
-
-		tty_driver_kref_put(driver);
-	}
+	if (!tty)
+		tty = tty_open_by_driver(device, inode, filp);
 
 	if (IS_ERR(tty)) {
+		tty_free_file(filp);
 		retval = PTR_ERR(tty);
 		if (retval != -EAGAIN || signal_pending(current))
-			goto err_file;
-		tty_free_file(filp);
+			return retval;
 		schedule();
 		goto retry_open;
 	}
@@ -2157,15 +2180,6 @@ retry_open:
 	read_unlock(&tasklist_lock);
 	tty_unlock(tty);
 	return 0;
-err_unlock:
-	mutex_unlock(&tty_mutex);
-err_unref:
-	/* after locks to avoid deadlock */
-	if (!IS_ERR_OR_NULL(driver))
-		tty_driver_kref_put(driver);
-err_file:
-	tty_free_file(filp);
-	return retval;
 }
 
 
-- 
2.7.0

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web